squealing noise on boost: SOLVED

can't really hear anything on your mp3
I'd be checking the intake plumbing, making sure connections are tight, seals are good
Or vacuum hoses maybe

Sounds like the manifold to turbo joint. Same problem I had. http://www.brick-yard.co.uk/forum/turbo-squeal-cure_topic57276.html

Mine didn't leave much soot or fumes like a cracked manifold. It only needs to be a small leak.

Edited by T5 TDI - 04 Dec 14 at 17:30

It's always a good idea to add your engine code. I'm guessing BXE? The old AXE and AXD engines didn't have a gasket. There was talk of an aftermarket gasket for those but I don't know if the later engine with the O/E cast iron manifold has one.

I could hear it perfectly on your first mp3 btw!       

sorry Engine code BPC -the one where the turob is bolted directly to the DPF

Im guessing its not vacuum prob since I can hear a sort of turbo-y sound in the shriek and it doesnt sound like its a vacuum suck noise
Since its only happening on strong boost, Im guessing its a pressure hose downstream of the turbo -maybe a hole, or connection.  the intercooler had a pinhhole -replaced it, so its not that. Ive also reseated all the hoses and the seals look ok. Im not keen on splashing out for a new set of hoses either sespecially if i find out thats not the cause...

Manifold gasket maybe but I didnt see any evidince of soot when I removed the turbo. Stupid me, I should have taken the manifold off to check when i had the turbo out but the turbo was such a ball ache that i didnt want to have to remove all the watercooled EGR manifold crap and chance I broken stud on the manifold when I didnt see any soot. EGR is blanked (electric control so a 10mm hole in the plate to keep the ECU happy) but it was squealing before i blanked it.

p.s. trumpet got no reed, you blow in it like your making a farting noise, saxaphone and clarinet do though


Edited by CMP260 - 05 Dec 14 at 11:00

Cheers for suggestion but t5 2.5 motor has no belts at all. gear drive or gates drive connector for all pumps and alternator. Cam is chain drive.

Edited by CMP260 - 07 Dec 14 at 20:49

I thought the cam was gear drive too but ive been corrected...

so I was right all along?
thanks for the pdf, could come in handy.

Now I'm wondering if they have both chain and gear versions?

anyway back to the squealing problem, yesterday I went for a 1/2 hour drive. It started running badly and stinking a bit like something burning from under bonnet. But it funnily seemed like it had more power and the boost squeal was gone?

After it cooled I noticed the antifreeze was down by about a pint, there was a trace of cream in the oil filler cap and the oil was also a bit low. -there is a small oil leak anyway. and I havent checked fluids in a while but I seriously hope I dont have a head gasket problem...

So, I topped up the fluids, removed the EGR blank plate completey since it caused problems before.
This morning, I took it for a spin: the squeal is back but it seems to be running normally... fingers crossed it was only condensation.

Ive decided to try to find the squeal by putting two mono condenser microphones under bonnet facing opposite directions, connected to laptop in cab running audacity using stereo-mono splitter.
then record a test drive and see which side the squeal comes from (which side of the stereo recording is louder). Then repeat to narrow down the location -its either that or put a dwarf under the bonnet and Im pretty sure that violates H&S regs


Edited by CMP260 - 08 Dec 14 at 11:03

ill use a laptop with audacity direct to the mics.

if i really wanted to get fancy (and had the time) and if people would send me recordings of various vacuum whistles and pressure shrieks it might be possible to setup a noise library to assist future troubleshooting. 

provided the sound you are troubleshooting is not "always on" you can use noise removal to get rid of most engine noise and then you can display the frequency spectrum - this might assist in comparison of different noises -it should be possible to loosely tie a frequency spectrum to a noise source.  At a minimum I would say it could discern between a vacuum or pressure shriek.

Cheers for that info. I've been thinking a bit. I replaced all turbo gaskets except the one to dpf from turbo. That wouldn't fit so I reused old gasket. The squeal is more common now than before I replaced the turbo. I assumed it was due to new turbo having more boost but maybe it's that bloody gasket.
I bent the new one trying to fit it. But it's still got a ridge unlike the old one I reused.
Is there any way that gungum might work in that jobs my? Or am I asking my for trouble with it being so close to the turbo vanes.