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Compression test figures


reb78
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Now this isnt strictly land rover, but the engine i am talking about was used in the south african spec defenders for a time, so perhaps the mods will leave this for a bit :P ........ It may help others as a general 'how to interpret compression test figures thread though'

I think the head gasket has gone in my 528 BMW - it has the 2.8 6 cylinder engine. I'm struggling to get anyone on the BMW forums to comment on the figures from the compression test and wondered if anyone on here had any ideas. They were as follows:

Cylinder 1 Dry - 14 bar, Wet - 17 bar

Cylinder 2 Dry - 12 bar, Wet - 16.5 bar

Cylinder 3 Dry - 15 bar, Wet - 17 bar

Cylinder 4 Dry - 8-12 bar, Wet - 17 bar (i thought i'd found the problem when this was dry at 8 bar, but repeated it dry and it returned 12 bar the second and third time)

Cylinder 5 Dry - 14 bar, Wet - 16.5 bar

Cylinder 6 Dry - 12 bar, Wet - 17 bar

The minimum pressure for this engine is 10bar dry. Now, the figures above were not what i expected for the wet test (oil in the cylinder) since i thought this would not improve if the headgasket was gone? The figures dont say head gasket to me, but the steam in the exhaust and bubbles in the coolant when revved do. Anyone any ideas? I'm at the end of my tether with this car and it is headed for the scrap heap i think. The repair is as much as the car is worth (and too complicated for me to do because of the special tools), but i wont have faith in it after that!

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I had exactly the same symptoms in my 200tdi - bubbling (but not hot) water in the expansion tank and steam out of the exhaust. Turns out that when I had originally rebuilt the engine, I had not located the head correctly, so it was not properly torqued down leading to pressurising the water jacket and water getting into the cylinders.

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Now this isnt strictly land rover, but the engine i am talking about was used in the south african spec defenders for a time, so perhaps the mods will leave this for a bit :P ........ It may help others as a general 'how to interpret compression test figures thread though'

I think the head gasket has gone in my 528 BMW - it has the 2.8 6 cylinder engine. I'm struggling to get anyone on the BMW forums to comment on the figures from the compression test and wondered if anyone on here had any ideas. They were as follows:

Cylinder 1 Dry - 14 bar, Wet - 17 bar

Cylinder 2 Dry - 12 bar, Wet - 16.5 bar

Cylinder 3 Dry - 15 bar, Wet - 17 bar

Cylinder 4 Dry - 8-12 bar, Wet - 17 bar (i thought i'd found the problem when this was dry at 8 bar, but repeated it dry and it returned 12 bar the second and third time)

Cylinder 5 Dry - 14 bar, Wet - 16.5 bar

Cylinder 6 Dry - 12 bar, Wet - 17 bar

The minimum pressure for this engine is 10bar dry. Now, the figures above were not what i expected for the wet test (oil in the cylinder) since i thought this would not improve if the headgasket was gone? The figures dont say head gasket to me, but the steam in the exhaust and bubbles in the coolant when revved do. Anyone any ideas? I'm at the end of my tether with this car and it is headed for the scrap heap i think. The repair is as much as the car is worth (and too complicated for me to do because of the special tools), but i wont have faith in it after that!

The cranking test pressures are used to indicate mechanical wear discrepancies between the cylinders, but may not show up a headgasket problem. This is because the pressure within the cylinder when the fuel/air is ignited is considerably higher than the pressures achieved during a compression test. So the headgasket may well be leaking, despite the compression test results.

Regards, Diff.

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Once you'd put oil into no.4 it would stay "wet" for quite a while if it's rings say, you need to check it again once it's been run.

Piston ring blow-by could cuase crank pressure which will blow oil into the inlet/turbo area.

The steam could just be the climate.

ow I wanted to buy a leak-down-tester for mine, far more detaiked test than a compression test because you can trace the leak.

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