Whining Cam Belt?

[rudidelange]

I have replaced the 2 belts, a roller, sump gasket (never again!!) and all the front oil seals on a '83, 944. Set the tension with the special porsche tool - all according to specs. Replaced the manifold gaskets, some hoses, and vacuum pipes. Car runs like a dream ... but it seems that my cam belt is whining. I find it difficult to locate the noise, does not sound like a vacuum leak - could be not sure, more like a high pitched noise that increases as the revs go up. Sounds like some small turbo or supercharger type-of-noise... I have rechecked the belts with the special tool after 1000 kilometers, slacked the cam belt to 3, but still its there
Car has 200 000 km's, oil was changed every 7000 - 9000 kilometers, mint condition.
Any ideas what this could be?

[mambodave]

Yep..they wine when you change the belts. All of mine did for the first 500 miles or so.

[mike944]

Sounds like you might have the balance belt guide roller set too tight. The guide roller is the one with no teeth, in the lower left (looking at the engine from the front of the car) just above the bottom balance shaft. This roller is by far the most difficult to adjust correctly, since it has so much slop in it. The roller is probably pushing on the straight belt run from the lower tension roller to the upper shaft. with the cover off, you can "eyeball" it. this roller should barely deflect the belt (0 - 1mm) when a tooth is sitting right against it. If it's not hitting there, it might be contacting the teeth on the back of the lower balance shaft pulley.

Sorry, this is hard to describe without pictures, but this roller is often the cause of belt whine, especially when everything's tensioned to spec.

[bluebullet]

mine does the same thing. My idler pulley for the balance shaft belt is worn out and sloppy as heck. I have the new one sitting in the glovebox for like 2 weeks now..just havent had the chance to put it in. I pulled the front covers off and ran the engine, and put a long socket extension in my ear and just went around putting the end on each pulley while the car was running. I got near the waterpump and it was a little loud, which had me fearing that I had to replace it, even though the motor was built less than 10K ago. Then I put it on the idler pulley and the noise was unbearable.

Should the idler pulley be putting any tension on the belt? or just enough to slide over it? That and when the car is off, I can push the timing belt off the driverside idler pulley with some force. Should I have it retensioned?

[Porsche-O-Phile]

Normal. It'll go away in about 1,000 miles. Don't forget the 1,500 mile retension!

[rudidelange]

Well, this weekend I'll remove the covers, listen with an extension where exatly the noise comes from, recheck the tension on the balance shaft belt, check the setting/position of the balance shaft belt tensioner, wiil report back after the weekend.

[Zero10]

It's quite possible one of the rollers/tensioners that you didn't replace has failed. When the belts were changed, the initial tension is much higher than the tension was on the old belt. The increased stress tends to cause older worn-out rollers to fail.

FWIW, 7000-9000km's for an oil change is a bit long, 5000km's is about right.

[bazar01]

My new aftermarket cam timing belt from Zims whined for about 2k miles even after retentioning at 1.5k miles. I used the 90 deg. twist method. Now the whine is gone after 2k.
The new timing belt has to seat in to the timing pulley profile so just give it some more time but keep checking on belt tension at 1.5k, 5k and 10k to be safe.

[hoff944]

Just had my belts changed too. Ditto on the whining stopping. My Mech who does the belts said it is normal.

[Zero10]

FWIW, mine still haven't quieted down, it's been about 7000-8000km's now. I think maybe the new belt tension killed one of my rollers, but I can't pin the noise down to any one.