final drive leak

1995 R1100RS Problem , oil coming out of vent cap. Other than being overfilled is there anything else that may cause this problem? The bike was ridden 8 miles in 80 degree heat two up with no load. The bike was parked in neutral and on the center stand when it leaked. Later that day rode the bike 25 miles with no leak. What do you think? Bike has BMW gear oil in it. Not synthetic. the bike has 13k miles.

Water contamination will do this also.

The short answer is usually foaming.

And as Anton said - water - moisture - is a common cause of foaming.

I'd immediately drain and replace the final drive oil. 90wt or 80w90 is spec. Synth or dino is your choice. I use dino. I also use a moly additive. Again, your choice.

It is the question I am about to ask that makes me realize I am not the smartest one in the bunch, not by a long shot, but how does the water get in?

Mark

Hitting the vent with a high pressure car wash hose will do it.

Condensation

Down here in the land of 98% humidity a 20 degree temperature changes can cause huge problems with condensation. It only takes a small bit of moisture mixed in with some gear lube then whipped to a froth by spinning gears to cause foaming which will ooze from then vent. As the others have posted, change the gear lube, then go for a nice long ride to warm up the final drive then change to oil again. All will be good.

The reason I revived the old post yesterday is because dino gear oil leaked out from the final drive breather cap. Yesterday's drive was a little unusual. I and a pasenger rode the bike up the Mt Washington auto road in New Hampshire. The road is eight miles long and up all the way. Elevation at the top is over six thousand feet. The road gains about four to five thousand feet from the bottom to the top. First and second gear all the way. Mostly first gear at twenty mph on the GPS. Air temp at bottom was mid 70's. At the top, upper 40's. We drove about ninety miles from home to get to the auto road. We noticed the leak as we were gearing back up to come down. It apears to have starting leaking on the way up as there was oil flung at different places around the circumference of the tire sidewall. There was enough oil on the chicken strip section of the tire that I was a littlte concerned about the ride home. Wiped it off as best as I could with paper towels. There was also about a teaspoon full acumulated on the rim. The bike sat on it's sidestand for about an hour while we enjoyed the museum and views. None appeared to leak on the way down the mountain or on the one hundred mile ride home.

I drained the final drive oil today and there did not appear to be moisture in with the oil. Oil was not at all foamy. I also checked fluid leval prior to draining and it was not overfilled, if anything maybe about an ounce low.

The final drive oil was changed three months and two thousand miles ago with the correct visosity oil. It is always oily around the vent cap area, not enough to drip or run, but enough to collect dust. The R1100RT has 28K and is new to me. This is the first time it has leaked.

I never use a high pressure washer to clean the bike. I just noticed the small hole on the side of the black plastic vent cap. I assume I should avoid this hole with the garden hose on wash day?

Just wondering is this something I can expect from time to time with changes in weather and humidity?

Sorry about being so long winded, just wanted to include as much info as possible. More than anything the oil on the tread portion of the tire unnerved me more than anything. No oil seems to have gotten on the brake disk or pads.

Thanks,
Mark

Was the oil spread evenly around the rim?? If so, you may find that the final drive main seal is leaking actually. I know that altitude changes may affect the pressure within the FD but I really think it is main seal. Pull the vent cap off the FD and see if the hole does really vent to make sure there is no dirt stuck in it.. Hope it helps.

The oil was not spread evenly on the rim. It was intermittent on the tire sidewall. The oil was definitely coming from the vent cap.

How do you remove the vent cap to check it? It it just a snap fit? Do I just pull straight up to remove?

Thanks,
mark

Re: Intermittent drips on the sidewall. This happened to me on my r1100r. It turned out to be the final drive seal.

mark from maine said:

The oil was not spread evenly on the rim. It was intermittent on the tire sidewall. The oil was definitely coming from the vent cap.

How do you remove the vent cap to check it? It it just a snap fit? Do I just pull straight up to remove?

Thanks,
mark

Click to expand...

It just pops off, straight up. I hope you find the issue...

I'm not even going to try to describe the physics - I can't. But it is quite common for BMW final drives to puke oil out the vent on high altitude climbs. My R90/6 did it at Pike's Peak. So did my K75 on another high road. And my R1150R too.

In all 3 cases I cleaned up the mess, checked the level, and got on with life. Neither bike did it again any time soon.

Final Drive Leak

I've had two final drive leaks with the first @50kmiles and the second @75k miles on my R1100RT. Finally replaced the drive with a new one for about 1.3k out the door. I now have 105k on the bike and shes running great . If its a final drive failure you will know because sooner or later it will leak like a sieve.

Thanks everyone for your imput. As always much appreceiated. We rode the bike a little over two hundred miles yesterday. All types of roads. No leaks. As suggested I did end up pulling the vent cap to check. Everything looks fine.
Mark