Pushrod Seals

[jimmyg]

So I just installed a fresh set of pushrod seals on my R75/5 and the right side is leaking again. I was anal about cleaning, prepping the area but still have a problem.

Any advice would be appreciated.

thanks,

jimmy

[enigmaT120]

Yours should still have the ridged piece that pushes the seal against the block sort of free to move, so that you can tap it in if you make or buy (Ed Korn's old company sells one) the tool for that job. Later ones like mine are brazed to the push rod tube. Maybe you already tried that?

[jimmyg]

Hi Ed, I tried that before I replaced the old, original seals last fall so I know of which you speak. Haven't done it with the new seals but that's the first order of business I'm guessing.

Strange, I've done quite a few of these seal replacements over the years on mine and others Airheads and never had this issue. Usually I seal the new base gaskets with an ultra thin layer of Permatex Ultra Copper and a very light coating of Loctite 517 sealant on the rubber pushrod seals with never an issue. In fact, I did my R90s motor four years ago and after two track days and a Blue Ridge Parkway trip, it's still tight as a drum.

thanks,

[sprints@pldi.net]

Are you sure the pushrod tube hasn't moved deeper into the head? I had one like that.

[Duane Ausherman]

If the tubes are not brazed in place, then it is mandatory to tap them into place with the new seal. You were just lucky to not have one leak a long time ago. BMW took a couple of years to learn just how to do it themselves. We often had to tap them into place when new.

You usually can't tap an old one in place, as it just is too hard and will just bounce the tube back.

[jimmyg]

thanks all,

Duane, it appears that the seals are compressed slightly against the engine block so one would assume that the pushrod tube is in the right position. But unless the heads are pulled I guess, would you be able to see exactly where the pushrod tube resides in terms of fitting into the cylinder.

I'm going to tap the collar down tight and see what happens. it would be a shame to have to pull this motor apart again, it's running so sweet right now.

thanks again.

[montmil]

A tool for the pushrod tube collars can be fabricated from PVC tubing. The plan attached is for a steel DIY tool so modify the tubing stock as required while meeting needed dimensions.

http://www.bmwr65.org/cgi-bin/yabb2/YaB ... l_Tool.pdf

[Kurt in S.A.]

The only think that I'd worry about using this "tool" is the possibility of pulling the tube out of the head, creating another leak area. There is also a proper "dimensional" relationship between that collar and the cylinder base. That should be checked prior to seal installation and corrected at that time. If it still leaks after that, then the problem is more serious.

In general, this is a stop-gap measure at best. Of course, we know what the proper fix is.

Kurt in S.A.

[Roy Gavin]

There are a few sub standard seals around - clue is the dont have the correct numbers on the bottom face, but you will need a known good old one and a new one side by side to check.

I think the dud ones are BMW supply, and they know they are dud, but keep trying to slip them out to unsuspecting dealers !

[StephenB]

There are a few sub standard seals around - clue is the dont have the correct numbers on the bottom face, but you will need a known good old one and a new one side by side to check.

I think the dud ones are BMW supply, and they know they are dud, but keep trying to slip them out to unsuspecting dealers !

You're not talking about the R65 seals that can be mistaken for the "right" pushrod seal? I think they were a little bit shorter with softer material and a slightly different shape and subsequently buckled upon installation into a /5/6/7 head/block. They did not seal properly. If memory serves correctly they were often (incorrectly) considered /5 seals.