Belt tensioner bolt torque setting: Recommend if you don't know

Someone told me that you couldn't over-torque or over-tighten the belt-tensioner bolt that leads to the a/c (in the N/A - figure its the same setup on the TT's) pulley. Well, ever since I last swapped the belt and tightened the belt tensioner bolt, the engine shakes when the a/c is turned on. I believe I have ruined the bearing in my a/c compressor due to noise I hear now and it nearly locking up the engine when I turn on the a/c now.

I can't find this information in the manual, so anyone with any knowledge of belt tensioning or having done it before please respond... What do you think the max torque should be set to to tighten the belt tensioner bolt (the one that leads to the a/c pulley)?

All I can find in the manual is a belt deflection value to be measured by pushing on the belt itself after its installed and I don't have a belt deflection measuring tool, nor do I wish to buy one. It seems like you could just use the torque wrench at a certain torque and it would put the belt at the right tension and that's. I know this seems like a simple thing, but its very important as to the wear on the bearings of all connected components.

*** DOWN WITH 3SI. LONG LIVE 3SGTO!!! *** - WOULD BE NICE THOUGH IF 3SI.ORG COULD BE SOLD TO ALAN, BUT I KNOW THAT PROBABLY WON'T HAPPEN.

The only way to really correctly measure the tightness of a belt is with a deflection value tool. Because rubber stretches, you can be exponentially tightening the belt without really changing the amount of torque needed on the bolt that is tightening the belt.

The best way to make sure you are not over tightening, is to just make it barely tight, run the new ac, and if it slips, just tighten a little by little until the belt no longer slips.

You can easily over tighten belts on both the AC and PS, the bolt on the AC/Alternator tensioner pulley makes it really easy to do so.

I've never seen a bolt torque to belt tension translation chart. Since I don't have the belt tension tool either, I start on the loose side and then tighten it more if it's starts squealing when it's wet out and under load (AC running, headlights on)

(I see we had a posting race going on and I lost)

My belt squeels like a motha trucka... gota fix that too.. Not sure if its the bearing or the belt though...

I overtightened mine and ruined my A/C belt idler pulley. Fun :( Just gradually tighten it until it doesn't slip when you spray it with water and have the A/C and headlights on.

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Originally Posted by Unknownvr4

My belt squeels like a motha trucka... gota fix that too.. Not sure if its the bearing or the belt though...

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Best way to find out, run the motor, spray some belt stop squeek directly onto the belt.....mine stops right away when its sprayed on the belt. damn gates blue racing belts

If you don't have a tensioner measurement tool , the shop manual says that the deflection when pressing on the top part of the AC/Alt belt (in the location show in the manual), should not be more than 5 mm (0.5 cm) for a used belt. That's not very much deflection.

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Originally Posted by TUFFTR

Best way to find out, run the motor, spray some belt stop squeek directly onto the belt.....mine stops right away when its sprayed on the belt. damn gates blue racing belts

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My experience is the belt dressing messes up the belt and pulley. Then you have to remove both and clean them or it will just keep squealing over time.

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Originally Posted by duke3k

If you don't have a tensioner measurement tool , the shop manual says that the deflection when pressing on the top part of the AC/Alt belt (in the location show in the manual), should not be more than 5 mm (0.5 cm) for a used belt. That's not very much deflection.

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You forgot one other key value, how hard you press on the belt, the FSM says 100N (22lbs). That's the hard part to judge or apply to the AC belt between the idler pulley and crank.

Thanks for all the replies. I figured I'd get good info seeing as this site is new and probably got the best people having joined it thus far.

Anyone know of a good belt deflection tool within reasonable prices and where to get it? I think I looked for this a while back and couldn't find one.

Thanks for the method/technique for tightening the belt to the right balanced torque amount. I understand now too why a torque setting isn't specified, due to the rubber aging and stretching over time. The water trick is a good idea too.

Thanks for the reference from the manual & the amount of force to push on the belt if you have a tensioner belt measuring tools.

I can agree too that belt dressing usually does make things worse eventually and needs to be cleaned off with hot soap/water or else the squeaking continues to get worse. Its kinda like using the Vicks Sinex nasal spray (or others with same ingredient), in that once you start you find you want to keep using it or the problem gets worse again.



Thanks to all!

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Originally Posted by steve

You forgot one other key value, how hard you press on the belt, the FSM says 100N (22lbs). That's the hard part to judge or apply to the AC belt between the idler pulley and crank.

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What does FSM stand for? F??? Service Manual? Because, I have found the belt replacement section in the chassis manual for the 3000GT 92-96, and for vehicles with Air Conditioning it says to press 77-132 lbs on the belt to measure a deflection of 4.0 to 5.5 mm ? That seems like an awful lot of force to put on the belt.

Nobody with the "keywords" as to what tool I'd be looking for if I wanted to get the tool instead of doing the technique?

FSM = Factory Service Manual

I pulled the spec I quoted from the Engine section (11) pages 11 and 12 of the 91 3000GT FSM Volume 1.
What you just gave is the tension measurement if you use a belt tension gauge. That's the keyword you want to use when searching for the tool.

I think you misread the Factory Service Manual. The ref. to 77 lbs is the actual tension in the belt that you would want to measure with tool. If doing a deflection test you want press with 22lbs .
Quote:
With belt tension gauge set to the belt midway between
the pulleys as shown in the illustration, check the belt
tension for standard value. Or apply a force of 98 N (22
Ibs.) to the belt to check the deflection for standard value.

Thanks guys. I see now. I tend to skip ahead and look right at the specs and I missed the 22lbs of push force in the instructions above the specs.

Makes sense now, so when I get my belt tension gauge, I'll be looking for the "specification" measurement. Hard to picture these things till you do'em. lol

Do ya'll think I should go ahead and get another belt since I've ran with the overtightened belt for about 2-3k miles? Its only that old.... but I guess it may be a bit stretched now huh?

I just wanted to follow-up for anyone else looking in the future. I always try to.

I finally found a cost efficient belt tension gauge online and its actually a pretty neat lil device and much cheaper than the over $100 belt tension gauges I've seen that the pro shops probably use.

It can be found online in various places (Amazon and Ebay), but I found it at NAPA Auto Parts for around $13. The NAPA part numbers for the belt tension gauges are:

NBH KR1
NBH KR2

Elsewhere I have seen them as:
Krikit V-Belt Tension Gauge (91107) by Gates
Gates 91132 Belt Tension Tester by Gates

Each of the 2 gauges handles a different range of tension. Since they are so inexpensive, if you are doing a lot of routine maintenance work on various cars you may own, I think having both gauges in your tool box is a good idea and it would probably eliminate the trial and error guess work method of getting the belt tensioned properly by cranking the engine on and off between adjustments.

It seems that these lil gadgets "sense", by pushing downward on the belt, when to "click" a little clicker in the gauge and as soon as you hear that click you stop pushing and read the tension. Pretty easy.

I have yet to experiment with it, but when I do I'm sure it'll be helpful. Hopefully I'll post back and let ya'll know how it worked out.

Check the service manual.