Oil leak

[plehman]

New to me '76 R90/6. Lots of improvements and it's now running pretty well. But I have a leak or two, something I'm not used to (the R850R is really tight). Couple of drips a day.

The boot for the drive shaft is one place that leaks. And there's motor oil coming from the pan directly below the motor. Is there a gasket at the bottom of the engine? I checked the nut where you dump the oil - tight.

Any suggestions?
thanks

[20774]

Drive shaft - check the clamps that hold the boot in place. Could be that the boot is old and cracked but needs replacement.

Engine - one place for engine oil to leak is the rear main seal. This oil runs down the back of the engine (hidden by the transmission and clutch) and exits through a small hole in the tranny bell housing. This oil collects on the "shelf" which is actually the extension of the engine oil pan. It could also be gear oil from the tranny. It will exit through the input shaft seal and run down the front of the tranny, possibly contaminating the clutch in the process. Smell the oil...you should be able to determine if it's gear or engine oil.

Yes there's a gasket between the oil pan and the block. You should probably clean things up very well and then run it for 30-45 minutes. Come back and spread talc on various areas of the pan and/or look for where the drops are starting from. The oil pan screws could be loose, or the gasket could be old. Be somewhat careful tightening the oil pan screws. There is a torque value but with the wrong wrench, you can easily strip these steel bolts in the aluminum block. Best to use a metric nutdriver...a screwdriver with a 10mm socket on the end. It's much harder to over torque these fasteners. But if the gasket is leaking, tightening may not fix the leak. You might have to drop the pan, clean up the mating surface, and use a new gasket (no sealant was used by BMW on this gasket).

[barryg]

Drive shaft boot oil leak. Boot can have a hole, split, crack. It can be old and dryrotted. It can leak due to improper installation. I think the boot is end specific. One is round and the other oblong. Round end goes to the trans. and oblong end goes to drive shaft. Also the clamps can be installed so that it leaks around them. Yes there is a gasket sealing the pan to the block. These get old and oil logged over time, remove and replace. Check tightness of the oil pan bolts, may not be tight and not sealing gasket. Drain plug uses a crush washer, alot of times previous owners would use same one over and over. Book says replace crush washer every time drain plug is removed. Will cause a oil leak at the plug. Good luck getting those leaks stopped.

[Raceydog]

So then the boot at the driveshaft should contain oil?

[beemerPhil]

"So then the boot at the driveshaft should contain oil?"

On his /6 and your toaster, yes! Only 150cc's, but it's still enough to leak if there's a way out.

Just one thing to add to the previous suggestions-:type

Check to see that the bolt that holds the battery ground terminal and the bottom end of the speedo cable is the correct hollow-drilled bolt- this is the vent for the trans and the driveshaft. Often it gets lost, and the do-it-your-selfer replaces it from the hardware store bin, resulting in oil pressure where none belongs-