Diehard914

Hello,
First posting, new to 928's with recent purchase of a "cheap" '89 S4. The timing belt has been done recently but poorly and the belt started to fail when I caught it, shut if off still running and towed it home. It shredded and smoked but did not break - Thanks God for the silly aftermarket air cleaner that the PO fitted b/c the cam vents were left exposed so I could see the smoke from the hood when the belt started shredding. I have found the excellent S4 timing belt posting and I'm working slowing and diligently to replace. I bought all the goodies that the PO probably failed to do, the timing pulleys, bushings, and new water pump. He may have simply failed to have it retentioned.

Anyway, here's the question. So far I played the winning lottery ticket, timing was mostly retained. But it looks like the stretch or possible slip may have the driver side bank off by one tooth even though the pass side is perfect. (Pass side photo only posted b/c driver side is not yet fully removed but I can see the slight difference in distributor angle.) I see everyone does the adjustment at 45 deg for obvious reasons but if I don't match perfectly at TDC than I can't make marks at 45 deg as reference. How does one rectify the timing at 0 deg safety so that the 45 marks can be made???

First photo was just belt condition, second was taken at TDC.

Thanks,
Diehard

Landseer

Close enough right now, assuming DS is approximately aligned and crank is at TDC mark.

The belt tooth spacing alone will get you very close on the reassembly.

Mrmerlin

from the looks of the belt either the water pump seized or the tensioner roller . Either way replace all of the parts in the belt run use a new WP i see you got one.
Having the belt one tooth off wont damage anything,
get the timing marks so that its at 45 BTDC then mark the cams they will be about 4 teeth BTDC.
NOTE after you remove the crank damper 45DBTDC will have the keyway pointing at 3 O clock
and TDC will be at 4 O clock as you look at the crank
Both of the rotors will be pointing at roughly 3 o clock when the engine is at TDC

Tampa 928s

Make sure you check all your pulleys, tensioner and water pump that was a close one! Something caused this to come apart you missed a bullet do it right

docmirror

One more thing. It's likely that the pax side cam will sproing into a different location once the belt tension is off. The cam is sitting on one of the lobes, and it tends to bounce off the lobe with no belt. So, be prepared to wrench it around to the right spot when putting on the new belt, and make sure you put your own marks on the pulleys before removing the belt.

Welcome.

Diehard914

Hello again,
I noted that both Rotors are pointed near 3 o'clock while at TDC but the Driver side looks to be one tooth different than the pass side which is perfect. Do I rectify the timing at TDC first and how would i do it safely? Or do I turn to 45 BTDC and make my marks based on the Pass side which MrMerlin suggests will be 4 teeth BTDC and do the same 4 teeth on the driver side. Are they fully symetrical? Is it safe to align the driver side cam backwards one tooth at TDC to rectify before advancing to 45 deg BTDC? I know counterclockwise is evil for the crank but how about the cam. I know I sound paranoid but I was lucky this far and don't want to ruin my luck.
Thanks!

Landseer

Your ok. Rectified as its gonna get. They say up to 3 teeth off is ok.
Rotate to 45 BTDC (if you think it'll make it that far) and start surgery.
I like to make the 45 marks on the gears, just in case.
Its also possible to do them at TDC where they are, but if a cam springs you have trouble to recover.

blown 87

You got very lucky.

docmirror

I do em at TDC, but the 45deg is safer.

Tampa 928s

Take your plugs out it will make the turning a lot easier and precise.

Cosmo Kramer

Wow you were literally seconds away from catastrophic failure, glad you caught it!

Like others said, turn to 45 btdc and mark the cam gears. Get a flywheel lock to you can remove the crank bolt and dig in.

At least your cam gears look good from what I can see.

Diehard914

Despite my worries from the distributor position, the timing was perfect on the driver side bank as well, so moot point. From the looks of the belt on the left side, I am glad I missed that traffic light and saw the smoke, next stop was the interstate and certain doom.

I can mark the gear now and proceed to 45 BTDC and follow the awesome posting.

Thanks all,
Diehard

Diehard914

After a hard day at work slowly dismantling, I found the root cause. Mrmerlin was correct that the water pump had seized. The pump was labeled "Laso" just like my replacement, but it had a Metal Impeller. I take it if it was still the original it would have said "Porsche." The bearing had worn laterally until the pulley jammed against the outside of the wp housing. Looks like maybe it was overtensioned. My replacement is a Laso but a plastic impeller. The look fairly similar otherwise and I hope the new version has come a long way internally from this older one. My very last water pump bolt sheared off in the block so I made more work for myself. Other than that I am on to removing the tensioner. The idler pulley seem fine but I have new ones. The lowest pulleys seem original and spin very freely but no play when I rock on them so I guess they will remain. If I remember that lowest pulley assembly is very expensive by itself and does not seem to be a key player in tension of the belt.

Thanks for the help,
Diehard

docmirror

STOP. Do not proceed. Contact Roger at 928sRus. Get the right pump, or you could be back here again.

roger@928srus.com

Landseer

I have 2 porsche pumps in the trash can right now, both siezed.
One may have been an original install.
Happens.

PS, listen to Doc above for sure.