K75 engine temp/cooling matters

[OfficerImpersonator]

For the past several days the radiator fan has been coming on intermittently. Sometimes it comes on and then immediately switches off in a fraction of a second - like my two year old and a light switch. Other times it will come on and stay on for a couple or ten seconds before shutting off again. This seemingly bizarre behavior is independent of it coming on when it's supposed to - which I think it does.

Also, for the first time this morning, the engine temp light came on just after I exited the freeway. For a while the engine temp light flashed in conjunction with my turn signals, but then it "settled down" and, like the radiator fan, stayed on until I turned the corner into a cool headwind. Then all was normal for the remaining two blocks to my parking garage. No temp light, no bizarre engine fan behavior.

The bike is a '92 K75S, 33K miles. The wiring harness was replaced a year ago.

Electrical issues? Thermostat issues? Any ideas?

[godzilla]

Don't mean to sound stupid, but did you check your coolant level? And if the overflow bottle is full, did you check the radiator itself? DAMIK.

[OfficerImpersonator]

I'm stupid for posting my problem before checking the coolant levels, but the problem manifested itself after I had been riding for 45 minutes so I thought I'd wait for a cold engine before this afternoon's ride home before I pop the cork on the cooling system.

I will be checking the coolant level - but even if I had a low coolant level, would that explain the weird behavior of the radiator fan and the temp light?

[jdiaz]

Any time I've had multiple unrelated light blinking at the instrument panel, it was battery related. Is your bike starting ok?

The quick on-off of the cooling fan could be related to the fan relay. There is a procedure at ibmwr.org showing how to test such things.

Make sure the fan spins nice and freely with your fingertips. Reach in there after the bike has cooled off.

Hopefully its just low coolant level.

[godzilla]

Ah didn't I say DAMHIK?

That is Zacky what mine did when I had a leaking water pump. It was fine as long as I was moving. Once I slowed down or stopped, the fan, then the light came on. Yours sounds alot more touchy than mine, but that sure sounds like it.

See, I took a long ride to Canada a couple years ago. I started noticing a couple, three drops of coolant under my bike every once in a while. Finally I checked the overflow bottle and lo! and behold! It was low. That got my attention. So at every gas stop, I would add water trying to nurse her home. On the final leg, she quit asking for more water. "Strange" Godzilla thought. "Oh well" Godzilla said.

About 40 miles form home after a long interstate slab run and after dark the temp light came on at a stop sign. "Uh-Oh" Godzilla said.

I got her home and up to Wilbur, my mechanic. He explained ( :doh Godzilla said) that once the coolant level in the radiator gets too low, it won't siphon out of the overflow bottle.

You asked, sort of.

[jdiaz]

Ah didn't I say DAMHIK?

That is Zacky what mine did when I had a leaking water pump. It was fine as long as I was moving. Once I slowed down or stopped, the fan, then the light came on. Yours sounds alot more touchy than mine, but that sure sounds like it.

See, I took a long ride to Canada a couple years ago. I started noticing a couple, three drops of coolant under my bike every once in a while. Finally I checked the overflow bottle and lo! and behold! It was low. That got my attention. So at every gas stop, I would add water trying to nurse her home. On the final leg, she quit asking for more water. "Strange" Godzilla thought. "Oh well" Godzilla said.

About 40 miles form home after a long interstate slab run and after dark the temp light came on at a stop sign. "Uh-Oh" Godzilla said.

I got her home and up to Wilbur, my mechanic. He explained ( :doh Godzilla said) that once the coolant level in the radiator gets too low, it won't siphon out of the overflow bottle.

You asked, sort of.

Wow. An awful lot of coolant has to come out that hole to drain the radiator!! The underside of the engine would be completely white.

[godzilla]

You'd think it would have been obvious, but not so! The drips were actually coming from the TRANSMISSION area! The coolant was being blown back around the engine somehow and dripping to the ground from there! Godzilla isn't lying!

The problem was the seal in the water pump.

[OfficerImpersonator]

Guess I'll take a couple of extra water bottles to the garage after work :)

I park inside - both at home and here at work - and I've never seen a drop under the bike. Of course, with the belly pan, how would I know if fluids were slowly dripping out from the bottom of the bike!

Thanks for the hints - I'll be very happy if this can be fixed with a quart of water instead of a new wiring harness!

[OfficerImpersonator]

Okay - just went and eyeballed the bike. The level of coolant in the overflow tank was just a tiny bit below halfway between the min and max lines. I added about six ounces of water to take it to the "max" line, under the theory that the level was too low to siphon from the tank and into the rest of the cooling system.

I noticed my oil level is just a tiny bit low, so that might contribute to a boost of a couple degrees in the engine temp, but I can't imagine that would be enough to upset my cooling system - especially since temps here have been in the 35-55 degree range the past six months.

