Serpentine belt chirping noise
 

I have a 98 E300 turbo diesel.

There was a chirping sound from the engine area. The engine has 199K on it and the belt has 96K on it (ie this is the 2nd belt).

I replaced the belt. The chirping sound was still there.

Last night, going home, when the air conditioner was on, a squeeling noise was coming from the engine. When I turned the air off, the sound went away.

This morning, I started the engine and left the air off. Whenever I reved the engine, the squeeling sound was there.

I would like to get some ideas on how to trouble shoot.

Thanks

Drop the belt on a COLD engine and then run it for 30 seconds. That will tell you if the noise is from one of the accessories the belt drives or if is elsewhere.

Also, how's your power steering fluid level? Those pumps can make some pretty bizarre noises on cars if they are sucking air. Also, once air gets in there, it can sometimes take a while (and some lock-to-lock turning) to bleed the air back out of the system.

Terry's suggestion is better -- start with the belt itself, then move down to checking the accessories like a PS pump. Just don't run for very long without the belt on! :eek:

Cheers, John

I checked the power steering level several months ago and added a bit a fluid.

Do you have experience taking the idler pulley off (ie the one in the center of all the pulleys)? Does the fan need to come off to take the idler off. I was going to loosen the serpertine and turn the idler to see if it was bad.

I appreciate your advice and will try it.

The key is to remove the belt, see if the noise is gone and if so, check every pulley by hand.

The idler pulley can be removed if the tenison on the belt is released. Is a 10 minute job.

I was going to short cut it. I will take your advice and remove the belt and see what I get.

Thanks for letting me know that the idler pulley removal is a 10 minute job.

The one item you cant check by hand is the tensioner pivot arm that the tensioner spring and damper shock attach to.

It has no bearings, rather a sacrificial sleeve insert that rides the 17mm hex head pin attached through the pivot arm into the timing chain cover.

The sleeve wears out eventually and can squeak; or wobble and cause vibration at the spring/shock. The easiest way to replace it is to pull the radiator. If you have small hands AND dont mind losing some skin IT IS possible to do so by pulling sheet metal crossmemebr and pulling the rad forward and only removing the shroud and fan itself.

Sounds like you need tto pay special attention to your AC clutch.

I have had the same squeeling sound when the compressor kicks in on my 85 380SE. I increase the tension on the belt on the idler pulley and no more noise. Sound is from the belt slipping on the pulley. I have to do this about every 3-4 months as evidently the pulley attachment works loose and tension is reduced.

From about the early nineties on the tensioner changed and tension was provided by a spring that pulled up on a pivot arm. Backlash is controled by a damper shock on the opposite end of the pivot arm.

I pulled the tensioner arm, without pulling the radiator. It seemed fine. I regreased the sleeve and washer behind it. I also replaced the tensioner spring.

I checked alternator, water pump, power steering, idler pulley, air conditioner compressor and fan clutch for ease of rotation. All seemed fine except for fan clutch. Fan clutch has resistance but turned smoothly.

There is no chirping or squeeling when car is running and fan belt is removed.

After starting the car, the chirping noise occurs for about 4 minutes; doesn't matter whether the air conditioner is turned on or not. When I rev the engine, I get a loud squeeling noise. After 4 minutes, no chirping or squeeling.

I need more assistance with troubleshooting.


Thanks

Confirm it is not caused by low fluid level of the PS pump. Assuming not, it sounds like you've got a bearing somewhere that only acts up when tension/torque is applied by the belt turning against it.

You may need to use your mech stethoscope (18" screwdriver or wood dowel) and carefully touch it down on each accessory in order to listen to their bearings while engine is running.

Power steering fluid is fine.

What do you think about the fan clutch? What kind of symptoms occur when it fails? It turns smoothly but it won't spin freely as it has internal friction.

take a bar of soap and rub it on the belt both sides of the belt, this quiets mine for a few days, mine is caused by a misaligned/bad tension pullley (cheap ass replacement Meyle) going to order the Febi pulley.

Ok, try removing the belt again and check each pulley for axial play (facing the pulley you want to see if you can press in on the left edge and pull out on the right edge or vice versa). I guess you could call it "wobble". I had the A/C pulley bearing go out on mine and found it by doing this.

The fan clutch sounds normal. Symptoms of a bad one are temperature gauge readings above 80 that don't resolve themselves and fan spinning for over three seconds after engine shutdown. With the hood open, you can hear it cut in and out once the engine is hot. Fan will "roar" when clutch engages.

A loud squealing noise would usually indicate a slipping belt. This could either be due to low belt tension or low belt friction - due to surface glazing, cracking, contamination, etc. As a slipping belt heats up, its surface may soften and the noise lessen. Belts are typically pretty cheap. Clean all pulleys, replace belt, and make certain tension is correctly adjusted before wasting time looking for other causes.

Steve