Performing Leak Down Test On XJ?

[Kingkong0192]

Just built a leak down tester for the jeep. Didn't want to buy any harbor freight garbage.

Anyways, i've never performed a leak down test on anything, and when i searched i just got individual results. No description on how to actually perform a leak down test.

oh, i forgot to mention. My coolant is disappearing and i don't see any visible leaks. I am trying to test to see if my headgasket is cracked or my head is warped. Is there a special way to test for this? It's a 99 XJ.

My questions;

Do i remove all the spark plugs first?
Do i do this on a warm engine or a cold engine?
Do i do a "Wet test" or a "Dry test"? (If wet, do i just add a few drops of engine oil to cylinder first?)
How do i find TDC so the exhaust and intake valve are both closed?
How much pressure should i put into each cylinder?
How long do i let the cylinder test for?

Sorry for all the questions, but i'm trying to learn and do things right.

Here is a picture of my leak down tester;

 

[lazyxj]

A cooling system pressure tester and combustion leak detector would be more appropriate if you are looking for the source of the coolant loss.
http://www.tooltopia.com/otc-tools-...utm_term=OTC7991&utm_campaign=pricegrabber_r1

http://www.tooltopia.com/lisle-7550...=cse&utm_term=LIS75500&utm_campaign=nextag_r1

A leak-down gauge is for finding the source and amount of compression loss.
http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/viewall.html

 

[Kingkong0192]

A cooling system pressure tester and combustion leak detector would be more appropriate if you are looking for the source of the coolant loss.
http://www.tooltopia.com/otc-tools-...utm_term=OTC7991&utm_campaign=pricegrabber_r1

http://www.tooltopia.com/lisle-7550...=cse&utm_term=LIS75500&utm_campaign=nextag_r1

A leak-down gauge is for finding the source and amount of compression loss.
http://www.carcraft.com/techarticles/116_0406_cylinder_leakdown_tester/viewall.html

Just bought the combustion leak detector, but i do not want to spend $100 on a pressure tester.

Once that dye comes in, and lets say i do find out i have combustion gases in my coolant, that means that my headgasket is shot correct?

My leakdown tester would be able to confirm between what cylinders the gasket was shot, correct?

Another question. I'm going to go perform a compression test. Do i remove all the spark plugs when i do this, or just one at a time? Also, do i need to remove the fuel injectors electrical connection so no fuel enters when i crank?

 

[lazyxj]

Once that dye comes in, and lets say i do find out i have combustion gases in my coolant, that means that my headgasket is shot correct?

My leakdown tester would be able to confirm between what cylinders the gasket was shot, correct?

Another question. I'm going to go perform a compression test. Do i remove all the spark plugs when i do this, or just one at a time? Also, do i need to remove the fuel injectors electrical connection so no fuel enters when i crank?

A leak can from from a bad head gasket or a cracked head or block.
If the leak is big enough, you can hear bubbling, at the radiator cap, when pressurizing the leaking cylinder. A spark plug, with an air chuck, can do the same. Most likely the location of the leak will observabled when the head is removed.

Do the leak down test hot, one plug at a time. The link I gave has instructions. Be care with a breaker bar on the crank, it can violently throw itself if the piston being tested is allowed move downward, break your jaw kind of violent.
Leaving the rest of the plugs in dampens this somewhat.

Definitely disable the fuel system. Cut the power to the fuel pump and make sure the pressure is bleed off.

 

[Kingkong0192]

A leak can from from a bad head gasket or a cracked head or block.
If the leak is big enough, you can hear bubbling, at the radiator cap, when pressurizing the leaking cylinder. A spark plug, with an air chuck, can do the same. Most likely the location of the leak will observabled when the head is removed.

Do the leak down test hot, one plug at a time. The link I gave has instructions. Be care with a breaker bar on the crank, it can violently throw itself if the piston being tested is allowed move downward, break your jaw kind of violent.
Leaving the rest of the plugs in dampens this somewhat.

Definitely disable the fuel system. Cut the power to the fuel pump and make sure the pressure is bleed off.

Thank you. I'm going to go do a compression first. I'll save the leak down test for later.

I'm just going to pull the fuel pump relay and then drain the pressure from the fuel rail. Should be sufficient.

That's effectively what i've made. I took an old spark plug and welded a 1/4" nipple onto it. Just finished modifying my leakdown tester to be a compression tester. Put a tee on it to release the combustion gases, and piped a check valve into it to hold them so it reads on the gauge.

I'm still learning, so bare with me. Haha.