jej3

I need to act fast and I need some advice....

So, I managed to have a squealing/slipping belt the last few days following my adding 134a back into the system following the Previous Owner's lead.

Air would blow like Ice front and rear but belt became noisy at low RPM. So I shot the belt with WD40 as I observed the slipping nd slipping would cease. I performed the wrong tightening procedure (read my other thread) and when seeing if it would squeal at higher RPM tonight on the highway, belt vanished.

I do not know if the compressor is the cause of the belt being trashed. I do know that I was planning on a Griffith/Kuehl replacement and complete flush/redo of many major AC things but was really optimistic that I'd get through my first SITM before I tackle that project.

I honestly just don't know if I have time to get the AC system redone before SITM with a holiday weekend coming up and my unique 1990+ AC Compressor. So, I'm contemplating buying a $10 belt from NAPA or some other local shop, putting it all back together and seeing what happens.

I was getting cold air right at the point the belt went and compressor switched off. No smoking. Nothing. Is it too much of a gamble to put another belt on and this time tension it correctly?

Your advice is very much appreciated!

Speedtoys

Mine tossed a belt after I bought ti last October.

Replaed the belt 2wks ago.

Been fine...if the compressor is roasted..a $10 belt wont hurt it anymore.


And..couldda just thrown the belt...

928 at last

and, what's gone before.....

Get a proper replacement belt. (I had to go with a slightly longer than stock unit due to a replaced compressor at some point). Roger can probably overnight the belt to you.

Get ALL the lubricant (WD40) off of the pulleys, (I mean really get it off with laquer thinner, acetone, whatever it takes to make sure it's removed). Just a note, I've never heard of anyone using WD40 as a belt dressing before.

Assuming the pulleys are aligned, (Should be if you haven't messed with anything), Install the proper belt and tighten to spec. (Don't know if you're aware, but the belts on a 928 are considerably tighter than what you may be used to). Do not under any circumstances re-apply a lubricant to the belt or pulleys.

the flyin' scotsman

what condition was the old belt?

If the belt was old and wrongly tensioned its perhaps possible you only had belt failure but I'd be inspecting the compressor thoroughly. A cheap belt may resolve issues for the short term but if it to breaks it may take out other parts and cause major issues.

jej3

Thanks for advice so far!

The old belt had 1500 miles on it. It was a Duralast belt from a local store as the Conti that Roger shipped me was the wrong length 1125 vs 1080. I've reached out to Roger on email a couple of times. He's a busy guy.

Yeah, I probably goofed spraying it with WD40 but I read on other threads here that people had done it. I'll definitely clean all the pulley surfaces.

I am pretty sure the alignment was sound but I did delete the Airpump and used the washer that everyone says we should use to re-mount the AC bracket. Hell, I may just put the Airpump bracket back on to rule out any alignment issue.

It was definitely not tensioned correctly as I learned today on this thread. I want to do things right for the short term (next 10-15K miles max) because the long term will have the compressor being replaced or rebuilt.

dprantl

Other reasons why the A/C belt would get tossed:

- Seizing up compressor
- Worn/enlarged mounting hole in the rear upper bracket that holds the compressor. With the A/C belt off and the compressor bolts tight, see if you can wiggle the compressor. It should not move even a little.

And +1 on cleaning all the pulleys as well as you can.

Dan
'91 928GT S/C 475hp/460lb.ft

jej3

Thanks, Dan.

How does one test if the compressor is seizing?

Also, I just found a NAPA belt online that is the AC belt for my application. It is the Gates belt and is the right size @ 12mm by 1089.

Anyone think going with a NAPA belt over a belt from our vendors is a bad move?

the flyin' scotsman

1500 miles on the old belt....that suggests that the issue is something more serious.

triple check the compressor, alignment and free running.

has the main pulley been off? the ac belt runs on a serperate pulley.

928 at last

Yes, but loose (most likely) and lubricated.......

jej3

Thanks, Malcolm -

Belt was replaced as part of a TB/WP procedure. I also deleted the air pump and who knows maybe the washer trick from airpump brackete that others suggest to fill gap created by airpump bracket is not the right answer. I thought/think it is.

I honestly believe the real problem is stupidity on my part in the form of bad tensioning of the belt and dressing the belt with WD40 which alleviated squealing.

I am sure the rest of the car is back together okay but will pay close attention to alignment but to check alignment doesnt' a belt need to be on it ?????

dprantl

If the stock belt is 1080mm, this one will be longer by 9mm, which is a pretty significant amount. I would probably go with NBH 259420

Dan
'91 928GT S/C 475hp/460lb.ft

jwillman

I am no expert but the old compressor I pulled that was siezed would not spin by hand with the belt off. The belt pulley should spin very easily if the clutch on the compressor is disengaged. The clutch should also turn by hand when not engaged but you will feel some resistance.

I am also struggling with the correct belt. I tried 5 locally sourced belts. Most were cross referenced against a Gates that showed to be the right belt on their website. I have a 79 but with a 6E171 compressor in place of the bigger Bosch. Finally got the Gates 9440 - 12.5 x 1125 to go on and snug up before bottoming out the adjuster. I am afraid that once the belt stretches a bit it will not be tight enough even at max adjustment. Anyone have a PN for a slightly smaller belt?

Tampa 928s

Turn key on engage A/C switch see if you can turn the compressor!
I would look at the alignment first, if you start the car look for the compressor jumping like it is locking up. Is the idle dropping a lot when you engaged it?

the flyin' scotsman

PET states the change to the 'shorter' belt was made in the '92 MY but its been inaccurate before. Theres also a change made to the a/c crank pulley part #.

You mentioned in the first post a unique AC compressor.....whats different?

It is possible to get the crank pulley on askew.....its worth the triple check as its very coincidental that this issue is shortly after the timing belt project.

any pics?

OK......I just read through many model years in PET......the belt size changes in '89 to the longer then back to the shorter in '92. I believe this was when the compressor changes were made and also when the R12 system was changed to R134a. what does this mean for you?.......the a/c compressor model should be checked as with the alignment of both pulleys.

Get the mechanics corrected then deal with a possible bad compressor.

ROG100

The reason your belt is coming off is not the width.
All belts of this V type are nominally ½” wide and when translated to mm comes across as 12.5 or 13 in most cases.
The difference between 12.5mm and 13mm is .0197 – that is 20 thousands of an inch.
If you measure the width of a belt it will be closer to ½” than 12.5 or 13mm. The tolerance on rubber belts is not that tight.
I just measured a whole bunch of belts and they are all nominal ½” even though they are labeled either 13 or 12.5.