Gus solved an overheating problem

Posted by HH56 On 2013/12/22 20:29:01

As some know, I enjoy the old Model Garage stories that used to be in Popular Science magazine. One I read today reminded me of a problem we keep hearing about on the forum.

The Model Garage was called upon to diagnose a car that had started overheating. Stan, the assistant couldn't find anything obviously wrong -- timing and exhaust flow was good, coolant level was proper, water flow appeared normal while looking in the radiator. Stan knew the car was well maintained and had been in for an engine overhaul a year earlier. He doubted the water tube was clogged and with everything else normal, was thoroughly stumped.

Gus came over to save the day and noticed a new looking radiator cap. On questioning the owner he learned the cap had been replaced because the old one started leaking. Looking at the cap, Gus found it was one with a higher pressure rating than the original. Using his phenomenal memory and great deductive skills, it was determined that the thermostat was still the original and that model car used one of the bellows type thermostats.

The gist of the story is apparently the bellows types are designed for no to fairly low pressure caps and won't work in higher pressurized systems. They can also age where the bellows can weaken enough to not overcome the normal pressure and open. The car was overheating because the thermostat couldn't open against the increased pressure caused by the new cap. Removing the radiator cap to check the system let the pressure out and thermostat opened so all appeared to be working normally until cap was replaced and pressure built up again.

Could any of our overheating problems be as simple as a tired old style thermostat. I don't know when Packard stopped using that type but my 47 has one so probably used thru 50 at least -- Maybe longer since the car in question was a mid 50's model. Probably none of our problems are that simple but if there is truth to the story and anyone still has an original thermostat, something to be aware of if installing a new cap with higher pressure rating.