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How to put piston at TDC for leak down test?

Discussion in 'Terminator Talk' started by doubleblack, Jan 23, 2010.

  1. doubleblack

    doubleblack New Member Established Member

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    Car started to run like crap so I pulled the plugs and found oil on the drivers side spark plug, closest to the front of the car. Is that piston #5?

    So I want to do a leak down test and don't have experience doing this. I just bought a harbor freight leak-down tester.

    What's the proper procedure to get the piston to exactly TDC for a leak down test? I couldn't find how in the service manual.

    Do I turn the crank w/ a ratchet clockwise? counterclockwise? does it matter?
     
    Last edited: Jan 23, 2010
  2. boosted2000si

    boosted2000si All good things end! Established Member

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    Drivers side plug in the very front is the number 1 cyl. I prefer the ole long rod on top of the piston to fine TDC. I actually use my OE antenna, lol, cause I have a shorty now.

    Always spin the motor clockwise. Spinning counter clockwise can do a number to the timing chains.
     
  3. wjurls

    wjurls More money than brains Established Member

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    Uh, drivers side front would be #5. But yeah a rod in the cylinder will tell you when the piston is on top but not neccesarily dead center but that's ok. Just make sure the rod doesn't bind and then snap off in the cylinder. I had that happen once with a wooden dowel DOH!. Also there are 2 TDC positions. One is the top of the compression stroke (this is the one you want) the other is at the top of the exhaust stroke (You dont want this one). If you have a 100% leak, turn the engine 180 degree's back to TDC and try again. On a cold engine you don't want to see any more than 20% leakage. Less on a warm engine.
     
  4. doubleblack

    doubleblack New Member Established Member

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    good info guys, I'll try the rod in the piston trick...spinning it clockwise...
     
  5. oldmodman

    oldmodman Well-Known Member Established Member

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    I got the Harbor Freight tester also.

    I sure hope it's accurate because I tested my Cobra while it was still just broken in and I got between 4 and 7 percent on each cylinder. And it was the last cylinders that I checked that read higher. I went from back to front, drivers side first, then passenger side. I think that since it took me a couple of hours that as the cylinders got colder they got "looser"
     

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