there must have been something wrong for it to fail that soon.

either you got unlucky and got a bad belt or something else failed or wasn't installed properly.

a timing belt should last much more than 18 months.

most people don't even change timing belts every 3 years. many cars timing belts are replaced every 90-100k and they don't fail.

I would think the teeth rip off usually if something seizes but mayb not.

I'd like to know the reason of the failure also.

 

This is an incorrect assumption. The crank has a nice heavy flywheel attached to it. The crank will not just stop when the belt breaks. The cam may stop pretty quickly, but will still move a little.

If you were lucky enough to avoid damage when the belt broke, the above will almost certainly do the damage. It's a natural reaction. When the motor dies, you think, oh it must have stalled and try to restart it. If any of the valves are open at that point, they will be bent when the piston comes up to meet it. The whirring is the classic sound it makes when there less compression than normal due to bent valves.

 

I'm confused too because if you tried to start the car after the belt broke, the starter is spinning the crank and moving the pistons, yes? As the piston contacts an extended valve I would also have thought it would bend that valve. Even turning the crank by hand could do it, couldn't it?

I hope all your valves are OK, but I can see why others are skeptical. Good luck with the fix. Please let us know how it turns out.

 

Sure, it's possible that there is no damage, but, in my opinion, and experience, highly unlikely.

I assume he checked with a compression test? What were the numbers?

 

Agreed.

Agreed.


If the motor is turning, even at idle, it will more than likely bend some valves. *Maybe* it will be less catastrophic than if you are on a hard 6000rpm charge.

 

Thanks for all the replies, I am also convinced that a valve or two are bent, though he still says I might be lucky. He has the new belts etc and I am almost tempted to order a rebuilt head & gasket set from 944online on a sale or return basis, just in case.

I had a chance to look at it again today, the old belt doesn't look cracked or frayed, just some teeth in a six inch section are totally stripped. No oil leaks, completely dry and all the rollers and tensioners are moving freely - I am at a loss as to why this would fail so soon, it's a conti belt new from the dealer and with a Porsche part#. I will post the date mark when it's off.

He is doing the work next week, too busy this week getting the race car out for a shake down on Friday at the new Moroso track I shall post pics and follow-ups here.

 

If the cam/cam gear is jammed somehow, it will cause the belt to strip. I have seen one head where the last person who removed the camtower left the dowel pin on the top of the head being kicked around by the cam lobes until it jammed against the camhousing stripping the belt and breaking the "P" out of the "Porsche" casting on top of the camtower. You may want to have the mechanic check the cam to see if spins freely just in case.

 

Order a replacement head?... Just take the existing head to a machine shop. I had mine fully rebuilt and milled both top and bottom for under $300. I'd expect the bill to be very similar if you are not milling it, but replacing a couple of valves instead. Pretty hard to find a rebuilt head in that price range, plus you'd have to deal with shipping and such.

 

i'm getting worried now. my belt is almost 3 years old now and 15,000 kms with new rollers, water pump. I'm going to replace my tensioner stud also when doing the belt.

if my belt breaks even with proper maintenance then i'd be pissed...... Are porsches just engineered to break and cost you more and more money?

 

944online offer a rebuilt head for $600 with a 1 year warranty, depending on the number of valves that need replacing I think that is a good deal and you can just bolt it on and not have to wait for a machine shop.

+ they are close to me so I can pick-up.

 

Porsches are engineered to push the performance envelope.

That comes with a price. ANY car that's 20-25 years old will require a lot of maintenance. Any performance car will require more.

You should see what repair bills are on a 20 year old Ferrari Testarossa. It would be cheaper to just buy another 944 every month.

 

Weren't you the same person that in another thread you were arguing with me when I said these aren't daily driver cars due to their old age and parts availability issues? Remember that conversation? You said something like washing and waxing and changing the oil were all that was needed or something like that?

Hmm.



They grow up so fast.

 

Wait, maybe it was V2 that said that. If so, I apologize. I get you two confused sometimes, I don't know why.

 

Thats interesting I got them 2 confused in the beginning too for whatever strange reason...

 

A machine shop should take 1-2 days, and you may want to ask 944online about what happens to the core charge when they find bent valves. You may not get the full core charge back.

$600 is pretty steep for a head rebuild. Typically machine shops will charge $30-$50 per valve, and ~$150 for a full head rebuild (including guides and seals), so in my $300 estimate that is 3-5 bent valves (Depending on pricing).

It's your car and if you are in a rush then take the quick route, but I'd still suggest calling some machine shops. Maybe the pricing down there is totally different and my advice is irrelevant.