Noises from engine compartment after front-of-engine-service

[ronined]

I recently had the front-of-engine-service completed on my '87 924S. I was driving the car around recently (first time since the service I have driven it) and notice a whine that increased in frequency as engine rpm increased. Also, before the service I noted just how silky smooth this engine ran, now it isn't so smooth, vibrating a bit and making an odd noise, sort-of a BRRRR noise that also increases with engine rpm. The car runs well, in the sense that there is no loss in performance. So what in the world is going on here? Is the timing belt too tight? The balance belt to tight/loose? Perhaps a bad tensioner?

TIA,

Ed

[dangerous]

The whine is normal when you have the belts and rollers replaced. It will fade away in time.

Unusual vibration may indicate the balancing shafts are not alligned properly. may want to tak eit back to where you had the work done and ask them to double check. If they don't work on 944s much, it is possible they got one of the balancing shafts 180 degrees off....but it's an easy mistake even if they do work on 944s.

[Icey1174]

Mine did the same thing. It is finally fading away.

[legoland951]

The balance shaft belt is supposed to have a 0.8mm gap between it and the idler roller. If the belt is actually touching the roller, which is not supposed to spin all the time, it will wear the roller and create the "whine", which is a familiar sound of a 944 but NOT supposed to be there when you have new belts and rollers. Also, the whine can be from overtightening of the timing belt, which will prematurely wear your tensioner bearing along with the water pump bearing. Take pictures of the belt assembly and have someone who is very familiar with a 944 specifically check your work.

[924Sman]

Yes sir^^^ what he said....Also the BS are off time. Never had a new belt whine, only if too tight or touching the idle roller on the BB.

Re check all the alignments and rollers. Make certain the can tensioner roller flange is nearest the block not the tensioner. It only takes a tooth or so off on the BS to cause vibrations.

Dal

[dangerous]

Originally posted by legoland951
The balance shaft belt is supposed to have a 0.8mm gap between it and the idler roller. If the belt is actually touching the roller, which is not supposed to spin all the time, it will wear the roller and create the "whine", which is a familiar sound of a 944 but NOT supposed to be there when you have new belts and rollers. Also, the whine can be from overtightening of the timing belt, which will prematurely wear your tensioner bearing along with the water pump bearing. Take pictures of the belt assembly and have someone who is very familiar with a 944 specifically check your work.

hmmm
Interesting.....my experience has been the opposite. I've never seen a 944 with fresh belts/rollers that didn't whine.

[Porsche-O-Phile]

Do the 1500-mile retension. The whining should diminish considerably after that.

[ronined]

Thanks for the replies. I will hopefully be able to take some pictures this weekend. The bad thing is that the shop that did the work is in my home town 230 miles away.

Ed