How much pressure should the radiator cooling sytem run at?

[Crankme69]

When hot after the T stat is open what should we get for pressure?

 

[ak diesel driver]

IIRC about 15 psi

 

[1999gmc]

That's what the cap vents at, either 15 or 16 depending on the cap. They normally only get up around that when they are really hot.

 

[buddy]

It probably depends on the flow of the water pump, somewhere around 10psi over atmospheric at normal idle I would suspect. I think with the separate reservoir the pressure in the radiator could probably reach higher with todays high flow water pumps. Since the reservoirs connect in on the cold suction side, the block and hot side of the radiator would be higher pressure, which will increase its boiling point.

 

[ak diesel driver]

on the older systems with the cap on the rad the only way the overflow volume changed was by venting of the cap which is 15 psi. so while it may not always be at 15 it certainly must be a fair amount of the time

 

[great white]

Shouldn't be any higher than 15 psi, that's the venting pressure on my remote res cap.

Anything under that, you're good.

Testing pressure for most cooling systems is to pump it up to around 10 psi.

In case you didn't know, pressure in the system raises the boiling point and helps prevent localized "steam pockets".

Well, it's a wee bit more complex than that, but that's it in a nutshell....

 

[chefmike]

so I should probably replace my crappy radiator cap? hmmm... I will stop by napa in the AM