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Hi,

I have a '93 1.8Ltr and I am getting a compresion test done and was wondering if someone can tell me what level I should expect to see from the results if everything was normal. The car has done 225K.

Thanks

brand new is about 200psi, you dont want to see a lot lower than 150psi (this is just about a drop in power as a fraction ie; 150/200 is 3/4 original power) Assuming you manage to do better than 160 or so your golden, a large variance in pressure indicates something like a valve problem or something.

Dann

Nicky,

A compression check is a good start, and as Dann said, a large difference between cylinders, or a pair together that are low can help diagnose the problem. To confirm a cylinder head / gasket problem, you can't go past the radiator pressure test and chemical test. They pressurise the cooling system,and have a liquid setup that chnages colour in the presence of CO, a major component of the fule burn process. If it changes colour, you know you have combustion gases in the cooling system, which confirms a head gasket problem.

Russell

1.8 compression test, figures taken from enthuasiast workshop manual.
12.8 kg/cm2 = 182 psi @ 300 cranking RPM
9.0 kg/cm2 = 128 psi is acceptable with no more than 2.0 kg/cm2 = 28 psi difference between cylinders.

I had my compression test done and 200 psi on three cylinders and 195 psi on the other.

That sounds surprisingly good compared to what xmx106 was saying it should be, I guess I should be pleased with that shouldnt I considering the high Ks on the clock.

Sounds like it was very good. Just needs 15psi of boost now and youll be set.

Dann

Those don't sound bad at all.

Next question did you find out where you lost the coolant and the cause of the white smoke when you start up cold.
Those compression pressures are excellent, no problems there, shows how good these engines are.
Some guys have reported 215 psi.

Hi guys,

Yeh apparently I was loosing coolant from the lower radiator hose due to a faulty seal around the clamp which he found by doing a pressure test. The white smoke is almost non existant on start up now. In KYP's opinion it is probably due to a faulty oil ring on the cylinder with low compression and/or faulty valve stem seals which Im not too worried about at the moment, my main concern was the loss of coolant and whether the two were related.
So all in all I am happy that I dont have a huge job to do at the moment, the cars running great. I guess in time if the smoke gets worse I will have to do something about it.
Time to get my road/track tyres which I had put on hold

That's good news.

Just for comparison, I did a compression test on my NA8 before dismantling the motor because of a buggared crank. At 175,000kms it held 187 on 3 cylinders and 183 on the 4th. After dismantling and cleaning, the bores and pistons looked absolutely new - you could still see all the original honing marks on the bores. All the rings were still within new factory assembly tolerances.

I'd say that if yours is reading 200psi then you've got no worries about pistons and rings for a long, long time.

whatever way you look at it 225k is well into old age- 18yo. Cars wear out but if it is running well and safe and not breaking down then go with the flow. Many owners never see 100K on their cars - traded or sold - long before they start to do major maintenance.

Thats because they dont do the minor maintenance.. or they bought an astra or vectra..

Dann

I did a comp test on mine last night...105 - 110 across all 4.......

sounds like you did it wrong. Do you have a really strong battery? And did you hold the throttle flat on the floor? And were all of the plugs out the whole time?

Dann

battery - unsure!
throttle to floor and all plugs out.