I'm interested to see how she performs on her way home. I'll be adding some oil once she cools down tonight. I'll keep you posted should the problems continue...

[brahma]

I didn't realize new pumps were available. My dealer told me they weren't for my 85 K100RT. I had them rebuild mine which was a nightmare I care not to go into, but eventualy, they figured out how to make it work- and yes, that's about my level of satisfaction I have with them. But I digress... Glad to hear they are available.

By the way, did you see your oil pressure sending unit wire in there? I'm trying to figure out how to snake mine through to replace it.

[OfficerImpersonator]

Before the ride home from work last night, I added about a cup of water to the coolant overflow reservoir, brining the level to the "max" line on the tank.

Last night, after the bike had cooled down for a couple of hours, I added about a cup of oil to the engine. Engine oil now covers roughly the lower two-thirds of the sight glass with the bike on the center stand.

The ride home was uneventful. The engine fan operated almost continuously once I exited the highway and while I rode the approx. 4 miles of surface streets home.

I was tempted to leave the engine running with the bike on the center stand to see if/when the fan ever shut off on its own, but I also didn't want to fill my garage with CO.

On the ride in this morning, all was fine until I exited the freeway and rode the approx. 10 blocks to the parking garage. After the equivalent of about 8 blocks of stop and go driving on downtown city streets, the temp light began to flicker intermittently for about a minute. Then it stopped completely once I began riding through the parking garage and remained off until I stopped the bike.

Is this all normal, or is the recent appearance of the temp light indicative of something wrong?

[jdiaz]

Is this all normal, or is the recent appearance of the temp light indicative of something wrong?

In almost 18 years of owning one K75, the temp light has come on twice. Both episodes were related to a dead cooling fan.

Does your horn work? If the horn fuse is blown, then the cooling fan is probably dead.

[OfficerImpersonator]

In almost 18 years of owning one K75, the temp light has come on twice. Both episodes were related to a dead cooling fan.

Does your horn work? If the horn fuse is blown, then the cooling fan is probably dead.

Horn works fine. In fact, I just added two huge Fiamm horns. Fan works - sometimes it comes on and off, on and off - for a second or for a minute. Other times it comes on and stays on until I shut the bike down.

[jdiaz]

You gotta get in there and see how easy the fan spins. Maybe its on the verge of seizing up?

Just pull that small black decorative cover on the bottom of the RH fairing panel, then the airbox intake tube. Then you can reach in and check the fan.

[OfficerImpersonator]

I know the fan is an expensive part to replace - how easy is the task?

[jdiaz]

I know the fan is an expensive part to replace - how easy is the task?
Two hours if you are familiar with taking the fairing off.. And the fan isn't expensive.....$138 from BeemerBoneyard.

But let's make sure that's it. If you find the fan is fine, then its time to check the fan relay and the coolant temp sensor next.

[OfficerImpersonator]

Two hours if you are familiar with taking the fairing off.. And the fan isn't expensive.....$138 from BeemerBoneyard.

But let's make sure that's it. If you find the fan is fine, then its time to check the fan relay and the coolant temp sensor next.

Baby steps!

Thanks for the suggestions - I'm sure the wife will be excited that tonight means another night of me laying on the floor of the garage, taking apart the bike :)

[jdiaz]

Thanks for the suggestions - I'm sure the wife will be excited that tonight means another night of me laying on the floor of the garage, taking apart the bike :)

Just check the fan during your lunch hour. It will take five minutes to get in there.

The other jobs might take longer. :D

[breyfogle]

....Is this all normal, or is the recent appearance of the temp light indicative of something wrong?

In 118,000 miles, the temp light on my K75 has never come on. The only time the fan came on was after slowing down to "in-town" speeds after a long high-speed run thru the desert in 100+ degree weather.

My normal daily commute is thru LA city stop and slow traffic. Even in summer, neither the fan nor the light comes on.

I think you definitely have a cooling problem.

[godzilla]

I know it is a pain to do, but check the coolant level in the radiator itself. Seems to me that I have to loosen the radiator cowling to get at the radiator cap. I don't THINK I had to loosen the gas tank, but maybe. Of course my K is nekkid, so there is no fairing to deal with. If the radiator gets too low, it will not siphon out of the bottle. I think if the level in the radiator is physically lower than the bottom of the bottle, it can't suck in the needed boost of coolant. That is what happen to mine...

