Z32 Engine knock

Discussion in 'Technical' started by beaver, Jul 24, 2020.

  1. beaver

    beaver southern zeds

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    Straight to it, about 4 or so weeks ago I pulled the upper plenum to fix a fuel weeping issue with the return line or so I thought. The smell was faint, wasn't there all the time, the car ran fine, but any fuel smell under the hood to me is no good. Plenum is off, ive checked the a/n fittings on the return and there good, then I notice that the fuel rails have a ring of light dust on them around every injector, I had a bit of a smell round the rails and I could smell fuel faint but there. Since I put the injectors in the rails, I figured id possibly pinched the orings. injectors are out of the rails, 6 pinched top orings. Later I had efi hardware (a local specialist) take a look at the rails and fit new orings. There comment was that the chamfer for the top oring was shallow and the fitting difficult, but all good now. The engine is back together a few days later, the car hasn't been started for a couple of months, I turn the key and it fires up,but runs at 2000 rpm, I replaced the iacv with new, but I also hearing a loud knocking from the engine. I've heard the same sound a couple of times before, but years ago, so I let the engine warm up and plugin data scan, timing is solid @15d, iacv is doing its job, oil pressure is about 10psi at 800rpm and increases with revs, everything looked good. I’ll say when it happened the first time the sound went away quite quickly, I’d put it down to lifters and cold outside temepture, and hopped I was right. This time it’s not going away though, I give the engine a small rev and the noise increases in sound and is in rhythm with engine revolution, what! The sound I thought, was coming from the top of the engine drivers side exhaust camshaft, that area anyway, which made me think a lifter-lifters hadn’t pumped up at all, and were now being hammered by the cams. The engine is apart now the driver’s side exhaust cam cover is of, I’m pushing on the tops of the lifters one at a time, every lifter is spongy, they all depress down about 10mm, seems the only thing holding them up is the internal spring. But I’m not convinced the lifters are the source of the knocking hammering shit that’s going on. To my untrained ear it sounds more like rod knock, the last thing you’d want. I ‘ve looked at a couple of ways to check for rod nock, and used the piston at tdc rotate a little until the piston being tested starts is downward movement, this they say will gap the offending rod bearing at the top, if a gap exists, and by pushing down with a blunt rod through the spark hole you’ll feel movement downward. So, I did it and no movement exists downward at all. The oil was dumped, there is no metals in the oil or oil filter..F/a. Atm I’m thinking of pulling the camshafts and rebuilding the lifters again, joe imbesi who built the motor rebuilt them at the time, he said they were good. Short of pulling the engine and checking the bottom end bearings, I’m stumped. Anyone here have anything similar happen? Ideas please.
     
  2. ivan129

    ivan129 Member

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    Are we there yet?
    If you think the noise is caused by some sort of clearance problem such as big end, use some Lucas heavy duty oil stabilizer. Say 20%. I can testify that this stuff makes a rattling engine sound like new. My Audi did the balance shaft bearing and wouldn't hold oil pressure at idle. Rattled like someone was shaking a bag of bolts. 20% fill of Lucas heavy duty oil stabilizer and it sounded like a new engine. This is only a band aid of course.
     
  3. beaver

    beaver southern zeds

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    Thanks ivan, I did put some liquid molly lifter free in it, and I can say it did shut the lifters up a bit at cold start up.
     
  4. geron

    geron National Petroleum Equipm

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    I think lifter issue. Not sure why it would idle at 2k though. Vacuum leak?
     
  5. beaver

    beaver southern zeds

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    I hope your right mate, It was idling high because I replaced the iacv and hadn't adjusted it yet.
     
  6. Martin Williams

    Martin Williams Well-Known Member

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    Sounds like you are not getting oil pressure to one of your lifters. I had it on a car that I bought once, sounded horrible. I cleaned everything and changed out one lifter that was particularly gummed up/worn
    That issue was caused by dirty oil.
    Air leak maybe upper plenum gasket.
     
  7. beaver

    beaver southern zeds

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    Yeah anything is possible right now, could be dirty oil clogging a lifter, when I pushed down on the lifters under the exhaust cam, they all pushed down really easy, like they no oil in them, that's not normal, they are supposed to be pumped up hard and not move down without a fair bit of effort. The noise the engine was making didn't sound
    like lifters to me, I've owned the car 18 years now, and lifter noise is something I'm familiar with, although I'm not ruling it out.
     
  8. beaver

    beaver southern zeds

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    forgot to mention, when the engine was running and knocking, I shut down the spark to the cylinders from 1 through to 6, the sound didn't change, I also turned the vtc's of-on this also made no difference to the sound.
     
  9. geron

    geron National Petroleum Equipm

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    Is the motor idling smooth? If it's sounding like a WRX and rough, I'd say a lifter. I had a Gazelle fitted with a CA18DET and drove it for years without any issues at all. After I bought the Z, (a very long time now) I sold the Gazelle to a friend. When we went to fire it up (and me full of confidence) it sounded horrible like a WRX o_O and no matter how much it was revved the engine wasn't smooth and horrible noise.

    Long story short, lifter issue.
     
  10. geron

    geron National Petroleum Equipm

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    Other than a tick, tick, tick, lifter noise, the other lifter noise you can get it can be a LOUD rattle followed by rough engine operation. It would sound like a serious mechanical issue but if you know your car (since it was last parked) and it worked OK, I'd say not a spun bearing but something on the top of the engine is causing the noise.
     
  11. beaver

    beaver southern zeds

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    Yes the engine ran smoothly, I put my hand on the plenum wile it was running and knocking, there was no vibration I could feel or see, every thing seemed normal except for the knock noise.
     
  12. beaver

    beaver southern zeds

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    [​IMG]
    Had another look at the dumped engine oil with a 800x scope, the bits are non magnetic alloy, there all through the oil, I couldn't see them before because there tiny. Looks like a rebuild:(
     
  13. geron

    geron National Petroleum Equipm

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    Oh dear, I hope it's not a daily, then you can take your time with it.
     
  14. beaver

    beaver southern zeds

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    No not a daily, more like a quarterly, spoke to lindisy zshop, yes there still going, and he may be able to get a built engine form a customer who smashed her car before the engine went in.
     
  15. MickW

    MickW Carntry member...

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    Bugger.
     

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