I compression tested my motor last week and got 220 across the board minus #4 cylinder which was 150. So I wanted to do a leak down test to pin point what the issue is.

So I bought a harbor freight leak down tester.

Like this one...




Instructions say to take the plug out and have the cylinder you're testing at TDC. So I did just that.

Had my compressor turned on and regulated to 90 psi.

Hooked the tester up and then hooked it to my compressor and turned the regulator on the compressor on until the right gauge was at 0.

I had the oil dip stick out, pcv valve off and the throttle wide open.

The gauge wouldn't read above 5% max.... there was a lot of noise from the intake itself but the gauge wasn't reading over 5%. So I was thinking maybe I wasnt on the compression stroke...so I turned it until it was at TDC again....and I did the same thing. It went to about 5% but I felt some air out of the pcv and the dip stick holes.

I don't think I'm doing something right.... the cylinder had 150 compression so it should have a lot more leakage than 5%.

Any clues?

I was using a smaller compressor but it was 2hp like recommended. I think it had a hard time holding 80 psi consistantly but if I turned the regulator on the compressor back up to 80-90 while it was going the gauge would jump to 20%. It did the same thing for cylinder 1 as well though... so I know that isn't consistent as cylinder 1 had 220 compression.


I just want to know what I need to fix... I also had the radiator cap off and it had no bubbles during this test...so I'm assuming it's NOT a head gasket.






Thanks

 

what was the reason for doing the compression test? was there a problem with the car?

also, when doing compression tests, i'm guessing you did cylinder #4 last? did you make sure the battery still had a good charge? if charge was low, your compression will probably read low too.

 

I've checked it several times since then... it being first as well.


Reason for doing it was just because I bought it from a kid who supposedly didn't treat it right.

I ran a buddies 93 nissan 240 (140hp) on the highway 40 to eh around 90 or so...and he was only 2 cars back.

I knew something was up then.... it's down on power.

New plugs...new oil..new diff fluid....compression is low in #4 for sure.

 

Try moving the cylinder down a bit (still on the compression stroke). If leakage increases, cylinder is scored

 

Did you do this test with the engine hot? if its cold yuor rings could be stuck causing blowby. make sure the piston doesn't move when you pressurize the cylinder. i'm still trying to figure out what the battery has to do with a compression test? the honda shop manual does not call for a leak down test, just a regular compression test. you just don't want to see readings less than 135psi per the book. good luck. hope the info helps.

 

honda service manual specifies RPM for the compression test. if RPM is low, compression will be lower too. weak battery = not enough rpm, therefore low compression numbers

honda service manual specifies maximum variance for compression. the thread starter's compression has exceeded maximum allowable variance therefore something is wrong w/ the engine.

anyways if a cylinder is scored near the middle or lower part of the cylinder, a leakdown test done with the cylinder at TDC will show good results. however, if you move the cylinder down, leakage will increase at the part of the cylinder that is scored.

 

I moved it all around.... and basically air came out of the PCV....


I added a tea spoon or so of oil to the #4 cylinder and compression jumped up 20.

Meaning piston ring....


I guess it's time for a rebuild.

Wheres the best place to look for a rebuild kit at?

 

Try this before you go to that. put a can of 4 cylinder restore in your oil. this stuff really works cause i've used it with great resuts. it will bring your compressions up and even them out across all the cylinders. think of it as your last resort to an overhaul. run it in your oil til the next oil change then do another compression check. keep us posted.

 

Which one? Theres a bunch of those compression restorers at Autozone.

 

perhaps you are suffering from damage due to oil starvation in cylinder #4...from the old oil jet bolts...