[98lee]

Like Godzilla said: If you are experiencing cooling problems one of the first things you need to do is make sure the radiator is full. This requires removing the gas tank as the filler is under the right front of the tank. If the little hose to the overflow reservoir (the one you topped off) is cracked, coolant will be pushed into the reservoir or onto the engine when the coolant gets warm. But, when it cools it sucks air into the radiator. After several times of this your radiator could be over half empty. This could happen over a period of weeks or a year. I purchased one of my K75s for $1200 and this was its only mechanical problem. Also a bad radiator filler cap will cause similar type problems. Next step: Pull gas tank and confirm that you have coolant all the way to the top of the filler neck. If not, top off and replace overflow hose.If hose was not cracked replace Radiator cap.

[breyfogle]

.... Next step: Pull gas tank and confirm that you have coolant all the way to the top of the filler neck.

On a K75S, the filler cap can be reached without taking the fuel tank off or removing any of the fairing panels. Open the seat, pop up the rear of the fuel tank from its two rear mounting pins and slide the tank toward the seat until the filler cap is exposed. The fuel tank only has to move back maybe 6 inches or so and there is more than that amount of slack in the fuel line hoses.

[OfficerImpersonator]

On a K75S, the filler cap can be reached without taking the fuel tank off or removing any of the fairing panels. Open the seat, pop up the rear of the fuel tank from its two rear mounting pins and slide the tank toward the seat until the filler cap is exposed. The fuel tank only has to move back maybe 6 inches or so and there is more than that amount of slack in the fuel line hoses.

Oh happy day! I had set aside Saturday as the day to remove the fairing side panels, remove the tank, and get to the radiator filler cap. Now I can try it this evening instead of this weekend since I don't have to completely remove the tank - and more importantly - the fairing!

To update the situation, the temp light only comes on during my morning ride in. Average morning air temperatures have been in the mid 30's. The temp light does NOT come on at any point during my ride home, when afternoon temperatures have been averaging around 60. I'll inspect the coolant level at the radiator this evening.

Could this be a thermostat issue?

[98lee]

I didn't realize there was enough slack in the fuel hoses. Usually when I go in there I'm going for something in the wiring which has required that the tank be fully removed and, while I'm in there, I always check the radiator level. I'll have to give that a try this weekend. Although I imagine you still have to disconect the electrical connection to the tank and the vent hoses and, if not totally remove the seat, at least unclip the stop arm from the seat to fold it out of the way of the tank. But if that works it definitely saves doing the worst part of the job: breaking the fuel lines. Thanks for the tip. The stuff you can pick up on this forum is definitely worth the price of addmission to MOA.:groovy

[OfficerImpersonator]

98lee,

I'd love to see a picture of your garage some time - 3 bikes identical to mine in one garage must be quite the sight!

[breyfogle]

I didn't realize there was enough slack in the fuel hoses. ...still have to disconect the electrical connection to the tank and the vent hoses and.....

If the two vent hoses are still connected to the tank fittings, that could limit how far the tank can be moved. BMW sells ( did sell?) a small under tank frame mounted plastic funnel thingy that sits directly below the tank vent spigots, but is not connected in any way to the tank. A single funnel drain tube runs from the funnel to the ground. It makes moving or removing the fuel tank MUCH easier.

[98lee]

dvandkq,

Currently only two of them are fully together. I just finished modifying my wife's bike last Novermber so she can ride it. She' 5'4" and she can flat foot it without heels. I lowered the suspension 2 full inches front and back, removed the toolbox and repositioned the fuel injection computer so that I could narrow and lower the frame rails under the seat. (the stock frame rails are so wide it's been said that it's like trying to stradle an ironing board). Then I had a custom seat pan and seat made at Corbin's down in Hollister. Oh yeah, then I had to modify the clutch lever arm under the trans because I found out that the 23lb. pull that was required to pull in the clutch lever would have been too much for my wife in stop and go bumper to bumper traffic. It's now at 10lbs.

Her's was an '88 with the black wheels and engine covers trans and final drive.I prefer the '87 like mine with the silver and natural aluminum. So I blasted and clear coated the engine covers,trans,swing arm and final drive and picked up some '87 wheels.

Three weeks after I got her bike done, a lady made a u-turn from the right hand shoulder on a 50 mile an hour two lane road right in front of my wife. My wife had slowed to about 35 as she thought the lady might do something stupid, like pull out infront of her, but she didn't expect the u-turn! She hit the cars door at between 10 and 15 mph. She got a severely sprained wrist and some cuts.

Their insurance adjuster was suprised when I told him I'd kill him if he even thought about declaring the bike a total. When he saw all the custom work and the fact that a new or replacement bike would not be rideable for my wife they agreed to pay what CalBMW said it would cost to repair it.

I didn't even have the S fairing parts on yet and even so they paid me more than Blue Book for the bike and gave me the bike back with no salvage title. But then I had to rebuild the bike.

I just finished rebuilding the bike two months ago (with all the fairing parts). So instead of working on the spare bike, we've been riding every chance we get. Maybe this summer I'll get a chance to finish the third bike.

