Pressure testing for head gasket leak

[Mooney 2]

Has anyone successfully pressure tested the cooling system and found their leak head gasket or other? Pretty sure I need a head gasket. Wondering if it's possible to find it with a pressure test. I' going to pressure test just in case it actually is something simpler to repair but all signs point to gasket. How much psi should I test it at? How long should it sit. Should I test it cold or warm or both? Thanks

 

[Yamadog]

Well I blew one last season it was so small that would run ok at 7 # of boost but 12# would push a small amount of coolant into the overflow causing a bubble and over heat. As soon as I would stop it would cool so quick that it pulled the fluid back in system and then run fine

 

[Mooney 2]

Mine is NA and it doesn't ever pull the coolant back in. It pushes out enough to fill the overflow and then with lack of coolant in the system it then overheats. Lower exchanger and rad are just warm not hot.

 

[Yamadog]

Mine is NA and it doesn't ever pull the coolant back in. It pushes out enough to fill the overflow and then with lack of coolant in the system it then overheats. Lower exchanger and rad are just warm not hot.

It depends on the size of the breach mine was less than a pencil lead and went right to a water jacket line

 

[Mooney 2]

How did you confirm that was your issue? Where you able to confirm before you took the head off?

 

[Yamadog]

Nope Allen Ulmer built it and said no way but ruined my year last year. Finally found a shop here that could time the cams without pulling the motor pulled the head bingo Arp studs and back together yeemaha

 

[Mooney 2]

Pressure tested ok. Did the blue fluid test that detects combustion gasses in the coolant and stayed blue indicating no combustion gasses in system. I'm lost guys We are going to try using a vacuum filler to fill the system tonight but I can't imagine it's been an air lock giving me all this trouble.

 

[grizztracks]

A bad radiator cap, thermostat or a restriction in a line or exchanger/radiator can all cause this problem. I've found these engines typically don't have a problem purging air out of the system. A couple of short heat cycles and topping off the radiator and overflow bottle when cold usually works all the air out. There have been a few reports of overheating being caused by a bad coolant pump so it may be worth checking that out.

I've worked on several of these engines with over heating problems that pushed coolant out the overflow. So far all of them have been bad head gaskets with slightly warped heads. Did you remove the plugs for the pressure test and have you looked for small air bubbles in the radiator? Sometimes when these leaks are small they only occur when at max operating temperatures.

 

[Mooney 2]

Plugs were in. I didn' think I would find the head gasket leak with the pressure test that was more so to find a leak other than the head gasket. I don' think at 20 psi the head gasket would show? Probably needs more pressure to leak. It doesn't push coolant out of the overflow it just fills the overflow to about 3/4 once it gets warm. Pretty much stays that way. Warm cold doesn't matter after it has pushed the coolant to the overflow. Cap thermostat sensor have all been checked or changed. Can only see bubbles for the first 15-30 seconds of running with cap off and refilling the system. Seems like typical bubbles for a system that is down on fluid and is being refilled. Then they stop. Once it starts to get some temp and the system has been filled while running it starts overflowing no bubbles just starts spilling out the fill neck.

 

[grizztracks]

Any mods or recent work on the sled? When you say it overheats what is the actual coolant temperature at that point? Also, have you seen the fan run?

After a heat cycle and coolant fills the overflow bottle can you add coolant to the radiator? If so add it but only when cold. Run it again until the coolant temperature increases enough to open the thermostat and circulate the coolant then let it cool again and recheck to see if you can add coolant to radiator when cold. Do this several times and if there is a problem the added coolant will eventually fill the overflow bottle to the point it overflows.

 

[scalise71]

Grizz, in another post the OP stated it used to have a turbo.

 

[yammitrip1]

Get something that you can't put in the coolant cap plastic molded part. Fill with coolant. Fire it up and let it idle till it gets hot hot. Like dang near when the fan gets on if you have to. Watch for bubbles.

 

[yammitrip1]

Pressure testing is a very poor way to test for a bad gasket. Cylinder pressures are really high, and in most cases the gasket will most likely seal off when not running if you did have a problem. In severe cases you would be able to tell, but you also would see coolant in the exhaust or it burning it on start up and smell it or it really over pressurizing the coolant system

 

[Mooney 2]

It to my knowledge has never had a turbo. Just to clarify. Tonight we vacuum filled the system and it seemed to have air in it. It took three bleeds to get all the air out. Idled in the shop for 20 minutes operating properly up to 195 fan comes on cools to 183 fan shuts off over and over. Went for a ride at fairly high speeds with some wot runs. Come back after 15 mile loop and the overflow bottle is near full again from starting at half. Let it cool to see if it would suck some back in after cooling, nope. Went out again on a bit shorter loop and it pushed more coolant to the bottle to absolutely full. Gonna do a leak down test next but im pretty sure its a head gasket. Shitty!

 

[Mooney 2]

Pressure testing is a very poor way to test for a bad gasket. Cylinder pressures are really high, and in most cases the gasket will most likely seal off when not running if you did have a problem. In severe cases you would be able to tell, but you also would see coolant in the exhaust or it burning it on start up and smell it or it really over pressurizing the coolant system

Didn't pressure test to find head gasket leak, tested to find any other leak.