83na944

I just changed out my timing belt and reused the old balance belt. I now have a small,strange vibration. I assume I have set one of the balance shafts off by one tooth. But the vibration is not as bad as I expected for an out of time balance shaft. It's more of a buzz. There is no visible sign of vibration when I look at the engine.

Has anyone had this experience? How much did it vibrate?

TIA.

Dick Dobson

I recently (December) had new belts and other done to my 968 ('92 with 185,000 miles) and it has a vibration at idle that was not there before the work by my friend and mechanic. I'm going to have him check it out for balance shaft alignment soon.

Dick

Conor

Why would you reuse the old belt? A replacment is so cheap, why risk it?

Micah

I'm guessing your balance shaft is out 180 deg. Check out:

<a href="http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic;f=24;t=000800#000004" target="_blank">http://forums.rennlist.com/forums/ultimatebb.php?ubb=get_topic;f=24;t=000800#000004</a>

Micah

83na944

The belts were only about 15 months old. Several months ago I replaced the water pump and lower balance shaft seal. I noticed that the timing belt had a small nick so the plan was to replace it as insurance, but I felt the balance shaft belt would be ok. I finally got a chance to replce the timing belt last weekend and noticed that the upper balance shaft was leaking, so I replaced it.

The symptoms are pretty much the same as described in the thread that Micah posted. On the other hand, I'm pretty sure I'm not 180 degrees off. The shaft keyways both point up when the shafts are in time.

So I'll plan to go back in this weekend armed with a new belt and very, very carefully time the shafts. As you say, the belts are cheap.

BTW, does anyone know where to find a thin wrench to adjust the tensioning sprocket?

adrial

You should replace the balance belt...

You're already there...you might as well...

That is unless you're going to replace the belts when the balance belt has met its service life (3 years/30k miles or 4 years/40k miles...whichever you go by).

If the balance belt goes it could take the timing belt with it...and you know what that means.

83na944

The vibration is much less today than yesterday, or maybe I'm just getting accustomed to the vibration. Anyway, I will replace the belt if the dealer has one in stock.

BTW, I've actually replaced the belts more often than recommended because of failed seals or water pumps.

I update the thread after I replce the belt to let everyone know what I found.

Ahmet

Belts are cheap? I see that the Porsche belt is $90, contitech replacement is $60, and an aftermarket no name belt is $20... These are my costs, chanses are unless you work for a parts warehouse or distributor you won't get them at this price (or maybe I'm being played a trick on, didn't look up these myself, but a balance shaft tensioner just locked up and I'm doing belts)...
Ahmet

ahofam123

I bought my balance shaft belt which I believe to be a contitech for $50. I'll check to see if it indeed is a contitech.

83na944

I ordered one today for $59, but that includes overnight shipping. I'll let you know the brand tomorrow.

Melchior

My shop checked the belts on my car '90 944S2 and they said that the timing marks are all lined up. The vibration that I have is very evident at idle and is a high buzz in the shifter at higher RPM's. At first, they told me that it was bad motor mounts, so I changed them with OEM mounts and $200 later the problem still exists. Now they say that perhaps the rubber center on my clutch may be deteriorating thus causing an 'out of balance' vibration. Or maybe the clutch has lost one of it's springs. The clutch was replaced 2 1/2 years ago and still has over half the usable thickness. Is this the possible reason for my vibration or should I take the car to a different shop? My current shop is Porsche Only and has been working on Porsches for 13 years. I am unsure have many 944S2's they have worked on but they seem to get a lot of 951's and 944 N/A's.

who1

FWIW, when I did my timing belt, I tried to line up the marks I made as best I could, but I got a vibration that I didn't have before. I can't remember if it was at idle and/or somewhere around 3000rpm. Anyway, I went back in and moved the balance shaft one tooth to line up my marks a little better and the vibration went away.

Brian Wilson

allzims.com has good deals on belts and pullys. $120 for the whole deal.

how's knoxville?

83na944

UPDATE
Removed the cover, checked the timing marks, everything was aligned. "O" showing through round hole in upper sprocket cover and through square hole on the lower.

Replaced belt, spent hours getting the tension correct, and buttoned it all back up. Buzz still there.

Removed the alternator/AC belt. Buzz still there.

Pulled the sprocket covers, everything looked ok, but decided to remove the sprockets to be sure. Everything still checks out.

Ran the motor without the balance belt. Still buzzes, not much different actually. That suprises me.

Anyway, I plan to retension the timing belt tomorrow. Then I'll try moving the sprockets one tooth to see if it makes a difference.

If anyone hasa any ideas, let me know.

83na944

Problem resolved.

As expected it was a balance shaft problem. I moved the lower balance shaft back one tooth and the engine runs smooth as silk. In other words, the balance shaft timing mark does not align with the mark on the rear cover.

I can't imagine how this happens. At some time in the past, the dealer or another shop apparently replaced the original sprockets with the newer sprockets that have no "U" stamped on it as the '83 is supposed to have. I seriously doubt the sprocket wore out. My bet is that they replaced the sprockets to prevent confusion. I really don't appreciate that.

Anyway, thanks for all the comments and ideas. ANd remember to paint the timing marks before you remove the sprockets, just in case they don't align.