If I get a chance next week, I'll email you some pictures of our two runners.

[98lee]

BREYFOGLE

Thanks, I'll check it out. What about the seat? Does it have to be removed or just the arm that limits it from hingeing all the way disconnected?

On my wifes bike (see previous post) I would have to remove the seat because the seat pan is very deep and it will not hinge past where the limit arm stops anyway.

Thanks for the info.

[OfficerImpersonator]

98lee,

You've just identified yourself as a bonafide expert on K75s - you'll be hearing from me again, my friend!

So last night, after the engine cooled down after the ride home, I pulled the fuel tank back (couldn't have been easier!) and opened the radiator cap. The filler neck had a 1/8" thick layer of brown/green slime that coated the inside of the filler neck and appeared to be covering the outlet to the overflow tank. I cleaned out the filler neck the best I could and added a half a gallon of water/coolant mixture to the radiator. I couldn't believe how much I could pour in there! Because of the awkward angle, it filled right up to the rim of the filler neck before I could stop the flow.

Throughout the process of filling the radiator I could hear bubbles and gurgling from the engine and radiator.

Because it had been mentioned as a possible symptom/cause, I checked the radiator fan while I was under the tank and it spins just fine.

I put everything back together, started the bike, and ran it at varying RPMs for about 10 minutes to bring it up to operating temp. As the engine got hot, I was hoping I'd see coolant flow from the radiator into the overflow tank, but I didn't. I was a little worried about riding in this morning, thinking I'd be going 60 when the thing started spewing coolant out the relief hole on the overflow tank - or even blow a hose - but the ride was uneventful.

No radiator fan, no temp. light. Just a happy motorcycle and thus a happy motorcycle owner.

I'll check the radiator again tonight (it really is that easy to access the cap under the tank) and top off if necessary. I suppose there's a chance my overflow hose is clogged up with the same gunk I found in the filler neck. Might have to find an air compressor and blow that line out. I couldn't figure out how to remove, clean and reinstall the overflow tank - even with the Clymer's manual right in front of my face. Looks like I'll have to remove the battery to get at it, unlike what the Clymer's manual says.

Does anyone know if the radiator cap has a relief valve/thermostat/filter screen in it? It appears that there are four holes covered with a metal mesh screen, and that there might be a mechanical thermostat (or some other device) inside the cap. I could envision how coolant could be released up through the device in the center of the cap (thermostat/filter/sacrificial zinc?), into the channel that exists inside the filler neck, and out through the hose to the overflow tank.

I took photos of this stuff and I'll try to post them later.

[jdiaz]

I cleaned out the filler neck the best I could and added a half a gallon of water/coolant mixture to the radiator.
Two quarts! The whole cooling system only holds 2.6 quarts.

Wow. I might suggest an oil and filter change right now as well.

[98lee]

dvandkq,

Well I'm glad your on the right track. :thumb Partially empty radiator. But filling the radiator got rid of the symptom not the problem. The problem is a water leak. The three most likely are: 1. the overflow hose, 2. the radiator cap, 3. the water pump.

By far the cheapest and easiest to fix are the overflow hose ($2 from any carparts store) and the radiator cap BMW part#17111464720 $16 list price from your dealer.

Personally, I would replace both of those. (I've had both go bad, so I replaced both on all three bikes as a preemptive measure). Then I would recheck radiator level in a week. If it's good, then check again in a month. If still good, in three or four months. If still good, problem solved. But still check periodically when doing routine maintenance.

[OfficerImpersonator]

dvandkq,

Well I'm glad your on the right track. :thumb Partially empty radiator. But filling the radiator got rid of the symptom not the problem. The problem is a water leak. The three most likely are: 1. the overflow hose, 2. the radiator cap, 3. the water pump.

By far the cheapest and easiest to fix are the overflow hose ($2 from any carparts store) and the radiator cap BMW part#17111464720 $16 list price from your dealer.

Personally, I would replace both of those. (I've had both go bad, so I replaced both on all three bikes as a preemptive measure). Then I would recheck radiator level in a week. If it's good, then check again in a month. If still good, in three or four months. If still good, problem solved. But still check periodically when doing routine maintenance.

Ride Safe, Ride Far, Ride Often

All good advice - especially your last line!

I understand the suggestion regarding the hose, but I'm curious as to what function (other than keeping the coolant in the radiator) is served by the radiator cap? Are there moving parts within the radiator cap? What can go wrong with the cap if there are no moving parts? A screw on cap is a screw on cap, right?

I'm very interested in not melting my engine, so I'll be keeping on top of my radiator situation. I'm about 800 miles away from a Level II - I'm going to ask my wrench to flush and pressure check my cooling system.

