Radiator overflow boiling and exploding

lulzpwndyah

TJ Enthusiast
Joined
Jul 3, 2020
Messages
329
Location
Los Angeles, CA
Hey all, I have a weird issue with my TJ. It keeps boiling the radiator fluid and anytime I lift the hood I see the splatter of fluid from it shooting out the overflow tank. I've got a new cooling system installed and have a new 18lbs radiator cap as well. I made sure there was no air in the system using one of the funnels that you put on the radiator and fill it with.
everything is mopar except the radiator which I got from an autozone when my radiator blew up in the mountains and I had no other choice.
TJ runs fine temp wise I believe, I have not connected a reader to read temp electronically I just go based off of the gauge. temp is always a bit left of the middle 210. any ideas? Could it be the radiator? could it be the fluid? I don't think I used HOAT since I had to buy what I could when it blew up on the side of the road but it is orange I think it's dexcool from looking it up right now.
 
Sounds like you have possibly a head/gasket issue. I would check for combustion gas in the coolant. I would also check your temp gauge as well.
 
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Its weird because that's what I think too but I have a new Jasper engine with sub 5k miles on its only had 2 oil changes... I've checked the oil and it's not milky or anything I'm hoping it's not a head/gasket issue.
I don't know if the radiator blowing up while I was pulled over with the engine off would cause the overheating issues you have when you keep driving ie head/gasket issues
 
ive Had the best luck using the factory radiator and thermostat fitted with small bleeder hole and small brass stopper, assuming the head gasket is good.
 
I would suggest borrow or go to your local parts store and get a “block tester” combustion leaks tester.

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Spark plugs can help diagnose a head gasket. If a 5000 mile spark plug looks clean and the others have carbon on them it is likely a head gasket.
Sweet I will pull one or two and see what’s going on.
Was also thinking of going with a mopar radiator and finally swapping this one out to keep as a spare.
 
Pulling plugs and reading them is a great starting spot. Don’t assume you’re head gasket is fine just cause plugs look good or you don’t have water/oil cross contamination.
Your problem is your cooling system is getting over pressurized. 2 things cause that, high coolant temps or combustion gas. Your gauge reads normal temps so I would lean towards combustion gas.
 
Radiator. Is really easy to do. Does you radiator bubble with the engine running?
No it doesn’t bubble but it’s pretty full and I don’t have anything to get some out of it.
I’m going to try this before pulling plugs though as it seems quicker and easier and can give me quick results.
I appreciate the help guys I’ll report back
 
Well I had filled the radiator all the way to the top using one of the funnels while I was burping the system and the overflow bottle I had gone over the full just a tad bit, but yesterday when I checked it was sitting on the "add" section of the bottle. I refilled it and then posted this today.
 
Well I had filled the radiator all the way to the top using one of the funnels while I was burping the system and the overflow bottle I had gone over the full just a tad bit, but yesterday when I checked it was sitting on the "add" section of the bottle. I refilled it and then posted this today.
The bottle should be 1/2-2/3 full when engine is hot. If too full it will spill over when engine gets hot.
 
The bottle should be 1/2-2/3 full when engine is hot. If too full it will spill over when engine gets hot.
so should it be sitting at full when it's sitting cold?
I went to run it right now anyway and I noticed coolant was coming out and bubbling from the hose that connects the overflow bottle to the radiator. I'm guessing that could be my culprit too?
 
We need to find out why it’s building so much pressure. You have a new radiator cap, correct? It’s hard to troubleshoot via text. Lol.
 
It’s my third cap.
First time I went stant
2nd time I used whatever autozone had
This last time maybe a week ago I put a new stant in again
All 18lbs
I’m about to head to the auto store and buy new hose clamp and the block tester to see if I can figure it out during lunch break.