Keith924S

951sickness; Just wondering if this noise is apparent immediately after cold start-up or after the engine reaches operating temp?

951sickness

Hi Keith, the noise begins after the car has reached operating temperature. Even under warm start stituations it will begin pretty quickly. When the car is ice cold, it is quiet.

Keith924S

Hello Sickness: We might be in the same boat. I have same sound when motor reaches operating temp. Fine on idle when started cold.

This is a brand new cam belt and balance belt on a 2.5 NA. The sound is somewhat of a grinding sound of varying pitch/duration but goes away when given a few hundred more rpm than idle. I can hear it from in the car with window down at idle and saying it's annoying would be an understatement. I noticed it when I first picked the car up but it wasn't as pronounced.

I spoke with the INDY shop owner that did the replacement and handled the sale of this (new to me) 87 924S. He is a very good guy and says that no matter what the findings are he will cover it. He actually called me to tell me that somebody just gave him a new black dash cover and it was free to me if I'd like it and that he got the rest of the keys from the P.O.

He ruled out the waterpump saying that out of hundreds and hundreds of re-built waterpumps he has had only 1 bad one and it went a month after installation. I've bought nothing but re-built waterpumps for many years on other makes and I've never had a problem either.

Guessing on the phone, he thinks one of the belts is on too tight. He says the motor goes "long" when hot and that might be causing it. I'm due very soon for the tension adjust. Not the same of course, but even on my 4 litre jeep, I notice when the serpentine belt is either too loose or too tight it makes the motor sound like sh*t (bizzare set-up on that jeep motor).

I will certainly mention the "dirty" cam belt thought to him. It's got to get fixed!

951sickness

Hi Keith,

I definitely sounds like we are in the same boat. At this point I would have to agree with the mechanic as I have gone through the pain of replacing three waterpumps, the last one a new unit. I'm going to get a factory belt and give it another try. The belt that is on the car now is supposed to be an OEM belt but was not sourced from the dealer and did not have "Porsche" marked on it anywhere. I should have the new belt installed by Thursday night. I'll keep you posted.

Gerry

Keith924S

OK Gerry, I'll let you know the results of my situation as well, although I don't expect to get the car down there until a week tomorrow.

Keith

Danno

Perhaps to build a knowledge base with some replicable data, could you guys get the belt tensions before and after your swaps? It'd be interesting to see whether the occurances of noise goes along with belt-tension. Thanks

Keith924S

OK Danno, I'll ask the shop to record the values before and after. Should be no problem as they are very much apart of the local Porsche club in this area and are very agreeable folks. (mantisracing.com/was only working on netscape last time I checked)

951sickness

Right now I have the tension set at 2.7 since the belt has been on and off the car over ten times and tensioned a few more times on top of that. I read in the 944 garage that the 87 and later cars with the automatic tensioner still need the new belt to be at the higher tension. At this point I'm going to set the new belt at the 2.7 and readjust often. It really isn't hard to do and it is really accurate (at least in my case). I was curious as to how accurate the automatic tensioner was so I tensioned the belt as the manual says then used the P9201 to measure the tension... 2.7 on the dot. Just picked up my new Cambelt from the dealer today ($35). From the look of it, it appears to be of higher quality. I'll let you know how it goes.

Danno

Hmmm, interesting. Another guy said his automatic tensioner sets his belt to 3.5.... Ok, at least I've got some data to compare now...

951sickness

Well, maybe I can explain this one. If the engine is not setup properly, it will set the belt at a tension different than the specified 2.7 If I remember correctly, if you bring the engine to TDC and then turn it counter clockwise 1.5 teeth and then release the tensioner, you will get a figure closer to 3.5 When I did this (yeah, I was kinda bored and was thinking "...hmmm, I wonder if...") I got a tension of 4.0, if my memory serves me correctly. The tensioner should be released when the engine is at TDC.

951sickness

Hello all. Well, the problem has been solved. It was the Cambelt that was causing the noise. I don't know if it was crud on the smooth side of the belt or the belt construction itself. With both belts side by side, you could more easily feel the bumps of the teeth through the smooth side of the belt on the belt that was not bought at the dealer. In any case I set the cambelt to 3.2 and the B/S belt to 3.9 (new style) and drove the car a little and let it idle for ten minutes...no bearing noise, just the whine of the belts. All I know is I will never use a Cambelt from any other source other than the dealer. BTW the belt from the dealer was made by Gates in the UK.

951sickness

Well, here is a shot of the section of belt with residue on the outer edge of the belt. In the picture it is the shiny stuff towards the lower edge of the belt. Hard to believe something so small can cause a bad bearing sound. Also it appears that the belt stretched significantly because when I put the new belt on the car the belt was 1/2 a tooth off.

Keith924S

My nasty sounding grinding noise (only when motor was hot)is now over as well. It was a loose balance belt. I got them both retensioned this afternoon along with a Dynomax Super Turbo Muffler which turned out great. Belts do suck, no doubt about that.

Keith924S

That was me that posted above and it came out as Stephen_B. Just thought I'd let it be known what the result was.