Matts2k87

I reattached all hoses and accessories to my engine, and refilled the coolant while bleeding out the air. It was late at night so I didn't start the car to cycle the system and check for any last signs of air so just rested cap on and called it a night.
I came out in the morning, removed the cap and turned my reds on for a few secs to get fuel pressure and then noticed coolant starting to drip on the floor. I've tried finding the leak removing as little as possible and cannot see it any where.
My question is, can I perform a compression test with a slight coolant leak without it affecting the results? I just put every back together so don't want to pull it half back apart.

Sorry for a noob question, it's my first compression test and just want to make sure it's done right. Thanks guys

99SH

Without knowing what work you just did on your car... it's OK to do a compression test in your current condition. Assuming you don't have a coolant leak seeping thru the headgasket into the combustion chamber.

Remember to disable the fuel system before doing the compression test. I personally pull the fuel pump fuse under the dash.

Matts2k87

Thanks for the fast reply, and yes I plan to pull the fuse for the fuel pump. No major work was done, just an inspection and a clean up of some oil under and in the inlet manifold, along with cleaning PCV valve. Now I just want to check my compression is right because the car doesn't seem to be going as good as it used to. Hoping my rings aren't failing

Matts2k87

Compression test rests;
All numbers averaged over 3 attempts

Cylinder #1

230 psi

Cylinder #3

226 psi

Cylinder #4

221 psi

Cylinder #2

214.75 psi

What do you guys think? Normal enough?

Slowcrash_101

Seems fine, sometimes the bypass hose from the bleeder to the intake manifold leaks, the clamp has to be on perfect. Otherwise it leaks all over your alternator.

Reckon

In and of themselves, the numbers look fine but when looked at all together, there seems to be a large difference, around 6%. The cylinders should all be within 10psi of each other. Perhaps another set of tests to see what you average out as you could have had set of outliers. A leak down test might be in order as well.

Scott@HKSUSA

7% variance is pretty good for a compression test. You really should do a leak down test as well to gauge the condition of the rings (and everything else that seals the CC).

I know this is personal preference but I've always preferred disconnecting the injectors for a compression test vs. pulling the fuel pump fuse. Reason being, there's still pressurized fuel in the line (trapped between the PR valve and pump check valve) when you turn the car off. With the injectors still functioning, that fuel has somewhere to go.

Matts2k87

Will do another comp test tonight and organise a leak down for tomorrow. Thanks guys

Matts2k87

2nd test came up very close:

1st: 233 psi
3rd: 224 psi
4th: 226.5
2nd: 213.5 psi

2nd cylinder seems to be lacking and 1st cylinder by far the strongest. Is this a usual result or just natural selection of which ever ring fails first?
Could find a leak down gauge today at any local automotive shop

Slowcrash_101

Try a leakdown test next, those compression numbers look good to me, to be quite honest. Factory fresh is supposed to be 220psi.