Moisture in engine

I have a 2001 BMW 325i. A few weeks ago I noticed creamy sludge under my oil cap. My first thought was a head gasket, but it’s not overheating and the heat works great in the car. I’m not blowing white smoke when the car is warm. Im also not losing a noticeable amount of oil or coolant. The weather has been cold with snow and rain lately. I cleaned everything off, even under the valve cover and after a 20 min drive I stopped and looked at the cap again. I noticed water droplets on the bottom of the cap. There is no noticeable sludge on the dipstick when I check that. I’m looking for any advice or ideas to diegnose this car without spending a fortune.

The creamy stuff you noticed is moisture getting into the oil. Be certain that the pcv valve is working correctly. As cheap as a pcv valve is, I think I would just change it. Also, make sure the hoses leading from this valve are open.
I’ve also noticed that some brands of oil are worse about the creamy stuff forming around the cap.

What’s the average mileage you drive the vehicle each day?


Very short distances. I live on base. An average day maybe 3-4 miles.

I think your problem is the short distances you are driving. Take the car out for a longer drive on weekends.

I will try that. I figured a 20 min drive would give it enough time to heat up and burn off the water but there were still droplets on the cap after that. Maybe not long enough?

That’s your problem.

Short driving distances doesn’t allow the engine to get hot enough to where it can drive off the moisture produced from the combustion process. This moisture begins to collect in the oil and you see this sludge.

So you have two a choices. Either drive the vehicle on longer trips to drive the moisture out of the crankcase, or change the oil more frequently.


Tester is right. I’ve had this problem on my truck that had an 8 mile drive to work. A new PCV valve and a few longer drives a week took care of it.

Right guys! This type of driving, especially with the long BMW oil drain intervals, gives rise to rapid sludge buildup. I would install a block heater and have it on 1 hour before starting up the car. I would also change oil and filter twice as often as BMW recommends.

A long drive on the weekends is also great for driving out the 'cobwebs".

Also, as soon as the oil gets hot enough to start to cook off the water (as steam), the hot steam will rise and condense on anything cooler–such as the inside of the valve cover and the oil cap. As others have mentioned, you need to get the motor good and hot regularly, especially in winter–this will go a long way to keeping the inside of the engine clean.

Take it for a good long drive once per week as others have suggested and check the PCV valve. You might want to change the oil soon too and keep an eye out for moisture. You are never getting this engine hot enough to really burn off the water that accumulates as a byproduct of combustion.

If most of your driving is such short distances, follow the “severe duty” guidelines for maintenance in the manual.

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Thank you all. This is very helpful. I’ll give it a shot.

I just bought a 2001 Ford f-150. It has the same symptoms. Am trying a new PCV valve and a gasoline additive HEET. Bought in February; it 200.2K miles on it.

Duly noted!