535i intake gasket problem

[Big Dog]

Our '91 535i keeps blowing intake gaskets on the number one cylinder. None has lasted over 3 years and it's always a the number one. Gasket is pushed out like the car backfired but I never hear it happen. Any thoughts?

Dog

[bonzo]

Has this ever happened on #5? Use to be common on the M60 block but not on yours. Have you had to replace Knock sensors on that side yet?

[Big Dog]

I don't think this engine has a knock sensor

[bonzo]

I think your right!! Not until 92... can't think of anything that would take three years to blow the gasket and not right away unless the mateing surface/s have a slight distortion and it takes 3 years to weaken the gasket enough to blow.

[Big Dog]

Talked to an older BMW master tech last night and here is the probable scenario.

I reused the old wave washers which had lost some of their spring. Over time the length of the intake and the heat/cooling cycles makes the outer cylinders flex a bit which with the older washers made the nuts back off a bit. Eventually they back off enough to cause a slight vacuum leak which then caused a backfire, thus the blowing of the gasket to the outside. Solution, don't reuse older fasteners or washers. Rookie mistake on my part.

[went4it]

I have had the same troubles on my '92 535im. I think you're correct, that anything causing a backfire into the intake will blow out the gaskets. In my case, it was a bad O2 sensoer which caused a stumble at throttle tip-in. Although I felt the stumble, I couldn't hear the backfire, since it is not very loud. Once, I had the hood open, and heard it, it sounds oddly like a sneeze.

Anything which causes a lean condition to the engine should be prevented, as it seems these cars have vulnerable intake gaskets.