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Thread: compression test

  1. 2nd September 2011, 11:41 PM #1
    escapee
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    compression test

    Hi all, been looking for a D2 for a little while now. Found a V8, 180k Km's, had a land rover mech do an inspection as the car did not come with a service history. He found a wide variation in values on a compression test. Cyl's 1,2,7,8 were within 150 - 140 psi (good) cyl's 3,4,5,6 were 140 - 120 psi (not good). I fink it might be telling me "burnt valves". A car nut at work says it might be the middle 4 cyl's getting the bulk of the crankcase vent gas crap and getting a bit coked up. The end end 4 cyl's, being further away not so badly effected. Does that sound about right ? any other explainations as to the varying values. The rest of the car checks out ok and I really want to be in a disco rather than reading about them in this forum, but... not want to get one that I'll regret.

    Thanks in advance for any thoughts.
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  2. 5th September 2011, 11:56 AM #2
    SteamWolf
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    Could be a multitude of things but carbon won't be one of them.
    Valves may be leaking slightly, or rings getting worn. If it's adjoining cylinders then it's just as likely to be a minor head gasket issue.

    It's signs of an old and worn engine. Factor that into your negotiations
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  3. 5th September 2011, 09:01 PM #3
    escapee
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    Thanks for the input. Just reading over the report again. No blow back in the crankcase means rings are good. comp test was done wet. Cyl's 3&5 are low 125 and 130 respectively. 1&7 are 145. 1,6&8 are 150,140&150, with Cyl No 2 being the black sheep at 120. The car runs nice and smooth, has plenty of go, and idles well. If I hadn't got it checked I wouldn't have known. So yeah, will use it as a bargaining point.
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  4. 5th September 2011, 10:28 PM #4
    PhilipA
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    I wouldn't touch it if no2 alone is down on that bank.
    3and 5 are next to each other and typical head gaskets leak between the two middle cylinders if the head has developed a warp.
    BUT no 2 alone is either a dud valve(unusual) or leaking into the valley( unusual in later motors). Or it it is a slipped sleeve.
    Not unusual if a later V8 is overheated as may be indicated by the other bank.
    Regards Philip A
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  5. 5th September 2011, 10:46 PM #5
    escapee
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    Quote Originally Posted by PhilipA View Post
    Or it it is a slipped sleeve.
    Not unusual if a later V8 is overheated as may be indicated by the other bank.
    Regards Philip A
    Thats sending alerm bells! Top end work I could live with but if its a liner sounds like a big deal from what i have casually read here on the forum. Is there any other tests that can be done or other indications i should look for? I'll try and do some searching on this site also and see what I can find. Thanks for the heads up!
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