Siren noise @ +5psi on td42ti

[Wulfen]

During a fun filled day on Stockton beach i noticed a siren/wailing sound as i was driving. Upon hearing this sound I started checking my gauges and noticed that the noise started when boost pressure rose above 5psi to max boost then die back down again with throttle off. You can quite clearly hear it inside the cab but no-one could hear it outside as i was driving past. i have removed all hoses from turbo to intercooler and then to inlet manifold checked them over for damage and re-tightened them. it is really starting to make me :furious:. any help would be greatly appreciated and many thanks in advance.

Cheers Josh.

[Timbo]

Not sure if this is the same noise I had.. took me MONTHS and MONTHS to find.

Turned out it was my Manifold. The bolts weren't tight and air was escaping causing a shrieking/Whistling sound and would happen on boost. Sometimes it wouldn't happen at all which was what made it hard. Other times, I could go up a hill in 3rd and do it on command.

Just check the bolts on the manifold haven't come lose. Squirt some WD-40 into them and soak them for a while and give them a tighten.

[patch697]

This may sound really stupid but turn your stereo right off (& I mean powered down here) then check for the noise..... Im not taking the pi55 here at all just try it & see if the noise goes away, & remember right off with the stereo not just turned right down.

[Wulfen]

it hasnt been on since the noise started. it is definitely turbo intake/exhaust related. im checking the exhaust now as timbo said and also the impeller to see if there is any shaft play

[Wulfen]

Well after a bit of inspection and mucking about tightening the manifold i thought while im here ill check the turbo. well after unbolting the intake i tried to wiggle the shaft and notice a little bit of play. i thought fair enough its a wet float turbo so a little play is expected until it has oil running thru it. so i started to turn it to see if there was any binding during rotation and i saw that the leading edge tip of one of the vanes was bent which would be enough to put the impeller out of balance. i then rubbed my finger around the inside of the housing and felt a tiny ridge on it. so that was the source of my siren noise which also means time to upgrade :D

[teleman]

Good find wolfen. And good points from everyone. Makes me very happy to find a thread that has solved a problem :)