Radiator pressure test pressure release?

[JHZR2]

Maybe this is a stupid question, but what is the right way to release pressure at the end of a cold radiator pressure test?

Yesterday I did a test on my truck, it gave me some useful insights, So I was ready to release it. I used the thumb actuated release, and a lot of coolant shot out all over. I thought I might have more control if I removed the actual hose, but when I did that, there was a fountain shooting upwards.

I had watched youtube and the folks doing it had nowhere near the mess or release. One had indicated to top up the system vs compressing air in the radiator. So it seems that they should be full. My radiator was completely full.

So am I doing something wrong? Should I leave some headspace in the radiator? Are the coolant fountains just edited from youtube? I get it that the energy has to go somewhere, but I’m also surprised that so much shot out.

Thanks!

 

[JohnnyG]

Any hydrostatic test I've ever done, such as on piping systems, must alway be DEVOID of air. Air is compressable, water is not. So, that means you had way too much air in the system for the fountains to last a while. Something was pushing the water out, and it wasn't compressed water.

Rubber hoses could contribute if they expanded I suppose, but that would be a slim possibility.

 

[JHZR2]

Any hydrostatic test I've ever done, such as on piping systems, must alway be DEVOID of air. Air is compressable, water is not. So, that means you had way too much air in the system for the fountains to last a while. Something was pushing the water out, and it wasn't compressed water.

Rubber hoses could contribute if they expanded I suppose, but that would be a slim possibility.

That’s what was odd. There was no air, the system was full. It has been full, I have been watching it closely. Heat works so it’s not like the heater core or something else has issues.

That’s why I don’t understand, other than maybe the hoses expanding?

The system is 6 gallons, not some little car system.

 

[JohnnyG]

I've pressure tested piping system hundreds of feet long of 8" ID steel pipe (steel doesn't expand either). Pressures ran to 350 PSIG. When the pipe is opened at the end of the test, you MIGHT get a quart or two of water out. That's it.
In fact, it is the main reason water is used. If there is a failure of a weld or gasketed joint, nobody will be harmed by the sudden release of pressure.
We could use nitrogen too, but that was a whole other story!

 

[JohnnyG]

I also remember certain engines, such as the Cadillac Northstar, had a high point air bleed line that ran from a hollow bolt at the throttle body, through a hose, and over to the coolant reservoir. The first thing to check if any overtemp conditions were noticed, was to make sure that hose flowed a steady stream of coolant into the resevoir. If it got plugged, and they did on occasion, air would accumulate in the block and cause probems.

 

[JHZR2]

I also remember certain engines, such as the Cadillac Northstar, had a high point air bleed line that ran from a hollow bolt at the throttle body, through a hose, and over to the coolant reservoir. The first thing to check if any overtemp conditions were noticed, was to make sure that hose flowed a steady stream of coolant into the resevoir. If it got plugged, and they did on occasion, air would accumulate in the block and cause probems.

Reality is I don’t know how much came out. It doesn’t take a lot to make a mess. Could have been less than a quart. Could have been less than that. It just pushed out hard and straight up into the hood.

If there’s an air bubble I can’t seem to find it! Might be worth putting the high funnel on and massaging all the hoses.