Hello,

I have a 1995 civic dx with 235,ooo miles on it which has been getting lower gas mileage and losing some coolant lately. The power seems good still. I did a vacuum test off the intake manifold and got a steady 22 reading. Then I ran a compression test and got initial/high readings of 80/120 for #1 and #2, 75/115 for #3 and 85/123 for #4. I ran each 3 times with the same results each time. The readings rose to their high points within 3 or 4 revolutions, so that seemed OK to me a tleast (having never done this before). Can anyone speak as to whether these are good results or might point to a problem? Thanks,

Andrew

 

You're not doing the test quite right but I think you're getting numbers that say compression is fine.

Compression tests should be done on a warm engine and cranked at least 4 times with spark plugs removed from all other cylinders. I have some reservations about removing spark plugs from a warm cylinder head, so be careful of fouling the threads.

If you test it on a cold head, then you're basically looking for uniformity between cylinders, which you're getting.

If you're suspecting a headgasket leak, they dont usually show themselves in a compression test. For that you would want to do a leakdown test on each cylinder at the appropriate cam location with all valves fully closed, and look to see if you have bubbles coming out of the radiator cap.

 

Thanks for your response boiler1. I actually did have the engine warmed up for both tests that I ran. I appreciate the heads up on being careful with the threads. Hopefully I was careful enough with them or that will be an awful mess. As far as running a leak down test, I did not have any luck with any of the auto parts stores in my area renting them out. Any suggestions on how to do this cheaply (or free preferrably). Buying the test kits for this is unreasonable if you're only going to do it once or twice, as they are much more expensive than for the other tests. Also, will a coolant pressure test tell me much about the head gasket? Thanks again,

Andrew

 

The hose from most compression testers can serve as a leak-down tester. Disconnect the quick connector at the gauge and set the gauge aside. Note that the connector is the same as used on most air compressors. Remove the check valve from the spark plug end.

Now you have an adapter to supply air from your compressor into a cylinder through the spark plug hole. Rotate the engine until both valves are closed and the air doesn't just blow out the intake or exhaust. Keep the cylinder under pressure and watch for bubbles in the radiator. Repeat with all 4 cylinders.

A simpler test is just to get the radiator completely full, then start the engine cold with the radiator cap off and rev it up. If there's leakage you should see bubbles or even coolant blowing out of the radiator in a severe case.

 

Yeah the leakdown test would give you better results.

Cylinder Leak-Down Tester

I bought this leakdown tester when I replaced my motor. The directions really really suck but the tool itself works pretty well for what it's worth. Look up on youtube how to use this tool. Took me some time to figure it out but once I learned it, it was fine and provided consitant results.