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Aircon belt flying off


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I have a 2001 factory TD 100 series with the 1HD-FTZ motor.  It has done about 455,000 km since I bought it new in May 2001.

I put a new compressor on the aircon in 2016 and have had no trouble until about April this year when I started to hear a loud "Click" when the compressor cut in.  I had my local aircon person in Bathurst check it but he couldn't find any problem.

Then after a few days it threw off the first belt.   We replaced it and had the gas checked etc, but ti happened again after a few days..  The Toyota dealer in Bathurst doesn't have an aircon ticket so I took it to Orange Toyota, where they found gas pressures out and replaced the TX valve and the receiver dryer and put on a new Toyota belt.  Cost about $600.

It threw the belt off after a few days, although it went about 1000 K's before it did.  So my local aircon man replaced the compressor in case it was locking up and causing the belt to jump off.  It went a few days and threw the belt again.  Cost about $850.

We then thought of the bottom pulley and replaced the harmonic balancer, which appeared to have a crack about half way around the rubber centre, so we hoped it may have been wobbling and that we had fixed the problem.  It threw the belt again after a few days.  Cost around $500.

We also tried a new second hand electronic climate control unit in case there was something in the electronics causing the thing to draw too much current or something.  It threw the belt off again in a few days, so we put the original dash control unit back in. Cost about $350 inc freight.

I have had various engineers check to alignment of the pulleys with straight edges and all agree that they look good.  The idler is the only thing that hasn't been changed and it looks and feels fine.  Yesterday, I even brazed a small guide onto the dustshield under the nut which tightens the idler, to stop the belt jumping off, as the belt sits a bit proud of the flanges on the idler.  A pulley with deeper flanges might be better, but it is still the original and worked fine for over 18 years.  But the belt flew off again in a 10-k drive this morning at low speed and revs.  It was still sitting inside the guide I made and appeared to have come off the compressor pulley first.  It had run against the guide I made hard enough to damage the front side of the belt, so maybe it is climbing the compressor pulley. but why when nothing has been changed?

So I'm at my wits' end and about $2500 poorer with no idea what is causing the belt to jump.  I've tried belts really tight, and just comfortably tight, but nothing makes a difference.  I've tried Toyota belts for $75, Gates belt for $38, and Repco belts for $28 and they all do the same.  I've been through about 6 now.  I've had the bolt out of the tightener and ran it in a lathe yesterday to check that it is straight and it is fine.  I can't think of anything else and no-one in Bathurst has a clue about what to do next.

Can anyone offer any ideas from experience they may have had??  Or even suggest an expert to talk to?


5:30 PM same day-

I may just have found a reason for my problem.  I took the idler pulley off the vehicle this afternoon and put it on my workbench to measure the offset if any, and I found the bearing is about 2-3 mm closer to one flange of the pulley than it is to the other.  There is a steel flange between the sheaves of the pulley and the bearing holder, and it is quite offset, so it is easy to see that you are putting the pulley on the same way each time.  But when I turned the pulley over and put it on with the other side facing the block, it definitely looks better and it is sitting slightly closer to the block.  If this works and the belt stays on, I think someone must have taken the idler off early in this process and put it on back to front without realising, and everyone else has put it on the same way ever since.  It may have been reversed at the first check of the gas pressures when looking for the "Click" noise that started all this..... 

Edited by GregM
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  • 3 weeks later...

Spoke too soon.  Belt still coming off.  Now done 8, I think. Checked idler pulley again, one flange is thicker than the other, so the bearing is actually centred.   To be sure i replaced the idler assembly with a Toyota unit including bolt and spacer as well as pulley and bearing.  No difference- belt still comes off, this time after 75 k's.  Has anyone any thoughts, ideas, suggestions?

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  • 1 year later...

Sounds like a very frustrating situation. If I had one of those Gopro cameras, I would've mounted it inside the engine bay and have it trained on the trouble area to and see what the heck is going on. Poor bloke spent too much money with no fix it seems.

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  • 2 years later...

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