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  1. #1
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    Unhappy complete loss of boost while driving

    Hello S15 owners

    i have a problem where my boost gauge will show boost for some time then completely drop off and show -7. I asked around and was advised it may be the spring in the wastegate actuator. As such i replaced this and the problems persists. I now have a feeling my turbo ( T25 bb) is goneeee... any advice or suggestions to fix my problem?

    cheers

    Abs

  2. #2
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    meddler is offline It's not easy being a green text speak nazi
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    try another boost gauge. can you feel the boost change or is it just the gauge? Maybe a vacuum leak somewhere.
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  3. #3
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    Is it while you are driving at a constant speed. Need a bit more information to provide a reasonable assesment.

  4. #4
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    Meddler - that's a good idea to try a new gauge- i did take it out and give it a once over and make sure none of the circuitry looks shot and a good spray of contact cleaner just in case. so i dont think its the gauge worth trying tho. i think i should revisit all the vacuum hoses to look for any splits etc.

    Auss15- yes while driving at constant speed but also happens pretty much at any time when accelerating, when standing still at idle. in 5th flooring it until the pedal hits the floor which i tried today it felt very under power and sluggish.

    considering a new turbo and new vaccuum lines as a whole. recently installed a new front and dump pipe. Might be worth installing a new bleed valve perhaps that might be shot. i have a gfb bleed valve sitting around at home. But i dont want to install that and blow up the engine in the process.

    i do want to apologise in advance im a newbie to turbo cars and cars in general i have done alot of reading and been bitten by car workshops ( exhaust shops, work shops here in Aus, doing less than par jobs, etc. the place that installed my front and dump pipe were so lazy as to just not bolt the front pipe to the dump pipe, leaving one bolt just sitting in there with not nut, so i have little faith in workshops atm)


    folks at this stage i have a feeling its the turbo thats busted...


    regards

    Abs

  5. #5
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    You haven't stated if you loose power when driving? Get rid of the bleed valve and get a electronic boost controller!

    Get a new gauge but make sure you have all the intercooler pipes tight, all vac lines tight and then worry about a turbo.

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  6. #6
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    Is it the boost gauge that comes from the factory?

    They have a reputation of becoming faulty and showing nothing sporadically with no apparent cause. Other times they work fine.

  7. #7
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    From what you have told us I would:

    1. Check every boost hose under the bonnet (especially the one to the boost pressure sender on the drivers side) take it off inspect it, they can hide cracks really well! Good opportunity to replace all the small vacume hoses with colourful aftermarket stuff
    2. Try another or buy a new digital boost gauge

    I wouldnt rush into replacing the turbo just yet unless you plan to upgrade anyway, I suspect it's a simple gauge fault or hose issue!


  8. #8
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    Quote Originally Posted by Abs15 View Post
    Auss15- yes while driving at constant speed but also happens pretty much at any time when accelerating, when standing still at idle. in 5th flooring it until the pedal hits the floor which i tried today it felt very under power and sluggish.


    regards

    Abs
    I wouldnt be to concerned about sluggish in 5th gear,its a tall ratio and if you are running low boost and light mods it will be slow to react in 5th gear.

    I'd start with the guage first and if that doesnt work, then work on the vacumm lines, tightening all clamps and squeezing the small boost hoses to look for splits

  9. #9
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    Thanks for the advice folks. ill be looking into the vacuum hoses first. so change them for good aftermarket silicon hoses or something of that sort. then have a look at sourcing a stock gauge that works for now. If anyone knows where to find the vacuum home diagram a link on here would be great

    thanks again, will post on here how it all goes.

    Abs

  10. #10
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    So ive had a chance to get new vacuum hose and clamps and have a look at all the vacuum hoses that might cause any trouble. I did find a loose hose connection between the intake just after the airflow meter where it links upto the stock bleed valve. had to use a little bit of loctite( just a few little drops were suffcient) to keep it in there and replaced that hosing

    Darren S15- i think you were on the ball with the boost pressure sensor on the drivers side. inspected and tidied that up( was in pretty good condition) but clamped where i could clamp then took it out for a test drive.

    I think these might have been the issue- on the test drive it reached the stock boost levels fir the first time since ive had the car. popping just above the 7psi mark and felt pretty good. real test is when i head to work to see if the boost is maintained over the 45minute drive.

    will let everyone know if it al worked out.

    cheers

    Abs

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