20 replies to this topic

[Ethel]

Compression tests aren't an exact science, apart from blow by  more charge can be lost before the inlet valve closes because it's turning that much slower on the starter. You certainly can't make calculations with the static compression ratio and expect to see the gauge read the same.

[BaronVonchesto]

Just wanted to follow up a few months later. Didn't want to start a new thread so that the history wouldn't be lost.

 

After 2 hours on the motorway, engine had a horrid ticking noise and wasn't sounding all that great. It also had noticeably less power on the road (at least compared to when i first did my rebuild 3 years ago).

Decided to do a new compression test. Here are the results for a HOT DRY compression test (within an hour after a 2 hours on the motorway)

 

No 1:  87.5psi

No 2:  85psi
No 3:  85psi

No 4:  100 psi

 

I'm guessing there's a head gasket leak? My exhaust is showing some steam and my coolant level in the radiator has dropped.

[Northernpower]

Just wanted to follow up a few months later. Didn't want to start a new thread so that the history wouldn't be lost.

After 2 hours on the motorway, engine had a horrid ticking noise and wasn't sounding all that great. It also had noticeably less power on the road (at least compared to when i first did my rebuild 3 years ago).
Decided to do a new compression test. Here are the results for a HOT DRY compression test (within an hour after a 2 hours on the motorway)

No 1: 87.5psi
No 2: 85psi
No 3: 85psi
No 4: 100 psi

I'm guessing there's a head gasket leak? My exhaust is showing some steam and my coolant level in the radiator has dropped.

It definitely needs a leak down test but because its so easy I'd take the head off.

[Spider]

I really don't put much faith in compression tests as they don't by a long way simulate what's going on when the engine's running, however comparison between cylinders may indicate possible issues (or can also lead you up the garden path too).

 

These variations could be from lots of things, but along with a head gasket issue, it could be the valves aren't sealing.

 

How much oil is it using ?

[BaronVonchesto]

I really don't put much faith in compression tests as they don't by a long way simulate what's going on when the engine's running, however comparison between cylinders may indicate possible issues (or can also lead you up the garden path too).

 

These variations could be from lots of things, but along with a head gasket issue, it could be the valves aren't sealing.

 

How much oil is it using ?

When you say "oil" moke, do you mean petrol or engine oil?

 

For petrol I havent found anything out of the ordinary, for engine oil it doesnt seem to be using any. It was last changed about a month ago. Filled with the full 5 litres of penrite. Level in the dipstick still appears near the full level.

 

However the collant burning off certain, and the weird sound of the engine is also another giveaway that something is wrong. Will take a video and post it shortly

[absx2]

If it`s any help my 10.3:1 998 economy engine has just tested 210 psi on all four cylinders and the mk2 Cooper motor 190 psi on all four cylinders stone cold with throttle wide open and no plugs fitted.

I had a 1098 showing low cold cranking compression that turned out to be the dot to dot cam timing was way off but all the evidence looks towards pulling the head off yours.

Personally I think 165 psi is about as low as I would like to see as a guide to condition on a A series engine