Low Oil Temp in the Rain...

[HFD190]

I have noticed recently while riding in the rain that the oil temp gauge is dropping way down to 1 or 2 bars. It makes sense that rain water hitting the cylinder heads would cause rapid cooling, but this seems like a new thing to me. Either that or I just never looked at the temp gauge in the rain before.

I am wondering if others have found the same situation…

[jingdog]

Yes and in the winter also riding in 40 degree temperatures. Wrecks the gas mileage. :cry I seem to get about 33 mpg when showing two or three bars. With five bars I get 45 plus...thats at highway speeds on the freeway. Been thinking about covering up the oil cooler with something for those conditions that warrent it. I have a 96 GS.

[beeryboats]

That doesn't make sense. If the oil is getting cooled, it would get thicker, and therefore higher pressure. My guess is a pressure sensor starting to short out? I would try coating the sensor with dielectric grease and then reconnecting the wire. This would eliminate water being the condecter between the wire and the engine case.

Just an idea.

Jay

P.S. My Sportster is for sale and I'm looking for an R1100RT! My first Beemer!

[rayadams]

The indicator is an oil temperature indicator...not oil pressure. You could try covering half of the oil cooler in the rain...but watch the temp gauge like a hawk.

[j-budimlya]

I'm guessing that heavy rain will cool the cylinder head....there is a lot of space for air/rain to "wash" the head....which will do alot of cooling of the oilhead motor.....

I too have noticed this.....

Can't wait to here the correct answer:lurk

[jingdog]

Well ifn you covered up the oil radiator and the temp didnt go up that would be a good indication its the cylinder heads. Come to think of it Ive removed the plastic "protectors" on mine. Perhaps I ought to put them back come winter.

[manicmechanic]

Consider that the rain water has a higher specific heat capacity than air, therefore the water will carry away more heat than the air does, cooling the oil and causing it to become more viscous (thicker). However, presuming that you are using multi-grade oils, as the oil cools, the oil becomes thinner, to facilitate easier cold-weather starting.

Now consider that your fuel-injected engine has a temperature sensor at the airbox. As air temperature decreases, the air becomes denser, requiring more fuel for the mixture that the O2 sensor and the computer require. So in cooler weather you can expect your mileage to be reduced.

[maxscycle]

I am guessing you do not have an oil thermostat, or your thermostat is malfunctioning. My 96 r1100rt stays at 5 bars, and only in the dead of winter does it "drop" to four.
max

[rinty]

HFD:

I'm glad you brought this up. I confess that I haven't checked my temps while rain riding. I would think that almost all of the extra cooling would be the result of rain, rain mist, and cold air flowing through the oil radiator. I doubt whether there is much air cooling going on from a type 259 cylinder head cover, as the fins appear just for decoration, to match up with the cylinder fins, which are real ones. There may be a bit of cooling from the rain striking the cylinder head cover directly. And how much cooling is going on in the finned sump area, which has cold air, road water splash, and spray, going across it?

According to Kevin Cameron's seminal article in Cycle World in 1993, when BMW designed the head, they put in oil passages around the valves, and I think all, or almost all, the cooling results from oil flow carrying the heat away. I recall that he wrote that it is not easy to design an air cooled 4 valve head., but I will have another look at the article tonight.

But this is just speculation on my part. It would be interesting to know the answer.

Rinty

[Mr. Frank]

In a cold rain (40's-50's) at highway speeds I've seen my gauge drop to four bars.

[GlobalRider]

In a cold rain (40's-50's) at highway speeds I've seen my gauge drop to four bars.

Same here, but no lower than four bars.

[GlobalRider]

I'm guessing that heavy rain will cool the cylinder head....there is a lot of space for air/rain to "wash" the head....which will do alot of cooling of the oilhead motor.....

I too have noticed this.....

Can't wait to here the correct answer:lurk


Well you asked...

As the rain hits your oil rad, a small percentage of the water is evaporating causing an additional cooling effect. But yes, so does the water hitting the cylinders and heads.

Wave your dry hand through the air. Now wet your hand and wave it through the air again. Does it feel any cooler? And we're not talking about wind chill effect here.

[jingdog]

Does anyone know if my 96 GS has a thermostat? How easy is it to get to and whats involved in changing it? Or testing it? My 96 definately suffers from riding in colder temps/rain. Ive seen as little as 2 bars riding around in the dead of winter at 50-60 mph on back roads. I would love for it not to do that.

[bikerfish1100]

[QUOTE=manicmechanic;224753]However, presuming that you are using multi-grade oils, as the oil cools, the oil becomes thinner, to facilitate easier cold-weather starting.

QUOTE]
really? then why does it pour slowly out of the bottle (room temp), but flow like crazy out of the hot engine? i believe your analysis of how a multigrade oil operates is faulty.


on any bike i've ever owned, splashing it with water (rain, fog, hose, mist, hurricane) would produce a distinct feeling (mostly on my legs) of lowered heat production. if a temp gauge was attached, it would record somewhat lower temps as well. water cools better than air, as it is denser, and therefore can absorb more heat.

[bikerfish1100]

HFD:



According to Kevin Cameron's seminal article in Cycle World in 1993, when BMW designed the head, they put in oil passages around the valves, and I think all, or almost all, the cooling results from oil flow carrying the heat away. I recall that he wrote that it is not easy to design an air cooled 4 valve head., but I will have another look at the article tonight.

But this is just speculation on my part. It would be interesting to know the answer.

Rinty

ever feel your cylinders/valve covers when the bike is hot? yup, they're hot too. hotter than the air, right? that means that as the bike moves through the air, heat will be removed to the relatively cooler air. i'd be willing to go with "most of the cooling results from oil flow carrying heat away:, but "all, or almost all"? no, doesn't pass the common sense test.

[rinty]

But the heads on a liquid cooled engine are hot, too. I still don't think the air carries much heat away from them, but you would have an engineer do a careful thermal transfer analysis to find out exactly how much of the the heat is transferred to the air, to the oil, and to the cylinders and cases, respectively.

The main thing is that the cooling system works very well. I don't ride in the south in the summer, but I've never seen more than 7 bars.

Rinty

[jingdog]

If its true that rain falling on the heads wont cool them much more than the oil already circulating in them is, the the additional cooling must be happening at the radiator. I wish I knew more about that thermostat!

[MCMXCIVRS]

Mine has always run at around two bars in heavy rain. I've seldom seen it go past three in those conditions. Having ridden in plenty of rain with no ill effects from the cooler operating temp, I'd say don't worry about it.

Much worse to have it run too hot.

[HFD190]

Thanks guys for some good insight. I would tend to agree that there is probably additional cooling at both the cylinder heads and the radiator. And as a few posts have said, it’s probably not that big of a deal. I was mostly intrigued because I have been in some heavy rain before and never noticed it, which I would guess is because I just never looked at the gauge. Hearing that several others have witnessed some lower temps in the rain makes me feel better, knowing that some widget on mine didn’t just fail and produce new symptoms, etc.