In one regard, this has been a useful exercise - I've discovered that my temp light and cooling fan operate correctly. I've also identified a potential issue (water leak) that I'd prefer to address sooner rather than later. I'm also glad I'm going to get this sorted out before the weather gets much warmer - not that it ever gets that hot here in Seattle.

[98lee]

dvandkq

By the way, I am not aware of any way of removing the overflow tank, other than removing the battery.

And, yes there is a sort of relief/check valve inside the radiator cap. If this does not function properly (gummed up, wore out, corroded) the normal cycle of the expanding warm coolant overflowing into the overflow tank (actually the correct term is expansion tank), and then being sucked back into the radiator when then coolant in the radiator cools and contracts does not take place properly. Usually it will push out but not suck in(and that SUCKS!)

[98lee]

If you just leave the cap OFF all that RAIN will keep your radiator topped off all year!!!!

(I was born in Seattle, but all that rain made me decide to move to California when I was three:burnout )

[OfficerImpersonator]

dvandkq

By the way, I am not aware of any way of removing the overflow tank, other than removing the battery.

And, yes there is a sort of relief/check valve inside the radiator cap. If this does not function properly (gummed up, wore out, corroded) the normal cycle of the expanding warm coolant overflowing into the overflow tank (actually the correct term is expansion tank), and then being sucked back into the radiator when then coolant in the radiator cools and contracts does not take place properly. Usually it will push out but not suck in(and that SUCKS!)

Okay - based upon your advice and the amount of gunk I pulled out of the filler neck and what was covering the cap I'm going to order a new one.

I'm also going to try and blow the expansion tank line out first - if that works, then I won't have to remove the battery and the engine management computer? above the battery to access and remove the expansion tank.

[98lee]

I would be more concerned with a CRACK in the hose from the filler neck to the overflow(usually near the clamps) than I would about it being plugged.

A tiny crack will break the suction and cause the radiator to suck back air instead of the coolant in the tank. REPLACE THE HOSE!!! Only $2 !! And maybe a couple of new hose clamps So okay, another $2.

I am pretty sure you can replace that hose(not positive, my bike is not upstairs here with my computer) without removing the overflow tank. Just snake it through.

If you can't get to the hose clamp on the bottom of the over flow tank, pulling the computer (2 minutes) and the battery (4 minutes) is extremely easy and something every Brick owner needs to know how to do with the tools in the bikes tool roll.

While you have the overflow (excuse me, expansion tank) out, you can replace that yellowed sight tube with a piece of tygon tubing from your local hardware store <$2ft. oh yeah and two more hose clamps $2 more.

See how easy it is for me to spend your money..:dance

Anyone else got any money they want me to spend???

[godzilla]

On cars, a guy can do a pressure check... hook up a gizmo, pump it up to whatever pressure spec the cooling system is supposed to have and see what happens. The system should hold pressure. If it slowly (or quickly!) drops pressure, you know you have a leak. Then you can pump her back up and start your search for the problem. Could be a pinhole in the radiator, a loose clamp or a cracked engine block. Thim gizmos even have an adaptor kit to check the radiator cap. Car radiator caps are spec'd for a certain pressure.

Would one of these work on a K radiator and cap? Or does BMW have another special tool for this? :dunno

[OfficerImpersonator]

I would be more concerned with a CRACK in the hose from the filler neck to the overflow(usually near the clamps) than I would about it being plugged.

A tiny crack will break the suction and cause the radiator to suck back air instead of the coolant in the tank. REPLACE THE HOSE!!! Only $2 !! And maybe a couple of new hose clamps So okay, another $2.

I am pretty sure you can replace that hose(not positive, my bike is not upstairs here with my computer) without removing the overflow tank. Just snake it through.

If you can't get to the hose clamp on the bottom of the over flow tank, pulling the computer (2 minutes) and the battery (4 minutes) is extremely easy and something every Brick owner needs to know how to do with the tools in the bikes tool roll.

While you have the overflow (excuse me, expansion tank) out, you can replace that yellowed sight tube with a piece of tygon tubing from your local hardware store <$2ft. oh yeah and two more hose clamps $2 more.

See how easy it is for me to spend your money..:dance

Anyone else got any money they want me to spend???

Easy for you to spend my money? According to my math, you've only spent $8 of my money. I have a wife and a two-year old with a college fund. $8 is nothing! :)

I'm guessing I can ride the thing for a couple of days while I wait for parts, as long as I'm adding coolant to keep the radiator full and paying attention to the warning signs (temp light, engine fan) - correct?

[98lee]

GODZILLA

I'm sure BMW, in their infinite wisdom:german , made the radiator cap and filler neck just a hair incompatible so that they could not be defiled with a Japanese or American substitue.

