View Full Version : Belt Tensioner Condition - Bboby?

04-01-05, 10:30 AM
I had replaced the belt on my 95 sedan deville thinking the operarting range indictor being off is due to the belt it self, but it seems that the tensioner is not as it should be, please see the attached picture, Do I need a new one? which might help in some vibration at the pulleys?

Also how long can I operate the engine without the belt to isolate the vibrations? since the water pump will not operate?


04-01-05, 12:19 PM
The water pump is turned by a cam pulley on the other side of the engine, not the primary serpentine belt. Circulating coolant is not going to be the problem. The problem will be the electrical system since you won't be spinning the alternator. You can run it for long enough to diagnose your vibration problem, I'm sure. I've had to drive a car (a 1986 Olds Toronado whose AC clutch broke off) with no serpentine belt for 15 minutes before, so I'm sure you'll be just fine.

Does the tensioner move freely? Does it put significant tension on the belt? Does the pulley spin freely and quietly? If the answers are yes, the tensioner is probably not a problem. There is, however, an idler pulley that could be giving you fits. If its bearing is on the way out, it could vibrate significantly. It's also very easy to replace. Not sure what the original problem was, though, so I might be on the wrong track altogether. Just a few thoughts to get you started anyway.

04-01-05, 02:02 PM
If the tensioner is moving freely and tensioning the belt I wouldn't worry about it. The marks are more a guide for measuring belt stretch/wear than an absolute measurement. The tensioner should have plenty of travel past the point that it is at. If you are unsure, mark the two sides of the tensioner with a scratch mark, take the belt off, release the tensioner and see where the marks end up. That would tell you how much travel the tensioner has left. As long as it is not bottomed out and out of travel it is fine.

With a 95 Deville you have a 4.9 or a Northstar..??? If it is a 4.9, the serpentine belt drives the water pump but you can still run the engine for 5 minutes or more with the belt off to listen for noises and/or isolate accessories. The Northstar will run for as long as the battery lasts (20 minutes..??) as the water pump is run off the end of the intake camshaft on the left hand head at the rear of the engine with a separate belt.

04-01-05, 03:57 PM
Gentlemen I cannot thank you enough for you opinions….

I have the 4.9 Sedan Deville, I had to call my wife to help me hold the tensioner while I put the belt back, and I read that the tensioner has to have 120 ft – lb. Force, which made me curious.

If the lights in the car ( interior or exterior ) flicker ( slightly) would that mean a problem with the alternator?

I’ll do the test this Sunday…. thanks

04-01-05, 04:31 PM
Before suspecting the alternator, I would look at the battery cables. Are they free of corrosion? Are they plenty tight? How about the wiring to the alternator, is it tight?

With the 4.9, as Bbobynski said, the water pump is driven from the serpentine belt. Are you having some problem with the belt or tensioner other than the flickering lights?