push rod tube tips

[yaktackler]

I have an oil leak from one of my Push rod seals on my 1976 r90/6 - I have replaced the seals but it looks as if the ring on the push rod tube is not pushing the seal into place. Is it possible for the tube to slide up into the head? Can you measure them?

Thanks for your help,

Yaktackler

 

[PeoriaMac]

If you have a Haynes manual (I believe) there is described a setting tool that pushs the rubber seal in tighter. You can make one from plastic pipe which works just fine. I'm at work, and don't have the info in front of me...
Anyone out there have a picture of one?? It's just a hollow pipe with a cutback business end which allows it to fit over the pushrod...

 

[pglaves]

I don't remember the year of the switch - but BMW did this assembly two ways. Initially the ring was a press fit on the tube and the tool described in post 2 was used to move the ring along the tube if it had slipped. Later the ring was brazed to the tube. Driving against the ring in this case pulls the tube further out of the cylinder.

The tube is not supposed to move in the cylinder, but it can sometimes happen. If it does then driving it back where it is supposed to be might work. There is a risk of developing a leak where the tube is in the cylinder if driven too far, so be attentive to this possibility. It leaves a little recess at the top of the tube where oil puddles and may seep out around the tube.

 

[barryg]

Snowbums BMW repair website has some pushrod tube info U may find helpful.

 

[20774]

I've not been able to find a definitive year that the collars were brazed to the tubes. Some say mid-70s on, other say beginning in 1981. I would think it is easy to tell upon close examination, especially when the cylinders are off. The brazing or soldering should be quite evident.

I agree with Paul, that trying to move the ring by pounding on it with the "tool" may only create more problems in the end. It may create a leak at the other end of the tube. It may also split the seal, resulting a real mess and having to repeat the job.

What sort of prep did you do to the seals prior to installation? Some smear oil on the seal; others use something like Hylomar to create a better seal.

As for a known position of the ring, it should be the same as the non-leaking pushrod tube rings? Can you measure from some of the others?

Oak provided a diagram of the proper position of the ring prior to installation. It can only be effectively checked while the cylinder is off. Recall that the pushrod tube is angled with respect to the cylinder bore. The ring on the tube will have a slight angle to it as compared to the flat edge of the cylinder base. This flat edge is what mates with the engine case. The ring on the push rod tube should be no closer than this flat edge on the base of the cylinder. Since the ring is angled relative to the flat edge, most of the ring will be farther away from the flat edge (ie, closer to the head), but one point of the ring will be exactly on the plane that this flat edge makes. Hopefully that makes sense.

 

[azduc]

I have re-set my seals several times using a large blunt screwdriver on the metal collar and lightly tapping with a small hammer, this was on a 73 R75. It cured the seepage and caused no other problems. Don't you think this would be worth a try before starting all over again with a complete renewal? You really have nothing to lose.

 

[pglaves]

I have re-set my seals several times using a large blunt screwdriver on the metal collar and lightly tapping with a small hammer, this was on a 73 R75. It cured the seepage and caused no other problems. Don't you think this would be worth a try before starting all over again with a complete renewal? You really have nothing to lose.

If his later model does in fact have brazed rings he does have something to lose. If moving the tube around in the cylinder recess causes it to loosen and leak (seep) then he will have a hard time getting it to seal. I recall a couple of cases where the cure was to install new tubes after an old one loosened.

There is a lot moving around on those engines as things heat up and expand, and cool down and contract. It is cylinder elongation that causes the need for an elastic seal at the pushrod tube joints in the first place.

 

[Bill Burke]

I have not done the following (my PR seals are new and not leaking) but I have read the following: wrap piano wire or packing wire around the tube where the top of the seal meets the compression ring on the pushrod tube. Pull as you wrap. The wire "fills the gap" and exerts downward (sealing) pressure on the seal. An allegedly invisible and functional fix.

 

[yaktackler]

thank you all for the advice. I will take a close look and report back.

 

[LOSTBOY]

Pushrod Tips

BMW began brazing the rings to the tubes for the model year 1981. A neat trick I once saw (not too different from Bill's piano wire trick) was hose clamps around the tube to keep the rings from backing up. If you disassmble the motor to fix your leak, put the rings back where they belong (it'll be obvious, as the ring leaves a mark on the tube) and braze them there. You'll have to repaint them, of course.