Questions and Answers

BMW 528i Engine Oil Leak And ATF Q. Vince, Hi, Since the past 6 to 7 months, I am having a leak under the car, it is confirmed to be engine oil leaking through the big round joint between the engine and the gear I suppose. It drips around 3 or 4 drops a day, may be more while driving the car but I cannot tell since the car is moving, and in the last six months I had to put around one liter of oil in the engine, I use Mobil1.

The mechanics confirmed the leakage is that of the engine oil. The labor and material estimates given to me for this repair by many mechanics is something like $500.00 US. Please tell me, can I give a shot at the engine leak stop treatment, sold by various companies like the STP? Will this solve the problem? Is it, in any way harmful to the engine.

I had recently had a oil change Mobil1 and do not plan to have another change for the next 5,000 kilometers. Will this treatment degrade my engine oil?

Another query, my transmission reads the oil as "lifetime filled". I don't feel any problem in the gear shifting, but do you think I need to change the oil, the oil is very costly, around $30.00 US a liter from BMW agency and it will take around 7 or 8 liters of oil. Can I just change the transmission oil filter as a preventive maintenance? Please advise as you did in the past.

• 1997 BMW 528i
• 528i (E39) 2.8 liter DOHC
• 231,000 kilometers
• Automatic Transmission

Regards,
Rashid

A. If the leak is between the engine and transmission, then the rear main seal is leaking. Not uncommon on a BMW. The seal is about $51.00 and takes about 8.0 hours to replace. A $500.00 estimate to replace it seems cheap enough and that would be what I would suggest to do.

I, personally, would not use an engine stop leak. At best they don't work and at worst it could damage the engine. In the long run I think you will be better served by having the seal replaced.

If you replace the transmission filter, you will lose transmission fluid and it will have to be replaced. I don't believe transmission fluid can last a "life time" so I would recommend doing a filter and fluid change every 80,000 kilometers. Don't get a flush, just replace what comes out when changing the filter.