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weirdo compression test...theories?

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suhweeed
Posts: 3
Joined: 6 October 2018
Year and Model: 1990
Location: nashville

weirdo compression test...theories?

Post by suhweeed »

So check this out. Ran compression test on all 4 cylinders, warm (after the 1 turn plug backoff and run that volvo recommends, distributor and injectors disconnected). results:

1990 b230f 400k miles with zero engine work
1-165
2-165
3-155
4-155

went back to cylinder 3 to add about a teaspoon of oil for a wet test to determine if rings or valves are making the difference. Probably added more like a tablespoon accidentally because it got away from me. But anyway, re-tested cylinder 3 and BAM compression jumps up to 240 almost immediately. Figured the extra oil plus the weak rings sealing was the reason. bummed. removed tester and cleaned oil out of its fittings. BUT then went back to cylinder 4 to do the same and ran it DRY again first just to make sure i got the same dry reading again on it. BOOM...180 with no oil added. Pulled off the tester and brand new fresh oil just like i put in cylinder 3 was inside the adapter fittings. THEORY: tiny head gasket leak between 3 and 4 allowing the oil i added to cylinder 3 to pass into cylinder 4. Please tell me i’m right because that wouldn’t spell doom for my rings!!

lummert
Posts: 1381
Joined: 29 January 2008
Year and Model: 760 1988
Location: Portland Indiana, USA
Been thanked: 26 times

Post by lummert »

Not uncommon for the head gasket to blow between 2 adjacent cylinders.
1988 Volvo 760 Turbo Wagon

suhweeed
Posts: 3
Joined: 6 October 2018
Year and Model: 1990
Location: nashville

Post by suhweeed »

with compression of 165 you think i’m ok to pull the head, replace head gasket, and put new valves, guides, seals, hushers, springs, and retainers? Kinda worried about putting to much pressure on the bottom end of rings are weak.

lummert
Posts: 1381
Joined: 29 January 2008
Year and Model: 760 1988
Location: Portland Indiana, USA
Been thanked: 26 times

Post by lummert »

Leak down test?
1988 Volvo 760 Turbo Wagon

suhweeed
Posts: 3
Joined: 6 October 2018
Year and Model: 1990
Location: nashville

Post by suhweeed »

went ahead and pulled the head. almost zero piston slap on cylinder 1. 2,3, & 4 had zero piston slap. head gasket was leaking between 3&4 a little, and leaking a tiny amount between 1&2 and 2&3. A couple valves were little loose in their guides. Evidence of lean condition in 3&4. Everything else looks perfect. crosshatches still there after 400k miles! 90 Volvo b230f w/o cylinder squirters. damn i love volvos.

lummert
Posts: 1381
Joined: 29 January 2008
Year and Model: 760 1988
Location: Portland Indiana, USA
Been thanked: 26 times

Post by lummert »

Time for head reconditioning or find a good used head.
1988 Volvo 760 Turbo Wagon

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