And it would insure that the correct pressure and return parameters for the bike were met. With only 2.6 quarts of coolant, I would imagine everything has to be working fairly correctly.

I am sure that a pressure check at a shop would cost more than buying a new cap and overflow hose.

I would bet that the overflow hose is bad 70%

Or the cap is bad 30%

Or it's one of the other hoses, the water pump, a cracked block, or glycol drinking Seattle garage rats 10%

110% ??? Well coaches always say that's what you have to give to be successful.:dunno

[98lee]

dvandkq

See my post from 12:22pm MOA time this thread.:laugh :laugh :laugh :laugh

[godzilla]

Yup, I agree. I just was thinking that a quick pressure check would be quicker than having to keep checking the rad level and it would save dvandkq from having to worry that something is wrong. Maybe the coolant level just dropped on it's own, though I highly doubt it. Maybe replacing the hose and cap (since we know we had crud buildup) is a great idea that couldn't hurt no matter what. But if it were me, I'd be worrying about it until I was darn sure it is OK. KnowwhatImean?

I threw the question out there, hoping that one of the REAL K-Bike mechanics might comment on it.

I mean shotgunning a problem is a valid way of fixing it. Done it myself as a car mechanic way back in the 70's and as a Computer Geek since then. But if you can lay your hands on the right tool, why not?

[OfficerImpersonator]

If you just leave the cap OFF all that RAIN will keep your radiator topped off all year!!!!

(I was born in Seattle, but all that rain made me decide to move to California when I was three:burnout )

That's funny! I was born in Southern California, and the best thing that ever happened to me was my family moving back to Seattle when I was 11. (Mom and dad were natives.)

I can't get enough of all the things all that rain brings - snow in the mountains, rivers in the valleys, water in the lakes and Sound - all the things that make it worth putting up with all those gray and damp days.

[OfficerImpersonator]

Yup, I agree. I just was thinking that a quick pressure check would be quicker than having to keep checking the rad level and it would save dvandkq from having to worry that something is wrong. Maybe the coolant level just dropped on it's own, though I highly doubt it. Maybe replacing the hose and cap (since we know we had crud buildup) is a great idea that couldn't hurt no matter what. But if it were me, I'd be worrying about it until I was darn sure it is OK. KnowwhatImean?

I threw the question out there, hoping that one of the REAL K-Bike mechanics might comment on it.

I mean shotgunning a problem is a valid way of fixing it. Done it myself as a car mechanic way back in the 70's and as a Computer Geek since then. But if you can lay your hands on the right tool, why not?

I've only owned the bike for five months. Almost all of the riding I've done since getting the bike has been done in relatively cool/cold weather (nothing over 60, not many days over 50). A super slow leak would take a while to manifest itself. It's entirely possible the bike came to me with a low radiator level and it's just taken five months for the problem to get to the point where there are now symptoms. I'm the third owner of a 16 year old piece of machinery - anything is possible!

I'm actually enjoying getting my hands dirty working on the thing. I've never considered myself mechanically inclined until I discovered how easy it is to follow the simple instructions in a good shop manual. If I can fix it in my garage some evening, it saves me not only money, but the day or two I'd have to spend without the bike - and commuting by bus - yuck!

I really don't have any objection to replacing the radiator cap and the tubing between the radiator and the expansion tank. The parts are cheap, access to the work area is fairly easy, and results should be easy to determine.

Now if we're talking about a valve adjustment, or a clutch replacement, or a radiator replacement, I'm going to go see my wrench.

[98lee]

That's funny! I was born in Southern California, and the best thing that ever happened to me was my family moving back to Seattle when I was 11. (Mom and dad were natives.)

I can't get enough of all the things all that rain brings - snow in the mountains, rivers in the valleys, water in the lakes and Sound - all the things that make it worth putting up with all those gray and damp days.

My brother moved back to that area 6 years ago after living in Sacramento. When I went to visit him (on San Juan Island) last September, I was really impressed with how green every thing was in Seattle, Anacortes(sp?) and on the islands. The smell of the salt air mixed with the smell of all the pine trees was incredible! It was gorgeous all week. It made me envious right up until the Dec.-March weather reports. Hey, I got to kid you, I'm from there!:stick

Keep us all up to date with your Brick. We're curious to find what it was. (but my money is still on the overflow hose) But , then again, that might be why I always come back with empty pockets when I go to Vegas.:uhoh

[godzilla]

I'm just happy that I actually got one right!!! :laugh Starting to scare myself!

[OfficerImpersonator]

Thanks to your encouragement and my Clymer's manual, I was able to easily remove the tank, tool tray, fuel control computer, battery and expansion tank.

Then I pulled the tube connecting the radiator to the expansion tank and pressure tested the hose and the expansion tank - all was fine. I cleaned out the inside of the fitting on the radiator filler neck the hose connects to and removed some gunk.

