This is on bastet44s 87 coupe.

When I rebuilt the engine, there was a problem with the AC compressor causing the belt to jump off. I fixed that - nearly 4 months ago!

Last week, the belt started to shread then jump off. Of late, it lasts 10 minutes, maybe, before it blows off! There was a real problem with the tensioner, which I have replaced.

Initially, it was coming off on the AIR and water pump pulleys.

This is what I have done so far:

1) removed the AIR/Alternator/PS pump brackets and checked all the bolts and such. Did find one bolt gone on the PS pump bracket, at the bottom, replaced.

2) Shimmed up the AIR bracket where it meet the head.

That improved things... but it still wanted to walk off the waterpump pulley.

3) removed the waterpump, inspected the shaft, compared it to new (it is a Milodon, unused, donated by a very generous fellow forum member!) and it all looked within spec.

4) added 4 thin washers (as spacers) to the water pump pulley.

Restarted things... much improved, but I could still see a problem with the relationship between AC compressor and the waterpump pulley. The belt was entering the waterpump pulley right on the leading edge of the pulley. Everytime the AC kicked in, the belt would tighten a bit, and I could see the forward edge of the belt start to ride up on the pulley.

5) removed the AC compressor, again, and added more washers between the head and the bracket. Things, again, look better, but the waterpump STILL wants to toss the damned belt.

My last stab at this will be after dinner. I must get this damned thing figured out... I am going to get more washers, thicker this time, to put between the pulley and the waterpump. Hoping to move the pulley forward.

The belt rides fine every where else, it's just the relationship between the compressor and the waterpump, now... there is a visable twist in things. Almost like the AC compressor is leaning backwards.

Any better ideas? Is this a problem with the Milodon? Is it endemic to them? The pulley looks like it is angled toward the engine at the top... but it does not wobble, a bit up/down, but not fore/aft.

Thanks!!!

 

oh, God, my lower back hurts....

 

Just a wild hair thought, but is it possible that the waterpump casting or pulley mounting is askew causing the pulley back-tilt you mention?

 

The stars have to be in alignment.

Well, 6 pulleys anyways.

The only thing I see differerent from before would be the water pump pulley and crank pulley.

It sounds like you're trying to line up the good pulleys to match the bad ones. The tensioner gives you a fudge factor, having no ribs, and the other ribbed pulleys are all on the other side far enough away that the belt won't skip a rib.

The crank balancer is hard to get on all the way to get the pulley to line up. Maybe that's out a little bit, which helped us keep crashing into the steering rack when dropping the motor. It can be slid on further, but it's a pain in the *** in car, at least on my car it was.

I remember we made a tool to pull that balancer on, but I don't remember what we used to determine whether it was located right. Did it just bottom out or...?

 

I checked the pump the best I could, and if the casting was that far off, I woulda expected this problem from day one.

that's what's so odd... the engine has been together for so long now... and no belt related problems - until the tensioner blew.

This all started last Thursday... she was on her way to Riverside and about half way out there, it shreaded the belt and tossed it...

I replaced it, ordered the tensioner and sent her on her way.

Friday, the belt blows again, this time, on her way home from work, near the house... so I get it home and remove the blown up belt (#2) and wait for the tensioner.

I get the tensioner, and installed it yesterday evening, with a new belt.

Tested same, all looked good...

This morning, I get another call, she got about 1 mile from the house, and it tosses the belt. So, we limp it home, sans AC, and I commense to taking it apart.

After posting this, eating food and taking some Advil for my poor lower back (owie - the damned thing is hot to the touch, not a good sign), I realized what may be causing some of this problem.

When I rebuilt the engine, I replaced one of the studs with a threaded rod and bolt - I am thinking that the home made stud may have a fitment issue in relationship to the existing stud.

So tomorrow, I am going to get the stud and replace accordingly.

It won't be fun... it means I need to remove the AC compressor again...

this will be tomorrows project.

Thanks, Pier!!!

 

I checked the crank pulley the best I could. This being an 87 means the crank pulley isn't any easier to reach... and as far as I can figure, we got that sucker planted when we put it on. The hub is right on the seal... or within a few mm's of it. With that said, the crank pulley looks great. The belt runs off that to the tensioner to the AC and that looks great. It's simply getting the belt from the AC to the waterpump...

I am going to replace the stud tomorrow, I hope. And then test again. If I need to, I will add more (or thicker) washers...

 

I've got the solution for you..

RTFM!!!

 

Which stud are you referring to?

Oh, and btw, I had that same PS bolt missing on my car for the longest time. Always wondered where that extra bolt in my toolbox went to.

 

one on the waterpump. It's the lower right (facing engine) water pump stud. I am concerned that the nut isn't the same thickness as the flanged bolt thingy on the top right stud.

Follow? If that bolt is too thick, then the bracket is automatically out of wack.

 

dude... my back is soooo sore... I have never felt my lumbar actually get WARM. It has ice on it now.

 

Forgive me because this is probably a really dumb question, but are you absolutely sure you are using the correct belt? As you know, some can be so close in size to others, that you can barely tell it's the wrong one. Maybe you got a defective one and it's a tad bigger than it should be. Have you yet tried a different belt to rule that out?

 

I have been considering that... infact, I will have to replace this belt (the edges are pretty frayed now)... so I will get a new one at NAPA. Hopefully, a different brand will help.

 

The belt tensioner has max/min marks on it... as long as it's in that window not a belt length issue. But I know how you are about tightening things.. I had a helluva time removing my slave cylinder!


I see what you mean on the water pump bolts. You'd probably be better off if both were the same, even if they were a little thicker.

Or if all else fails, put the thicker one on top, or even replace it with a regular bolt and just have one holding the a/c bracket. You'd think the top bracket bolts would keep it from getting misaligned.

You're probably gonna have to get that at a Chevy dealer. The nuts are all pretty much standard thicknesses, unless you go and order from mcmaster carr (1-2 day shipping). Grind one down a little thinner.

 

Sucks, those belts are expensive. It's gonna be awhile before the next trivia prize too, so spend accordingly.

 

the belts I have been getting are Kelly-Springfield... and are about $18.00 each.

The next one is gonna be a Goodyear or Gates.

the bolts are studs and rather big with flanged nuts in the middle. I am going to test first... then determine what I need to buy.

Rather big... 3/8-16... but the length and bolt thickness is my current concern.

 

Well, there's two of em that are identical on my 85, so it shouldn't be hard to match something up if you haven't lost both.

In fact, if you can keep the stud/nut combo, it's much better. I always found it a bitch to pull the a/c bracket over the heads of those two fasteners.

 

Aren't the stock studs shouldered to locate things?

Let me come over and sock you in the back. You'll forget all about that nagging ache

 

yea, the stock studs are shouldered... I suppose that has to do with location, but I can't see how it effects the AC compressor... except for the thickness of things... that's my concern. If I am 1mm off at the mount, it turns into 4 mm at the belt. And 4mm becomes a mile.

 

I got the belt problem fixed!

It is a combo of things:

1) The ac bracket is bent... I can see it.

2) I adjusted the bracket by forcing it forward on the manifold bracket.

3) added spacers to the inside of the waterpump pulley.

All of that has kept the belt on for a long time.

tonite, two plug wires decided to no longer stay attached to their respective plugs. :

AND... rocker bolts no longer want to stay tight!

I am afraid to contemplate what could happen next...

 

Glad to hear you got that figured out!!!