Leak down testing help Options

[tornik550]

My engine was recently rebuilt and had about 250 miles on it. I was having some issues with cylinder number 3 and I needed to remove the engine.

My buddy gave me a harbor freight leak down tester and I decided to play with it. I do not have the head on cyl 3,4 so I played with cyl 1,2. I have never used a leak down tester. I realize that the engine should be warm however I cannot warm the engine since the other half is out of the car and I cannot wait to play with my new toy until the engine is back in. Here is what I did and the results (I should mention that I was getting good compression numbers from cyl 1,2,4 prior to pulling the engine)-

I set cyl 2 at TDC (also had the rockers removed so TDC probably doesn't matter).
Hooked up the hose to the spark plug hole
Hooked up the gauge section of the tester to the air hose, turned the gauge until the leakage gauge reads 0% (the other gauge read at around 10 psi?)
Then I hooked the coupler up to the hose from the spark plug hole
Read the gauge- 35%

Did the same thing with cyl 1- same results 35%

Just to play around, I decided to leave one of the valves open. I thought it would read 100% leakage- it read 35%- WTF.

It seems that I am not doing something right. Is this simply because the engine is cold?

ALso- Bonus question- How can I tell if my cylinders are glazed? I figure that now is a good time to find out so I can get them honed if necessary.

THanks!!!!

[messix]

glaze??


look for galling, long scuff marks from the top of the cyl. to the bottom.

with only 250miles you should see very clearly the cross hatch of the honing.if you not not see a nice even and gall free cross hatch you should get them honed again.

[john rogers]

There are lots of things that can affect leakdown and some matter more than others. The two sixes I had put in the race car both had a leakdown done as they were sitting for over two years each and even though cold, etc they had less than 5% so they were considered okay. On the other hand there was a REAL Porsche 917 at a vintage CA speedway race years ago that had approximately 75% leakdown, smoked like hell when started but within a couple minutes all smoke stopped and it ran like a monster! 75%, never seemed to matter I guess to the engine I guess.

[messix]

i really don't think you can trust a leak down as you are doing.

are you using 10psi to pressurize the cylinder?

you will need much more [like 90psi] than that to get the rings to seat and give an effective seal.

here is a bit more info http://www.carcraft.com/techarticles/116_0...ster/index.html

[tornik550]

I think that my results are not very useful since the engine is not hot. I also am not too worried about the numbers since I will be going over the P/C and heads shortly.

I really think that I am not using the gauge correctly. When I try to set the leakage gauge to 0% prior to hooking it up to the cylinder, the pressure gauge goes all the way down to 10 psi. If I set the pressure gauge on the leak down tester to a higher number like 90 psi, the leakage gauge needle shoots way past 0%. In the instructions it says that I am supposed to set the leakage gauge at 0%. FYI- I have my air compressor set at 100 psi.

How do I set my psi to be higher AND also have the leakage gauge set at 0%

[SLITS]

I have one ... never seems to read correctly I guess.

Probable solution is to replace the cheap gauge (percentage gauge) with a good gauge that reads 0 - 100 psi then you can do your own percentage calculation. I believe that someone did this to get the HF to read correctly.

Oh well, it was cheapinexpensive. (IMG:style_emoticons/default/smile.gif)

[VaccaRabite]

I owned a HF leak tester for about a week. It was defective out of the box. Always read 45%. I got a second, which worked once (ie, 1 cylinder, not even the whole engine) and then always read 32%. Took it back and did not try a third.

I got a real leak tester, and it works great. For what it's worth, I have never used it on a warm engine. I always use mine at 100 PSI.

Zach

[tornik550]

I owned a HF leak tester for about a week. It was defective out of the box. Always read 45%. I got a second, which worked once (ie, 1 cylinder, not even the whole engine) and then always read 32%. Took it back and did not try a third.

I got a real leak tester, and it works great. For what it's worth, I have never used it on a warm engine. I always use mine at 100 PSI.

Zach

Where did you get the second one? I have never seen another for sale?

Are there any other adjustments that i can make on the gauge other than the big black plastic knob? I do not want to run by harbor freight if I do not have too because it is somewhat far for me.

I said earlier in the post that I always get readings of 35%- I actually always get readings of 32% just like you. The wonderful thing is that I get 32% when the valves are closed AND if they are completely open!!! Crazy.

[VaccaRabite]

Nope just the big knob.

10PSI is not enough pressure to run the test. Try it with 100 PSI and see if it still reads 32.

Zach

[tornik550]

Nope just the big knob.

10PSI is not enough pressure to run the test. Try it with 100 PSI and see if it still reads 32.

Zach

I am having a hard time figuring out how to run the test with more than 10 psi. My compressor is set at 100 psi. If I turn the black knob so that the pressure gauge reads more than 10psi, the leakage gauge shoots past 0%. I turned the pressure down so that the leakage gauge would read 0%, then the psi goes back down to 10.

[VaccaRabite]

Nope just the big knob.

10PSI is not enough pressure to run the test. Try it with 100 PSI and see if it still reads 32.

Zach

I am having a hard time figuring out how to run the test with more than 10 psi. My compressor is set at 100 psi. If I turn the black knob so that the pressure gauge reads more than 10psi, the leakage gauge shoots past 0%. I turned the pressure down so that the leakage gauge would read 0%, then the psi goes back down to 10.

Return the HF tester. I have yet to see one work.

if you don't want to buy one, you can usually rent them from your FLAPS. I got mine on Ebay.

Zach

[VaccaRabite]

Check this out:
http://cgi.ebay.com/ebaymotors/DUAL-GAUGE-...omotiveQ5fTools

[tornik550]

After reading a bit online about leak down testers and specifically the HF leak down tester. It appears that the leak down tester from harbor freight is made incorrectly. The leakage gauge is only setup to do a compression test between 10-15psi- even though the box and pressure gauge says 100 psi. So bottom line- worthless. I was able to fix it though. I had a 100 psi gauge laying around. I unhooked the leakage gauge and hooked up a 100 psi gauge. It now works perfectly.

I redid the leak down test with my new setup. I got 7 psi leakage from cyl 1 and 2. Much better.

[VaccaRabite]

Good on you!

Now, what did Cyl 3 say?

Zach

[tornik550]

Good on you!

Now, what did Cyl 3 say?

Zach

Not sure because I have the cylinders off 3 and 4. I found a new problem. Here is a link to my new issue.
http://www.914world.com/bbs2/index.php?showtopic=111168

[VaccaRabite]

D'oh!

Zach