Overheating issue

let me start off by telling you a little about my car. It's a 1972 Mercury Comet with a mildly built 306. Never had overheating issues until just recently and I live in Florida and drive this car in 100 degree wheather and did it daily as I drove this car to and from high school and work! Car had an aluminum radiator and a flex fan to start off with. I started to notice the bottom radiator hose would collapse as I rev the engine.. ahh! Stuck thermostat I say. Changed the thermostat and nothing.. same thing happens. So I decide to take the thermostat out all in all and see the same issues. I then put a new water pump on the car and radiator cap along with a new bottom hose with a spring in it and it still wants to collapse. Check compression as i did blow a headgasket about 2 years ago and replaced them both. all cylinders reading a good 150. So I figured there must be a blockage in the radiator. Put a new 3 core aluminum radiator and upgraded to a electric fan set up as well because I had everything apart. I am still having the same issues of the hose collapsing. This must mean there's a blockage in the engine I'm assuming. Any ideas guys?

 

The first thing I would have said was replace the hose with one that has the spring inside, since you have done that I am not sure. do a pressure test on the system and maybe flush it, since you replaced the thermostat and water pump I will assume the bypass is open the pump seems to have plenty suction but is not being displaced fast enough

 

seems it's displacing it faster than it can refill, being the reason it's sucking the bottom hose shut.

 

A water pump "pumps" from lower section of radiator, if hose collapses at high RPM basically means the pump is pulling more coolant than radiator can supply... BUT!! Some degree of collapsing is normal, that is why the better hoses have a spring inside, along with system pressure prevents collapse...

As theorized, if flow into radiator is restricted then of course it can't supply necessary amount of coolant, though I'd be surprised if problem was internal to engine...

 

Frank is correct and if we apply some high school physics to it, there is a vacuum being applied inside the hose and the atmospheric pressure of 14.7 psi is collapsing the hose. (Don't mean to sound like an egg head). This would say there is communication between the suction of the pump and the hose. Hate to say it but looks like a blockage in the rad. Maybe disconnect the lower hose and flush the rad. If a bunch of crap comes out or if nothing comes out and the rad overflows, you have your answer. So how would a new rad plug? Maybe some crud inside the engine got displaced to the rad. Good luck.

MD

 

Hi VC :
You say the care ' came ' with an aluminum radiator .. It may be a good idea to FLUSH it ..You might have some
trash in the inner cores that is restricting the flow enough where it causes the problem. There is a place in Sanford,Fl that flushes them and does a good job for a fair price.ED's RADIATOR - 407-323-8915 open 9:00 till 5:00 Monday - Friday..Closed Saturdays.. I've had Ed flush five of my own radiators for different cars we've built and its definitely an improvement. Just my thoughts.( By the way , I HAVE an extra Griffin Aluminum Radiator we switched out for my Maverick build that I'd part with if you need one. Come on by and take a look , you know where my shop is. I have it in a cardboard box on the shelf.
Cometized
(Chip)

 

One more crazy idea. Somehow engine vacuum is being applied to the water passage. There various gizmos on a stock manifold that re-direct engine vacuum depending on the water temperature. Some have check valves in them. Not sure if you still have them on your intake manifold. If you do, pull the hoses and plug them with golf tees. Try running the engine again.

Normally you would think this that would just suck coolant into the engine but the check valve might complicate the issue. Just reaching.

MD

 

Or a slight intake manifold leak pulling vacuum into a water passage. Have
you been losing coolant?

 

If you haven't checked it, make sure your radiator cap is allowing pressurization.

 

I really like these problem solving sessions but sometimes we pass by things because we say " since it was replaced, that can't be it." That new "3 core rad" might have a higher pressure drop than the old one. The new lower rad hose with the spring inside might just be too weak. Try buy a lower rad hose with a beefier spring. I checked the web on the issue and most people suggest a hose with a stronger spring. Some suggested a ribbed hose because the spring is moulded in. Good luck.

MD

 

I agree with the ribbed hose they are tougher but are not the prettiest.

 

Thanks, Chip! I just bought a new 3 core radiator for it and it still didn't solve the issue I am having. I still have yet to swing by and grab that mirror from you. I'm sorry it's taken me so long. Being busy mixed with working on the Comet and my other cars non stop can get in the way. I PROMISE I'll swing by soon.

 

Alright, guys. I spent another LONG day working on the Comet today. Here's the deal. I went to the parts store and got a ribbed hose and stuffed the spring inside. Wah lah! No more collapsing. It still tries to collapse but it can't with the hose being so tough. Filled the car back up with fluid and proceed to take it around the block. I'm watching the temp gauge STILL climb well past 220 degrees. I'm at a loss. There HAS to be a blockage in the motor. Every cooling part outside of the engine is new and in working order. Thanks for all the help on this guys. This site is seriously the best around. I truly don't use it enough either.

 

I have used 3 different caps I have laying around. Still the same deal.

 

Not loosing colant at all. Well... besides it puking it. Haha.