Help w/Leakdown Test

[OneQuikSix]

I'm performing a leakdown test on my car and have tested each of the passenger side cylinders thus far. I'm not sure I'm doing everything correctly though. This is my procedure:

1. Engine hot
2. Move respective cylinder to TDC
3. Both valves closed (heads brand new BTW and recently back from good machine shop)
4. Pressurize cylinder using leakdown tool attached to shop air compressor
5. I open pressure regulator valve until leakage gauge reads zero/set and stop
6. Now, according to the instructions, I'm supposed to read the same leakage gauge for my resulting leakage for that cylinder.

On all three cylinders, I performed this procedure exactly as described. When the leakage gauge shows zero/set, the pressure gauge (0-100psi) shows 15psi for all three cylinders. The other thing that confuses me is I hear a steady current of air moving through the crankcase; which to me sounds like a blown headgasket.

This is a fresh rebuild and I don't think the car drives badly enough to have three cylinders leaking compression as badly as they are. The only path the air can travel with the valves closed is either past the rings or through the headgasket right? The car doesn't smoke and doesn't appear to be using water. I do notice what appears to be steam coming from the passenger side valve cover breather and was concerned enough to do this test for the first time.

Any ideas???

 

[DailyDrifter]

+1 on leak down testing.

If your hearing it in the crankcase its the rings, but as long as they are under 15% (if memory serves me right ) you are good. Your coolant would be bubbling if the HG was blown. Keep in mind your engine is still somewhat fresh. IMO I think your engine is fine, the smoke in the breather is nothing to worry about. Keep the tune safe and Let It EAT!!!

 

[OneQuikSix]

Thanks for the reply. I guess I'd feel alot better if I knew I was reading the gauges correctly. I'd love to be able to confirm there was nothing wrong with the headgaskets without removing the heads.

 

[TurboBuRick]

I have to agree with D.D. Your going to have some leakage past the rings.

Are you seeing vapor out the breather @idle? Are you running a pcv?

What do the plugs look like? Are they consistent?

 

[OneQuikSix]

I'm running a PCV but I've got it bypassed for the purposes of troubleshooting a knock issue I'm having. I've read where some have installed an oil catch can to help, but I thought it would be a good idea to make sure I had a good seal first; eliminate a possible problem.

I just tried again and I do not hear any noise from the tailpipe while performing the test. I do feel a small amount of air escaping through the oil dipstick which I suspect is normal. I'm only confused because the more I increase the air pressure on the tester, the lower my leakdown gauge reads...I mean well past zero. It will actually go into the negative reading and hit the needle stop. Everything I read online says I'm performing the test correctly.

With the PCV connected, no excess oil vapor through the breathers. Spark plugs all look great so far.

 

[gsgns4me]

Thanks for the reply. I guess I'd feel alot better if I knew I was reading the gauges correctly. I'd love to be able to confirm there was nothing wrong with the headgaskets without removing the heads.

If your tester has 2 gauges that read PSI, set the first gauge to 100 PSI, then put air to the cylinder and read the 2nd gauge. If the 2nd gauge reads, as an example, 95PSI, then you are reading a 5% leak down. Using 100 PSI on the first guage makes the math easier.

If the 2nd gauge is the type that shows the percentage, then green is good, yellow and red not so good.

 

[OneQuikSix]

After some research, I found many people have reported the same problem using the particular U.S. General leakdown gauge set I purchased from Harbor Freight. There are even a couple videos on YouTube where one guy is asking for help using the gauges on his WRX.

Since everything has cooled off, I'm going to button everything back together, purchase a compression test gauge, and perform that test first. Then, if any cylinders appear to have lower compression than the others, I'll perform a leakdown test using a different gauge set. At this point, I'm not even sure there is a problem. I'm just trying to rule things out.

 

[JayC]

Leakdown tests are great and my preferred method of diagnosis for headgasket issues however for about 90% of the headgasket cases you'll run into, a compression test will tell you what you need to know.

If you didnt remove the pushrods from the engine, you're probably have issues with the valves not being closed all the way. You can sometimes get away with a leakdown with the pushrods still in if you leave plugs in all the cylinders you arent testing but most of the time, the pressure from the air pushes the piston into a position the valves are closed all the way.

 

[OneQuikSix]

If you didnt remove the pushrods from the engine, you're probably have issues with the valves not being closed all the way. You can sometimes get away with a leakdown with the pushrods still in if you leave plugs in all the cylinders you arent testing but most of the time, the pressure from the air pushes the piston into a position the valves are closed all the way.

That thought did cross my mind. I removed the rockers to be sure.

 

[JayC]

That thought did cross my mind. I removed the rockers to be sure.

Sounds like you were good then

 

[OneQuikSix]

I just finished the compression test and all cylinders read between 140 and 145. It looks like all is well with the world! If I can find my receipt, I'm returning that leakdown tester to Harbor Freight Thanks for everyone who replied.

 

[TurboBuRick]

So are you still having the issues that led to the comp test?

 

[OneQuikSix]

So are you still having the issues that led to the comp test?

I just wanted to make sure the amount of oil vapor coming through the valve cover breather was not a result of a blown head gasket. Now that those look good, I'll be shopping around for an oil catch can to install inline with my PCV. That should eliminate the oil vapor escaping the breathers. I originally disconnected the PCV hose to the throttle body to see if the oil vapor introduced to the airstream was the source of my 0-1psi boost knock. Disconnected, the car seemed to run much better but I need a permanent solution...hence the catch can.