Radiator Cap Pressure - Diesel Forum

Canyonero · 03-22-2005, 07:27 PM

I drained,flushed,and refilled my radiator (including fleetguard) and replaced the upper and lower hoses to try and eliminate sources for the occasional coolant leak. While squeezing the new upper hose after getting the engine hot, it seemed fine. The next day after driving for a 40 miles, it seemed much harder. (the hose) I think the pressure cap on the radiator may be wrong or inoperative. Is 16 pounds the proper pressure cap? If I had a head gasket problem, the pressure would be blowing by into the reserve tank, no?

Thanks

cdnsarguy · 03-22-2005, 07:39 PM

The cap pressure is 13lbs, and coolant will swap out of the rad into the overflow tank and back if it is working correctly.....

Canyonero · 03-22-2005, 07:48 PM

Then I have the wrong cap, though it does swap some. (coolant) I used to fix the hueys you guys would use. Search and rescue, right?

cdnsarguy · 03-22-2005, 07:53 PM

I was SAR in Canada only, USAF PJ brothers are stateside...

studbacker · 03-22-2005, 08:03 PM

i have no pressure in my radiator. is that because of the cap being wrong. also i have a small leak somewhere, it only dripps slowly when engine is runmning, and the radiator isnt all the way full. is that why i have no pressure? didnt mean to steal thread but looks like his post was answered. thanks jake [img]/ubbthreads/images/graemlins/smokin.gif[/img]

cdnsarguy · 03-22-2005, 09:49 PM

Stud...
Your rad should be full, check the hose to the O/F tank see if it is plugged or not close to the bottom of the tank. The tank has hash marks for cold and hot fill it to the cold level and run it after filling the rad up. The system should swap fluid back and forth as required....... Cap pressure 13lbs.

d9d · 03-23-2005, 02:09 AM

Stud, what he (Pete) said.

Plus, you wouldn't normally have pressure in the radiator, if you're checking it when cold. Truck has to get pretty warm before there is noticable pressure. 3 minutes running probably wouldn't do it.

Regarding leaks...

I had quite a scare a week ago, after bringing the 1991 home. Was laying under it for something else, and noticed coolant leaking from the head-block joint. OH NO! HEADGAAASSSKKEETTTSSS....

But with a little closer examination, I discovered that the upper hose was leaking slightly, where it clamps onto that tall thermostat housing. Repositioned the clamp and tightened it up, and all is well now. [img]/ubbthreads/images/graemlins/grin.gif[/img]

thomaschew · 03-23-2005, 09:23 PM

While we are on the subject, does anyone know if the Stant (standard) pressure tester kit will work on our trucks, or do you need to buy the truck adapter add-on kit?

Thanks, Tom

dbennett48 · 03-23-2005, 10:30 PM

I don't see why not. It is a standard radiator cap so it should work just fine. Not all things on these trucks are weird.

Dave [img]/ubbthreads/images/graemlins/smile.gif[/img]

Birken Vogt · 03-23-2005, 10:36 PM

I think the truck adapter is for the extra-large caps that some trucks use. Which these trucks do not have. There are only 3 sizes that I am aware of. The standard size, a small one such as some Japanese cars and motorcycles have, and the large truck ones. As well as various proprietary ones in recent years.

Birken