Compression test and what to expect???? 94MY 850 T5 2.3

[Wheelspinwardrobe]

Hi all

On A Volvo 850 T5 with 130k + What psi should I expect from a compression test - what psi is ok ?? and what psi is bad????

Not sure I read Haynes correctly....

Thanks Phill

[Tim Williams]

140-150PSI is normal, you ought to not have more than 10PSI difference between the best and worst. 160-170PSI is about the highest you are likely to see and that would mainly be due to carbon build up.

[Shinsplintz 101]

Iirc you want around 150 plus psi per cylinder & variation wants to be with 10 psi across the 5. Could be wrong. I'm on morphine atm :)

Lol as Tim says above - see I do listen! Just can't type as quick

[Wheelspinwardrobe]

All 5 cylinders where between 150-160 psi.... I thought they would be higher than that a little....

[t5 pete]

That sounds right our s70r with 120k has 160 all across clyinders the gul has 182 all across with a new built engine

[960kg]

Of course the psi has to be ok within the recommended but when actually testing the readings are all relative as it depends what temp. the engine is when tested.....lower when colder and higher when hotter.

On a std. motor the difference between any pot should be no more than 2 bar = 29psi

[Wheelspinwardrobe]

Of course the psi has to be ok within the recommended but when actually testing the readings are all relative as it depends what temp. the engine is when tested.....lower when colder and higher when hotter.

On a std. motor the difference between any pot should be no more than 2 bar = 29psi

Mine was 150 - 160 psi cold ....

[t5 pete]

Yes I also did mine on the gul on a cold engine and warm engine on s70

[Wheelspinwardrobe]

So 150 - 160 psi isn't so bad then??

[t5 pete]

Correct

[weagie]

Out of interest what compression testers are worth having? I've looked at a few and to be honest they all look the same but have wildly varying prices.

[T5G]

For those worried about keeping the mileage low, my 850 T5 with 300k miles and no engine work has compression between 150-160 psi :-) just oil changes every 10k.

[Doingitsideways]

All 5 cylinders where between 150-160 psi.... I thought they would be higher than that a little....

Don't confuse the N/A engine's figures if you're going from the Haynes book of lies.
A N/A engine will give much higher readings.

[960kg]

It doesn`t matter what the compression is!... one doesn`t have to compare with any other engine just your own readings on your own engine as you have five pots to choose from so they all won`t all give knackered readings......

They could read 120psi which is ok as they ALL are the same as you have used the compression tester in the same way for all pots at the same engine temp.......if one or more was minus 29psi then there is a problem!

Some owners put a teaspoon of oil in each pot and after 20minutes get a compression of 185 or even more .....which again is ok, so long as they are all very similar.

[Doingitsideways]

Yes, but he said he was expecting them to be higher.

Was just saying that if he's mistakenly looked at the N/A figures in Haynes, his engine has a lower compression ratio so would be expected to be lower.

[960kg]

This should help...

As you can see it doesn`t really matter if the OP has read the Haynes book wrong for psi details as they almost overlap if one type engine is lower than another type.

A turbo engine with a teaspoon of oil in the chamber will probably read higher than a higher compression NA model with a worn engine.