sharky47

The other day I found out what was wrong with my car, the brand new timing belt had lost all the teeth where it looped around the drive pulley. What would cause this, everything else seems to be in good condition, except the valves of course. Why would a new belt start to shed teeth, it is an '87 so it has the auto tensioner. I ordered a new belt yesterday and I'm hoping I got away with little or no valve damage since it happened at idle, but I don't want to go through this again. I need to determine the cause of this to avoid having it eat another belt, any ideas?

Bill

Sharky47,

That is an interesting avatar you have. You didn't by chance live in Waco at one time did you?

As for the Question,

EDIT: Just noticed you have an 944S, that is a two cam motor isn't it? I don't know much about the two cam heads but I believe most of the below will apply. I also remember reading about a nylon block that fails on the S heads. Anyone with an "S" car that can add to my list?

1. Belt installed with timing marks incorrect.
2. Belt tension incorrect (factory states that the auto tensioner must be checked with belt gauge).
3. Pulley or Idler seized.
4. Water pump seized.
5. Belt threaded incorrectly.
6. Belt tensioned on a warm engine (must be dead cold).
7. Do you have the updated water pump that has the belt separating plate? If not, belt caught onto itself at the waterpump.
8. Cam/Lifter/Valve seized.
9. Rotor on distributor seized.

Thats about all I can think of.

I allways GENTLY spin the motor by hand after the installation of a new belt. If it is incorrect and the engine locks, you have no valve damage.

To determine if you have bent valves perform a compression check or cylinder leak down. No compression = bent valves.

My guess is that you bent one or more of your exhaust valves. The starter motor developes enough torque to bend the valves.

Good Luck.

sharky47

All the rollers and water pump are in good shape, the pump is the updated kind and look fairly new. I guess it could be a valve/lifter/cam.

mouse

Though you probably bought the belt yourself, how do you know that it was a brand new timing belt? Is it because someone told you it was new, or do you know for sure it is? When I bought my car the sales guy showed me the belt through the check hole and told me it was brand new. Turns out it wasn't, and it cost me when it broke just weeks after buying the car. Just wanted to throw that out there.

Bob S. 1984 Silver

Sharky...

You live in an area with a lot of sand and grit. Everything the others say, I agree with. However, I did one job in which the culprit was the lower timing gear(cog). The owner had been running it without the engine shroud and over time, sand wore down the teeth of the cog to the point where, after a brief time, the belt would begin to shred. Just another thing to check!!

sharky47

As far as the new t-belt goes, yes I bought it new from vertex and changed it myself to make sure something like this wouldn't happen. Bob S., are you talking about the actual drive pulley on the crankshaft?

Bob S. 1984 Silver

You Betcha!!!

sharky47

Maybe I'll pull it off and check it, if it does need to be replaced, where do I get one?

Tremelune

Did you retension it after 1500 miles? Did it even go 50?

sharky47

It went to about 1900, and yes I did reset it at 1600.

951and944S

Sharky This may sound like a dumb question but are you sure you have the 'S' belt.
It's wider than the 944na and turbo belt due to the extra stress of having to turn 2 cams via the coupling chain.
As a matter of fact it's recommended that you use the 968 if I remember correctly, it's interchangeable and is even wider than the original S belt.
Lastly, the S had an extra idler (smooth roller) that the turbo and NA do not have. You won't see it in any parts illustration if you're not looking at S/S2/968 specific pictures.

OK so NOT lastly....
What procedure are you following to do the timing belt change...? Simple removal and install..?

I know if I purchased an S/S2/968 I'd follow the factory procedure to the letter at least for the first belt replacement and to insure that someone didn't make any mistakes prior to purchase.

The 944S and others in that engine family have very high compression (little clearance at piston-valve). The 944S and family have a slotted camshaft drive gear and adjustable rotor IIRC.

The proper procedure requires the valve cover to be removed. Mount two affixable dial gauges to the cylinder head to access (with handcrafted extensions i.e. thread one end of a coathanger with a mild curve at the end) the #1 intake lifter and the #1 piston. Bring the engine (rotating by hand) up to TDC (highest reading on dial indicator on piston), set to -0-.......

Shucks. Sharky....Email me, I'll scan and copy the correct procedure for you..

Cam timing is critical on these engines for optimum performance. The procedure is strongly recommended to assure proper camshaft timing.
IIRC the margin of error is .056 of an inch when degreeing....

944t@bellsouth.net

I purchased an S car 7-8 years ago with the engine in a box, I assembled the engine and have driven the car for 7 years and 150,000 miles with NO cam chain trouble, oil tensioner, cambelt, bent valves.....etc.
There are guys here with nearly 300,000 miles on these engines. Don't let the "oh no the S" opinions scare you away from this great car...
Out of ALL the 944's for normal production you own the rarest of them all....

sharky47

Thanks for all the feedback! I did specify that the belt was for an "S" when i ordered it, but who knows if they got it right. The first belt I ordered from NAPA was visually thinner so I ordered another one from vertex and it matched up with the one that was on it.

951and944S

sharky maybe there's someone here who has all of the technical service bulletins on a database, I'm quite certain there's one recommending the 968 belt.

afx

The same thing happend to my car. A strip of about 8 teeth just came off, and killed my exhaust valves. I think in my case it was just because the belt was getting old that the teeth came off. Either way, I just replaced all the rollers and water pump just to be sure.

Bill

</font><blockquote><font size="1" face="Verdana,Tahoma,Helvetica">quote:</font><hr /><font size="2" face="Verdana,Tahoma,Helvetica"> The first belt I ordered from NAPA </font><hr /></blockquote><font size="2" face="Verdana,Tahoma,Helvetica">NAPA....NAPA???

Sharky,

Do not risk thousands of dollars (Valves, Cams, Head) to save a couple of bucks!!!

GO TO PORSCHE TO GET THIS CRITICAL PART!!!! <img border="0" alt="[nono]" title="" src="graemlins/nono.gif" />