Coolant Explosion

Your radiator cap should be for about 16 PSI.

 

So I refilled the coolant and let it idle. Temperature slowly increased. When it got near the top of the green line (about 10 minutes) I shut it off. There was a strong shake that didn’t sound great, but nothing crazy. Some coolant leaked out of the overflow, but not much. 2o mins later I checked the coolant, and it seemed to be good. I started her back up, and the temp went up high, but not outside the green line (damn near the edge though). I decided to do a slow drive around the block. The temp actually dipped a bit when I got moving, and then it went up to that same spot (top of the green line), but otherwise seemed to be okay. Feel like there were some “new” noises that became less pronounced as I drove.

 

I would drive it normally but gently, and monitor it frequently, including under the hood.

In December you posted that you had a mechanic's report, about a "leak from the head." Also another evaluation listing "corrosion on the bottom tank" of the radiator.

Were both those issues resolved prior to this 'explosion?'

 

Negative. He told me it was barely leaking and wasn’t a big issue. I will get that fixed though. The radiator corrosion was also barely noticeable. The fan belt is showing some wear, so I plan to replace that as well.

 

A very small leak might still have added up over time if not watched closely. An example of why older vehicles need more love.

A worn and/or loose fan-belt can contribute to overheating, since it operates both the fan and the water pump.

 

Sounds like you're describing a stuck closed thermostat?

 

IMO, one of the best things noted was to get a coolant system pressure tester. Pump it up to 16psi and let it sit and see if it bleeds down. If you have a leak in a hose, heater core, you will see dripping. You can easily rent from any of the bigger auto parts stores or go to Harbor Freight and buy one.
There are test kits for head gasket etc that will change color if it senses combustion gasses in the cooling system. But that test is a ways down after you have done the other, and fixed the previous issues you spoke about.

It is sounding like a stuck thermostat, but you really need to pressure check it to find the obvious if it is there. Maintenance on my 72 is much more checking, looking around then any of the newer vehicles I have. Get a GOOD strong flashlight while you pressure check and shine front/rear of the radiator at the top/sides/bottom and look for green/yellow crusties in those places.

 

Another suggestion: A failed or failing water pump can cause the problems you are describing including the new noise you are hearing. You can check the water pump by grasping the water pump's pulley with your hand and tugging on it to see if you can feel any movement (like moving back and forth or has any kind of wobble). If so, you need a new water pump. Check around the shaft behind the pulley for any leaking from the neck of the water pump. If you find leakage, you need a new water pump. When replacing a fan belt do not over tighten it or it will cause premature bearing failure in water pump. You will want about 1" to 1-1/2" deflection in the belt when you push down on the belt halfway between two pulleys.

Hope this helps,
Martin

 

Compression check showed that the radiator was shot - went with a new aluminum replacement. Also, replaced the thermostat. She’s running super cool. Appreciate all the advice.

 

If that was an original copper/brass radiator, I hope you are saving it.

 

What’s that worth?

 

I don't know about a 1980 Jeep, but the early ones are far heavier and more durable than modern radiators. Well worth reconditioning, IMHO.