Compression test questions

[mr walker]

This is my first post here, and it's likely in the wrong forum (not in N/A engines). This forum appears to get a lot more traffic and it looks like there's a few technical questions here as well.

I recently purchased a 1996 BG (Outback) 5 speed with 148,000 for $700 as it needed a clutch. It has the EJ22. The body is in remarkably good shape, even though it was used as a farm truck to haul hay around (no, seriously). It starts and appears to run great, and came with some decent service history. I'll be pulling the engine to replace the clutch, t-belt/idlers/tensioner, misc. seals, and also head gaskets.

I figured I would do a compression check beforehand to get a baseline of the engine's overall condition. The results were 125-140psi. The test was done TOTALLY COLD. I know it's supposed to be considerably higher, but I wasn't sure if the engine being cold or hot could have that big of a difference.

So, with all that being said, I suppose my question is are these results with a cold test cause for concern?

Your thoughts or opinions are welcome and appreciated!

[Thomistopheles]

IIRC it should be 155-185 psi. Did you try adding a bit of oil and rechecking?

Reads higher = piston rings.
Reads same = valves or head gasket.

[rougeben83]

cold will affect your psi readings (lower).

[jjay03]

If it will run ide do the test with the engine warm and make sure to hold the throttle open.

[mr walker]

IIRC it should be 155-185 psi. Did you try adding a bit of oil and rechecking?

Reads higher = piston rings.
Reads same = valves or head gasket.

Does a wet test work reliably/accurately with our boxer engines?


cold will affect your psi readings (lower).

That's what I'm really hoping...but 30psi+ seems like a lot.


If it will run ide do the test with the engine warm and make sure to hold the throttle open.

I had the accelerator pinned while cranking. With the current state of the car it would take a bit of work to allow it to reach operating temperature, but if this means my engine may be dying then I suppose it's worth it to get it hot and retest.

Thanks for the replies so far guys, much appreciated.

Edit: I should have added that I used a compression tester purchased from Harbor Freight...yeah. It IS brand new, but still...