I have a new serpentine belt (about 10,000 miles) on my 1995 SC400 and after the car runs for a few minutes the belt begins to screech. I believe it's the belt because I sprayed some WD40 on the belt and the noise stops. Is the belt too tight, too loose or the incorrect belt? If it's too tight or loose how do I adjust the tensioner? Thank you.

 

Did you purchase the belt from the dealer? Typically when it is squealing that means it's too loose, then again there could be the possibility that it's too tight and wearing at a disgustingly fast rate.

 

WELCOME






..to the engine forum.

 

Don't spray with WD-40 it's a solvent not a lubricant, in the long run it will hurt the longevity of your belt. Spray a rubber lubricant on it. It might be your belt tensioner wearing out as well. Or the bearings on something

 

There is a mark on the tensioner which tells whether the belt is within spec. I believe it suppose to be in the "A" range normally, however a new belt should be in the "B" range when first installed according to the FSM.

Make sure you have a good quality belt, the belt should be on proper grooves with all pulleys aligned.

Make sure water or any of the fluids are not getting on the belt once running. It may not take much in the right place to cause a little noise.

Test the tensioner by applying about 22lbf to the top part of the belt to see if the tensioner moves. Should be able to push down on the belt a little to deflect it around an inch to make sure the tensioner moves and feels okay.

Silicone oil (which is WD-40) can break down and expand rubber so you may consider replacing the belt or carrying a spare to avoid being stranded. Even belt dressing (supposedly made for these belts) should not be used since a properly operating system will be quiet and last longer without it.

You can also remove the belt or just lift the tension off the belt to check each pulley to make sure they are spinning freely without wobble.

If all the above is okay then something like an accessory (AC/PS pump etc) could be freezing up or loading the belt more than normal causing the squeal.