Diesel Compression Test HOT or COLD

[Red Rover]

The book says HOT. I have always done them hot, but some diesels mechs say they do it cold, so in my opinion they can't be goin by the pressures in the book, but working off their own. Anyone shed any light on it?

[mkpatrol]

A compression test is supposed to be done hot with the throttle valve fully open. With experience a mechanic an determine the condition of the engine without going through this process. A compression test is generally looking for major differences in the compression readings (10 percent) which will vary greatly in a deisel engine if it has a problem. Testing with the throttle open, cold or hot wont make any differnence to the test if the vehicle has a burnt valve which will drop the compression dramatically. Most times when a mechanic is doing a comp test the engine wont run and he has no choice but to do it cold.
Compression testing is not an exact science, more a quick way to check engine condition.
If you want an exact condition report on an engine have a cylinder leakge test done these are more accurate.

[Shadow]

what sorta mechanics can do a cylinder leakage test

and how do they do it?

I noticed in the toyota forums that jhetland had a compression test dont and was given the following results

--------------------------------------------------------------------------------
I got the compression test done today, these are the results:

Davoe gave me the desired numbers:
Desirable- 2746kpa
minimum- 1961kpa
maximum variation between cylinders 196kpa

And these are what came from the compression test today:
Cylinder 1: 1708kpa (350psi) 88% leakage to sump
Cylinder 2: 1611kpa (330psi) 90% leakage to sump
Cylinder 3: 1806kpa (370psi) 86% leakage to sump
Cylinder 4: 1806kpa (370psi) 84% leakage to sump & inlet
Cylinder 5: 1855kpa (380psi) 76% leakage to sump
Cylinder 6: 1855kpa (380psi) 44% leakage to sump & inlet

So the engine is beyond the recovery stage, and almost within the maximum variation. Any opinions? Im going to tassie for easter, and Cape York in June. I shouldnt have any problems doing that, should I?

Jo

is that a simple compression test or as you say, a cylinder leakage test?

[mkpatrol]

what sorta mechanics can do a cylinder leakage test all should :?

and how do they do it? with a cylinder leakage gauge :?

I noticed in the toyota forums that jhetland had a compression test dont and was given the following results

--------------------------------------------------------------------------------
I got the compression test done today, these are the results:

Davoe gave me the desired numbers:
Desirable- 2746kpa
minimum- 1961kpa
maximum variation between cylinders 196kpa

And these are what came from the compression test today:
Cylinder 1: 1708kpa (350psi) 88% leakage to sump
Cylinder 2: 1611kpa (330psi) 90% leakage to sump
Cylinder 3: 1806kpa (370psi) 86% leakage to sump
Cylinder 4: 1806kpa (370psi) 84% leakage to sump & inlet
Cylinder 5: 1855kpa (380psi) 76% leakage to sump
Cylinder 6: 1855kpa (380psi) 44% leakage to sump & inlet

So the engine is beyond the recovery stage, and almost within the maximum variation. Any opinions? Im going to tassie for easter, and Cape York in June. I shouldnt have any problems doing that, should I?

Jo

is that a simple compression test or as you say, a cylinder leakage test?

The first part which is quoting kpa pressures is a compression test and the second part which is quoting percentage is a cylinder leakage test. Looking at those figures the enine has done a few kays.

[Shadow]

what sorta mechanics can do a cylinder leakage test all should :?

and how do they do it? with a cylinder leakage gauge :?

I noticed in the toyota forums that jhetland had a compression test dont and was given the following results

--------------------------------------------------------------------------------
I got the compression test done today, these are the results:

Davoe gave me the desired numbers:
Desirable- 2746kpa
minimum- 1961kpa
maximum variation between cylinders 196kpa

And these are what came from the compression test today:
Cylinder 1: 1708kpa (350psi) 88% leakage to sump
Cylinder 2: 1611kpa (330psi) 90% leakage to sump
Cylinder 3: 1806kpa (370psi) 86% leakage to sump
Cylinder 4: 1806kpa (370psi) 84% leakage to sump & inlet
Cylinder 5: 1855kpa (380psi) 76% leakage to sump
Cylinder 6: 1855kpa (380psi) 44% leakage to sump & inlet

So the engine is beyond the recovery stage, and almost within the maximum variation. Any opinions? Im going to tassie for easter, and Cape York in June. I shouldnt have any problems doing that, should I?

Jo

is that a simple compression test or as you say, a cylinder leakage test?

The first part which is quoting kpa pressures is a compression test and the second part which is quoting percentage is a cylinder leakage test. Looking at those figures the enine has done a few kays.

sweet thanks

so what sort of mechanic can do a cylinder leakage test?

my 2H is also getting tired and wanna know if its worth doing the Head.

[mkpatrol]

How many kays?

[Shadow]

How many kays?

370k

but its got a head leak, and i dont wanna spent a shitload getting head and fuel system overhauled if the bottom end is too tired to bother.

im assuming it will be pretty tired thats why i havent bothered doing the injectors or head yet, but it would also be good to know for sure.

[mkpatrol]

Rebuild it, ereconditioning the head will inrease the compression and place extra pressure on the rings causing them to fail.
Does it run rough and bloe white smoke when it first starts and if it does, for how long?

[Shadow]

runs a little rough when it starts,

blows some black smoke when it starts for about 10 seconds