Oil cooler drain screw

[jmerlino]

Hey, I'm getting ready to do a full oil/filter change, and I don't have the little screw that you use to drain/refill the oil cooler. Do I need to acquire a particular part, or can I make something that will function the same way?

[Boxerkuh]

I don't want to sound dumb or ignorant... but what screw are you referring to? I have an oil cooler, but I don't do anything special to it to drain it, but hang the lines down for a bit... change the filter and put everything back together.... How frequent are you changing your oil? (miles and time) :hungover

[manicmechanic]

I wish I could remember the correct length, but the screw to which you refer just has to be long enough to open the thermostat. So a 6mm screw about an inch or so long may suffice. Remember, you're not tightening a fastener, just opening a spring-loaded valve.

[jmerlino]

Boxerkuh -

According to the Haynes manual and to this article (http://www.airheads.org/content/view/189/49/) you need to open a valve using a little screw. Evidently, the cooler will drain without using the screw, but you need to use the screw in order for the cooler to refill. I suppose it's possible that this may be overkill, but I tend to trust the stuff I find on airheads.org.

MM -

I can find the length. (I think it says in the Haynes manual). Haynes makes a big deal about the thing having a rounded end so I wasn't sure if I need to grind down the end or something. Do you happen to know the thread pitch? I suppose I can just take out the other one that's in there and get one the same.

[Boxerkuh]

I don't trust the Haynes or the Clymer manual when it comes to that. I learned from a BMW Master Mechanic of 40 plus years and he has never said anything, but I will call him tomorrow and ask him. I will let you know what he says... This might be a question for Oak. If you email him he will let you know pretty quick... Let me know if you find out. I am still learning myself...

[manicmechanic]

I think it's 6mm x 1mm pitch, just round over the end of the threads.

[lkchris]

Length needs to be 23 mm from bottom of screw head to end of screw.

The reason for using the screw is for refilling the cooler.

With thermostat closed, cooler won't refill until engine is warm and then a bunch of air will go through the system, sort of like an embolism. Screw manually opens the thermostat.

You can't remove the filter cover/thermostat without the cooler draining.

If you ever monitor the function of the oil cooler thermostat, you'll note it only ever opens except at high-rpm highway driving, i.e. when the engine gets really hot. With engine at high rpm is an especially bad time to interrupt oil pressure while cooler fills. The engine doesn't get hot idling, unless you idle for 1/4-1/2 hour or so.

This doesn't apply on R100GS which doesn't have thermostat.

Screw is part number 11 42 1 335 376 and is still available from your dealer. You can't afford to be without it.

So is an Owners Manual, which you really can't operate a bike without.

[Boxerkuh]

All excellent advise. I called my Master Machanic today and he informed me that this is for thermostat oilcoolers only (I don't have a thermostat since I have supertrapp 2into1 exhaust and no clearance for it). He stated that he would not recommend to mess with it... the oil cooler only has a little oil in it and is not really worth all the effort and hassle. For those that don't have a thermostat, just unscrew one of the lines or both if you like and let gravity pull it out... good luck :laugh

[The_Veg]

I wondered what the hell you guys were talking about for a while there, as my R100R has no thermostat either.

[rinty]

Veg: I think they're only found on the R 100 bikes that have oil coolers. I don't think the R 100 R's have coolers, or need them. The special screw compresses the oil thermostat, causing it to open so the oil can drain out for an oil change. Also, left in after the oil change, the screw permits immediate oil circulation through the whole system when you start the engine, so you can fill to the exact level required without a lengthy warm up run.

You don't know how much fun you're missing.

Rinty

[jmerlino]

Right. My bike (I just found out) is actually an RT that had the fairing removed, so I've got the oil cooler with the thermostat and the whole deal. Anyway, I was able to pick up the part from my mechanic (had to make a run up there anyway). He says that he never bothers with it, but when I told him the Haynes manual refers to it as "critical" he said he might have to revisit the issue.

