I read several post about coolant issues. please help.

That does not sound good. You can do an internet search and see what that could mean, the bubbling especially. I'm not real familiar with these issues so I'm sure you'll get some input from other drivers. But head gasket is what an internet search comes up with on the issue.

 

could be a cracked head, a bad head gasket, a bad cylinder liner., a cracked engine block, that is making this happen. in some instances, it can be a bad thermostat.

 

It also can mean that you should wait until it is cooled down to put coolant into the system. The pressure that it is under is 15 psi and I would expect it running to be a problem with it being open.

If you have a leak and get it fixed, it may be alright then.

 

What kind of Truck what engine?

 

It shouldn’t have pressure after only 5 minutes but definitely at 125 degrees. Bubbles aren’t good sign. Some older trucks had heater valves that work off air and can cause excessive pressure when bad

 

Sometimes there is air trapped in the system, when there is a release of pressure, some of that air will go to the highest place in the system, in most truck engines, that is the surge tank.

 

When opening ANY type of valve: you hear hissing..it means STOP, something is escaping: fluid or air. If you would have stopped turning the cap, coolant would have bubbled out..... but probably not SHOT out of the surge tank and on to the windshield. Wait for the hissing and or bubbling to stop and fill your tank with fresh coolant. Better luck next time.

 

I am glad someone mentioned that it is highly recommended to wait for the coolant to cool down before opening the reservoir. Some caps have warning signs about hot coolant. I always use paper towels to cover the cap and open it slowly. You are very lucky the hot coolant did not touch your skin!