LR4 - Coolant Under Pressure When Cold

[greiswig]

It's hard for me to tell from that video whether that's releasing positive or negative pressure, and the way this thing is plumbed I'm not sure what to expect out of the coolant level in either case. I'm not near my vehicle so I can't check mine for you.

Any sign of white smoke on startup? Any other symptoms of any kind? If you're feeling really squeamish about things, a compression test would help alleviate some concerns, more than likely. You could also do a leakdown test on the coolant system (pressurize it artificially when cold, see how it holds the pressure). Then look for that white smoke on startup to see if it forced coolant into a cylinder.

The other thing that I suppose might cause this is if your system isn't fully bled. A pocket of air somewhere expanding and contracting with the temperature change might contribute to more of this than in a system where there was zero air.

FWIW, it would not surprise me or alarm me to see some pressure differential after 12 hours of cooling as long as there is no clear loss of coolant, no white smoke, and no overheating or puddles on the ground.

 

[f1racer328]

That’s a good point about the coolant not being fully bled out, didn’t OP just replace their crossover pipes?

Maybe you just need to spend more time bleeding out more air. Telling you, vacuum bleeder is the way.

 

[M32H32IS]

I know it had a leaking pipe going from the back crossover to the heater core.

I bypassed the heater core and bled the system. It seemed OK for a bit but this started happening again.

I may have residual air pockets or a new leak. The prior leak was nearly undetectable. I happened to see a drop of coolant one day, squealed the hose and it exposed the crack.

 

[ApolloActual]

Did you find anything that was causing this?

I'm getting my LR4 ready for a cross country trip and I noticed it hissing when I opened the expansion tank to top it off.

 

[M32H32IS]

Head bolt had loosened slightly and combustion gasses got in the coolant.

Shop that did my reman engine fixed it at no cost.

 

[RoverTide]

Reviving this thread... I started the engine this morning and a large cloud of white smoke/vapor blew out of the exhaust pipes. That never happened before and it dissipated pretty quickly, so its not oil, and it stopped emitting any vapor at all after about 30 seconds. I have noticed that the coolant in the expansion tank is not returning to the cool level when the engine is completely cold. When I remove the cap, the pressure is relieved, and the coolant level rises to the normal cold level (just like the OP's video). The pressure seems really high though. I have not noticed a drop in coolant levels and no overheating issues. Should I completely flush the system and vacuum fill before doing any exhaust gas tests and compression tests? I think I want to rule out air pockets first, right?

 

[Jimmy Brooks]

Reviving this thread... I started the engine this morning and a large cloud of white smoke/vapor blew out of the exhaust pipes. That never happened before and it dissipated pretty quickly, so its not oil, and it stopped emitting any vapor at all after about 30 seconds. I have noticed that the coolant in the expansion tank is not returning to the cool level when the engine is completely cold. When I remove the cap, the pressure is relieved, and the coolant level rises to the normal cold level (just like the OP's video). The pressure seems really high though. I have not noticed a drop in coolant levels and no overheating issues. Should I completely flush the system and vacuum fill before doing any exhaust gas tests and compression tests? I think I want to rule out air pockets first, right?

head gasket... sorry to be the bearer of bad news. these are all just classic bad head gasket symptoms. I believe you can buy a tester kit to put on top of the expansion tank and it will turn a fluid a certain color if there are exhaust gasses in the coolant. thats the first thing I would do, but others might have better advice.

the white smoke out of the exhaust is normally a key indicator.

 

[greiswig]

head gasket... sorry to be the bearer of bad news. these are all just classic bad head gasket symptoms. I believe you can buy a tester kit to put on top of the expansion tank and it will turn a fluid a certain color if there are exhaust gasses in the coolant. thats the first thing I would do, but others might have better advice.

the white smoke out of the exhaust is normally a key indicator.

Definitely could be a head gasket, or cracked head. Hard to say. Burnt coolant usually has a pretty distinctive smell...kind of sweet...and it doesn't dissipate very quickly. "White vapor that dissipates pretty quickly" could just be that it was really humid that morning, and the water vapor formed more of a cloud than usual. Smell the exhaust after a startup, and/or test it as @Jimmy Brooks suggested.

 

[RoverTide]

Definitely could be a head gasket, or cracked head. Hard to say. Burnt coolant usually has a pretty distinctive smell...kind of sweet...and it doesn't dissipate very quickly. "White vapor that dissipates pretty quickly" could just be that it was really humid that morning, and the water vapor formed more of a cloud than usual. Smell the exhaust after a startup, and/or test it as @Jimmy Brooks suggested.

Nightmare scenarios are head gasket and cracked block/head, for sure. I am just curious if I should perform the exhaust gas test or flush coolant to eliminate a potential air pocket issue first. What's strange is, when I started it up this morning, there was zero vapor cloud, with similar weather conditions outside. Since I just did all the crossover pipes and water pump, I am wondering if an air pocket is a likely culprit. i guess it can't hurt to do an exhaust gas test first, since I assume it would probably be an issue whether I flushed the system or not.

 

[greiswig]

I'd say if you're willing, test the coolant for exposure to combustion gasses first. But based on what you've said, I suspect you'll get null or marginal results from that test. Leaks like that are pretty consistent once they start. If you haven't had a repeat episode, it may have just been water vapor. If your results from that test are negative, for peace of mind you can burp your system with a vacuum filler or do a very careful bleeding.