ammonman

Good bit of sleuthing. I wonder if the pivot bolt could be made of a less ductile material without getting it so brittle that ANY over-tension of the belt breaks the bolt instead of bending it. The bending of the bolt as a consequence of over-tension is a better failure mode than outright breakage in my opinion.

Mike

Leon Speed

If you add the washer is it might be a good idea to retrofit the support bracket used on later models. Only disadvantage is the bolt will be out more again.

worf928

We could also be seeing a difference between "German Metal" and "Chinese Metal"...

Absolutely agree on that.

worf928

It's not that easy. You need the 87+ water pump, idler, carrier arm, and pivot bolt. And you have to modify the center belt cover, or buy the '87 cover. And that will only work for the '86 US 32v - I think - since it has the the updated tensioner housing (as per TSB above.) If older, a new tensioner housing might be needed also.

For the 16v motors you'd need all of the above and you'd have to hack the center belt cover as the 32v center cover is quite a bit different where it meets the side covers (I know this for a fact as I once had an '89 for a belt service with a 16v center cover on it. And it was a mess.)

And all of that probably misses a few fine points (like the dip stick...)

worf928

I have with 100% certainty determined the exact cause of the failure mode of the bent pivot bolt. And it is ...

... wait for it ...

... the idiot installing it. And that would be me.

Here's the blow-by-blow:

I usually install the tensioner last. It's pretty easy when the air pump has gone mysteriously missing. With the air pump, however, it's a bit of a pain. This time around, the air pump was mysteriously still installed, so I decided to install the tensioner first and then the roller carrier.

On the old-style roller carrier you need to turn in the pivot bolt while making sure that the carrier doesn't slip off the shoulder of the bolt as you turn it in. If it does slip off, you risk the shoulder taking out a chunk of the posterior (new) bushing.

As you hold the carrier on the bolt head with one hand and turn-in the bolt with the other the carrier get closer and closer to the pump and at some point you need to get the tensioner piston into the ball cup on the carrier.

The problem is, if you clock the carrier far enough counter-clockwise to clear the tensioner piston, the back edge of the carrier where the nut for the main roller is will just hit the water pump casting. And then if you keep turning in the bolt - which you're doing with a wrench or ratchet (because you cannot turn it by hand with new carrier bushings) - you will not feel the resistance of carrier hitting the pump until it's too late.

So, yup. I bent the second new pivot bolt.

I think that's the first time I've ever made the same mistake twice on a 928.

Bill Ball

Uh, I had this happen once as well, but I didn't do it a second time and I never figured out how I bent the shoulder bolt. Thanks for the through expose'.

skpyle

worf928, thanks for this detailed thread. I think you may have solved my issue on the timing belt on my 1986.5. If nothing else, you have provided clues to look at.

Thanks!

Seth K. Pyle

RFJ

My lord ,all this fuss when you could just put a one of Kens tensioners on it. Ask me how i know?

worf928

Keep the bickering in the bickering threads. Don't pollute my thread with it.

Mrmerlin

FWIW I found a similar issue with a roller not fully supporting the belt,
I then fitted a new Laso with plastic impeller and then this brought the arm assembly back to a more full contact with the belt.
So a waterpump could also be part of the reason for the mismatch

JBGold07

My 86.5 also had this problem. When it landed with me the belt was riding on the front lip of a cam gear. The bolt was clearly aged, as were the bushing though too.<br/>The attention to detail required is....<br/><br/>I put on the porken black 3 years ago. That has to be thrown out now.<br/>Still deciding on how to replace

John L. Gormley

Interesting thread. I'm in the middle of this same project. Anyone got the torque setting for the upper pivot bolt and the lower tensioner bolt for an 85 32v. Can't seem to locate them in the WSM. I believe it's same as 86.5 in this thread correct? Thanks Sent from my iPhone using IB AutoGroup

RFJ

come on,just put a porkententioner on it,solve all your problems ask me how i know????

John L. Gormley

I might someday. But I've already bought all the parts to rebuild the original setup. I search inside rennlist using search and could not find an answer. But using google I found a 2016 rennlist post that confirms the WSM to not have a torque value for the pivot bolt. That thread said use 15 lbs for an other wise unspecified 8mm bolt. Guess that is what I'm going with unless someone has a better idea?

Sent from my iPhone using IB AutoGroup

worf928

Spec book says 15+1 for a generic 8mm. That's what I've used.