Unbelievable......

[alpine944]

On Tuesday, I was on my way to my mechanic to have my timing belt retensioned and all that good stuff. I'm about 10 miles away stopped at a traffic light, and the car stalls. Won't start back up. Great, have it towed to the shop. THis morning, I get a call from my mechanic, and he tells me my timing belt is broke. Bent valves (probably since the engine was running ) Can you believe the timing of this.... if I would have took it in one day sooner, the would have caught it before major damage would have been done. Happy New Year's to me......

[AFJuvat]

Damn......

My sympathies.

AFJuvat

[Mike B]

That is bad luck...When did you have the new belt installed...Wondering why it broke if it was new...I would want to look at that belt...

Hopefully with the engine idling you did only minor damage...Best of luck.

[alpine944]

No, it wasn't a new belt. It was replaced at 60,000 miles. I purchased the car a year and a half ago with 66,000 miles on it. Right now it's got just under 80,000. So, I was just going with some preventative maintenance so to speak. But, I guess you shouldn't count on every 30,000 to have this done.

[Diesel]

What a pain. Why do these belts break so often? I've had cars with timing belts for years and never a problem. Even a few diesels. Bad design or something.

[Blackfoot]

that really is too bad. i was going to say that the belt might not have had much mileage on it but it could have been an old one, not run often, but then i reread your post and that doesn't seem likely. not even 20k and it lets go...bad.

[SoCal Driver]

Why do the 944 timing belts break more often than other examples?

I think it's the water pump. The belt is bent backwards to friction drive the water pump. This dictates that the belt has to be fairly high tensioned compared to other examples where the belt is not bent backwards.

Also there is a tendency to over tension the belt when installed because the mechanic doesn't have the tool. Note that the newer water pumps come with a fence to keep the belt teeth from hitting because of possible slapping -- a loose belt.

Combine these stresses and you have the belting fracture and a broken belt.

I don't deny that the idler/tension pulleys, these are the toothed ones that have the eccentric for adjusting, may bind and cause belt breakage. I've never seen one frozen in the last 19 years. I've replaced a couple that had very worn bearings. Note these are NOT the smooth surface rollers that almost touch the belts.

[overkill]

Dude, stay away from me!!!! Argh, that is really BAD LUCK!!!! Damn!

[alpine944]

Update: Just talked to the mechanic, 2 bent valves for sure. Estimate is at $1300 and growing (depending on more valve damage).

[SoCal Driver]

The lesson here is to never, never, never ever trust the PO's last timing belt replacement.

First thing you do to a used 944 is CHANGE THE TIMING BELT!!!!

[thamlin000]

Sorry to hear that.

I took my car into the shop a few weeks ago due to a knocking noise I was hear upon cold start ups. It lasted about 20 sec. This noise went away after the the car was reved up a bit and/or warm. My shop told me that my t-belt was loose and that the noise was the belt flapping against the cover! Pretty scary since I dove the car for a week or so in this condition with no idea it was t-belt related. It was a surprise since I replaced the belt 3.5 years and 30k mi ago. So now I'm safe. I guess from now on I'll replace it every 30k mi.

BTW, what all does retensioning the t-belt involve? I plan on doing it in 2k mi.

[Blackfoot]

i think he meant that he just had the belt replaced while in the shop and needs retensioning in 2k.

[Moneyguy1]

Water belt may or may not be a factor, but I just changed a belt on a 1997 Chrysler V6 which also runs the water pump off the back of the timing belt in the V between the cylinder banks. 85k on the belt; some crazing, a couple of loose teeth, but otherwise OK. I think the 944 problem is a lousy design in the first place complicated by the expansion inherent in an aluminum block. The Chrysler is an iron block and the belt actually "bends back" on itself, taking the linearity curse out of the expansion. Posts on this and/or other such sites have made statements like "I change my belt every Spring and don't have any problems." Wow. OTOH, I have had a Porsche mechanic tell me that the new belts do not require retensioning. I don't know what to tell you. Maybe it is partially harmonics set up on the long side of the belt. Did Porsche ever come up with a fix? Nope...even though this has caused many 944 cars to be permanently taken off the road. Not so many 928s, though, since the expansion differential is partially offset by the v-8 configuration described above.

Sometimes I wonder about the so-called engineering excellence of Zuffenhausen.

[ae1969]

I agree with moneyguy it was truly a bad design with no fixes for over a 9 year run on the production of the vehicle (82-91 ROW)....... and frankly I would throw in the #2 rod issue as being a close second for bad engineering flaws......

Overall these cars are incredibly well built. You really only appreciate the precise engineering that went into putting these blocks together when you actually put one back together......

(As I wait for my lower crankcase to shrink in the freezer)

[todwic]

HeHe. I'm putting new rings and rod bearings in mine. I got two in and had to come in and listen to O.P.P.s for a little while so that I can get unmad. g/l with that, ae.

[ImClueless]

hey todwic, how is it going, im getting ready to do the same thing myself. Any pitfalls or tips..

[todwic]

I finally got the rings in, and the rod bearings and caps on. My biggest tip is: Don't try to jimmy the rings in, get a compressor, and use lots of motor oil and they'll glide right in. I tried putting the bearing on the rod and then pushing the piston in and the bearing kept falling out. what I ended up doing is pushing the piston in sans bearing and when it's almost all the way in, gobbing on assy. lube and sticking it to the crank. I then spun the bearing around untill it was even with the rod face, and pushed it onto the rod, using a pair of picks to line it up in the niche. Then pushing the piston the rest of the way in. worked great.

[ImClueless]

cool, thanks man. im sure this is going to be a nightmare. Sounds like were doing the same thing, just about a complete rebuild. I think the only thing im not replacing will be the actual pistons.

[todwic]

I'm keeping the oil and water pumps, crank, rods pistons and caps, the head, valves, n such (just had a head job 20k ago; just taking everything apart to get all the little bits of stuff out of it.

[ImClueless]

to be honest the only things im going to replace is what comes in the ZIM'S rebuild kit.

LOL