Sander_Baas

He guys,

I’m new here and have a question about some sound that comes from my timingbelt I think

But first I will quickly introduce myself.
I’m Sander Baas
27 years old
Live in the Netherlands (city: Eindhoven)
Work as Engineer at DAF Trucks (a PACCAR company like Peterbilt and Kenworth)
This is my first Porsche (since February 2012) But definitively not my first car or motorbike

Some info about the car:
Its an S4 form 87 (km on car 290.000 (kilometers not miles))
Has an engine from a GT year 89 (km on engine 170.000(kilometers not miles))
5 speed manual
Full maintenance history of the car, sadly not the engine

The problem:
The car has since I replaced (TB, WP, tensioner rebuild, including Rollers) a rattle/moaning sound. This sound comes up if the engine is warming up. If the engine is cold you don’t hear it. And then slowly it builds up till this rattle/moaning sound.

I first thought it is the new water pump and tensioner roller that need to wear in, but now 300km further it is still there.
I checked with a screw driver as stethoscope on the water pump but there the sound does not come from. Before I start pulling stuff I first want to ask you guys what you think.

I uploaded two YouTube movies one “cold” no rattle


and one “warm” (5min warm-up) with rattle that I hear.


What do you guys think it is? I personally think it’s the tensioner roller, although I replaced it.

Btw the belt is a Conti one (I know some disagree with this one)
The waterpump is a Laso one
Tensioner does still leak (think there is still some air trapped that heats up and expands and pushes the oil out thru the rubber boot)
Belt runs good on the gears, (if I look thru the top holes of the belt cover not 100% in the middle but does not slide about orso)
No air-pump any more. so that one can not be it

and here a picture of the car:

WallyP

Failing ball or roller bearing.

I would not run the engine until it was replaced. If the bearing comes apart, you could wipe out the engine (bent valves - many Euros to repair).

supercedar

I had a similar noise when I accidently lost coolant up front replacing hoses. It did go away after awhile, the belt does not like getting wet is what I figure.
Thomas

WallyP

One quick test that might help.

Have a squirt bottle (or squirt gun) full of water ready.

Crank the engine. Squirt water on the crank pulley, so that the water gets on the friction surface of the accessory belts. If the noise changes, it is likely to be an accessory belt that is worn or loose - they can make some strange noises.

If the noise is definitely coming from under the timing belt cover, I would replace the faulty bearing ASAP.

PorKen

Even new water pumps can be bad.

I hear the noise, albeit quieter, in the cold video, too.

It sounds like a power steering pump foaming noise, but that usually is bad cold, then goes away when warm.


If you do have to take off the covers again, might as well replace that leaky tensioner and wobbly roller with a PKT.

dfrhodes

+1 on bearing, or possible loose accessory pulley?

Leon Speed

My guess would be alternator bearings or power steering pump. Easily checked by taking the belts off. Then again, WallyP and Porken have much much much more experience then I do, so listen to them

Btw: why no A/C?

Oja, welkom

davek9

How did u tension the belt, could b the belt tension is set too tight.
That's why it makes noise when hot and eng expands.

Sander_Baas

Thanks for all the reply`s so far.

@WallyP, I checked with the bottle trick. did not do anything,

@PorKen, I don’t know yet about your tensioner. I’m still a bit skeptical about it. As an engineer I hope my colleagues at Porsche designed the stock tensioner like this for a reason.

@Leon Speed, (from the country that won from us with soccer on the European championship )
Why no AC? sadly the old owner took the pump and condenser out. still looking for one and some hoses, so if you have any let me know.
Und danke für die holländische Begrüßung !

@davek9, I tensiond the belt with the Kempf tool.


So I now took the covers off and saw that the belt does not align so good on the pulley of the tensioner it sticks a bit over.

You guys have any thoughts on that? It’s the S4 water pump so no bolt to hold the idler but the little shaft. Seems unlikely to me that, this one is bent. Even has the extra arm going back to the water pump for support.

think I pull the whole stuff of again and check If I see anything that’s faulty.

Bilal928S4

Please post a picture on how the belt is tracking over the CAM pulleys.

Sander_Baas

Here is a picture of how the belt tracks, bit tricky to see. but have the top covers back on to run the engine with the middle one removed.
It does not run perfectly in the middle but still kinda okay (bit on the outside)

I took the middle cover off to listen on some points with a stethoscope, this proved that the sound is the strongest at the tensioner roller so i think its clear that this new one is broken.

order now a 100% original Porsche one hopefully that one wont fail.

dcrasta

Looks like the belt is not centered on the tensioner pulley. This makes me think the arm or the bolt is bent.

Keep in mind the 928 factory tensioner was designed ~ 1979. PK'tensioner is pretty nice. You tensioner hardware looks much better than most, however I would not rule out bad bearing in the pulley. Also, is that a continental belt ?

Bilal928S4

There are bushings that need to be replaced when the pulleys are R&Red. Did you replace the bushings? The other thing is that the pulley should be centered on the bearing. It is just a press fit so it can move. Use an appropriate socket and vice to center the bearing.
Hope that helps.

928porschemangreg

I would look at the rear of the covers to see if anything like the belt is rubbing, scratching the inside of the covers especially the lower cover.

dfrhodes

is the crank gear on all the way with both flange washers curved out? if not, could be pushing the belt out some before it reaches the tensioner pulley.

Of course this would affect the oil gear tracking too, but hard to tell from the pick. more importantly though - where is the sound coming from now that you have the covers off?