Problems? Heat and Pressure.

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moparbarney

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So I have not owned this car long. 69 Plymouth Valiant 440, 727. Champion radiator and cap. When I got it it had no exhaust so I put flowmasters with full 2 1/2 pipes all the way back. Then that is when the problems start to creep in. Runs hot!!! 230 and it might go more but I shut it down. So I decide to change the easiest thing the thermostat. I open it up and it has a 180 in it already. I drill the 1/8 hole in the new one and button it back up. Start the car and let it run until the thermostat opens. Keep topping off the coolant as it is burping. At this point it never goes over 185. So its been idling for 20 mins alteast. I start to notice I am smoging out the neighborhood. I decided to put the new radiator cap on and see if it will get hotter than 185. 3 mins later a bottom seam on the radiator is gushing out like the falls!! I feel that its building no pressure so I remove the cap and the leak stops!! Hello! So I shut it down and let it cool and it seems to build pressure as it cools. This morning i remove the cap and I get the hissing pressure noise. I decided to borrow the radiator pressure tester from work and cold at 30 psi applied i can not get this radiator to leak again? I test the old cap and it releases at 14 psi. I think I have a head gasket problem.
 
I lost ya. The radiator sprung a leak and you think it's a head gasket???
 
But it does not leak cold. What caused it to spring. Looked like it has leaked at
this spot before but I have never got it to do so until last night.

I lost ya. The radiator sprung a leak and you think it's a head gasket???
 
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Metal expands as it heats up. That's why it leaks when hot. My theory and I'm sticking to it.
 
That doesn't speak to the rising temp tho.And the stat only sets the minimum running temperature. I see an IR gun in your future.
Was it overheating with the cap open and the rad full. Or did I get lost too?

But if liquid came out of a seam, the rad needs to come out for repairs,That's all there is to that. Once it is out and upside down mark the spot and start grinding it out, you will soon see the fracture line.
 
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I guess I am just thinking that a bad head gasket caused all of this. Because I got the car this way and am trying to trace back how all this happened. Trying to get ahold of the old owner for a better idea. I am confused also.
 
I guess I am just thinking that a bad head gasket caused all of this. Because I got the car this way and am trying to trace back how all this happened. Trying to get ahold of the old owner for a better idea. I am confused also.


While that is possible, it is highly unlikely. Usually the cap blows off the pressure, or a hose is the weak spot.
 
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You need to check it for exhaust gasses in the radiator with a tester. This will tell you if you have a head gasket or cracked head problem
 
While that is possible, it is highly unlikely. Usually the cap blows off the pressure, or a hose is the weak spot.

Coming back from the airport in Phoenix one day in the summer the top of my tank split wide open more than half way across the top engine side seam.
I pretty much always have a fair amount of good clean water in the trunk, so I beat it back down with my tire iron and smeared RTV all over the split, took the thermostat out of it, filled it with water and drove home with the cap off.
It came in hot but not too bad.
No head gasket leak on that either, because I questioned that till I did a comp test.
Replaced the radiator and it was fine ever since.
 
A head gasket, or any other cause, will not "blow" a radiator unless it's weak, anyhow. The rad cap will blow off pressure. So, don't know what your cause is. Might be more than one.
 
A head gasket, or any other cause, will not "blow" a radiator unless it's weak, anyhow. The rad cap will blow off pressure. So, don't know what your cause is. Might be more than one.

On inspection the top seam had been resoldered and only a small strip of the solder had reattached to the core.
You could see the new tear line in the solder where it ripped loose.
 
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