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E28/E34 M5 Paper Throttle Body Gaskets
Help prevent intake leaks

E28 M5 and E34 M5 paper throttle body gaskets

This is another one of those tricks that comes to us via BMW guru Don Fields. It is well known that the rubber throttle body isolators (intake gaskets) on the S14 engine are prone to intake leaks where the join the cylinder head. This is partially due to the fact that the bolts holding the throttle bodies to the head go along the bottom and near the centerline of the throttle bodies, but not along the top. The weight of the plenum and airhorns is "cantilevered" off of the rubber isolators, and tends to pull the isolator away from the cylinder head at the top edge. This effect is exaggerated by the vibration-prone S14 engine. The under-spec'd pressed steel bracket which is meant to support the plenum does not solve this problem, it simply is not stiff enough for the task.

E28 M5 paper throttle body gaskets installed on an isolator

Both the E28 M5 as well as the E34 M5 use paper throttle body gaskets. Note that these two cars had cylinder heads with an almost identical design to that of the S14, save for the number of cylinders. These paper gaskets are perfectly adaptable to the S14 rubber isolator. The E34 M5 paper gasket is about twice as thick and might be a better choice, but both styles work well. You simply place the paper gaskets between the S14 rubber isolator and the cylinder head. I prefer to use a light coating of Hylomar on BOTH sides of the paper gaskets, but other users have different preferences. One thing is for sure: if you employ the paper gaskets, your rubber isolators will function leak-free for a long time.

If you are really ambitious, it is not difficult to fashion your own paper gaskets to go between the throttle bodies and the isolators (i.e. on the other side of the isolators). Gasket material can be had at any V8 speedshop and it's easy to cut. I tried this and it worked quite well.



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