belt tensioner on 3.1 GM v-6

[Pluto5]

Can anyone explain how to tell when the belt tensioner needs to be replaced and whether the mounting nut is supposed to be torqued to a specification?

 

[KC Strip]

I've replaced a couple of them on my wife's Olds Cutlass Supreme 3.1L. I assume you have a Cutlass, Lumina, Grand Prix, or another GM car, right? The way I can tell my tensioner is worn is if the belt seems a little loose both while running and when the engine is off. There should be very little play in the belt. Belt tensioners are not terribly expensive (last one I bought at http://www.rockauto.com - Gates part #38105 for under $40.00). If you choose to replace the tensioner, I would definitely replace the belt at the same time (Gates part #K060710).

This next bit of info comes directly from the Gates website related to your issue ...

November 2005
Form No. 433-0796
How a tensioner works and when to replace it

The vast majority of vehicles with serpentine belt front end drives − over 100 million − use automatic belt tensioners. Tensioners are built into the drive system for several reasons. They are designed to:

• Maintain proper tension for the life of the belt.
• Reduce maintenance by eliminating the need to manually retension belts on a periodic basis.
• Provide consistent and correct belt tension, thereby
increasing the bearing life of the accessories.
• Prevent belt slip. A belt that slips can be noisy, can
have reduced service life and can cause accessories to function improperly.

Tension is provided by a powerful spring located within a small canister-like housing and the tensioning arm. The arm pivots around the spring housing and generates a constant belt tension. The pulley is attached to the arm. The spring-loaded tensioner consists of seven parts:

1. Base: stationary part of the tensioner that is bolted to the engine block or an accessory. Base designs vary. Some base components are very complicated and may include bracketry or conduits that carry engine coolant.
2. Damping Mechanism: a composite mechanism that smoothes system vibrations. Tensioners with worn out damping mechanisms need to be replaced.
3. Tension Spring: preloaded at the factory, it provides force to tension the belt.
4. Arm: connects the spring to the tensioner pulley.
5. Pulley/Bearings: the pulley is made of thermoplastic or steel, and may be grooved, flat or flat with flanges. Pulley surfaces should be inspected regularly for damage or wear. For a pulley to function properly, the bearings must be properly lubricated. The most frequent cause of pulley failure is loss of lubrication in the bearings. Do not attempt to put new bearings in to an old pulley.
6. Sealing Disk: prevents internal contamination to the bearings.
7. Bolt: connects the pulley to the arm.

Tensioners, like any other part, don’t last forever. To
reduce belt warranty problems, comebacks and labor claims, Gates Corporation engineers recommend that the serpentine belt and its automatic tensioner be replaced at the same time. It is highly probable that the source of belt system
damage (excessive belt wear, tension loss, vibration, misalignment, etc.) is the result of a worn tensioner.

Gates Corporation
Denver, Colorado
www.gates.com
Printed in the U.S.A.

 

[onion]

When they're worn out, they'll generally do one of two things. Either the arm itself will wear out, so that the tensioner cam move around and misalign with the belt. Or the bearing in the pulley will fail- in which case it, can be loose, rough, noisy, and/or all of the above.

I've had three GM 3100 engines, with only one tensioner failure. The tensioning arm pivot wore out- the joint was loose and the pulley was running about 1/4" off the belt.

 

[Pluto5]

Thanks for the info. One more question: do you just snug up the mounting nut or torque it to a spec?

 

[KC Strip]

I've always made sure it was snug but not overtight.

 

[mechtech2]

More than snug. The tensioner is spring loaded and requires a good seat of the base.

 

[pbm]

I have not yet replaced the serpentine belt/tensioner in my 3.1 with 85K. What is the life expectancy of these items? I'm glad I saw this thread because I hadn't thought about replacing the tensioner (I already had purchased a belt with my last Rockauto order).

 

[chas3]

never had a problem with the tensioner itself, usually just the bearings in the pulley itself. i couldnt buy a tensioner pulley without getting the complete tensioner for my one vehicle. depending on your belt rotation, the bolts might be left-hand thread.

 

[Drew99GT]

You can tell it's worn out because it has kind of a gauge on it; the spring in the tensioner seats into the base of the tensioner and into the arm; when the little notch on the tensioner arm get past the mark on the body, the spring is worn out.