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Blown CT20B turbo

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MC
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2012/10/09 23:04:56 (permalink)
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Blown CT20B turbo

Hi there.  Got a bunch of questions about turbos, have done a few quick searches but not found much conclusive info.  Please point us in the right direction if these questions have been answered before.
 
Just bought a sw20 mr2 on the weekend.  Looks like I made the schoolboy error of getting one with a blown turbo, judging by the amount of black metallic pasty oil all over the inside of the intake plenum and intercooler piping.  Not really familiar with turbo cars - I'm guessing the turbo's blown it's seals a fair while ago for there to be metallic paste there.
 
Planning to pull the turbo out this week (and probably a compression test too) - if it looks ok, might have a go at rebuilding it myself.  Apparently it's got a CT20B (CT26C2?) - are these reasonable to rebuild? I read something about shops replacing the turbines with steel (so effectively a CT26?) and something else about there being a high chance of breaking the ceramic turbine if I do it myself...
 
If it's pretty rooted, where should I look for a replacement?  Would replace with the same unless the CT26 is much cheaper.
 
Would appreciate any help as I'd like to drive the thing again soon!
post edited by MC - 2012/10/09 23:08:25
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    MR2QIK
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    Re:Blown CT20B turbo 2012/10/09 23:31:56 (permalink)
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    How's it spooling/boosting? Sure that oil isn't from the factory catch can if yours is Gen3 motor? I'm thinking it may be since you have a CT20B.

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    #2
    TIPSIDUECE
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    Re:Blown CT20B turbo 2012/10/09 23:48:16 (permalink)
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    yeah if the cars boosting fine then my guess would be accumulation of pcv gunk over the years. if it was blown turbo seals wouldnt it come out thru the exhaust???

    Why do people say "grow some balls"? Balls are weak and sensitive if you really wanna get tough, grow a vagina! Those things take a pounding!
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    just_ace
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    Re:Blown CT20B turbo 2012/10/10 00:10:41 (permalink)
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    the ct26 is mucuh  cheaper, but the difference is not the steel turbine. the st205 WRC grpA had the same ct20b but with steel turbine.
     
    most jdm ct26s also have the ceramic turbine.
     
    the ct20b is a better turbo.
     
    as said it's most likely blowby from the cam cover accumulating over time without maintenance. its is possible to blow the oil seal on the compresssor side, but then you'd have pools of oil in the intake etc
    #4
    MC
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    Re:Blown CT20B turbo 2012/10/10 01:43:01 (permalink)
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    Ok no I'm not sure it's from the catch can - I'll check it out tomorrow, would be great if that's all it is.
     
    It seems to spool up pretty well but don't really have a baseline to compare to.  There's a little smoke for a few seconds on startup and sometimes leaves a plumb of dark smoke under full boost.  I thought it was just rich until I looked in the intake.  Looks a bit like this:

     
    Tipsiduece, are you saying I'd see smoke from blown seals? Because I really don't know how much to expect.
     
    Thanks for all the responses, I'll let you know what I find.
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    MR PLOW
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    Re:Blown CT20B turbo 2012/10/10 09:12:17 (permalink)
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    lol that pic's a classic

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    3sgeTurbo
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    Re:Blown CT20B turbo 2012/10/10 09:40:36 (permalink)
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    I would check to see if the car smokes from the exhaust while under load first,
     
    Also check your turbo for shaft play, and I would clean out the hot pipe with petrol then go for a drive if you see oil back in the hot pipe again then you know the seal is leaking.
     
    On the CT series the seal is round like a mini piston ring, so the only time it will leak is when the bearings / shaft on the turbo is worn and you have radial play, the ring and bore on wears down and oil escapes, the way these seals work is when the turbo is in motion, the faster is spins the more it seals so somtimes it can be normal to get very small amount of oil in the piping system.
     
    I rebuilt a few CT26's before and I would suggest to take photo's as there are a lot of little parts inside and you might need an oxy torch to heat up and separte the exhaust housing, also 100% you will need to take it to a turbo specialist to have it balanced afterwards.
     

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    MC
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    Re:Blown CT20B turbo 2012/10/11 00:04:48 (permalink)
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    Yeah so it's a rev2 engine with no catch can, just a hose from the top of the valve cover to the intake.  With some more of the intake off, there's not as much oil in there as I thought, mostly just black and sooty. 
     
    I can definitely feel some radial play from the compressor side (haven't pulled the exhaust side off).  Feels like I can move the compressor 0.5-1mm side to side, but not along the shaft axis.  Spins smoothly and freely and couldn't see or feel wear on the housing.  Does this sound normal or worth actually measuring the play?  If that doesn't sound too bad you guys, I'll try the cleaning the hot pipe approach.
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    3sgeTurbo
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    Re:Blown CT20B turbo 2012/10/11 09:58:42 (permalink)
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    A bit of oil in the pipes and bit of shaft play is normal for the 3SGTE,
     
    Once you can see the wheel is wearing down the side of the comp cover its time for a rebuild.
     
    How many kms has your two done?

    1991 MR2 Black Turbo Targa Gen 4 3SGTE w/ GTX3076r
    1984 AE86 Toyota Sprinter 4AGE 16V ITB's
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    MC
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    Re:Blown CT20B turbo 2012/10/11 15:40:13 (permalink)
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    I had a better look in with all the piping off this morning and most of the oily crap was between the pcv hose and the intercooler with nothing really past the intercooler. The first hose I'd undone happened to be where it had built up the worst.  Have given it all a bit of a clean up and will see how it goes.
     
    The motor has apparently done 130,000km, odometer reads 240,000.
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    3sgeTurbo
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    Re:Blown CT20B turbo 2012/10/11 16:13:03 (permalink)
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    Sounds like regular build up to me, does the car smoke from the exhaust?
     
    Also with those kms I would inspect the timming belt, you would not want it snapping at 6000rpm.

    1991 MR2 Black Turbo Targa Gen 4 3SGTE w/ GTX3076r
    1984 AE86 Toyota Sprinter 4AGE 16V ITB's
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    TIPSIDUECE
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    Re:Blown CT20B turbo 2012/10/11 22:01:02 (permalink)
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    There are two oil seals, keeping oil from escaping from the bearing - one on the intake side and one on the exhaust side.

    If the exhaust side oil seal fails then oil will leak into the exhaust system, where it may burn if the exhaust temperature is high enough, or may not. This can lead to different smoke colours, depending on if, or how much, the oil is burnt.

    If the intake side oil seal fails then oil will leak into the intake system, where it will be drawn into the engine, and will be burnt along with the fuel, creating blue smoke.

    Why do people say "grow some balls"? Balls are weak and sensitive if you really wanna get tough, grow a vagina! Those things take a pounding!
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    elshaug22
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    Re:Blown CT20B turbo 2012/10/11 22:24:01 (permalink)
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    a little smoke is to be expected of turbo's this old but definately worth a check up, hope it all goes well mate.
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    MC
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    Re:Blown CT20B turbo 2012/10/13 02:27:44 (permalink)
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    Yeah it only smokes for a few seconds on startup or under full load but to my eyes it looks like dark fuel smoke not the blue oil smoke.
     
    Put it back together today.  Not getting boost up to the boost controller setting (getting 1.1bar not the 1.2bar it's set to) but sounds like I might not have got the intercooler hoses sealed.
     
    Apparently timing belt was done 30,000km ago but will try to check it before taking it to the track next week :D
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