Low Compression/excessive blow-by
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Low Compression/excessive blow-by
Hey guys,
I have had my 1995 Volvo 850 GLT 190k for over 3 years now, and I have learned to work on this car pretty good.
I am trying my best to keep this car alive and in good running condition. I was very fortunate when i bought the car, the guy had all the service records, so i know what was replaced when. I got a really good deal on it bc when i bought it, the ac didn't work, the interior wasn't in the best of shape and the instrumentation wasn't lighting up, but i have fixed those problems fairly easy. The a/c just needed a new low pressure switch (pressostat) and the instrumentation lighting just needed a new fade switch, and a few new bulbs. I noticed I had excessive pressure in the crankcase and smoke coming out of my dipstick, so I completely replaced the PCV system a while back, but it seems it hasn't fixed the problem. I did some research and found out that the smoke and crankcase pressure may be due to excessive blow-by. I did a compression test wet and dry to see the difference, and it looks like this may be my problem. I was wondering if anyone had the same problem with their Volvo and what they did to remedy the situation.
It seems I may have stuck rings and/or scorn walls, which I don't understand bc this car has been taken car of since day one, but old age must have taken toll. I did notice that the owners manual does recommend 91+ octane fuel to be put into these cars and maybe that so many years of low grade fuel may have something to do with this problem.
I have been trying Seafoam hot soaking to possibly knock my rings lose, but I don't know how effective it is. I would hate to have to take the whole head off to get to the pistons, but it may be my only option at this point.
Here are my wet and dry compression numbers for each cylinder.
Dry
1 - 140
2 - 138
3 - 142
4 - 132
5 - 145
Wet
1 - 175
2 - 175
3 - 175
4 - 180
5 - 185
I have had my 1995 Volvo 850 GLT 190k for over 3 years now, and I have learned to work on this car pretty good.
I am trying my best to keep this car alive and in good running condition. I was very fortunate when i bought the car, the guy had all the service records, so i know what was replaced when. I got a really good deal on it bc when i bought it, the ac didn't work, the interior wasn't in the best of shape and the instrumentation wasn't lighting up, but i have fixed those problems fairly easy. The a/c just needed a new low pressure switch (pressostat) and the instrumentation lighting just needed a new fade switch, and a few new bulbs. I noticed I had excessive pressure in the crankcase and smoke coming out of my dipstick, so I completely replaced the PCV system a while back, but it seems it hasn't fixed the problem. I did some research and found out that the smoke and crankcase pressure may be due to excessive blow-by. I did a compression test wet and dry to see the difference, and it looks like this may be my problem. I was wondering if anyone had the same problem with their Volvo and what they did to remedy the situation.
It seems I may have stuck rings and/or scorn walls, which I don't understand bc this car has been taken car of since day one, but old age must have taken toll. I did notice that the owners manual does recommend 91+ octane fuel to be put into these cars and maybe that so many years of low grade fuel may have something to do with this problem.
I have been trying Seafoam hot soaking to possibly knock my rings lose, but I don't know how effective it is. I would hate to have to take the whole head off to get to the pistons, but it may be my only option at this point.
Here are my wet and dry compression numbers for each cylinder.
Dry
1 - 140
2 - 138
3 - 142
4 - 132
5 - 145
Wet
1 - 175
2 - 175
3 - 175
4 - 180
5 - 185
Last edited by gch23775; Sep 7, 2019 at 01:56 PM.
Senior Member
Joined: Dec 2008
Posts: 461
Likes: 0
Number is not great, but they are even which what's most important.
What parts did you use for the PCV?
You might need bigger hoses.
https://www.matthewsvolvosite.com/fo...=77278#p413610
What parts did you use for the PCV?
You might need bigger hoses.
https://www.matthewsvolvosite.com/fo...=77278#p413610
Thread Starter
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Junior Member
Joined: Sep 2017
Posts: 8
Likes: 0
I used genuine parts from FCP, cleaned the block ports and my EGR port good.
I originally got the wrong size PCV valve box with the kit i ordered, so i had to order the bigger one that fits my car.
I'm pretty sure I used big enough hoses, I even used a bigger size hose coming from the PCV valve to my oil trap, so i don't think that is the problem.
I originally got the wrong size PCV valve box with the kit i ordered, so i had to order the bigger one that fits my car.
I'm pretty sure I used big enough hoses, I even used a bigger size hose coming from the PCV valve to my oil trap, so i don't think that is the problem.
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