I topped of the radiator with about a cup of coolant and then put it all back together.

I started the bike and almost immediately coolant started dripping from the bottom of the chin spoiler. I traced the leak up and discovered there is a hole in the radiator. I think it's a safe assumption that all of my problems trace back to a small hole in the radiator. Based upon the relatively sudden onset of symptoms, I'm guessing it happened very recently.

I know it's all dependent on the size of the hole, but I'm wondering if Stop Leak or equivalent is a good first step in my attempts to plug the leak. Is Stop Leak not recommened for aluminum motorcycle engines? If Stop Leak doesn't work, then I'll likely need to replace the radiator, but I'd like to try the $5 solution before I move on to the $500 solution.

[Eric1514]

I wouldn't use stop-leak or any other product that attempts to seal from the inside.

However, I have used a Permatex product.

The Permatex item number is #80884.
The product is called "Gas Tank and Radiator Repair"
The product is also known as GTR-1

It comes blister packed on a blue card and looks like a 4 inch black rubber cigar.

I drained my radiator when I did the repair to make sure everything was dry. I also used a toothpick to push the stuff inbetween the fins.

That was almost two years ago.

YMMV,
Eric

[OfficerImpersonator]

Is Stop-Leak going to harm the cooling system, or is it just likely that this attempt will fail?

[godzilla]

Is Stop-Leak going to harm the cooling system, or is it just likely that this attempt will fail?


I used that crap in my pickup truck one time for a pin hole leak. It didn't fix the leak and the truck started running hot. A mechanic buddy of mine told me that the Stop Leak may plug the hole, it may not, but it may also plug the radiator itself. He siad that he wouldn't use it. Ended up replacing the radiator.

Maybe take the radiator to a a radiator repair shop to see if they can fix the leak. I've done that with old cars in the past with good results. :dunno if that works on a bike.

You might try looking for a radiator off a wrecked bike or one that's being parted out. I found a good, used instrument cluster that way. See http://www.engelandmoto.com/index.html

Seemed like a nice enough guy and he'e an MOA memeber.

[OfficerImpersonator]

Beemerboneyard.com has a couple of used K75 radiators on their site for not too much money. I'm just trying to avoid having to remove and replace the radiator. That's a lot of fairing parts to remove and piece back together. :banghead

[OfficerImpersonator]

Just to close out this thread, I think I've decided to have my 'wrench replace my radiator. I'll ask him if he's okay with me finding a used radiator for him to install.

I was just reviewing the Clymer's manual on removing/reinstalling the radiator and there are a lot of hoses attached to that thing. On a 16 year old bike, I'd prefer to have a trained eye looking those hoses over for wear and damage and replacing whatever needs replacing.

I'm sure it will cost in the neighborhood of $300 for the parts and labor, but I think it will be money well spent if it revitalizes the cooling system.

[98lee]

dvandkq,

Lost another bet! No wonder I never come back from Vegas with any money.:dunno

In all your posts, including the one after you filled the radiator for the first time, you never mentioned seeing any fluids on the ground after a ride. ( Or was it because all that "Natural Seattle Fluid" obscured the puddle?)( again , just kidding):jester

I'm glad you found the root of the problem. I concure, don't try any sort of stop leak inside the system. Most of them will put a gunky film inside the whole system which can hurt the heat transfer. Alumaseal is one product that will not do that, but it is still a temporary fix. You don't want to be 100 miles from anywhere and have the radiator start leaking again.

Like Godzilla said, look for a good used one. I've had very good experiences with Phil Engel at the site Godzilla recomended.:thumb

[OfficerImpersonator]

These are all guesses, but I think the reason there was never fluid dripping from the underside of the bike before I filled the radiator was because there was never enough fluid in the radiator to rise to the level or pressure required to squirt the coolant through the hole.

I think that perhaps the cold November - March weather kept things cool enough where the bike didn't need the full capacity of the cooling system. Now that things are slowly warming up, the problem manifests itself.

I'm positive I would have noticed a puddle of coolant under the bike in my parking garage at work, and there are no coolant stains on the concrete under where I keep the bike in the garage at home, so it appears there hasn't been any leakage for as long as I've owned the bike. It wasn't until I topped off the radiator with about a half-gallon of coolant that seems to have raised the level of fluid in the radiator to the leak as well as increasing the pressure in the system to enhance the leak.

In all honesty, I don't know for a fact that the radiator is leaking. It could be a hose or fitting behind the radiator that's leaking, and the coolant then either spews out onto or drips through the radiator, and that's what I see dripping down behind the mesh screens on the chin spoiler and radiator trim panel. Either way, the radiator will have to come off to address the problem and I'm hesitant to tear apart my cooling system considering my limited shop skills and the facts that I have a day job and a two year old competing for my time and attention.

