High pitch squeeling upon letting off throttle 2009 Mk5 Jetta

**Black tsi** · 01-10-2017, 02:32 PM

Hey all, hoping someone can help out with some advice please.
Just done a road trip, Sydney to Toowomba 800+kms one way. Approx 12 hours.
Dropped off then headed back, maybe 30 mins down time.
We tag team drove but the car didn't get much rest.
Some serious kms but we used cruise control most of the way and didn't get heavy on the right foot at all.
It didn't miss a beat, she actually seemed to love it, getting around 6.4-6.5 litres per hundred on 98.

All was well until we hit the motorway on the way back just after Newcastle, around 100kms to Sydney.
Sitting on 110km/H cruise control on, a high pitch squeeling started out of no where.
i pulled over immediately.
Symptoms; squeeling and running rough (whole drive chain bucking around) high pitch squeeling coming from the engine bay.
Upon acceleration or mildly keeping pressure on the accelerator the noise goes away.
as soon as you let the accelerator off at all the high pitch squeeling comes back.

We had a rest on the side of the road for an hour off to let things cool down (didn't over heat but 20+ hours of solid driving, we thought she deserved a rest)

The noise was still there. I babied the car back home, short stints, staying below the speed limit but on the accelerator enough to stop or keep the squeeling at bay or to a minimum.

No loss of power, no issues with the gears up or down shifting etc.
Today, started the car up and no noise until everything was up to temp. Approx 4mins in, slight squeeling in park. Took her for a drive, still drives normal when accelerating, but the deceleration squeeling was evident and continued when stopped. When stopped also car revs were up and down a bit along with the drive chain still unhappily bucking around similar to running on 3 cylinders kind of.

Taking off again the squeel dissapears and the car actually feels more responsive then before the long drive, obviously she like the long drive to clear out the city driving stop start gunk.

It seems like some sort of idler bearing or tensioner maybe that could be causing this but as I'm still new to the VW scene.
And it seems a little tricky to see let alone get into anywhere near the serpentine style belt. I tried some Wd on the belt but could only get to near the alternator and ac compressor area of the belt from the top side of the engine.

Any ideas, suggestions or even answers would be awesome!
Not sure if the belt squeel due to belt tensioner not working correctly any more or something else completely.
Got worried at first thinking it was the thrust race for the dual clutches (which I'm still hoping it isn't) but the sound is more noticeably coming from the front of the engine I think.

The belt seems to have life still in it.
I hooked up a cheap diag tool, which actually showed up cylinder 2/3 running rough at first. Cleared the errors and they didn't come back up. (I should have copied the codes I know)
Dont think the actual issue will be attached to a sensor tho tbh.
Seems more mechanical then electronic.

Any help or suggestions would be awesome!
Thanks for your time, appreciate you reading my novel!

**Umai Naa!!** · 01-10-2017, 05:13 PM

2L FSI Turbo?

PCV chamber, by the sounds of it.

**Black tsi** · 01-10-2017, 06:42 PM

Thanks for your reply.
The pcv chamber would cause the squeeling noise on deceleration?
Yeah it's a 2L Tsi or fsi I guess, the 147kw engine. Think the code is CAWA.2009 model.