motoist

First some baseline info:
1987 944S
128k miles


Well, my engine is locked up- ie will not turn over. I took off the timing belt, and it seems to be in great shape- almost new looking. The balance shaft belt on the other hand is worn, and off the bottom balancer shaft sprocket. I haven't looked at the timing chain yet either. I am thinking that perhaps the starter may have shorted or something. The engine will start to turn then come to a grinding halt. It quit very quietly one day, like it ran out of gas or something. Can the balance shafts cause this? Is there some electrical failsafe in-case I run out of gas? thanks
any help is appreciated

nine-44

Doesn't sound good man, I'd be checking the tensioner and cam chain

SoCal Driver

Pistons are hitting something. Possibly a broken valve head. Or it could be what is called hydro lock.

A leaking injector will fill the cylinder and the fuel will not compress. Pull the dipstick out and smell the end. If there is a strong gas smell pull the plugs and see if the engine can be rotated.

Note on the timing belt. The proper way to pull a timing belt is to lock the engine at TDC with a special toothed clamp at the flywheel. This is an interference engine and will bend the valves if the timing belt is off more than two teeth. With the "S" model there is a cam drive chain and tensioner under the valve cover. This fails and can either jam the works causing the timing belt to break or just drop the intake cam from the engine cycle. Either way this is very bad.

Tensioning the timing belt is critical too. If it's too loose the belt will slap and jump teeth. If too tight it will fail prematurely. If it's just right then you can get 30,000 out of it but most of us change it at 15,000 just to be safe.

Manning

You change yours at 15K? Holy crap! The last time I changed mine it had close to 50K on it.

I had understood that if your lose a balance shaft belt you can run into a contact issue as a result. Yea or nay?

tifosiman

I've never heard that. Mine snapped and I limped it home. I think that it is bad, though, because of the chance that the balance shaft belt may get tangled in the timing belt and then ka-boom.

Tifo

SoCal Driver

Sometimes the balance belt takes out the timing belt. Sometimes it doesn't.

I had my balance belt break and just wrap up in the bottom of the belt covers. Didn't take out the timing belt. Yes I replaced them anyway.

I think that 50,000 miles is driving on borrowed time.

Us early 944 drivers don't have any auto tensioner so we play it safe.

Tabor

I think Porsche says 45,000 miles for a timing belt. I know some people that replace them at 30,000. I just replaced mine at 32,000 and it looked warn but good. On the other hand my balance shaft belt teeth were getting very brittle.

Dave951M

Just for peace of mind, you should really replace it at 30k or yearly. It's cheaper than a broken one.

SoCal Driver

On review the balance belt might have gone under the timing belt and caused it to jump teeth. Would have broken the timing belt if there was not an auto tensioner.

Peckster

It quit while running, so it couldn't be hydrolock from gasoline. Now if you hit a big puddle, maybe.

Tabor

You seem to be confused as to what type of auto-tensioner the later 944 cars have. They do not constantly tension the timing belt like the hydraulic tensioner on the 968. Their is merely a spring loaded arm that you use to tension the belt by releasing the spring pressure, then tightening down the arm. The only purpose of the "auto tensioner" is so that you don't have to pay $500 for the P9201.

Edit- Except you do still need a P9201 for the balance shaft belt.

SoCal Driver

You are saying that the spring tensioner does not keep spring pressure against the belt?

Hmm... Not having one in front of me I would think the idea of an auto tensioner is just that; to keep the belt tensioned. Guess I'll have to check the manuals.


Either way I bet his valves are more than likely toast along with a few valve seats.

Tabor

The spring can only be compressed when the car is disassembled and not running. With the car assembled the spring can not be compressed because just like the earlier cars, the tensioner is "tightened in place." The spring is only used to set the timing belt to a pre-determined tension, while you have the car disassembled.

Scootin159

or yearly? I have no problem with the 30k replacement (which is still quite a bit before the reccomended 45k, but what if you're like me and drive less than 10k/year? Mine does sit over the winter, so that's probably not too good for the belt, but I do start it and let it run about once a month or so.

Tabor

Maybe every 3 years? The belt I just pulled off of my car was 3.5 years old with 32k miles on it. It still looked to be in decent shape.