Regardless, this has been an educational and enjoyable experience. It won't be enjoyable when I'm writing the check to my wrench, but the results will be worthwhile.

[OfficerImpersonator]

Final final wrap up is that the bike goes to her wrench on Wednesday for a new (used) radiator. Estimate is $200, parts and labor.

If I knew my wrench was going to ask $200 for a new (used) radiator installed, I would have stopped stressing out about this a long time ago!

[mrich12000]

I used that crap in my pickup truck one time for a pin hole leak. It didn't fix the leak and the truck started running hot. A mechanic buddy of mine told me that the Stop Leak may plug the hole, it may not, but it may also plug the radiator itself. He siad that he wouldn't use it. Ended up replacing the radiator.

Maybe take the radiator to a a radiator repair shop to see if they can fix the leak. I've done that with old cars in the past with good results. :dunno if that works on a bike.

You might try looking for a radiator off a wrecked bike or one that's being parted out. I found a good, used instrument cluster that way. See http://www.engelandmoto.com/index.html

Seemed like a nice enough guy and he'e an MOA memeber.

:blah Phil who owns Engalnd motors is a great source of K parts and many more as well.


Also a local ral shop ccan do wonders with a small or major leak source ot one in your yellow pages you will be surprized how cheap it will cost :wave :wow

[kbasa]

I didn't realize there was enough slack in the fuel hoses. Usually when I go in there I'm going for something in the wiring which has required that the tank be fully removed and, while I'm in there, I always check the radiator level. I'll have to give that a try this weekend. Although I imagine you still have to disconect the electrical connection to the tank and the vent hoses and, if not totally remove the seat, at least unclip the stop arm from the seat to fold it out of the way of the tank. But if that works it definitely saves doing the worst part of the job: breaking the fuel lines. Thanks for the tip. The stuff you can pick up on this forum is definitely worth the price of addmission to MOA.:groovy

I think I saw you and your sweetie on Lucas Valley Road a couple weeks ago?

[98lee]

I think I saw you and your sweetie on Lucas Valley Road a couple weeks ago?


KBasa,

Sweetie?? Are you talking about my bike or my wife?

That was us.:wave :wave Me on Mine, Her on Hers. We were on our way to Point Reyes lighthouse. Was that you that went by when I was on the shoulder tightening my mirrors?

I had just put a pair of factory hand guards on mine to block the cold air on the back of the hands. But I discovered on that ride that my aftermarket mirrors will pivot on the slippery plastic of the hand guards unless they are really tight. It was no fun trying to hold my left mirror with my thumb all the way across the San Rafael bridge!

But, now that the warm weather is here the hand guards are off. They just mount to the mirror stalk.

By the way if any of you cold weather ( read Northern or Eastern) riders want factory hand protectors for your K75s, they are BMW part#71602315870 $25.00 a pair from Chicagobmw.com.

[OfficerImpersonator]

I'm just back from visiting my bike at the shop. Here's what happened:

The shaft of my radiator fan had enough play (~1/8") that it dug into the back of the radiator, causing the hole. It's also likely that the fan would occassionaly "engage" the fins on the radiator, stopping the fan from spinning. This explains a couple of issues I've been experiencing, so I'm glad this situation was discovered and fixed.

$200 installed for a new (used) radiator
$50 installed for a new (used) radiator fan
$50 to replace the tranny fluid, final drive fluid and brake fluid (not related to my cooling system issues, but why not, since it's been three years since these were last renewed by the prior owner?)

[jdiaz]

I'm just back from visiting my bike at the shop. Here's what happened:

The shaft of my radiator fan had enough play (~1/8") that it dug into the back of the radiator, causing the hole. It's also likely that the fan would occassionaly "engage" the fins on the radiator, stopping the fan from spinning. This explains a couple of issues I've been experiencing, so I'm glad this situation was discovered and fixed.


Wow. I've only heard about this a few times over the years.

[OfficerImpersonator]

I wouldn't have believed it unless I'd seen it myself.

My mechanic said it was obvious the radiator and fan were original equipment, so this problem could very well have been 16 years in the making.

I'm so glad I took this to my wrench, because if I had done the job myself, I would have only ordered a new radiator ahead of time. When I pulled the radiator and discovered the true problem, I would have had to order a new fan, further delaying repairs.

I've certainly never heard of this phenomenon before, and based upon the reactions of my wrench and his assistant, they hadn't seen this before, either. Hopefully that means it won't happen again for at least another 16 years!

[jdiaz]

Btw, if the radiator was only damaged in the fin area, get it repaired at a radiator shop and put it on a shelf. These things are only going to get more hard to find in the future.

[mrich12000]

Very Good Point:bolt :lurk