[Big_CG]

So I'm in the process of fixing up my 06 325i. I have replaced the valve cover gasket, oil filter housing gasket, and valvetronic motor gasket as they were all leaking pretty bad.

I still have a bit of a leak at the oil pan gasket ( I presume) and possibly the front main seal. Need to have a better look. Unsure about the rear main seal.

In typical BMW fashion, they designed a truly remarkable engine with the N52 with some tragic design choices for gasket materials. Its a smooth, powerful, fuel efficient and pretty solid engine that is just a leaky SOB.

Now that most of them are 100k+ and 7 years old or so- have you guys dealt with fixing the oil leaks or just left it? Im trying to decide if the annoyance of a few drips a night is worth the massive headache of oil pan gasket and front seal.

Really the stuff on the top of the motor is the most important, I feel your pain, it feels so terrible to have to spend so much money and time replacing cheap gasket material that does not last, pretty much every seam in the engine is guaranteed to leak.

I would monitor the oil pan gasket and replace if you start loosing a lot of oil between changes.

The front main seal leak isn't common and the rear main seal is commonly confused with a oil pan gasket leak (very common). If you look in the transmission cut away slot where it mates to the engine if its all clean of oil its not leaking.


My car is getting ready to be on its 3RD valve cover gasket.

[Big_CG]

Gotcha. Ive been researching the DIY on the oil pan gasket where the guy didnt drop the subframe...just kinda wiggled the new gasket under the oil pump pickup and did it that way. Was looking to see if anyone could confirm that method, it would be sooo much easier than taking the damn subframe apart

[hassmaschine]

neither of mine leak.. so far so good.

Older BMW motors were much worse. the M20 for example, there wasn't any point in even trying to stop it from leaking. call it rust protection.

how about loosening the subframe bolts and just lowering it down a bit? the thing is if you try to wiggle it in you won't be able to clean it well and it might leak again.

what's the N52 pan gasket made of? most 24v motors have been steel and they don't seem to leak, but the N52 is made of a unique material.

[Tim603]

Only leak ive had so far is the Oil Filter Housing Gasket and the Pinion seal on my front diff if I remember correctly

[Soul_Glo]

I think its worth it. I had a weeping rear main seal and it turned into 1 litre every 1500 miles. So I just replaced it and it pushed me up to 1 litre every 3000 miles.

[Big_CG]

Had the car up today and noticed that several of the oil pan bolts are way loose. I tightened them up a bit, will see if that does anything. Accidentally snapped one off in the rear passenger corner. Left hand drill bit, shop vac, and replacement bolt should take care of it. Had to do the same thing on a broken vc bolt. It's nice that the broken bolts come out so easily on this car

They are not torqued very tightly, they are aluminum bolts that are torqued beyond their yield (stretched). Tightening them further usually breaks them.

[Big_CG]

Yeah, I kinda suspected that there was a high probability of breaking one off. Had my torque wrench set to 200 in lbs when the bolt head sheared.

So no drips on the ground tonight despite breaking that bolt head off. Normally there would be about 5-6 drops at least.

Spec on the bolts is 25 nm (221 in lbs) + 90 degrees. the ones I tightened up were like finger tight.

Wonder if it would be worth it to try replacing the bolts one at a time and tighten them properly to see if that does it

[TheSt|G]

Originally Posted by hassmaschine

neither of mine leak.. so far so good.

Older BMW motors were much worse. the M20 for example, there wasn't any point in even trying to stop it from leaking. call it rust protection.

how about loosening the subframe bolts and just lowering it down a bit? the thing is if you try to wiggle it in you won't be able to clean it well and it might leak again.

what's the N52 pan gasket made of? most 24v motors have been steel and they don't seem to leak, but the N52 is made of a unique material.

That's because steel would cause lovely galvanic corrosion.

BMW sells a special tool to remove gaskets on this engine that doesn't mess up the alu/mag surface:
90-88-6-114-470

[bernard54321]

Originally Posted by el_capitan

Gotcha. Ive been researching the DIY on the oil pan gasket where the guy didnt drop the subframe...just kinda wiggled the new gasket under the oil pump pickup and did it that way. Was looking to see if anyone could confirm that method, it would be sooo much easier than taking the damn subframe apart

Drop the sub frame, im speaking out of experience... save yourself the pain, headache and possibly having to redo the job, drop the subframe, its 6x 16mm bolts (or 18mm i forget).. not really a pain, remove both wheels to remove some weight and thats it, it shoud give you enough clearance to wiggle it out.

Dont force anything, aluminum everything, so be careful, clean both mating surfaces before reinstalling new gasket.

P.m. for questions

[007_e350]

my pan has cracks towards transmission side has anybody else seen anything like this ? rear main seal also drips I lose abt a qrt every 3500 .. changed vcg, ofhg, ocg, rear turbo inlet needed an o ring, ... finally put 0w-40 and its much better, but im gonna wait till things get worse