When I was checking the timing belt last I remembered that it did not seem to have rounded teeth, which I thought the cam belt for a 91 S4 should have. According to PET there are four different t-belt part numbers, the early belts 78-82 which part numbers end in 00, the 83-86 and 88-90 belt that ends in 40, the 87 belt that ends in 30 and the 91-95 belt that ends in 50.

The shop ticket from the guy who put my new belt on has the correct number 928 105 157 50, but the belt just does not look the way I expect it to, more trapazoidal than hemisperical at the tip. I have included a few digital shots showing some different views of the belt.

I have driven the car about 1500 miles and some of the identifing numbers are gone. There are two sets of numbers that are readable but don't fit the 928 part numbering system.
Can anyone tell me if this looks right.

Thanks
Chuck

<img src="http://www.users.qwest.net/~ccadams/109-0919_IMG.jpg" alt=" - " />
<img src="http://www.users.qwest.net/~ccadams/109-0929_IMG.jpg" alt=" - " />
<img src="http://www.users.qwest.net/~ccadams/109-0931_IMG.jpg" alt=" - " />

 

What year is your 928?

 

Orest,
1991 S4
Chuck

 

This is what my recently installed belt looks like. It seems quite different! <img src="http://www.momentoffame.com/uploads/aa47b4508cc8cad3455656faee9de345Belt-fit%20s.jpg" alt=" - " />
<img src="http://www.momentoffame.com/uploads/6a95804009a02c68473d07564bd18d3cnew%20belt%20numbers%20S.jpg" alt=" - " />

 

You have the old belt on your car. Looks like the shop guy screwed up. Even if his supplier furnished the wrong belt, the mechanic should have noticed.

Given that a belt failure will severely damage your engine, I think that the shop should change the belt to the proper one - ASAP!

 

The belt appears to be the correct belt but it looks like at one point it has slipped and knocked off the top of the teeth. Another possibility is that the crankshaft or oil pump gear is the wrong type and is wearing the top of the new belt off. Either way it needs to come apart.

 

It does look like something is takeing the top of the tooth off.

Only one way to find out. She's gotta come apart. Yuck.

Question, unless I'm mistaken, there is no reason for the belt to be missing identifyer numers. Expecaly after only a few thousand miles. I know I habitualy put white out on my belts, to mark which ones goes to what, that away I don't have to look up the part numbers. The white out doesn't come off. Neighter does the belt's markings, usualy.

I do know, before my old t-belt went, it mannaged to get realy lose. In the process it was continualy slapping on the houseings, and this rubbed the markings off. Later, before I retensioned my new t-belt, the belt got lose enough to let it slap something, and that smeared some of the markings. The lose belt was because I screwed up on the first tensioning. That was a lucky catch.

Don't want to scare you, but I can't think of a reason that would remove the markings on the belt, AND not be scary.

Good luck

 

If the 83 cars have the new belt (HTD), soes that mean that the 83 and newer cars have the same tooth profile for belts, pullies, etc.?. Is the "round" profile the HTD, or is the angled profile the HTD? -Ruf (with HTD belt, pullies etc. from Mark A.'s place, by PO)

 

Ruff

83+ has the round tooth design.

The round tooth design is the HTD.

All the pulleys are the same for 83+

IIRC, the 83 was the first year that got the additional idler. Not realy used, much, but helps to stabilize the belt. (also what froze, and screwed up my old belt...)

 

I posted the same question about a week ago and got the same reply - wrong type of belt.

My belt looks exactly like yours. The teeth are supposed to look like that, the tops have not been knocked off or whatever. That's how it looks when new.

I still haven't changed my belt, but I guess I have to.

What I really wonder about is that some belt manufacturers that make general purpose toothed belts for different sorts of belt-driven applications, have belts with a tooth profile like yours, yet they claim that the belts CAN be used in HTD pulleys which have the round tooth shape... However, considering the damage that can be caused by a broken timing belt, I want to be absolutely sure. Does anyone have any cold facts on this?

Best regards
Niklas Kampe
1987 S4 5-speed manual
Finland, Europe

 

Niklas,

I called my local shop today, Exotic Motorworks in Phoenix, they looked at the picture of my belt and are certain that it is OK. That is the way this manufactuer belt makes this belt.

By the way, Exotic is NOT the shop that put this belt on. The belt was installed by a guy up in Denver where I purchased the car.

I guess I am at least as confused as I was when I posted. The fellow at Exotic specializes in water cooled porches, 928, 944 etc. and has at least a decade of experiance to back up his opinion. However I have to respect the tons of experiance that Wally and Mark have.

The question might be "Do I feel lucky...well do I, punk".

Niklas, do you know who manufactured your belt? Are there any numbers you can read? We might have the same part.

Mark,
The belt does not look to be abused, cut or otherwise crushed into this shape by a pully with the wrong shape teeth. Also the cam, pully marks all line up OK so I don't see how it could have slipped. Also the belt is uniform in quality throughout its length.

 

Look at the two red boxes.

Is this a rough spot on the gear causing the wear seen on the belt?


Greg

 

928quest, After seeing the "red boxes", all I can say is "Will ya break 5 teeth or 6?" - Ruf

 

Why not contact the belt manufacturer & have them put their seal of approval on it?

 

As my 85 is having it's belt done this week I have been curious about this post. Is the Porsche OEM belt too pricey or not as suitable as aftermarket belts? My shop said they only use OEM parts.