Want to be

About a mile away from home i noticed my timing belt light turn on. My first thought the car was running fine and it was a false alarm due to the OS temperature. The car then began to make a weird chatter noise, i then decided to turn her off.

I called a wrecking truck and her taken home. I don't know the extent of the damage but i would guess i have some bent valve. Go figure, my winter project was to replace the timing belt.

Charley B

It sounds like it was still running OK when you shut it off. If that's the case I doubt you have valve damage, since it wouldn't be running if the belt actually broke. Something has obviously gone awry in the front of the motor so you need to pull the front covers and see what's up.

FiveElements

What year is the car? Not all 928 cars bend valves if the belt slips or beaks. If the belt does slip or break, the car would likely not even run. Check the belt rollers for bearing noise. Check the tensioner & connector to it.

FredR

Phil,

You did the sensible thing in the circumstances but like Charley said do not torture yourself suspecting the worst until you have diagnosed the problem [whatever it may be]. If the belt had snapped you would have known about it immediately- that a strange noise suddenly appeared whilst the engine was still running is bound to be worrysome.

Get the cambelt covers off and have a good look in there to see if you can spot anything obvious.

Good luck

Fred

jcorenman

Phil, what is the history of this car? It looks like you purchased it a couple of years ago, but I didn't find any info about it. From your comment I assume the TB has not been replaced since you purchased the car, but has it been checked? With 236K miles all four sprockets are likely due for replacement, if not already done.

But a non-fatal de-tensioning-- with new noises-- is most likely the water-pump bearings failing. The first step is to pull the covers and see what you've got, it's not a big job. Distributor caps, crank pulleys and belts, front engine harness, and some other bits-- no big deal. There are some good write-ups out there.

Please post some pic's of what you find.

From Phil's signature, I would say that it is a '87 S4 with 236K miles. Definitely an interference engine.

Want to be

It's an 87 S4

Tb needed tighten per the owner but had been changed.

The started to make some noise and I was afraid to press the gas pedal and shut her off.

Yes. I'll post what happen

Ifs it's the valves, I am sure I can get a friend to help me replace or repair.

The car was going down for the winter.

jcorenman

That was a sign of likely troubles to come, TB's do not need tightening unless something in there is failing.

The good news is that if the engine was running when you shut it off, then-- as mentioned above-- the belt did not jump timing and the valves are probably fine.

Jim Devine

This is one of the best write ups on doing the TB/WP. Shows what comes off & when with lots of pics.

http://dwaynesgarage.norcal928.org/1...0Procedure.htm

Imo000

But it would run if the belt jumped.

Charley B

Shhhhh.

Want to be

I was able to spend five minutes on the car today. Anyways the inspection window of the belt on both sides displays an intact belt. My mechanic friend said it was likely the belt skipped a tooth. In the cold weather the belt becomes hard and if it is loose, it could have skipped a tooth. I asked him how many teeth can the car skip. He said maybe one but he was not sure since he has never worked on a 928. 944's he has though

SeanR

If it's loose enough to jump teeth either something has broken in the timing belt assembly (roller/bushings/etc) or you would have been getting a warning much sooner. I'd pull the passenger side cam gear cover and check the tension of the belt properly. Until you actually get in there and look at it, everyone is just guessing what has gone on.

Have your mechanic pull both cam gear covers, set the engine to Top Dead Center (TDC) and then measure. If all three spots can be set to TDC then you've not skipped any teeth. Try this first and then report back to us.

destructo_low

My car jumped timing this morning on the way to work. I ran/ walked a mile to work. I arrived on time only because I left to try to get there early. Thank god for non interference sixteen valve motors. It's time for a tensioner and belt.

*edit - As far as running with a skipped belt, yes, it will run. Mine would idle incredibly bad and incredibly lean. My wideband was showing 22.4; 22.4 is what it reads in open air. I had fuel pressure, and my injectors are brand new. It will not have any power, and it will probably die if you even touch the gas.

I'm sure my belt has slipped because I had just downshifted, did a pull in second, and upon shifting to third, the car just coughed up a lung. I imagine the belt got pulled taught, then slackened when my rpms dropped during my shift, and it allowed the belt to slip.

I have had every accessory belt on my 928 engine snap because one was lose. The same thing happened, I was revving the engine, the belt(s) got pulled tight, and when I let off the gas, the slack threw one or more of the belts off, and it took out the others with it. I have a dent from the inside of my hood outwards, because I had no hood pad. The snapped belt slapped the underside of my hood, and it even knocked a big chip of paint off.

Hilton

Don't try to second guess - just lock the flywheel at 45degrees BTDC and take it all apart. At 236k miles and n unknown belt change by a PO who gave you the classic "it just needs a tighten" line, you really need to buy all the belt parts (sprockets, new water pump, bushings etc) and do it properly for peace of mind.

Also if the belt has stripped teeth,everything will still look normal through the inspection ports. Do NOT try to start the car because you think the belt looks ok from the back.

rgs944

At 236K I would bet the cam gears are in poor condition. Anyone know anything about someone making a replacement. I have not heard about that for a while now.