compression test result help needed

[artfulflounder]

Hi guys with regards to volvo 940 turbo.

Got positive crank case pressure but know its not the pcv system...also loosing some water.(max to min level in 140mls).

No obvious signs on oil filler cap and dip stick still looks clear....maybe a gnats c*ck on the bottom.

So I bought myself a compression tester so I could check.

Results are as follows..

#1 142.5 psi
#2 137.5 psi
#3 140 psi
#4 140 psi

Not what I expected, first time using one and thought I'd see obvious signs on the readings.

Am I still on right track?? Can the head gasket still be at fault without showing on readings??

Any experience or advice greatly appreciated.

Cheers guys.

[stribo]

I'd check for a water leak, you may have a pinhole in the radiator, that only leaks when the car warms up. As for the positive crankcase pressure, that could just be a sign of the engines age, and the piston rings not sealing as well as they once did.

[artfulflounder]

Thanks for ur quick reply.

I did think of rings but again would have thought I'd have seen a low compression reading on which ever cylinder.

I understand a leak down test could check for this but I dont own a compressor or relevant tools.

I changed all pcv system and belts a few months ago and had no issues with positive pressure. Seems to be a recent issue.

[claymore]

put a little oil in the cylinders and re-do the test, if the results are a lot better, then that would point to worn rings.

[artfulflounder]

put a little oil in the cylinders and re-do the test, if the results are a lot better, then that would point to worn rings.

As suggested above....

#1 175 psi
#2 180psi
#3 200psi
#4 175psi

So deffinetely #3 ?

Now whether to re-ring and know that its been done or take chance on scrapper engine with dubious history I pressume then?

What about the procedure of dipping a hose into a jar of water through vacuum hose into inlet while running to clean valve train and piston tops etc.
Will find link for an example.

[Harvey]

Number 3 could be a bit high if you put a little to much oil in there..?
The water loss have a good look at all the hoses,the heater matrix is not leaking under the dash ? Are the carpets dry?.

Just thinking is the car a auto ,do they have a oil cooler in the rad like the newer cars have ?.

[artfulflounder]

Just thinking is the car a auto ,do they have a oil cooler in the rad like the newer cars have ?.

Yes it is an auto and i do believe there is an ATF cooler in the rad............i will check the ATF oil for coolant or increased level..

[rikcougar]

Compression readings are fine, using oil in ther bores always increases the readings

Wouldn`t suspect a head gasket but a sniff test will tell you for sure

[960kg]

As suggested above....

#1 175 psi
#2 180psi
#3 200psi
#4 175psi

So deffinetely #3 ?

Now whether to re-ring and know that its been done or take chance on scrapper engine with dubious history I pressume then?

What about the procedure of dipping a hose into a jar of water through vacuum hose into inlet while running to clean valve train and piston tops etc.
Will find link for an example.

I think your compressions are fine also......don`t forget you are talking proper pucker Volvo engineering here not like the later motors.

I knew two Volvo mechanics that had the 940 turbo and each one was over 400,000 and still on the same original turbo.

The water jobby does work ok ...i used to do this with my 6 cylinder 960 to clear the crap out.....but be careful about 1 second dipped in the jar only otherwise you may get a hydraulic lock which will damage the engine.

I know where your link is and also do the Italian Tune Up as by Aber Crombie ....doing this properly at those revs. revolves the valves on there seats and cleans them. Have a read of it.

Good Luck

[Dangerous Dave]

Excess crankcase pressure could also be the valve stem seals. If they have never been done they will be worn and brittle and won't seal properly against the pressures in the inlet/exhaust ports.

Had the same problem with my 850 (and my 940), when I did the head gasket I changed the seals, the seals were that worn the valves just dropped out and the new ones held the valves tightly. No more excessive crankcase pressure after that (also cured all the oil being forced into the intake).

Water loss could be anything. Check the heater matrix (somehow LOL, its a nightmare to get to) and radiator. Also check the water pump gasket, I've just changed the heater matrix on my sister's 940 which was losing a fair bit of water (wasn't the headgasket as we've not long done that) and whilst in the engine bay I noticed a small amount of water in the undertray, turns out the gasket on the bottom of the water pump was pi$$ing out, so whilst we were at it I whipped it off and made a new gasket for it. I could literally squeeze the rad pipe and watch coolant leak out the bottom of the pump LOL

[artfulflounder]

Thank you soooo much guys....lots of info and advice given.

Going to go ahead with head gasket set, check shims and what not. Thermostat and waterpump will be changed at same time from above advice.
That gives me opportunity to check water system, no signs of water from heater matrix or contamination of oil so possibly the radiator plastic end caps.

Again thanks guys and I'll update you with progress.