Coolant spraying... What is going on?

[Rawze]

(10-25-2017 )Waterloo Wrote:  Ok, did the overhead, installed new CAC, put everything back together, went to start and I have coolant spraying everywhere! Coming out of the coolant bottle, and somewhere else. I shut it down, thinking WTF! Now what!

When I took the coolant bottle off to replace the CAC, I drained about three gallons of coolant out of the system to drain the bottle. I filled it up after getting everything back together and burped the motor.

I looked all over the motor, pressure tested the cooling system, nada.

Restarted the motor, purring like a kitten, the coolant is keeping its level in the bottle. Sits overnight, and pressure has built up in the system near as I can tell. Could it be something as simple as a bad radiator cap?

Now I start it today, and same thing! Spraying coolant everywhere, after sitting overnight. Restarted and all is fine...

Don't tell me a head gasket.

Thats a typical prostar problem. here is why it acts so strange ...

The heater core in the cab of the truck is at a higher level than the coolant tank. It is quite common when excess amounts air gets into the coolant system, it gets trapped accumulates in the heater core and blows about 1.5 gallon or so of coolant out the cap. Run the truck for a while, and the coolant level will show 1.5 gallons low,. so what does a good truck owner do? -- Fills it back up. -- Then the cycle repeats.

This explains the strange behavior, but leaves only one question.... Where is the air coming from that is building up?


Well, since it happened all of the sudden after draining the system and then putting back the coolant...

* Did every single drop you took out go right back in when you filled it up? -- If not, then there was an air pocket and that is a really bad thing on a wet liner engine. I have seen my share of engines destroyed by people not burping the system correctly. Personally, I use a vacuum pump and fill the coolant system from the BOTTOM OF THE RADIATOR after pulling a full vacuum on the entire coolant system. When you do this, every single last drop of coolant goes back into the system and there is no possibility of an air pocket.

If you have an APU, the problem is much worse and all the air from the APU and lines can damage an engine 20 minutes down the road after you think you have it all back in.


My suggestion,... drain about 3-4 gallons then pull a full vacuum on the system. Make sure the vacuum holds, and it is not sucking air from the compressor, turbo, or some place else. I have even seen them suck air at the thermostat housing gasket under vacuum when helping others here in the past. Pulling a full vacuum on the coolant system should be standard procedure if you ask me.

After pulling a vacuum, fill the system back up from the BOTTOM drain plug (without letting air in) or pour a gallon in then pull as much vacuum as you can, pour more in, pull vacuum again, and keep doing that until it is topped off.

Run the engine with the cap off until it gets to 185-F and stays there for a good 5 + minutes (total run time about 25-30 minutes). Make sure it does not need more coolant.

After purging all the air, ensuring its topped off, and everything is right,.. put the cap on and test drive it. If it happens again, you have a serious issue that was most likely caused by not burping the system properly the first time.