[kostadinov]

Can you, please, look at the pictures and tell me what is the reason for the oil leak?
I took one picture from underneath the car, then spent 3 hours with a rag and electrical contact cleaner. Cleaned and dried everything that I could reach around the engine, including the valve cover gasket and oil pan gasket. Drove the car for 20 min, somehow aggressively in the last 5-6 minutes. Checked for oil leaks and there it was, right between the engine and the gearbox. There is small, round plastic cover that I removed, but it looked dry inside. The second picture that I took clearly shows where the oil appeared. Have you experienced anything like this? What needs to be fixed in order to stop that leak?
The car is 2007 328i with 148K miles on it and I just purchased it.
Thanks in advance for any suggestions.

[big boost M]

It looks like it could be your rear main seal

[volkswackin]

Oil pan gasket

[PA66400]

I agree with oil pan gasket. They often leak at the right rear. $1300 repair if done at the dealer in my neighbourhood. Probably similar in your area. They have to drop the subframe to get the pan off. Around 7 hours of labor if done flat-rate. Add to that the cost of a crankcase of oil, gasket and new bolts.

[medusacomp]

Oil pan gasket, mine is doing the same

[Efthreeoh]

try re-torqueing the pan bolts first. At that mileage, I'd bet most are loose. I have a high-mileage 325i and had a pan gasket leak in the right rear of the engine. I found all the pan bolts VERY loose. I re-torqued them and the leak is stopped, or very minimal.

I'd don't know the specs for the pan torqueing nor the pattern. The Bentley service manual doesn't have them. So I just torqued them down clockwise from the right rear corner of the pan. I can tell you they don't require much torque and be careful because they are aluminum bolts.

[kostadinov]

Originally Posted by Efthreeoh

try re-torqueing the pan bolts first. At that mileage, I'd bet most are loose. I have a high-mileage 325i and had a pan gasket leak in the right rear of the engine. I found all the pan bolts VERY loose. I re-torqued them and the leak is stopped, or very minimal.

Thanks for the suggestion, I will check the bolts next time I jack the car up.
Now...if this is the case...there is something very wrong with the idea of using aluminum bolts. How do they get loose, when if torqued to the required specs, the bolts are supposed to stretch a bit and hold tight... I keep reading the forum here and can't believe how many people are complaining about leaking gaskets- valve cover, oil pan, oil filter and so on....caused by loose bolts or worn gaskets.

I have a 2008 Civic with 135K miles on it and there is no leak whatsoever. The engine is so dry and clean. The civic gets new full synthetic oil change every 8000 miles, brake pads every 60-70k miles, brake fluid flush every 2 years, new spark plugs every 100K miles, coolant drain and refill every 3 years, transmission fluid drain and refill every 30K miles, filters change every year. All of this is DIY and the car does not have any issues at all.

I am trying to get the BMW on a similar regime but that oil leak is driving me crazy, just because it is there....Is the BMW engineering inferior to that of HONDA?

[Meeni]

Looks like main bearing seal leak, but other said that oil pan might be the offender, and it is easier, always start with the easier target

And yes, BMW engines a prone to devellop a number of leaks in a variety of places that japanese never heard off. That is a minor but infortunate annoyance.

[Efthreeoh]

Originally Posted by kostadinov

Thanks for the suggestion, I will check the bolts next time I jack the car up.
Now...if this is the case...there is something very wrong with the idea of using aluminum bolts. How do they get loose, when if torqued to the required specs, the bolts are supposed to stretch a bit and hold tight... I keep reading the forum here and can't believe how many people are complaining about leaking gaskets- valve cover, oil pan, oil filter and so on....caused by loose bolts or worn gaskets.

I have a 2008 Civic with 135K miles on it and there is no leak whatsoever. The engine is so dry and clean. The civic gets new full synthetic oil change every 8000 miles, brake pads every 60-70k miles, brake fluid flush every 2 years, new spark plugs every 100K miles, coolant drain and refill every 3 years, transmission fluid drain and refill every 30K miles, filters change every year. All of this is DIY and the car does not have any issues at all.

I am trying to get the BMW on a similar regime but that oil leak is driving me crazy, just because it is there....Is the BMW engineering inferior to that of HONDA?

Every car I've owned has eventually developed loose oil pan bolts and loose valve cover bolts; I don't think it is abnormal. The N52 uses aluminum bolts because the engine block is magnesium. Using steel bolts would cause galvanic reaction between the steel and magnesium and eventually eat away the hole of the engine block where the bolt screws into. Aluminum does not react with magnesium, which is why aluminum bolts are used where parts are bolted to the engine block.

[BuellsterR1]

Originally Posted by Efthreeoh

Every car I've owned has eventually developed loose oil pan bolts and loose valve cover bolts; I don't think it is abnormal. The N52 uses aluminum bolts because the engine block is magnesium. Using steel bolts would cause galvanic reaction between the steel and magnesium and eventually eat away the hole of the engine block where the bolt screws into. Aluminum does not react with magnesium, which is why aluminum bolts are used where parts are bolted to the engine block.

Great info!! Thanks for the explanation.