mouse

Well, it's the second time my timing belt has gone in about one and a half years of ownership. (For those not familiar with my story, see "timeline of sorrow" in the archives) Anyway, it happened a few weeks ago, in the middle of christmas traffic at a local mall. I got it towed to my mechanic, and they confirmed what I had feared, it was the timing belt. They got the head off last week, and there's four bent valves. The timing belt looked just like the last one when it went-- several of the teeth were ripped off and disconnected from the outer part of the belt. As pissed as I am that I'm going to be paying a ton of money, again, I still love this car...but I can't afford to do this annually. Any thoughts on what could be causing this to happen and what I can do to fix it?

I originally thought when the belt went last year it was because the PO was overdue for a change, and that the dealership had lied to me when they said the belt was "newly replaced". But now I'm wondering if maybe the belt really was new, and there's some other problem that's causing the belt to slip.

For those wondering, I did get the belt retensioned after they replaced it last year. I now have a better mechanic than the one who did the first timing belt / valve job, one that I trust more. In fact my new mechanic had a hell of a time getting the crank pulley off, he thinks the guy that did it last time did a poor job. They're going to replace all the bad rollers, but that's what they did last year as well. Is it possible the old mechanic just did a ****ty job? I have a hard time believing that, because it had been nearly 15,000 miles since the first belt went and the car was running great. I would think if he did a crap job it would have went a lot quicker than that.

I'm having them replace both cam chain tensioner pads while they're in there, anything else I should have them look at? (I had the water pump replaced last year) It's pretty frustrating how much money I've put into this car, it's to the point where I could easily have bought a really nice 951 or 968 for less money. I guess the only positive in this whole mess is that now that my car is in peices I can easily install the wiring for my full boat Iceshark lighting kit!

Antonio951

Good thing you can see some light in the situation(iceshark lighting kit). Really sorry to hear what happend.

SeaCay

What brand was the belt?

pete944

Real sorry to hear that. How are your front seals? You might as well have them addressed while everything is opened up.

SoCal Driver

Teeth get ripped off when they hit each other passing at the water pump pulley. Belt slap from a loose belt. Should be a metal barrier mounted on the water pump to stop this. Also the extra smooth rollers are there to stop the timing belt from slapping.

I would also check that the depth of the teeth on the crank pulley are with in spec.

mouse

It's kind of hard to say what brand the belt was, the old mechanic listed a 944 part number for the belt on the service receipt, but that really only means it's a belt meant for my car. Most of the text is worn off the belt, but "made in UK" is legible, as well as the number "152", if that helps. My new mechanic is going to replace it with a Continental brand belt, which is an OEM supplier for Porsche.

Pete: I agree on the replacement of the seals, I'll have them check it out.

Socal: Can't there be other reasons for the teeth coming off, other than the belt slapping? My mechanic suggested the teeth on the crank pulley could be too sharp, is that possible? I said before that it was one of the rollers he had trouble taking off, but now that I think about it, it was the crank pulley...they're replacing that anyway.

Dave

I can't help noticing that the belt was just about due for it's second retensioning and I wonder if this had anything to do with it. If the tensoin had been wrong early on, it would be that much worse by 15,000 miles. You mentioned that you had the belt retensioned once, what was the mileage? If the first retension had been done too early, it might be the cause IMHO since it would not have had time to streach as much as it should before the retension, and could have been too loose shortly after the retensioning. Another posibility is that the first mechanic didn't set the tension properly, maybe he relied on the "automatic tensioner" which are not always accurate (Porsche specifies that the auto tensioner should be checked with the 9201).

mouse

The place that replaced the belt the first time said for me to come in at 800 miles to retension the belt. I thought that was a little early, so I put about 1200 on it before I brought it in to the shop. I wasn't aware of a mandatory retension at 15,000 miles, is that standard? About 3 months ago when my car had been running great for an eerily long period of time I went to my (new) mechanic and asked if he could check out the timing belt to make sure it was all in good order, and he said it wasn't necessary. Most people don't turn down easy work, so I just assumed he knew what he was talking about.

triscadek

That does suck, I'd think about checking it every 10,000 mi. or so in the future, regardless of what the mech. says.

jonnybgood

Sorry to hear of your disaster. You and I have had similar problems. I raised the issue of the crank pulley being worn or out of spec and was put off by my first mechanic. I will look in the PSM for the specification for the teeth on that pulley.

