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  1. #1
    VXRed azza15's Avatar
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    24th May 2018
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    Default Loud hiss while on boost

    As the title says I've got an incredibly loud hiss when the car comes onto boost.. I've done a few searches but I'm afraid of wondering into a minefield of could be this could be that..

    The car doesn't feel down on power but it for sure doesn't sound right at all so I'm curious what would be the absolute obvious things to check first and what would I be looking for with them exactly?

    Any help would be greatly appreciated thanks

  2. #2
    VXRed VXR-Carlos's Avatar
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    13th May 2017
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    Mine makes a loud hiss/whistle as well. It is at the moment. My problem is that the manifold nuts always seem to come loose, just one or two but itís enough to let the exhaust gasses out. Could be the same issue.


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  3. #3
    VXRed azza15's Avatar
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    Funny you should mention that as I've very recently had to tighten mine again as they were loose enough to be taken off by hand! Definitely made a difference but I still have this hissing sound unfortunately

  4. #4
    VXRed VXR-Carlos's Avatar
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    I had 3 loose this morning, tightened them up and the sound is still there. Checked pipe work and canít find anything obvious. If you happen to find out whatís causing yours Iíd be interested to know.


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  5. #5
    Are you VXR enough? Andyb712's Avatar
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    It's probably the fact they have come loose so your gasket has been damaged

    The manifold gasket can be replaced without removing the whole manifold and turbo but you need to remove 4 left side studs aswell as all the nuts to gain enough access to change it
    2009 Astra H Vxr arden blue uprated gearbox endcase with bigger bearings, 3" cobra catback non res with toyosport 2.5 double decat, mtc crossover delete and tophat

    Planning to go stage 3/3.5 eventually

  6. #6
    VXRed azza15's Avatar
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    Fingers crossed thatís what it is! Will let you know what I find


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  7. #7
    VXRed azza15's Avatar
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    Quick update Iíve had the manifold and turbo off, found a hairline crack near the wastegate and the manifold studs were in the wrong way as far as I can tell..


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  8. #8
    VXRed VXR-Carlos's Avatar
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    Is that a new mani and then? Was it easy to take off?


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  9. #9
    VXRed azza15's Avatar
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    The manifold wasn't too difficult to take off at all really but it looks like I need a new one unfortunately(I really should've noticed the crack when I put the downpipe on). I got very very lucky and had all of the manifold bolts come peacefully with non of them shearing the studs which was a huge bonus.

    Other than the manifold bolts it's just things like the oil feed and return pipe to disconnect along with the coolant pipe I had to block off temporarily(still got drenched in coolant). The downpipe and pipework from the airbox and intercooler need to come off too along with the vac line to the recirc valve.

    I had a lot of cleaning to do once it had all come out and I definitely need my valve stem seals doing but after cleaning it all up and sticking a new gasket on it does seem to have quietened it down an awful lot!

    Still unsure on what kind of effect/problem this hairline crack near the wastegate would cause me though so if anyone can shed some light on that I'd appreciate it, will have a new one stuck on soon hopefully.

  10. #10
    VXRed azza15's Avatar
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