When does upper rad hose pressurize?

[Timothy B.]

This may be an odd question, but when if ever should I expect the upper rad hose to feel pressurized to the touch? I have recently replaced my rad with a new Dewitt's reproduction, new hoses, new thermostat, etc. It hasn't been too hot here in Texas yet, but even with a good extended drive the upper hose has been "easy to squeeze". Does this just mean my new rad is working well? I recall that with the old brass unit the upper hose often was pressurized like a balloon. Is there a relationship between what the temp gage indicates and when the hoses pressurize? My temp reading has been running in-between the first unlabeled mark and the 210 mark, but never quite to the 210. Infrared reading of the thermo housing has been showing about 195-198 or so. Your feelings or experiences would be appreciated.

By the way, thanks to all who have been fielding my myriad of off-the-wall questions in the past several months. This forum is the greatest thing, and I learn soooooo much!

[Doug Flaten]

Re: When does upper rad hose pressurize?

Could it be that the differences in what you are seeing between the hoses is related to the age / construction of the old versus new hose? It seems to me that hoses soften and weaken with age tending to balloon as you describe. Time, temperature and pressure are the factors that dictate the service life of an elastomer in a particular service.

[Craig S.]

Re: When does upper rad hose pressurize?

Tim - I assume during your conversion back to the correct DeWitts reproduction aluminum radiator, you also installed the correct expansion tank and pressure cap, and associated plumbing. If so, it should retain pressure just like the copper/brass radiator did. The radiator cap controls the 15lb pressure in the system, and with that pressure, the hose should be firm after warm up. I would check for leakage around the cap at the expansion tank on the RH fender first...Craig

[Timothy B.]

Re: When does upper rad hose pressurize?

Yes, I have every part of the original system in place. I have seen no leakage anywhere, and the expansion tank is about half full when checked cold. I have a 15 lb cap in place. The cap is one of the GM replacements that has the smaller handholds, but should be functionally the same as the original. The only thing that is non original right now is that the heater core is bypassed until I get a chance to replace it. The hose to the heater is simply curved around back to the expansion tank tee fitting.

[Craig S.]

Re: When does upper rad hose pressurize?

Tim - the heater bypass would not affect anything. I would do two things, first, pressure check the cap and then pressure check the cooling system itself for leaks. Folks like Snap-on and MAC make a tool to do both. Auto-zone has a tool borrowing service, I would check with them to see if they have a pressure testing tool. Basically, it is a pump and guage with a special fitting that can attach to the radiator cap and cap mount flange in the system to verify if there are any leakdown problems with either... Craig

[Chris D.]