I had to have my belt re tensioned after 380 miles and then before the re tension on that I noticed excess rubber dust coming out of the inspection hole. I took it in for re tension to a new good mechanic and he could see nothing wrong. Being a bit up tight about T belt issues I told him to replace the belts. By taking them off he discovers that the tensioner roller had lost its grease and was spinning much more than a new part. The first mechanic swears it was new and I am sending it up north to him. As well I am making a warrantee claim. It could have been a bad part out of the box or he could have been lazy and not replaced the tensioning roller. I am describing all this because perhaps your original mechanic did not replace the tensioner roller. Apparently it requires taking out the tensioner and putting it into a vice to replace and some shops skimp there and don/t replace it.
I agree about the 15k re tension and a bit surprised that your mechanic didn't do it!?
I really enjoy my car but with the money I now have in this car I too could have had a turbo or a nice S2. I didn't want to have to replace an expensive turbo that was worn out. Well a turbo is cheap compared to what I have into this cylinder head. Oh well.

Dave

Normally the first retensioning is ~2000 miles, some say 1500-2000, some say 2000-2500, there should be a card that comes with the belt that tells you which interval is recommended by that manufacturer (I have had one of each). From there, Porsche recommends retensioning at 15,000 and 30,000 with replacement at 45,000. The first retensioning is due to the belt being stretched in it's first few cycles, if done too early the belt may stretch quite a bit more in the few hundred miles after the retensioning. this would leave you with a loose belt for a long interval!

SoCal Driver

I would like to see the teeth profile on the crank pulley if they pull it off. Possibly compare it to a new pulley.

I would think that if any pulley would wear it would be the crank as it sees a lot of road crud.

Dave951M

Ditto on the crank pulley. Those things do wear over time and it is quite possible for it to be putting extra stress on the belt because of worn teeth. It is also possible to put the crank pulley stuff on wrong resulting in a belt being slowly machined away until it fails.

Granite 944

Man, am I sorry to hear about your blight!!
There is a AAA mechanic's shop right here in town. There is a beautiful '73 911 Targa thats been sitting out back of his shop for about a year or so. (Breaking my heart, I've been trying to buy this car, the woman who owns it won't sell it) I've talked to the shop owner, he says the car is there because they can't come up with an injector pump, or parts for it! This is just an example (IMO of course) of why I REALLY believe in finding a mechanic who is pretty familiar with working on these Porsche's. A typical run of the mill type mechanic who doesn't deal much with these european cars ("bring it in for retension at 800 miles") is going to have some trying times........and their sure as hell not going to say anything to you about it. I don't know what your options are around there for mechanics, but if I wasn't going to do the work myself, I would indeed find a "certified/experienced" PORSCHE mechanic somewhere if I could.
You must have the updated water pump with the belt rail in your car. Maybe its a combination of to much slack in the belt (Dave above), and possibly bad tensioner or setting? I don't have enough experience with these cars........yet. I suppose it could be a bad crank pulley sprocket, but I bet its just not good mech. work....... anyway you look at it.
Hope you have much better luck with your mechanics and your car! God, thats gotta HURT!

RedlineMan

Bummer... But...

You obviously need to get WAAAAAY more fastidious about your belt maintenance. You also need a new mechanic... again! One of you should have insisted on checking the tension. If it were me as the mechanic, I would have in no uncertain terms.

I recommend tension at 1000-1500 from new, then every 10,000, change at 30k for track cars or 45k for street cars. Maybe overly cautious to some, but then again, it's never sucked to be me like it does to be you right now!



Teeth come off for the following reasons: Belt too loose and hitting itself (this will usually only wear them down unless the belt is too old). Roller seizure. Belt too old and teeth are dry rotting off.

I change the belts every year on my track car, and check tension before every event. I've used belts from every manufacturer out there, it seems, and they have all been good to me. Belts do not stretch the way they used to. In the old days, the factory belts were so soft and pliable they would almost fall off in 1000 miles. Nowadays, I rarely have to retension the cam belts much, if at all. The balance belts stretch a tad.

Rollers, belts, seals, pump, interval. The Fab Five!