Leak Down Tester?

[Hudson]

I keep losing coolant from my jeep. I'm trying to rule out a HG or even a head problem. Have all the parts laying around my house to build a leak down tester, i'm just half clueless on how to build one, because i've never used one.

Can someone please tell me if i should be using option A (first picture) or option B (second picture)?.

I do not see anyone else with a ball valve in any of their leak down tester which is why i'm confused.

Here's my thinking;

Option A;

It's setup like everyone elses. First gauge (right of picture) shows the incoming air pressure from my air compressor, it goes through the pressure regulator and the second gauge shows the pressure it's reduced down to. Makes perfect sense.

I'm going to weld a 1/4" coupling to the third picture, and then thread a 1/4" NPT x 3/8" barbed fitting into it. Barbed side goes into 3/8 Tygon tubing, and on the other side is going to be another 3/8" barbed x 3/8" NPT fitting.

Option B;

Same as option A, except i added a ball valve after the pressure regulator. I was thinking that if there is no way to stop the flow of air, how the hell can i check the pressure leakage if the compressor just keeps pumping air in as it leaks out of the cylinder. Don't i have to put the cylinder to 100PSI, then close the ball valve, and watch the gauge to see if it drops? How can people use no ball valve?

Is my question even clear? Sorry for the ramble.

[ct67_72]

Do it like #2 so that you can disconnect the air supply and watch for actual leakdown on the gauge. Do it this way because you are building it your self.
A 2 gauge leakdown tester is designed to be set to a specific pressure on the first gauge, and the second show you the percentage of leakdown from said pressure. Since I dont think you can accurately do this your self, a ball valve will work as well. It wont be specific to pressure, but you can see how many psi per second/minute etc.

[Hudson]

Do it like #2 so that you can disconnect the air supply and watch for actual leakdown on the gauge. Do it this way because you are building it your self.
A 2 gauge leakdown tester is designed to be set to a specific pressure on the first gauge, and the second show you the percentage of leakdown from said pressure. Since I dont think you can accurately do this your self, a ball valve will work as well. It wont be specific to pressure, but you can see how many psi per second/minute etc.

So build it with the ball valve as a cutoff?

I don't understand though. On the 2 gauge leakdown tester what is stopping the compressor from just pumping air into the cylinder as the pressure in it "leaks down"?

I know that a compression test tests for the pressure in a cylinder while a leak down test does the exact opposite. Which would be better for determining a shot HG or head problem? Or should i do both?

[ct67_72]

Nothing stops the air from coming back out. The second gauge is basically measuring how much is passing through from the first gauge to the cylinder. There is always air pressure.
I guess you could do the same. Im just not sure what kind of gauge it would take to do it.

[ct67_72]

Oh and the leakdown is definitely better. You can presurize and look for bubbles in the coolant, and narrow it down to an individual cylinder. You can also just pressurize a cylinder and do the same. The idea is at leas to be able to see which cylinder has the highest leakage first.
With a small leak you dont always see a problem with a normal compression test.

[Hudson]

Alright this is starting to make sense. Thank you for dummying everything down for me.

I was just going to ask about not having a ball valve, but i figured fuck it, i might as well just leave it on, and that way i always have the option to cut air off to the cylinder.

If you were personally building this, would you do anything different?

I'm going to fill up the nipple right after the ball valve and right before the tee with epoxy, and then drill a .040 hole through it to act as a damper. I don't know why this is recommended and honestly i wasn't going to do it, but EVERY build i've read on this suggests it. Might as well do it.

Off topic but I just saw your jeep on Craigslist. I've been following your build. Why are you trying to sell it?

[Hudson]

I do not have a .040 drill bit. The smallest i have is a .0625.

Think this is too big to drill out the damper? Is that 225 thousandths going to make or break this?

[ct67_72]

Jeep probably isnt going anywhere. Wanted to see if any one would give me what I wanted.
I just read into making them a bit more, and about the orifice. Im sure you could go bigger, but I think on something with low leakage the larger orifice would allow the cylinder to fill too fast and register a lower leakage reading.
So technically you wouldnt need a ball valve to test leakage but I still like it being there.

[Hudson]

Jeep probably isnt going anywhere. Wanted to see if any one would give me what I wanted.
I just read into making them a bit more, and about the orifice. Im sure you could go bigger, but I think on something with low leakage the larger orifice would allow the cylinder to fill too fast and register a lower leakage reading.
So technically you wouldnt need a ball valve to test leakage but I still like it being there.

Ah. I just look at my jeep as a project that i'll never sell because i know i'll never even come close to breaking even.

Thank you. I was reading all sorts of websites as well, but no one seemed to blatantly state why you didn't need a ball valve. Went ahead and piped it all together. Works perfect. Just need to make the piece that goes from the leak down tester to the spark plug.

That should be done tomorrow. Actually made a writeup that i'll post up here in case anyone is interested in making their own. (Not that it's rocket science.)

[ct67_72]

Loos good. What did you use for an orifice? Also, with the ball valve you can do compression tests. Since you cant have a schrader valve inline the ballvalve will hold the compression as long as the second gauge reads high enough. Then you can just release the pressure with the valve.

[Hudson]

Loos good. What did you use for an orifice? Also, with the ball valve you can do compression tests. Since you cant have a schrader valve inline the ballvalve will hold the compression as long as the second gauge reads high enough. Then you can just release the pressure with the valve.

Epoxy. I filled the nipple like 1/2 with epoxy and then drilled a hole through it.

I'll probably tap out the inside of another nipple and screw a plug into it then drill the .040 hole into the plug. Will work a lot better than epoxy, but for now that should be fine.

Hm. I'm not following you. As soon as i stopped cranking wouldn't all the pressure leak back down into the cylinder if i didn't have a shredder valve or check valve?

I think this below would work as a compression tester.

First picture shows the leak down tester setup.

I think the second picture should work as a compression tester, correct? That's a check valve so it should stop all the pressure from coming back into the cylinder. Should work perfect.

[Hudson]

Got the nipple welded to the spark plug.

It's done. Going to check each cylinder in the jeep now just need to read up on how a leak down test is actually performed.







Oh, and just took it apart and added another tee with another valve to release the combustion gases. This is now a complete leak down tester and compression tester in one. Made it for free too!

[ct67_72]

Nice! Just make sure you are perfectly on tdc when you use it. A little off and it will spin the engine right around.
I like to pull the rad cap, and dipstick too. Then you can listen for air from the crankcase from blow by, check for bubbles in the coolant, and also put an ear to the intake and exhaust.
I had a Ford v10 the other day I could feel the air from the exhaust and dipstick.

[Hudson]

Well, i got the thing working. Put 100 PSI into cylinder #1, and according to my gauge there is 100% leakage in cylinder #1 through the throttle body.

I guess my intake valve is shot? I can hear air rushing out of the intake.

Could this be a result of me not finding true TDC? I'm going to keep going on my cylinders and see what happens. Will make a video and upload it here.

[ct67_72]

Well, i got the thing working. Put 100 PSI into cylinder #1, and according to my gauge there is 100% leakage in cylinder #1 through the throttle body.

I guess my intake valve is shot? I can hear air rushing out of the intake.

Could this be a result of me not finding true TDC? I'm going to keep going on my cylinders and see what happens. Will make a video and upload it here.

Yes it could. I would imagine that you are on the intake stroke and not the compression stroke and the intake valve is open. You need TDC compression