[lkchris]

Screw not needed to empty thermostat, only to fill it.

[rinty]

"If your motorcycle is equipped with an oil cooler, replace the bottom screw on the oil cooler thermostat by the service screw... to allow oil to flow out of the oil cooler" - BMW Rider's Manual - U.S. models

"...the oil cooler bleed bolt, which is inserted into the base of the oil cooler adapter...allow[s] the old oil to drain from the cooler and new oil to enter it on refilling." - Haynes BMW Twins

Not to put too fine a point on the above, but at my age, Alzheimers is always a concern.

Rinty

[jmerlino]

Well, if you take the thing off to change the filter, it will tend to drain regardless of whether or not the bolt is in. I know this because there's big oil stain on my driveway right now. :huh

[The_Veg]

R100R's do have oil coolers but not thermostats, same for R100GS's (at least '87-on).
At least I'm pretty sure that that little radiator-looking thingee with oil lines going to it is a cooler... :D

[lkchris]

Well, if you take the thing off to change the filter, it will tend to drain regardless of whether or not the bolt is in. I know this because there's big oil stain on my driveway right now. :huh

That's correct.

There is an entrance hose/fitting and an exit hose/fitting on the cooler.

Only the entrance hose/fitting is blocked by the thermostat.

The o-rings at the filter block oil exit from the cooler, but of course these are displaced when the thermostat is detached from the engine block to allow replacing filter. If this did not occur, the cooler would drain back to the engine sump whenever the engine was not running. Especially if engine stopped while hot and thermostat open.

I've never used the screw prior to refilling with oil, always add the prescribed amount of oil, and have never had overfilling, which leads to conclusion cooler drains itself nicely simply from disconnection of thermostat from block. Now, I must admit, I always disconnect lines from cooler before removing thermostat since there's no way to get it back with lines attached without displacing o-rings. Perhaps I'll try the alternate procedure next time and observe results to verify my position.

[BMWRich58]

Most will tell you to leave alone. No significant amount of oil stuck up there is gonnna make a difference.
But:::::
Factory manual says that pressure must be regained before operating or else damage can occur to engine.

So if ya do empty the cooler...run starter until oil pressure rebuilds before allowing engine to run/operate. Oil pressure light should also be "out" indicating proper oil pressure has been acheived.

[jmerlino]

I did what is says to do on airheads. I drained everything, changed the filter, put the therm back on, put the bolt in, filled it, and cranked the engine till the oil light went out. Then I took the bolt out, and put in the other bolt. Took it out for about a 150 mile ride today, and it seems to be running nicely. I also changed the gear, shaft, and bevel drive oil, which it liked a lot. Shifting is nice and smooth.

I will admit that I find getting the therm off and the filter out to be extremely cumbersome. Was it really necessary to put it right behind the header pipe like that? Also the drain bolt for the gearbox is direcly above a crossover tube, which means you get gear oil all over the tube. Nasty. IMO, doing an oil change - even a major one with a filter replacement - should be really, really easy, so as to encourage people to do it more often.

[R100RS]

Screw is part number 11 42 1 335 376 and is still available from your dealer.
That part number is for the entire thermostat assembly.

Do you mean 11 42 1 335 394 ?

That appears to be the longer of the two screws at the bottom of the thermostat housing.

[lkchris]

That part number is for the entire thermostat assembly.

Do you mean 11 42 1 335 394 ?

That appears to be the longer of the two screws at the bottom of the thermostat housing.


Yes, sorry.

[Boxerkuh]

[QUOTE=BMWRich58]Most will tell you to leave alone. No significant amount of oil stuck up there is gonnna make a difference.

My Airhead Master Mechanic has yet to be wrong and with 40 plus years of experiences I trust him 100+++%. Leave it alone!!! :nono :nono :nono The amount of oil left in the oil cooler is so insignificant that it is much better to leave it alone than to mess with it.

