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william_b_noble

HELP totally Bizarre 944S timing belt issue

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note - this same issue is also posted on the renlist site in case different folks read the two sites - so if you've seen it there, it's the same problem....

ok, we have here a real WTF situation - perhaps one of you folks has encountered this before and can offer some thoughts -

1. the car - 1987 944S - the 16 valve kind

2. the situation - replaced front seals (crankshaft and balance shafts), which involved removing the old timing belt, tensioner, the pulley and sprokets on the crank, replacing the seals and putting it all back together. no problem, right?

WRONG ---- put it back together with new tensioning roller and new belt. Set tensioner to minimum position to install, and belt would not fit - about one or two teeth two short.

So, what have I done:

1. removed new belt and new roller, replaced wtih original belt and roller - the original combo is too short.

2. verified proper belt (1 inch wide) with proper number of teeth. verified proper part number on new and old roller.

3. removed drive sprocket from crankshaft and reversed it - didn't think this would matter, and it didn't - still too short. Note that the manual for the regular (8 valve) cars shows a sprocket on the crank that has a flange, and the flange goes away from the engine and towards the balance shaft drive sprocket - I had speculated that I might have reversed this and the belt might be riding on the flange - well, the sprocket in my car has no flange, so reversing doesn't matter.

4. checked part number on original sprocket - it is cast with the

part number 944-105-125-05. So, just to be safe, I look up in PET 6 (and

also in the PDF you can DL directly from Porsche), and (it's MG1, SG 2) you

find this part, item 14 on the exploded view, and the part number is

944-105-125-06. -- ok, minor WTF, but this sprocket was on the car and working, so it couldn't have grown or something.

5. took tensioner to my milling machine, enlongated the adjustment slot by about 3/16 inch - put it all back together again - that helped, but belt is still too tight if I force it on, and tensioner still on stop (max spring compression).

6. started car (with belt too tight) and let it idle for about 10 minutes and shut it down - tensioner still on stop.

So, this makes no sense - I noticed nothing amiss when I took it apart, so I am pretty darned sure the tensioner was not bottomed out at that time. I have not removed the head nor the sprocket on the cam shaft - only the sprocket on the crank and the tensioner. Didn't mess with water pump either. Old parts don't fit, new parts don't fit, and they are too close for it to be something really stupid like putting the tensioner in wrong (after all, it goes over those 3 studs - you can't put it in off by a "tooth" or something like a distributor on a 38 plymouth.

So come on guys - someone must have a theory on this - I realy don't want to just mill the slot a little longer and make the problem disappear, though I may have to. (oh, and I notice that the S has a different tensioner too than the regular cars - wonder what the difference is?)

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the S motors were the first to come with the wide belt and automatic tensioner. the interesting thing is that you state you put the original parts on and they are too tight, talk about WTF?

the new ones were tight going together, you would have to get them started on the cam gear and roll them on. these belts also stretch quite a bit, thats why you have to retetion after 2,000 miles.

I never had to mill out the adjustment slot so I don't know why that had to be done. did you use a Porsche belt?

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