I've bought a new water pump for the 276 Hemi in my 53 Desoto. I also put a thermostat in to control the water flow. My shit still over heats, and it blew out the front seal on the new water pump. I got another water pump, put it in, and it still is over heating. Question? If the radiator cap wont let the pressure relieve, (mind you it's a 7 lb cap but I think it's to deep), could that cause it to blow out the water pump seal and over-heat the car. This is geting very flustering.
In my opinion the radiator cap itself will not cause your engine to overheat. If the engine DOES overheat the cap is intended to be a relief valve and keep the pressure in the system to no more than the caps rated pressure and thereby reduce the chances of harm to cooling system components. Not knowing any history of your car, the engine, radiator etc., I can only offer the following suggestions for your consideration. 1. are you certain you don't have a head gasket leak? That could contribute to overheating and excessive pressure in the cooling system. A compression test MIGHT reveal significant differential in cylinder pressures and if one or more are considerably lower than the others (15% or greater variation) it bears further investigation. That condition could also be a burned or poorly seating valve(s) too, so by itself it is not an absolute indication of a head gasket problem. But if all the cylnders are reasonably even, then the problem is PROBABLY somewhere else. 2. have the block/heads been THOROUGHLY backflushed to dislodge and remove accumulated rust, crud and debris from the water jackets? An amazing amount of junk can build up in the lower areas of the water jackets and reduce the volume and flow of water through the system. 3. are you absolutely sure you have the engine timed correctly? engine timing can play a major role in engine temps. 4. have you had the radiator cleaned/flushed/flow tested by a competent radiator repair shop? 5. are you running tthe correct fan and if originally equipped with a shroud, is that shroud in place? Thes are the most common things that come to my mind. There may well be others who can contribute more/better suggestions, but you won't go too far wrong beginning with these. Best wishes, Ray
Actually water boils at a higher temp as the pressure increases. It'll overheat sooner & at a lower temp with a 7 lb cap than with a 13 lb cap. Does it still have the 4 blade fan?
True enough George, but wouldn't you agree it shouldn't be overheating in the first place, even with a 7 lb cap? Even with no pressure it should take 212* to boil, 7 lbs would raise the boiling point somewhat higher as you correctly indicate. IIRC cars of that era used the lower rated pressure caps and utilized 180* thermostats but as time progressed the cap pressure specs elevated to the now common 16 lbs or so because of increased operating temps (195* - 210*) for emissions reduction on later model vehicles. That shouldn't be an issue on the OP's '53 DeSoto. Ray
I'll jump in and agree with what has been said. As Ray suggests, alot of garbage collects in the bottom of the water jackets and does not transfer heat very well. I also would suspect a combuston leak of some sort into the coolant. This can be verified by checking for hydrcarbons in the radiator top tank. If even a small amount is detected then a teardown is in order. .
Ray, that's an excellent list of things to check! My g/f's '55 Coronet had an overheating/vapor lock issue we chased around for nearly a year. We never had to replace the water pump, but we did have to change some of the freeze plugs (they were leaking). I was AMAZED at how much crud came out of the bottom of the water jackets. There's no way water had been circulating near the bottom. The other big thing we did was to replace the original 4 blade with a 6 blade flex fan. The original fan basically moves zero air. Even with a fan shroud, it moves almost nothing compared to a more modern fan. We installed a Summit brand 6 blade flex fan . This is for a 17", although they make a few different sizes. Unlike a lot of Summit brand stuff, this fan was made in the USA (at least it was a few months ago). It helped the cooling a lot, and moves a pretty impressive amount of air. No more issues.
Yeah, something, headgasket or cracked head, is pressuring the system big time to blow a W/P seal. I'd think the cap would be blowing like a steam whistle before a W/P seal would go. Strange.
My brother had an overheating problem with his Land Rover. Was driving him nuts. Turned out the radiator needed to be rodded and flushed. No more problem. Lots of people have never heard of rodding. They take on tank off the radiator and run rods through the tubes to drive out the scale. That scaly buildup can act as a good heat insulator. Bill
Thank you all, I will try all avenues suggested and post the final result of the problem. I would hate to do a complete rebuild on her, she runs strong other than this.
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