PeachParts Mercedes-Benz Forum - View Single Post

psfred · #8 01-20-2008, 01:53 PM

Here's what I've been told about that leak:

The leak is usually NOT the seal itself, although they do eventually, like all German rubber, get hard and shrink. Leaks a LOT then.

The real cause of the leak is failure of the sealing compound to adhere properly to the front cover/head/seal intersection, and since oil sits on there any time the engine is running, it oozes out.

The correct method of sealing is to clean the groove in the front cover and the bottom of the top cover spotless. Use brake parts cleaner, etc and get any and all old sealant out.

Place a 1/4" spot of Loctite 5910 or 5900 sealant (and only one of these) in the corner and trace 1/8" bead of it around the seal surface on the head.

Wipe a thin trace of silicone grease on the bottom of the top cover.

Install seal DRY into the goove, press home in the corners. The sealant must contact the full corner AND the ends of the seal Seal must be squeaky clean and dry, especially at the ends.

Place cover on camshaft, making sure the camshaft seal goes in place correctly (there is a tool $$$ for this). Press cover down and in to engage locating pins, and then PRESS DOWN while pushing in at the bottom of the cover to fit into place. DO NOT rotate the cover downwards using the locating pins as leverage, this rolls the seal over. The silicone grease enables the cover to slip on the seal enough to get the cover in place without rolling the seal over.

If you do not put the sealant in the corners, use anything but Loctite 5900 series (soft set, high adhesion), or rotate the cover into place rather than sliding it straight on, it will leak.

Check to make sure the seal didn't flip over, too, before you tighten to bolts up.

I would recommend Loctite 5910 -- it's easier to find, and has a set time of 20 min rather than 5 min.

Perfectly installed, it should give you at least 30,000 miles of leak free operation. Probably not more, though... bad design.

Peter