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Thread: One piston low compression...can I just replace the rings?

  1. #11  
    deltaolds
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    compression test ain,t gonnat tell you where the leack is, it can be valves or rings,
    imo, it ain,t rings, 120psi diff, due to rings, gas blow by, would boil your oil, prbly valve isn,t seated right, but i might be wrong, in any case take the head off first, use cyliner bore guage to see how bad your cylinder walls are off, and see if they aren,t out of round.
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  2. #12  
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    Quote Originally Posted by 92oyale4x4
    Don't need to take the spark plugs out. It will work fine the way I did it and that is how it's been done.


    Again...what is a cylinder leak down test?

    Google it.
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  3. #13  
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    Quote Originally Posted by Txchevy
    BTW-a Cylinder leak down tester can be picked up at any parts store. You stick it in the spark plug hole and turn the engine with the starter per the tester instructions. It will give you a psi reading.
    How did you come up with the 180 and 60 psi readings?
    Wtf are you talking about??? Thats a compression tester.

    Cylinder leakdown is a test used to narrow down where the problem is. Much like a compression test, a hose is used to thread into the spark plug hole. However, you then hook up an air hose to this hose and inject compressed air. This has to be performed the the tested cylinder at 100% perfect, spot on top dead center or the air pressure will simply shoot the piston down to the bottom and open up one of the valves.

    After the air is put in, listen to 3 places:
    1. Exhaust tail pipe. A hissing sound here means a bad exhaust valve
    2. Intake. This means a leaky intake valve.
    3. PCV valve/whatever ventilates the crankcase means bad rings.


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  4. #14  
    Cars R A Habit nota Hobby CF Senior Member
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    Quote Originally Posted by 99hondaaccord
    Wtf are you talking about??? Thats a compression tester.

    Cylinder leakdown is a test used to narrow down where the problem is. Much like a compression test, a hose is used to thread into the spark plug hole. However, you then hook up an air hose to this hose and inject compressed air. This has to be performed the the tested cylinder at 100% perfect, spot on top dead center or the air pressure will simply shoot the piston down to the bottom and open up one of the valves.

    After the air is put in, listen to 3 places:
    1. Exhaust tail pipe. A hissing sound here means a bad exhaust valve
    2. Intake. This means a leaky intake valve.
    3. PCV valve/whatever ventilates the crankcase means bad rings.
    You know what,Your a *******. Even guys like me make mistakes. I haven't used one in about tens years. BTW-assclown the PCV valve is on the valve cover 100% of the time, which would mean a bad valve seal. I dont know what the phuc ur problem is lately but ur really starting to piss me off with all ur "knowledge".
    Drive fast, take chances.
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    Quote Originally Posted by Txchevy
    You know what,Your a *******. Even guys like me make mistakes. I haven't used one in about tens years. BTW-assclown the PCV valve is on the valve cover 90% of the time, which would mean a bad valve seal. I dont know what the phuc ur problem is lately but ur really starting to piss me off with all ur "knowledge".

    If it didn't ventilate the crankcase it probably wouldn't be called a Positive Crankcase Ventilation Valve.
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  6. #16  
    Cars R A Habit nota Hobby CF Senior Member
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    I thought about it. Really if you have that big of difference between 180 psi and 60psi you know something is very wrong. Either blow by, which is the ring or a valve seal is gone. At that point you know its got to come apart. Why even bother with a leak down test? With that big of a difference I would bet money its the piston ring.
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  7. #17  
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    Didn't know this thread was still going.

    Anyway. I had the head checked. The valves were o.k, but it needs a valve job to be back to a good shape. He said that when he tested it, that the valves were holding at 60%, still not enough to be 120psi off. I still think it's the rings in that one cylinder. I am going to buy some rings and replace that one piston on Monday...unless I absolutely HAVE TO hone it...do I?
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  8. #18  
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    Yes the cylinders need to be honed anytime the rings are replaced. If not it will take FOREVER for the rings to break in. A honer only costs about 15 or 30 bucks, depending on the type you get. There are two types to speak of, the "deer turd" and "bicycle brake", I prefer the bicycle brake because I find it easier to get the text book cross hatch pattern.

    I'm not trying to poke at anyone here but 92oyale4x4 basically just sated why its important to use a leakdown tester when diagnosing compression problems. No sense in wasting money on parts or machine work that doesn't need to be done, especially if you don't have the spare cash.

    I wanted to throw this in too. Its not that the cylinders are 120 psi off of each other. I never look at the book for specs on compression. There is a good rule of thumb for it. Cylinders hit poorly under 100 psi, and below 90 they usually don't hit at all. Anything over 125 is decent and I'd 180 psi is excellent. So if the other cylinders are in such good shape I'm very surprised the rings are only worn in one.
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  9. #19  
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    Thanks, can I hone it myself?

    Also, if it's not the head then what could it be? Not the head gasket!
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  10. #20  
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    Yeah if you own a 3/8 drill and honer you got it covered.

    In all likely hood it probably is the rings, I would say make sure the piston isn't cracked but you said you were buying a new one. So you should probably check the ring lip on that cylinder wall, just to make sure that cylinder doesn't need to be bored. I'd say if its much thicker than your thumbnail you may want to have it checked.
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