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HELP!! Weird noise when boosting

Discussion in 'A3/S3 Forum (8L Chassis)' started by bp1984, May 18, 2010.

  1. bp1984
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    bp1984 New Member

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    [May 18, 2010]
    can anybody help me? My car is a a3 1.8t sport 1998 and the other day i pulled away from lights after at least half hour of driving, I put my foot down to leave some stupid corsa boy trying to race me. When i settled down into 4th gear i let the revs build and as the turbo started to spool there was a loud whining noise, the noise happens everytime the turbo spools up now and gets louder the more it boosts its defo lost pressure aswell. I can only explain the noise as sounding like a supercharger?? A friend told me its blown or split a hose but ive looked at all the pipes i can see under bonnet and under car, It only makes the noise under load thats whats making it so hard to find. A mechanic told me its a common fault with these engines but couldnt tell me where it was and was to busy to look his self! Anyone else had this problem please help
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  3. Welly
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    Welly VX220 SC Driver :)

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    [May 18, 2010]
    Yep - a boost leak.

    Known commonly as a 'squeeler' LOL.

    Check all boost hoses, especially the jubilee clips. I'm sure it will make itself apparent.

    A tip for looking for boost leaks is check for damp oil around pipe joins - this normally indicates a leak.

    Don't panic, simple problem and common on turbo cars.
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  4. bp1984
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    bp1984 New Member

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    [May 18, 2010]
    Cheers mate good advice
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  5. Welly
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    Welly VX220 SC Driver :)

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    [May 18, 2010]
    We aim to please.... LOL.

    If all else fails, many places will be able to sort you a pressure test - which involves pressurising the charge system. This makes leaks pretty obvious.

    Most leaks you should be able to find yourself though. Replacing all the Jubilee clips is generally a good idea. They get a bit rusted and **** after a while.

    I guess your engine is an AGU due to age. There isn't all that much pipework on the 1.8t engine - it comes out of the turbo, along the back of the head, drops down to the 'Pancake' pipe, then into the SMIC, and from the SMIC to the throttle body. All the turbo pipework is on the driver's side of the car.

    Worst case really is a cracked intercooler - in which case I have a spare one!
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  6. bp1984
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    bp1984 New Member

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    [May 19, 2010]
    How much u wanting for the intercooler mate? its looking that way now ive double checked all the pipes even sprayed easy start all over the pipes while engine was idleing in the hope that the hole would suck it in making the engine rev up but no joy.
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  7. Welly
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    Welly VX220 SC Driver :)

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    [May 19, 2010]
    OK, before we go too nuts then, check the inlet manifold area for leaks, check that the diverter valve isn't leaking, and check the N75 pipework. I'm not out to sell you an intercooler, I'm out to make sure that you fix your problem!

    Inlet manifold area is a common place for leaks to crop up as there are a lot of vac pipes around there. There will be 3 main hoses coming off of the bottom of the inlet mani. One is bigger than the the other two.

    The large one comes out somewhere around the middle of the inlet manifold. This is a VERY common pipe for splitting. Check this one over. The other 2 are the diverter valve vac feed and the fuel pressure regulator vac feed. Best thing is to take them off and inspect them properly. I would personally replace them with silicone hosing at the same time.

    The diverter valve one may go into a metal pipe and then back into a rubber one. This is normal on these engines, bypass the metal bit of pipe if replacing with silicone.

    Lastly, check the diverter valve and N75 piping. This is all up around the turbo area. Check the 2 pipes coming off the charge pipe first. Make sure there are no splits and that they're tight. The small one from the charge pipe goes to the N75 valve. Check for splits and again make sure it's tight.

    Testing the diverter valve is easy enough, see the link: http://www.vaglinks.com/Docs/Misc/VAGLinks.com_DIY_Testing_a_Bosch_Diverter_Valve.pdf.

    If all of these checks come back OK, we'll go from there.
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