[rinty]

Was it really necessary to put it right behind the header pipe like that? j merlino
BMW's development of its boxers has been an evolutionary process. When major changes were introduced in 1969, a faired airhead was probably not in the cards. After the RS was introduced in 1977, the designers thought it would be a good idea to incorporate a cooler, but no accomodation had been made in the frame or the engine for one, and the result was a compromise. I agree that it's a pain in the ass to unbolt the oil filter cover and get the hinged filter in there (I have my specialist do it), but the design is actually quite elegant, given what they had to work with.

Leave it[the oil in the cooler and lines] alone. Boxerkuh

There is one quarter of a litre of oil in the cooler and lines, so if it's not changed, you will have approximately 10% dirty oil circulating with your clean oil. I agree that this is no big deal. However, if you are talented enough to get the oil filter cover off, figure out the o-ring and gasket stuff, and install the hinged filter, you are more than up to the task of screwing in the bleed bolt to get the dirty oil out. Simply leave the screw in while you put in the new oil and then start the motor. The Eaton oil pump kicks out more than enough pressure to circulate oil within seconds. The real danger is in cranking an engine over on a boxer that has solid state ignition, with the plugs removed and grounded on the barrels. If there is any interruption in the plug to ground interface, you may blow the ignition unit.

Question of the day: would a typical BMW owner be satisfied with an oil change that has 90% clean oil circulating in his/her beloved airhead?

Rinty

[jmerlino]

The real danger is in cranking an engine over on a boxer that has solid state ignition, with the plugs removed and grounded on the barrels. If there is any interruption in the plug to ground interface, you may blow the ignition unit.
I didn't feel like pulling the plugs, so I emptied the float bowls instead. I didn't think the filter was that hard to figure out, getting the white gasket to stay put was the hard part. (I'm not even sure it did. :dunno )

[The_Veg]

All of the knowledgeable types I've heard opinions from will tell you that the cooler is completely unnecessary. I still like having it though since I live in a hot climate. Best thing to do if you want the cooler is get the R100R/GS setup without the thermostat. Easy to open, easy to drain, no worries.

[rinty]

It probably is unnecessary, but I agree it's nice to have. The fact is that the hottest part of the engine is the combustion chamber, and on a boxer that part is hanging way out in the breeze. The cooler is not going to do much good when you really need it: in a traffic jam where you are forced to idle for extensive periods of time. A friend of mine who has an RS with a Luftmeister thermometer dip stick says the oil temperature will hit 260 F in traffic, and that's where dino oil starts to break down.

...getting the white gasket to stay put was the hard part...j merlino
The gasket will stay on with a bit of grease. The toughest part for me was getting the top allen head bolt on the filter cover loose; it's an angle access on my bike. You should use one of those T-handled hex wrenches with the ball end, and I don't have one. And on some RS's the frame is right opposite the bolt and you can barely access it at all. Anyway, I don't wrench a lot anymore. As Coach Ditka says: "The highs aren't what they used to be, and the lows are a lot lower."

Rinty

[manicmechanic]

When I had the '84 R100RT I drilled a hole in the lower fairing, and then could use a ratchet handle with an extension and a hex-driver to remove the top screw. Plus, if you never looked for the hole, you'd never see it.

[lkchris]

All of the knowledgeable types I've heard opinions from will tell you that the cooler is completely unnecessary.

Haven't heard Oak, then.

[The_Veg]

I guess I haven't. So why do older engines not need them?

[lkchris]

I guess I haven't. So why do older engines not need them?

BMW put coolers exclusively (or almost so) on the 1000cc machines.

Some of the older 1000cc machines ('77-'78) could certainly benefit.

Smaller displacements can probably get by without, especially if fitted with Nikasil cylinders.

[nealart]

Excellent information. I just picked up a 1981 R100RS with the oil cooler thermostat on the filter cover. Guess I'll pick up the special bleed bolt!