noticed a squealling noise from my focus couple of weeks ago, only there once warm and at idle speed (900rpm)
When I first heard the noise and had a quick listen to the area I assumed Alternator as in that area of the engine bay (driverside towards bulkhead) also seemed that it was when lights and blower on etc....
Anyway ordered new alternator and fitted it today, noticed the belt tensioner was worn so also replaced that (£72!!!!!!) and a new belt.
fitted back together...warms up and the idle drops to 900rpm and you guessed it squeal................ raise the revs slowly and its gone by 1100-1200rpm.
When I turn the engine off while squeal is there it continues almost as a pressure drop??? I'd say its slightly longer than the final engine rotations as the ignition is switched off.

Any ideas? has new alternator,belt and belt tensioner. noise is from the top side of the engine driverside towards bulkhead(near end of fuel rail)

its doesn't effect how the car drives or idles in anyway.

hopefully someone out there on this cold winters night that knows!! lol.

 

Did you fit a new belt idler pulley at the same time as the tensioner. This was the problem with mine. Bearing had gone in the centre of it.

See the diagram here:-http://www.focusfanatics.com/forum/showthread.php?t=43557

 

Didn't replace it but checked all of the pulleys to see if any needed replacing while apart, Thats how I found the tensioner pulley was worn.

 

no ideas anyone?

 

not the aircon pump?

 

no the aircon pump is near the front of the engine and the noise is at the back top of the engine, but it continues for approx 2-3seconds once the engine is switched off as though its pressure dropping from something?

 

no clever guys here?

 

had similar prob on my FRP, i drowned every moving part with WD40 a couple of time, job done, squealling gone

 

Is it effecting the performance at all Dan?

 

performance is fine, even before the alternator and tensioner change.
To me its not a mechanical squeal thats what is confusing.

 

Problem solved and if didn't cost a penny.

 

And the survey says......................

 

Was it an air leak or something on the inlet? ST170's are prone to problems with the inlets and the cam that switches from long to short runner inlet.

 

It was actually caused by the breather pipe from the cam cover being blocked off, Reason being it has a powertec induction kits and where the breather pipe fitting is welded on the filter is actually blocked from the inside by the mass air meter once fitted and tightened up.

This caused pressure in the cam cover, released the oil cap and pressure come out then noise stopped, tightened cap and couple of minutes running and squealling noise again!!

All sorted now though. give it a service also and drives great now.. Not sure wether to sell it or keep it now as been thinking about a Impreza, Leon cupr R or Octavia vRS hmmm