98 S70 GLT warmup noise when not driven for days

Post by **Atis** » 15 Dec 2014, 16:45

Hello all,

I have a new symptom...

If the car is not driven for some days, there is a strange noise above ~1500 rpm. It is proportional to the engine revs, but higher pitched and sounds like a rotating plastic is getting contact with a nother plastic. Somewhere between a whining and a sssshhhhh noise. It does not lasts for long, so as soon as it starts to warm up, it disappears.

I had this noise before, but as I was just before the timing belt and serpentine belt change (with all associated part), I was hoping that it will solve the issue. After the belt change everything went well, but yesterday the noise was there again.

So if any of you had something similar before, please help in the diagnosis.

Post by **misha** » 15 Dec 2014, 17:19

As soon as possible,URGENTLY,check if timing belt makes contact with it's plastic shield.
If not...it would be a serpentine belt plastic roller or air pump.

Does it makes sound even if the car is not moving,or just when driving?

Post by **scot850** » 15 Dec 2014, 23:15

I'd follow misha's suggestions in order as the most likely to cause expensive damage. The fact that it coincides with going away when warm chances are it is the air pump failing. This only runs as the car warms up and pushes more air into the engine to reduce emissions. These fail when the valve (is the GLT a turbo?) which sits by the turbo fails they tend to fail open, which allows condensation to run down the feed pipe to the air (SAS) pump filling it an eventually it seizes.

Neil.

Post by **Atis** » 16 Dec 2014, 06:38

I will check it as soon as I can get back to the car.
As all of the rollers and waterpump was changed (OEM or bluebox) I do not suspect a roller failure.

It is a light pressure turbo 2.0 model B5204T2 with manual transmission.
As it does not have SAS system, we can rule out the airpump.

What are the symptoms for power steering pump, alternator or AC compressor failure?
(these are the things which are in an untouched original state and rotating proportional to the engine rpms)

Post by **misha** » 16 Dec 2014, 07:52

I was talking about serpentine belt roller.

Ac should be turned off if there is no need for it.

Could be that alernator or ac compressor bearings are going bad.

Check a plastic serpentine belt roller.

Post by **Atis** » 16 Dec 2014, 09:52

I have changed timing and serpentine belt with all and every roller they are making contact with, so everything is brand new and the noise was there before the belt+roller change.

My wishful thinking is alternator or compressor, my fear is TB contact with plastic cover.

Post by **scot850** » 16 Dec 2014, 10:51

Just pull the timing belt outer cover and look. I had an issue with a warped belt cover on an 850, and eventually had to replace it to prevent the rubbing. They also become brittle with age, and the lower locating clips and the ones on the front side (closest to the alternator) warp and don't lock down.

I bought a new front cover, photo-copied the labels on the front of the original cover and stuck them to the front of the new cover with clear plastic film over them.

Neil.

Post by **Atis** » 03 Jan 2015, 14:08

It seems, that I have finally eliminated the problem.
I have checked the alternator by removing the serpentine belt and rotate it by hand. It had a slight rattling noise. It had some radial play but only in certain positions.
So I bought a set of bearings, plastic bearing "housing" (?nest?), slip rings and brushes.
At the end I kept the original brushes and slip rings and changed only the bearings, and the noise has gone (hopefully stays like this).

Pictures about the bearing change will come soon.

Post by **misha** » 03 Jan 2015, 19:43

Good job!

Post by **Atis** » 10 Jan 2015, 16:37

Thanks Misha!

Unfortunately the story continues.
The majority of the noise has gone but the plastic like sound remained.
It is much-much more quite, but to increase the plastic-y feeling there is a melt/burnt plastic smell within 20 second of start.
I am not that convinced right now that is engine rpm dependent...
At idle/revving I can not hear it only if the car is moving. It sounds a bit louder during engine brake.
It is a "constant" noise, not "whoosh-whoosh-whoosh" like.
After full warm up it goes away.

I have checked the TB contact 3 times, but did not found any conspicious. Tomorrow I will check it again.
To be honest I run out of ideas...

So any further advice will be highly appreciated.