Cooling system pressure

[richard5933]

I had the shop run a pressure check on the cooling system this week. I wanted to be sure that we didn't have any leaks after the system apparently had a 2-1/2 gallon burp of air.

Everything was good and no leaks were found.

They said, however, that the pressure valve on the rear of the surge tank was in need of replacement, since it is only keeping 3-4 psi in the system. They said that it should be about 7 psi.

I called Luke and he said that he never heard of a problem with low pressure caused by the valve, only leaks. He said not to worry about it.

Running at 60 mph in rolling hills at 78 degrees ambient temps the engine holds steady a tick above 180 on the gauge.

Thoughts?

[Geoff]

The radiator pressure relief is supposed to be 4psi.  That is what Detroit sez.

[richard5933]

Sounds like I'm spot on then. Maybe the shop was thinking of a newer engine...

[bigred]

I have a related question.I can let my Prevost  with the 8v92 sit for as long as six weeks at a time and I can still get a 'whoosh" when I remove the coolant tank cap. Normal?
'

[Geoff]

Holding pressure is a good sign of a tight cooling system.  BTW, some engines have "cold leaks", that stop once the engine warms up.  If you have seepage, it is time to tighten and maybe replace clamps.  Double clamping is a good idea.

[richard5933]

Holding pressure is a good sign of a tight cooling system.  BTW, some engines have "cold leaks", that stop once the engine warms up.  If you have seepage, it is time to tighten and maybe replace clamps.  Double clamping is a good idea.

Been there, done that. We had lots of clamps to tighten as we entered the cold weather last fall. Luckily they needed nothing other than a tightening to stop the seeping.

[chessie4905]

The manual lists opening pressure at 3 1/2 to 4 1/2 psi. Maybe the 4104 was 6 psi. dont have manuals for it any more, went with coach.