Serpentine belt idler pulley... 1997 B5254FS

[giovannibianco]

Hello Everyone,

I possibly have an upcoming problem with my serpetine belt... Original symptom is
periodic squeal tha only happens once the car is warmed up.

See:

http://www.volvohowto.com/volvo-850-s70 ... g-diagram/

* Replaced the tensioner assembly and new belt (length 17xx mm) (noise still present)
* Changed routing of belt (new belt length 12xx mm) to avoid the A/C compressor in case
it was source of noise (noise still present)

Figured next test would be to change the idler wheel as it "seems" a bt loose.

Remove front wheel, serpentine belt etc. But...

The 12mm bolt that holds it on has been tightened by a gorilla! To the extent I can see
the bolt head is getting shiny i.e. starting to strip. Even using 6pt brake spanner. Damn!

My immediate thought to remove is to heat with my amazing induction heater... but this
will probably melt the wheel in the process.

Otherwise I notice that the tensioner assembly and idler wheel sit on some sort of bracketry
on the end of the engine... maybe the PS and AC pumps also attach? From below I can put my
finger up to the open end where the idler wheel bolt is threaded. Has anyone gone this route?
Drop the PS and AC pumps and remove this bracket (if I'm correct). Then remove aforementioned
bolt at leisure from the bracket on my work bench?? If indeed there is a bracket then bolts should be easier as
it's bolted to an aluminium block?

Or soak the idler wheel bolt threads in penetrating fluid for a week or so and re-visit?

I suppose I need to check the PS pump and alternator in case they are the noise source?

[scot850]

Is your induction heater small enough to reach the exposed thread at the back of the bracket? Penetrating oil is great if you can afford the time to let is soak (just don't use regular WD-40).

There is a large bracket as you have found that mounts the A/C compressor, PS pump, idler and alternator and you can remove it. May be worth considering if the first 2 suggestions don't work, especially if the bolt rounds the head or breaks.

Neil.

[giovannibianco]

Hello,

Thanks for the reply. Indeed once the PS pump is loosened off the bracketry (no need to disconnect any lines to get it out of the way) it was quite easy to remove the bracket. There's one very long bolt accessible from the alternator side that holds it.

With the bracket/wheel on the bench it required a long extension on a 6pt socket to safely remove the bolt. There's no way it was 25 Nm!!

But still even after:

* Tensioner changed;
* Idler wheel changed;
* AC pump bypassed

The belt squeal/squeak is still present! It is not constant as I can open the windows at times and there's silence, apart from normal engine noise.

I figure if it was the PS pump it would change noise wheel steering wheel is turned. The alternator feels smooth.
So the next conclusion is it has to be something on the timing belt circuit?
This was supposed to be done by a garage 2/3? years ago.
I'm wondering if the water pump could already be suspected as I did have to
top up the coolant lately.

Maybe should take off the timing covers and see if the water pump is dribbling...

[giovannibianco]

So an update to my previous update...

I mentioned that a squeaking noise still persisted after changing the tensioner and idler pulley on the serpentine (accessory) belt. I thought it might be the water pump as other possibilities had been "eliminated".

Well... I got the car up on a lift as the noise seemed to be coming from further back and indeed it seems that a baffle inside the muffler box has come loose/out of place. By moving the exhaust tip I could change the tone of the squeak. By holding the muffler I could eliminate it entirely. O2 sensors were firmly in place.

As the exhaust is not leaking I will not touch. We have two-yearly inspections here and a exhaust leak will be an instant fail.

It's an annoying noise but I will live with it as it means no more playing with the belts. I suppose whatever has come loose will eventually change place and the squeak may go away in time.

So, if you have a suspected belt noise... check around under the car first. Might save some time and bother?

[scot850]

Thanks for the update, and that is sure a weird issue. But glad you found the cause and now you know what it is you can decided when or if to fix it or live with it.

Neil.