Whats the best way to diagnose stem seal failure? And do you need to

Discussion in 'Technical' started by AndyMac, Nov 21, 2005.

  1. AndyMac

    AndyMac Better than you

    remove the heads to replace them?

    Qu: if a stem seal fails completely is it possible that combustion in that chamber would cause enough pressure increase in the crankcase that it would blow out the dipstick?

    I've pulled the plenum off, all intake piping, theres oil all through the lower intake piping (ie not the piping to the TB's, but the ones from the turbo's to the IC's) The plenum was full of oil and so was cylinder 3. When it all happened there was a fair amount of noise from the top of the cylinder, kinda like valve noise...but not sure.

    If a stem seal get blown through due to it being worn already and a spike in pressure in the crankcase,
  2. rob260

    rob260 Administrator Staff Member

    Leakdown test
  3. Tektrader

    Tektrader Z32 Hoe, service me baby

    does that work Rob??

    If the valve is shut how does any of the pressure get to the stem seal?

    My understanding is that the leakdown test, tests the integrity of the valve to cylinder head seal.

    IS that right? please explain.
  4. MexiCandu

    MexiCandu Grumpy of the Grampians

    I would say that the heads have to come off

    to replace stem seals. Don't know how you would be able to compress the valve springs and re-seat the collets without removing them. I had a very similar situation to yours last year. Turned out that I had blown the landings out of piston #4 I ended up pulling the engine and doing a full rebuild.

    If you have oil in the IC piping chances are you're sucking up a lot of oil on #3 and it's going through your PCV system into the ICs.

    I pulled my engine and did a full rebuild (bearings, rings, re-seated valves and new seals and gaskets) for about $1700. I spent a further $840 and replaced the whole engine bay wiring loom while the engine was out.
    Sorry to be the bearer of bad news but I think this is what you are looking at doing too.

  5. rob260

    rob260 Administrator Staff Member

    I could be wrong -read it on another forum

    and never been in that position myself...
  6. beaver

    beaver southern zeds

    Drain your sump

    and see whats mixed in with the oil. damaged worn rings could be the cause off increased preasure in the
    case, the stem seal cant fall into the chamber, if im understanding this correctly.
  7. doesn't sound like valve seals.

    I'd replace the PCV valves first and if that doesn't help I'm afraid your #3 piston is toast (either cracked, a small hole or broken ringlands)

    leaking valve seals can cause small amounts of oil leaking past the valves into the combustion chamber..but not the other way around.

    usual signs are smoke while decelerating.

    the seals can be replaced with the heads in the car.
    I've done it once that way and it's a little easier to have the heads out, but still then it's a dog of a job.

    You'll need to remove the camshafts, lifters and valvesprings (using a special springcompressor tool...look in the service manual).
    Also, very important: if you are removing the valve springs with the heads still installed on the engine, make sure the piston of that particular cylinder is in the top position, otherwise the valve(s) will drop into the chamber !

    Removing the old seals themselves is usually very hard as well, because they get stuck to the valveguides after 10+ years ...best is to get a special tool for this.

  8. Dan

    Dan New Member

    Another symptom of valve stem seal failure is

    Lots of smoke out the rear of the car after it has been idling for some period.

    At idle the oil can pool around the valve stems. When you go to accelerate the oil is sucked through the bad seal and poof.

    But what you describing dosn't sound to good. Agree with Eric about the piston. Go see a mechanic to make sure.


  9. AndyMac

    AndyMac Better than you

    Is there anything else on the top end that could possible

    cause these symptoms?

    I personally don't think it's the stem seal, but before it happened the car had developed a fair bit off valve clatter at cold and at around 4000rpm and then under hard acceleration it just went, dipstick blew out and theres oil flooding through that cylinder and into the intake...

    I have the gut feeling that it's piston, but I'm trying to link it to the noise i was getting before hand.
  10. noises are usually hard if not impossible to diagnose over the internet.

    could have been anything from rod knock to "lifter tick" or maybe even a foreign object in the combustion chamber
  11. Gazza

    Gazza Active Member

    I guess the easiest way is by doing a compression test....

    ... of the cylinders and check for oil on the plugs while doing the test. That way you can see from the plugs condition if there is oil present in any cylinders, and testing the compression will let you see if cylinder wear is a factor for any oil found. Generally a cylinder with a leaking oil seal will have wet looking black spark plug tip.
  12. AndyMac

    AndyMac Better than you

    You may have missed my earlier post...

    I have almost no compression on cylinder 3, the rest are ok, plug on 3 is saturated with oil, and there is oil all through the intake system and and pooled in the exhaust I started it this morning for about 10 seconds and obviously it was smoking something cronic. Pulled the intake piping off and there was smoke coming out from the IC's and the Throttle bodies.
  13. Gazza

    Gazza Active Member

    Yep, missed it. Ive now read it :sick:....

    ....my guess would be either:
    1) Cylinder 3 was running very lean and has burnt out the rings and the rattle could be piston slap or piston hitting damaged area on wall.
    2) Catastrophic failure of a valve that has smashed a hole in your piston and rattle is the peices in the cylinder. You can pull the spark plug and check the pistons surface for damage to see if this has happened. You will need to use a rag on a stick or similat to clean the oil up first.
    The excess oil and popped dipstick is going to be from the increased crack case pressure from the failed cylinder, pushing oil through the pcv valve and into the intake (they can only withstand normal crank case pressure). The oil in the cylinder and exhaust could be from the crank case or it may be that the head gaskit has blown out in cylinder 3.

    Sorry mate but that sounds expensive
  14. minivan

    minivan Guinea Pig Test Monkey

    Re: You may have missed my earlier post...

    either way.. no compression on cylinder 3 means she needs to be pulled down.

    let us know what happens post mortem

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