b

Hello everyone,

I'm a complete novice & am confused with belt terminology. are people writing about the same thing when discussing the timing belts or cam and balance belts? i have a hayes 944 repaair manual that discusses the cam and balance belts and doesn't address 'timing belts' and a 944/968 book that has a brief paragraph on the 'cam timing' belt. can anyone clarify the differences for me?

also, i got the cam and balance belts, rollers, balance tensioner, etc. replaced recently, but i wasn't told to bring the car back in after 2000 miles, and i've driven about 4k since the work. will this pose any problems, and should i take the car in now?

thanks,
bcy
'87 944s

ps. the last time i posted i had a question about an intermittent thumping/knocking from the rt rear. i got some wonderful advice, which prompted me to take the car into a mechanic, who (only after pulling the rear end apart) found that the rt rear axel was damaged at the gearbox. so if anyone has those symptoms & it's not the bearings or the cv joint, you may want to check the axel itself.

jim968

Timing belt / cam belt, same thing... a toothed (synchronous) belt that transmits power & mechanical timing from crank to cam shaft. All (?) four-stroke engines have either a belt, chain, or gear drive for this purpose. For an interference engine like ours, big nasty stuff happens when the belt breaks (actually, usually strips off teeth). Also drives H20 pump on 944's.

Balance shaft belt... toothed on _both_ sides; only used on a few engines; located in the same general area as the timing belt; drives eccentrically-weighted shafts that counter the vibration inherent in a big four-cylinder. Also a problem if it breaks, since it may take the timing belt with it. Transmits just enough power to spin the balance shafts.

Yep, even if your car has the auto-tensioner, it's only on the timing belt... so you need a re-tension on the balance shaft belt, at least. Since it's a much looser belt, I'm _guessing_ that it's less critical, but I really wouldn't want to be wrong....

Jim, returning to the salt mine....

b

Jim, thanks for the info. i'll plan on taking the car in then

--bcy

Tabor

No!!!

You NEED to have you belts re-tensioned. The "auto-tensioner" for you cam-belt does not "auto-tension" while you drive. Only when you loosen a bolt/nut combo.

You really need to have your cam-belt retensioned at:

1,500 miles and 16,500 miles after you have a new one installed. At 31,500 miles, have a new one installed.

Dan in Pasadena

I also was (am?) a novice to 944's. Bought my NA in March and had the timing and balance shaft belts as well as a host of other stuff done just like you. $1850 worth!
But it probably saved me thousands.
All because this board was nice enough to give me a heads up and tell me NOT to start/drive this 6 years-stored car before having the belts changed. But no one mentioned re-tensioning after 1500 miles. I was going along thinking I could just wait til 30K miles and have them swapped out again. So far, 7K miles and it runs like a champ. The car is in fact faster than it was after coming back from the shop, if that's possible. So my question, how crucial is it to have the re-tensioning done? Is this real or Porsche paranoia? Like 1500 mile oil changes?

Bob S. 1984 Silver

True or not, my old Porsche trained mechanic in Roachester (before I moved I had the whole magilla done) told me that belt technology has "done away" with the need to retension.

As I said, this is what I was told. My car is a 1984 with about 75k. It is driven quite sanely (some might even say too conservatively...I'm old....) So, if the engine tanks sometime in the future, I will probably part out the poor old dear and buy something that doesn't generate so much paranoia.

Bob S. (well within the speed limit; driving everyone absolutely nuts)

Tabor

When I re-tensioned my belt after 1,500 miles, it have streched noticably.

However, when I re-tensioned it after 16,500 miles, it had hardly streched one bit. I would at least retension it after 1,500 miles.

jim968

Tom... your old Porsche mechanic obviously had not seen the balance shaft belt on my 968... replaced by PO, apparently never retensioned, I inspected about 7K after it was replaced... dam' good thing I did. It was so floppy-sloppy it was pitiful, and a minor miricale that it hadn't either jumped time or come off.

Jim... who actually scared himself with that one...

Crackhead944S

b

I noticed that you have an "S". Not to give you any more worries, but here goes. You have a timing belt that drives one cam and a chain that runs from one cam to the other. Depending on your milage you may want to inspect/replace the tensioner and chain.

I am a novice as well and it took me less than hour to replace the tensioner with the instructions from the following site: Tensioner replacement

Actually, it took me under an hour if you don't count the time wasted on the stripped bolt on the reinstallation. I successfully installed a Heli-coil in about an hour and I tapped it so SLOWLY my bother was laughing.

BTW he had a great recommendation for tapping. Dab grease in the hole to be tapped to collect filings. Simply wipe away the grease when you are finished.

Good luck

Mark
88 944S

b

thanks everyone for the advice. i haven't motivated to take the car to the shop yet, but, i'm planning on running a pca autocross on sunday & will definitely have the tech inspectors take a look at the belts.

thanks again
--b

T86951

hey B

You have 4000 miles on the belts and they for sure need re-adjusted cause they do streach in the first few thousand miles so they most likely are a little loose now. get them retensioned by a person that knows what they are doing. Bacially they need tightened a hair but just a hair. At least take it back to the shop that did the work and ask them to check them. Last time I put belts on mine I went like 20,000 miles without retioning and they were flopping real bad, I could hear it on a winter cold start, goes away when warm cause the motor expands. A loose belt strips the teeth off the belt and bends valves. I have had that happen. Get it retentioned!!!

Mark944na86

It is said God looks after fools, horses and little children. Idiots who don't take tensioning their timing belts seriously are on their own, however. If you want some motivation, read some of the recent threads concerning the results of Craig944's timing belt breakage.

-Mark 86 944 NA