Ethre

Updated: Looks like this was the result of a worn gear. See last post for information.

Hello all - you've got a great forum going here. Its really quite an extensive resource.

I'm the proud new owner of a 1982 5-speed (US). Its far from perfect (front seats need redoing, minor hail damage to hood/roof, general wear and tear), but that's to be expected with a 30 year old car. It is a pleasure to drive.

Anyway, does anyone have any experience with timing belts on the 16vs failing prematurely? From what I have found and read, this could be due to:

-Wear on the camshaft gears
-Over-tension on belt
-Bent camshafts(?) due to over-tension on belt?
-Stuck waterpump
-Failed tensioner
-Others?

The reason I ask, is that I had an almost new (<5000 mile) the timing belt slip ~20 degrees two weeks after I bought my 82*. Right now its at the shop waiting on a new belt to arrive (courtesy of 928 Intl), and I am praying that none of the valves are damaged.
I would have assumed this was incorrect tension, but it appears that my car has been through several timing belts rather quickly. I was going through my receipts (have a nice big folder), and found that the previous owner replaced the belt twice, once in November of 2008 and once April of 2009. After contacting the previous-previous owner, I discovered that the belt had broken on him - which explains the need for one in 2008 (water pump was also replaced, so it may be that pump failure broke the belt). However, I can see no reason at all for a replacement five months later (this was something that only dawned on me recently - I had at first not noticed that the water pump replacement kit came with a new timing belt).

On the other hand, could it be that the previous owner didn't realize the timing belts needed to be re-tensioned after being broken in(they do, right?)?
I would ask him if he did, but for some reason he doesn't seem to want to talk to me.

I appreciate any of you taking the time to read this.

*I should have checked the timing belt myself when I got it, but after seeing that the accessories belts had been correctly replaced I made the (apparently incorrect) assumption that the previous owner could competently replace the timing belt.

hacker-pschorr

Round tooth belt with square tooth cam / oil pump gears?

Ethre

Hacker - According to the receipts(from 928 Specialists), both belts were the 77-82 Continental. That should be square toothed, correct? There's nothing in the receipts to indicate the gears were updated, so I am inclined to believe they would be the originals (for the square toothed belts).
Unfortunately, I can't go out and verify this myself, as the car's at a mechanic.

ammonman

What was the failure that allowed the timing to change? Did the belt teeth strip or is it just out of time?

Mike

blown 87

Turn your PM's on.

hacker-pschorr

IIRC you need to have X number of posts before you are allowed to PM

Mrmerlin

if you have a good mechanic he should be recommending that you swap out the square tooth gears for the new updated HTD gears.
this should take care of a failing belt also consider to run the belt at the lower end of the Kempf tool window

Ethre

Active Member feature - fixed now I believe.

Ammonman: I don't believe any of the teeth stripped, however again I can't verify this right now. I will be giving the mechanic a call in the morning to ask.

GregBBRD

Relax, the valves will not hit the pistons, on your engine.

The "early" engines (yours) had different cam, oil pump, and drive gears. They have a "square" profile. These usually get changed to the "round" profile gears, when they wear out. You probably need to determine which version of gears your vehicle has, in order to get the proper timing belt. Make sure that all four gears are of the same design...miss matching will cause belts to wear out very quickly!

The cam and oil pump gears are hard anodized aluminum. If the hard anodized coating wears off, the aluminum will wear very quickly and quickly damage the cam belt. This is easy to determine...if the gears have shiny aluminum showing....they are worn out.

On high mileage cars, I've seen engines that have had the cam and oil pump gears replaced, but the small gear on the crankshaft doesn't get replaced, because it is steel. This gear does all the actual work and also gets very worn. This can quickly chew up a belt.

Any oil that gets on the belt will quickly soften and ruin the belt. These early cars have cam seals and o-rings that have a tendency to leak. Any oil leaks, in this area, need to be repaired, prior to any belt replacement.

One of "our" members invented a replacement tensioner assembly, which seems very adequate for these 16 valve engines. This eliminates the need to retesion the belt and might be perfect for your needs. While the inventor doesn't have an engineering background and designed this device "by trial and error", this replacement tensioner seems to be working very well on many engines. You might take a long, hard look at his replacement tensioner. It would save you a lot of time and effort trying to adequately rebuild the stock tensioner and "idler" arm. "Porkensioner" on your search engine should get you good returns.

Dean_Fuller

Where is Alabama are you?

Ethre

MrMerlin - The newer gears are supposed to be easier on the belts, correct?
Wouldn't setting to the low end of the Kempf window increase the odds of slippage though?

Thanks for the reassurance Greg. I've read several times where the 82US is supposed to be non-interference, but I'm still going to be tense until I get the all clear.

I know the two camshaft gears have been replaced (1998), but the replacement gears are listed as the square-toothed versions. One of the idler rollers seems to have been replaced with a 85-86 version though. Verifying this has just gone to the top of my list though.

I have no mention of the crankshaft gear being changed though - so (even if it somehow is in good condition) this sounds like something that to do asap.

I've looked at the porkensioner, and may consider that in the future.

ROG100

Good advice to update to the later style tooth design but not totally necessary if money is tight.
I would never want to argue with Mr Brown 8>) however you will find that your all your four gears are steel and hard to wear out (unless they have already been replaced). Unlike the later aluminum cam and oil pump gears.
On my early cars pre 83 I have stayed with the earlier design of belt and had no problems. If you are going to track the car take Mr. Merlin’s advice and upgrade.
Let me know if I can help with your parts supply.

pcar928fan

My '81 w/ the same engine as you '82 broke a T-belt long before I got the car but they just retimed the cams and put a new belt on...no harm no foul! Piece of cake!

Landseer

I've had to replace a couple of worn metal gears. A crankshaft gear and an oil pump gear on 84. They developed some sharp edges too.

Mike Frye

I'm going to go with this.

On mine, the gears were badly worn and 'dished' on the face, but if you looked at the profile (or an inexperienced mechanic did) you might not have noticed that the edge of the belt had a little burr or lip that could only be felt with the edge of your finger or fingernail.

If the shop that changed it didn't notice this, they may have just swapped out the belt. Also, since your engine is non-interference they may have figured they could just let it go that time without any real potential damage if they were wrong.