Smell of oil in the cabin – BMW with automatic transmission

BMW driver’s question – Why do you smell the oil after the change?

On my own, I performed an oil change operation on the automatic transmission in my BMW 5 F10. However, I still have a problem with a noticeable oil smell in the cabin.

A description of the steps I performed: Changing the oil in the automatic transmission (original ZF 8HP kit) according to the procedure. Oil temperature between 30° and 50°C. Maintain engine speed at 2000 rpm for 30 seconds. Leave the engine at idle speed. Check the transmission oil temperature – temperature from 30° to 50°C. Select the P, R and D position manually turn on D1 and D2. Hold the gear for about 10 seconds each time. Check the transmission oil temperature from 30° to 50°. Unscrew the screw of the oil fill hole drain the excess turn the screw off.

After changing the oil, I still have problems. When the transmission warms up to about 90°, I can smell oil when I stop the car. I read on the forum that it may be a problem of excess oil. I performed the oil level checking procedure again as above. I topped up the level by about 50 ml. The problem still occurs. I should add that I do not have any leaks. I have cleaned everything with break cleaner. Thank you in advance for your help.

The problem was BMW 5 F10 with automatic transmission, but it may also occur in other models.

BM Cars service response on transmission oil problems

The described problem of oil smell after stopping the vehicle is not necessarily related to the oil change in the transmission. However, as far as the transmission itself is concerned, the ZF procedure cited in the body of the inquiry pays special attention to checking the oil level each time after successive fill-ups.

If the oil flows out in a thin uniform stream when the fill screw is unscrewed, it means that the oil level is correct. Checking should also be done at an oil temperature of 30° to 50°C. Additional topping up of the oil level, can result in excess oil.

Too much oil in the box will cause leaks through the box vent at the top of the box. Since the leak will only appear when the box is operating at higher temperatures, the momentum of the moving vehicle may scatter the leaking oil over various components along the box up to the rear bridge. It will not be visible on the box cover or where the vehicle is parked. Since the odor of the oil used in 8HP transmissions is extremely irritating, it can be smelled while the vehicle is stationary and even while driving.

Repair recommendations according to BM Cars

1. Re-checking the oil level in the transmission, following ZF’s stated procedures, and draining excess oil if necessary.
2. Checking for leaks from the transmission (transmission-engine connection under the connection cap) – leakage from the seal under the torque clutch.
3. Verify if there are traces of oil leaks on the covers under the gearbox and under the engine.
4. Visual inspection of engine leaks with special attention to the intake system – turbine intake manifold, valve cover. If there are any traces of leaks especially on the right side of the engine (leaks on the exhaust manifold), seal the areas with leaks.
5. Check for signs of oil leaks on the covers under the gearbox and under the engine.

Of course, we are able to perform all the above-mentioned activities in our Service Center.

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