Boost leak..? Only on partial throttle/boost..

[Johnno92]

Recently Ive noiced a quite audible gushing sound under partial throttle as the turbo is spooling up usually between 1800-2200rpm.. Strangly when throttle/boost increases the noise stops and there is a noticeble jump in power as soon as it stops..

To me this suggests a leak from somewhere, and normally I wouldn't have bothered posting about it.. However I would have thought a leak would get worse the more boost pressure increased..? but in this case the phenomenon only occurs at low pressure and increasing it appears to resolve the issue..

 

Has anyone else experienced this..? or can point me towards a potential culprit..?

[Kgod1991]

Same issue let me know if you find a solution as I've checked all pipes (replaced most)

[Beard]

Same here. I've replaced all the original pipes except the pancake pipe and it still does it. It's got me round the ****ing bend.

I'm thinking maybe the intercooler has a crack in it or something?

Sent from my XT1032 using Tapatalk

[Johnno92]

I'm thinking with it being intermittant I may be a joint that is not fully sealing until it gets a significant amount of pressure on it.. Sounds like mine is originating somewhere near the firewall so ill have to have a scout around at some point..

[sepulchrave]

Is the VNT mechanism working properly, it sounds like the vanes/actuator mechanism may be stuck leading to slow spool, cavitation noise and a sudden jump in power when it finally does come on boost.

[Johnno92]

Is the VNT mechanism working properly, it sounds like the vanes/actuator mechanism may be stuck leading to slow spool, cavitation noise and a sudden jump in power when it finally does come on boost.

Best way to check..? I thought if the vanes were sticking it would lead to it overboosting under hard acceleration and going into limp mode..? On mine it all works fine under hard acceleration..

 

:EDIT: Unless its possible that the mechanism is not fully closing as it should whe coming off boost..?

[sepulchrave]

Best way to check..? I thought if the vanes were sticking it would lead to it overboosting under hard acceleration and going into limp mode..? On mine it all works fine under hard acceleration..

 

:EDIT: Unless its possible that the mechanism is not fully closing as it should whe coming off boost..?

 

Check VNT operation manually to make sure it's closing fully.

[jamwatn]

I never EVER found the source for that noise on my vrs. Used to drive me mad because the car felt much slower when it happened making it clearly a boost leak.

[Johnno92]

Right.. Been busy so only just got round to updating this..

 

Took of ASV, EGR valve and EGR cooler to get access to the top of the turbo to check the operation of the VNT, lever moved easy enough and sprung back so the problem was not there although you can probably see the area is covered in oil and carbon..

 

 

While removing the EGR valve was concerned to find one of the bolts on the underside was in finger tight, if you look below you can see on the valve which one was loose. And thus where it was leaking past the seal and covering everything underneath with carbon and oil fro the CCV and EGR system..

 

 

First time I've had the EGR valve off so god knows how long its been leaking for, but started the noise about 6 months ago.. Anyway, refitted it all properly and now noise has stopped.. Happy days..!

[Beard]

Well I guess my EGR is coming off this weekend. Might as well check it as it will need a clean anyway