what do these compression test results tell you ?
Discussion
Right following on from this thread http://www.pistonheads.com/gassing/topic.asp?h=0&a... z12xe engine swap I thought i'd start a new thread to get a bit more exposure as it developed.
Corsa 1.2 sxi 03 reg.
Heavy blue smoke all temperatures, worse when cold.
very little on tickover but increases when rev's are increasing
used 5L of oil in 1 week!
no missfire, slight flatspot on changing of gear.
Plugs 2+4 were very black but dry. 1+2 were clean and as should be expected.
so far i've serviced it (oil + air) and fit new plugs cleaned the throttle body + breather pipes out (nothing in there to be honest)
So here are the results for both wet + dry tests .
DRY TEST
1 220psi
2 260psi
3 240psi
4 260psi
WET TEST
1 270psi
2 270psi
3 300 psi
4 290 psi
Theese to me say possibly valve stem oil seals?
any suggestions are appreciated
thanks johny
Mods i'm going to try and lock the other thread now but if i cant manage it please do it for me thankyou
Corsa 1.2 sxi 03 reg.
Heavy blue smoke all temperatures, worse when cold.
very little on tickover but increases when rev's are increasing
used 5L of oil in 1 week!
no missfire, slight flatspot on changing of gear.
Plugs 2+4 were very black but dry. 1+2 were clean and as should be expected.
so far i've serviced it (oil + air) and fit new plugs cleaned the throttle body + breather pipes out (nothing in there to be honest)
So here are the results for both wet + dry tests .
DRY TEST
1 220psi
2 260psi
3 240psi
4 260psi
WET TEST
1 270psi
2 270psi
3 300 psi
4 290 psi
Theese to me say possibly valve stem oil seals?
any suggestions are appreciated
thanks johny
Mods i'm going to try and lock the other thread now but if i cant manage it please do it for me thankyou
Blue smoke increases when revs are increasing is saying bore-related wear to me.
Valve stem seals/guide wear tends to be big cloud of blue smoke at start up (from oil that has leaked down while the engine has been standing), that burns off after a minute or two.
Standard test to confirm this is (or used to be, when I were a lad - they've probably got a computer these days) to run the car up to operating temperature, then go down a nice, long hill in gear but off the throttle (ie. with the engine on over-run). The engine 'sucks' the oil down the valve stems on the over-run, so If you get a haze of blue smoke as you go down the hill, or a cloud of the stuff when you go back on the throttle at the bottom, it's seals/guide wear.
Blue smoke under hard acceleration (as you seem to be suggesting you have?), tends to be bore/ring wear as the combustion pressures leak past the piston rings. Could be worth checking the breather system, though, as sometimes it's something as simple as a blocked breather.
Has the problem developed suddenly, or has it been burning oil for a while?
ETA: and, yes, unless you fancy a bottom-end rebuild that'll cost more than the car is worth, you'll be looking for either a second-hand engine or a gullible/careless buyer.
Valve stem seals/guide wear tends to be big cloud of blue smoke at start up (from oil that has leaked down while the engine has been standing), that burns off after a minute or two.
Standard test to confirm this is (or used to be, when I were a lad - they've probably got a computer these days) to run the car up to operating temperature, then go down a nice, long hill in gear but off the throttle (ie. with the engine on over-run). The engine 'sucks' the oil down the valve stems on the over-run, so If you get a haze of blue smoke as you go down the hill, or a cloud of the stuff when you go back on the throttle at the bottom, it's seals/guide wear.
Blue smoke under hard acceleration (as you seem to be suggesting you have?), tends to be bore/ring wear as the combustion pressures leak past the piston rings. Could be worth checking the breather system, though, as sometimes it's something as simple as a blocked breather.
Has the problem developed suddenly, or has it been burning oil for a while?
ETA: and, yes, unless you fancy a bottom-end rebuild that'll cost more than the car is worth, you'll be looking for either a second-hand engine or a gullible/careless buyer.
Edited by Sam_68 on Sunday 4th December 21:52
i've only had it a week, got it durt durt cheap, and tbh second hand engine was my initial thought and was what i had set my mind on.
I also thought it was more terminal due to the shear amount of oil it had used.
I will try your over-run test and see what the crack is< thanks
johny
anyone else?
I also thought it was more terminal due to the shear amount of oil it had used.
I will try your over-run test and see what the crack is< thanks
johny
anyone else?
They tell me very little given they are far too high for a mundane road engine which should be showing no more than 200 psi even in perfect condition. 300 psi is diesel engine territory. So I surmise that the test was done with a cold engine with so much oil in the bores that it distorted the readings or the gauge was misread or doesn't work properly. Try the test with another gauge and the engine hot so any oil that has leaked into the bores overnight has burned off.
5 litres of oil consumption per week is more telling. It's pretty pointless worrying too much about the exact cause if the engine is that shagged.
5 litres of oil consumption per week is more telling. It's pretty pointless worrying too much about the exact cause if the engine is that shagged.
Pumaracing said:
They tell me very little given they are far too high for a mundane road engine which should be showing no more than 200 psi even in perfect condition. 300 psi is diesel engine territory. So I surmise that the test was done with a cold engine with so much oil in the bores that it distorted the readings or the gauge was misread or doesn't work properly. Try the test with another gauge and the engine hot so any oil that has leaked into the bores overnight has burned off.
5 litres of oil consumption per week is more telling. It's pretty pointless worrying too much about the exact cause if the engine is that shagged.
Unless he does 20k in a week...lol5 litres of oil consumption per week is more telling. It's pretty pointless worrying too much about the exact cause if the engine is that shagged.
Leaving aside the numbers, the compression drop and issues being across 1 and 2, makes me think it might be a head gasket blow between those two pistons, which has spread to include an oilway. If the engine is coming out otherwise it seems a sensible idea to whip the head off to take a look.
I've lost count of how many head gaskets I've done on these little babies. The only hardship will be supporting the engine to take the side casing off to get at the cam chain. I'd be very surprised if it's anything less than a head gasket failure. I've never had one with failed rings or bore problems other than sticky rings through bore wash caused by an old woman who drove it less than a mile a day and it never got warm.
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