Blown turbo symptoms?

Discussion in 'Technical' started by Cliff, Feb 12, 2019.

  1. Cliff

    Cliff Member

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    Well, even after replacing all the valve stem seals, my car still produces smoke under the same conditions...

    I just have no clue. I posted the pictures that showed definitively there was oil draining down the valve guides and onto the pistons. As unlikely as it was, I replaced all 24 valve stems seals since somehow they all went at the same time. On the first drive out the exact same conditions bring an embarrassing amount of smoke. There is no way all 24 went at the same time again. There is no way I made a mistake 24 times. There is no way the machine shop that built the head the first time messed up all 24 valve seals. What the heck is happening?

    I can drive my car smoke free if I put it in neutral down hills (no engine braking). I can drive my car smoke free if I stay off the boost (no excessive vacuum or boost psi).

    This is my 4th Z and I am literally about to write it off as a lemon and sell it. I have NEVER had any car with issue after issue like this particular Z.

    Picture through a spark plug hole shows a beautiful drenching of oil after 13 miles...

    Screenshot_20190418-113732_Gallery.jpg

    I seriously have not 1 clue how this is even possible
     
  2. Martin Williams

    Martin Williams Well-Known Member

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    Was the inlet manifold wet with oil when you removed it. Oil in cylinder can only come from two places. past the rings or through the inlet valves, whether that be via worn inlet valve stem seals or upstream equipment. If all your cylinders are wet, then the problem lies upstream as it is extremely unlikely that all inlet valve stem seals have failed or that you have broken or damaged piston rings on all pistons.
     
  3. Cliff

    Cliff Member

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    Thanks for all your help Martin. The inlet manifold (plenum?) seems pretty dry. There is some residual oil in there but none in the intake pipes leading up to it. I removed the intake pipes from the throttle bodies and gave the car a little rev (after several minutes to get the forged pistons up to temp), and still had blue smoke come out the exhaust.

    I may tear down the engine one final time to replace every single gasket, seal, copper washer, ect. This will also allow me to record every clearance measurement to compare with my measurements from the original rebuild that held strong for a whole 3,000 miles. I'll also be able to have the rotating assembly balanced again since my flywheel has been resurfaced since the original balancing. Furthermore, I will be able to inspect all the new bearings for wear to make sure nothing strange is happening there. And lastly I will install new valve guides and new valve seals just for the sake of it since the cost is negligible compared to the entire rebuild. So basically an entire rebuild from step one using machine shops when necessary.

    If she smokes after this a for sale sign will be purchased.

    It may take me a month or so before I can start this latest endeavor but this time I will try and have a build thread as I go. Maybe some input along the way will highlight a potential problem.

    Thanks again to all for the suggestions. Stay tuned.
     
  4. LitlElvis

    LitlElvis Z32 Servant

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    What are you using to install the seals? A tool with a counter-bore (see attached) should be used to drive them onto the guides... the counter-bore should be large enough and deep enough to allow the neck of the seal to fit inside while the larger diameter of the tool carries all the load and pushes only on the outer metal jacket of the seal during installation. If you installed by pushing on the seal neck, that could easily crush this critical area.

    Also, use some petroleum jelly on the seal ID for lubrication so the rubber doesn't tear on the valve guide during install.
     

    Attached Files:

  5. Cliff

    Cliff Member

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    Thanks LitlElvis. I didnt use any special tool to put the seals on. I used a deep well 10mm socket which might just be my issue since I cant say if it was pushing on the neck or the outside metal jacket.

    I guess the heads will still have to come off either way but this time around I'll definitely have one of those valve seal installation tools in my toolbox.

    Thanks for the info and providing the 'why' behind the 'what'
     

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