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Re: '89 750il Engin Oil Leak (archive)

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Posted by soo on January 06, 2000 at 10:16:35:

In Reply to: Re: '89 750il Engin Oil Leak posted by Alex on December 24, 1999 at 18:22:40:

: : I am usually good in figuring where oil leaks come from. I've changed the chain tensioner o-ring which fixed the leak from the front passenger side of the engin. I have also changed one oil host to the oil cooler which is responsible for the leak in the driver side front part of the engin. I have also changed the oil pan gasket. Since then, I had gone under the car five times and still could not figure out the exact location of the leak which resulted in oil near the middle to the rear part of the engin. Oil appears to come from the driver side and extends all the way to the transmission. The upper engin block is clean, oil appears on the lower engin housing. Do I need the change the gasket? BMW dealer told me that I need to remove the engin to replace that gasket. I also suspect the oil return host which is connected to the lower engin case through a fitting. Is there any o-ring in the fitting itself? I hate o-rings in a ten year old car. Thanks.

: I had a slow oil leak for two years that was driving me mad trying to find it. It turned out to be one of the bolts holding on the crankshaft sensor on the front of the engine. Apparently, this is a common problem.

: The longer of the two bolts passes through or into an oil channel in the block. Total time to fix about fifteen minutes. Add some thread seal to the bolt before re-installing.

: Incidentally, my car is a '92 735i so I do not know if the crankshaft sensor is in the same physical location as the 750iL. One giveway on the 735i is oil on top of the A/C compressor.

: Alex Lynch
: 1992 735i 166,300 miles

Thanks Alex. I am trying the sealant now.



My mechanic just told me that my upper and lower oil pan gaskets are
leaking on my 1990 750. How tough is this to do in a home garage on
jackstands? Do you have to remove a cross member or anything? Is it a
big deal?

Hi Eric

The lower oil pan gasket is easy. The upper one is much more difficult and requires removal of the engine or the removal of suspension components. The upper gasket seals the lower engine case to the main case. The aluminum sealing surface is machined to be flat and should compress the gasket evenly with careful tightening of the bolts.

What I did up to this point was to change the lower gasket myself. Tighten the bolts on the upper gasket. To my surprise, I still found oil all over!. Then I noticed that there were oil on the head of some of the bolts. Now I suspect the gaskets cracked allowing oil to reach the thread on those bolts. I put some non hardening sealing compound on the bolts and put them back on. I do not know whether this will work because the car is still on stands. I am changing the brake bomb now.

Be careful when you go under the car. Good Luck.

David Soo

Eric Ide wrote:

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