Tried my own leakdown test - Honda Prelude Forum

99Prelude_LC · 12-08-2002, 09:25 PM

Ok I tried doing this test according to http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm

I removed the plugs, and placed a wire down the #1 cylinder. I rotated the crank and stopped when the wire hit its highest point to bring it to TDC. I then stuck my air contraption down there and cranked it to 100psi. Well the first time i did this i didnt realize the air was turning the crank so it was moving the piston outta position. and i was getting air comming out of other cylinder holes. So I went back and tried again while slowly bringing the psi to 100 so the crank wouldnt move.

On cylinder 1 i got a faint wisp of air comming from the intake and exhaust

cylinder 2: no intake, faint wisp from the exhaust

#3: no air escaping anywhere

#4: no intake, faint wisp from exhaust

and these were my compression test results from awhile ago
165 195 90 205

So why did nothing come out of #3 when the compression was 90. Also when I did hte test the last time I didn't get any air out of the oil cap.

The first time I did the test i did #3 adn #4 had a lot of air comming out of the intake, but i don't know i got frusterated since i was doing it bymyself and called it quits. what did i do wrong?

oh and also, from my last thread, yeah i looked at my boost gauge, it sits aroud 15psi and moves around but not in a steady fashion if i remember right, just kinda goes from 15-18 to some other random pressures in between but it doesn't move fast, just will change every now and then. and when i drove my car out back i got a CEL misfire in cylinder 3

Danomite · 12-08-2002, 09:41 PM

Quote:

Originally posted by 99Prelude_LC
Ok I tried doing this test according to http://www.geocities.com/dsmgrrrl/FAQs/leakdown.htm

I removed the plugs, and placed a wire down the #1 cylinder. I rotated the crank and stopped when the wire hit its highest point to bring it to TDC. I then stuck my air contraption down there and cranked it to 100psi. Well the first time i did this i didnt realize the air was turning the crank so it was moving the piston outta position. and i was getting air comming out of other cylinder holes. So I went back and tried again while slowly bringing the psi to 100 so the crank wouldnt move.

On cylinder 1 i got a faint wisp of air comming from the intake and exhaust

cylinder 2: no intake, faint wisp from the exhaust

#3: no air escaping anywhere

#4: no intake, faint wisp from exhaust

and these were my compression test results from awhile ago
165 195 90 205

So why did nothing come out of #3 when the compression was 90. Also when I did hte test the last time I didn't get any air out of the oil cap.

The first time I did the test i did #3 adn #4 had a lot of air comming out of the intake, but i don't know i got frusterated since i was doing it bymyself and called it quits. what did i do wrong?

oh and also, from my last thread, yeah i looked at my boost gauge, it sits aroud 15psi and moves around but not in a steady fashion if i remember right, just kinda goes from 15-18 to some other random pressures in between but it doesn't move fast, just will change every now and then. and when i drove my car out back i got a CEL misfire in cylinder 3

If you Vacuum is jumping around like that then I am 100% sure that your valves are bent.

To answer your question for the why you had a lot of air coming out of your Intake, its most likely because you were on the Intake stroke instead of the Compression stroke. In order to do the test correctly, you must be at TDC on your Compression stroke. Thats when both your valves are closed and shouldn't have any leaks at all if they are seated correctly.

Just out of curiousity.........what percent leakage did you have in each cylinder? About the no air coming out of your crankcase, thats impossible. You must have done something wrong because there will alway be air coming through your crankcase when performing a Leakdown test.

99Prelude_LC · 12-08-2002, 11:03 PM

well the crankcase was virtually quiet, compared to a wispy noise or even a loud wooshing noise. I didn't do percent leakage, i tried with a guage but it didn't work, i already know the compression is bad i don't need numbersj ust where its bad at!

if its not at TDC would tha explain the air shooting out of another cylinder hole?

Danomite · 12-08-2002, 11:16 PM

Quote:

Originally posted by 99Prelude_LC
well the crankcase was virtually quiet, compared to a wispy noise or even a loud wooshing noise. I didn't do percent leakage, i tried with a guage but it didn't work, i already know the compression is bad i don't need numbersj ust where its bad at!

if its not at TDC would tha explain the air shooting out of another cylinder hole?

Air shooting out of another cylinder port? Hmmmmmm, have you checked your oil or coolant since this incident?

Being at TDC is one thing, you also have to be on your Compression stroke in order for the leakdown test to be done properly. If you're not at TDC on your Compression stroke.......your engine will spin right when you hook the air up to it.

99Prelude_LC · 12-09-2002, 11:05 AM

so how do you get it exactly at that point? since you can turn it for a short amount where it doesn't even move up or down anymore. ahh it was confusing to say the least

also this was on a cold motor.

Danomite · 12-10-2002, 02:02 AM

You can get exactly to TDC by looking at your timing mark on your Flywheel for Cylinder 1 and 4. For 2 and 3 you can take off your Cap and look at the rotor in your Distributor.

So have you checked your oil or your Coolant since the incident? I am curious to know this.....since you said that you were getting air out of a partner cylinder when you did the leakdown. Which Cylinder were you on....and which cylinder did air come out of?