Radiator boiling after replacing entire cooling system (including radiator)

[JohnJ78]

That was sound advice, especially for your climate. Antifreeze actually does raise the boiling point a bit, but doesn't cool as well as water and with your radiator cap on and functioning, it should be a non-issue. So does it boil when you know the system is topped up with coolant? If not, that changes the troubleshooting dramatically.

No it does not boil when its topped up with coolant. Originally it was boiling when I had the old 16psi cap, then I changed to 18psi cap and it was fine... then the other day it boiled over, I assume because the coolant level was low (for some reason). Literally the very next day I drove it 100 miles in the heat, no problem at all. So cap WAS a problem a while ago... but there could be a secondary issue maybe where I'm losing coolant? Maybe a slight boil after driving may be evaporating coolant out header tank each time?

Also I bumped this thread rather than starting new one.... bit misleading as issue has changed slightly.

 

[JohnJ78]

We are into this this far so let's continue ! See if it overheats or boils after driving without using a/C. Don't use it and see what happens, then change fan clutch like I suggested. Fan clutch pulls air over radiator and condenser !!! The temperature of a/C condenser get get well over 300 degrees in your climate. The condenser is attached to radiator and must have air flow to keep pressure/temp correct. Check air flow or blockage at condenser.
Those big lights in front can reduce air flow through radiator/condenser while driving buttttttt fan clutch should be able to pull air over them if shroud is ok and there's no blockage. So try driving without a/C on and see what happens.

Good idea. It might be a combination of A/C, failing fan clutch and headlights.

 

[JohnJ78]

This^^. Boiling after shut off is definately a sign of loosing pressure somewhere. Pressure drops, lowering the boiling point of the coolant, and it starts to boil. Most likely the cap. I believe you said you had replaced that as well, but it sure sounds like a cap problem. Did you get the correct 18 pound cap?

The exact thing happened to me. It would run fine, and when I parked it I would come back to coolant all over the ground. Turned out to be a cut in the cap gasket. Fixed that and I’ve not had a problem since. But, it took me months to figure it out.

Yeah I have a brand new 18 psi cap. Only other thing is I have a FlowCool radiator (repco) which has a plastic top where the cap sits. Just from experience with other vehicles, it does not seem to require any where near as much force to push down then turn into place. I'm wondering if the bit where the cap attaches is manufactured slightly incorrectly.... maybe I should try a double rubber washer or a 20psi cap. Might take it to radiator guy to have a look.

 

[JohnJ78]

And not that it’s going to help the boil over problem that much, but if you used anything other than an OEM temperature sensor then what your seeing on the dash gauge is nothing but fallacies.

I just went thru a similar situation of what the dash gauge was telling me versus what the engine was really doing. Fortunately when the gauge was i the red, the engine was at proper operating temperature.

And FAIK - a “high flow” thermostate is another fallacie of thought. Todays cooling systems are well designed for extreme ambient temperatures, to include the thermostats.

And, you need to make sure the A/C condenser coil is clean. As others have tried to tell you, I doubt the lights are your problem, but if you think they are, take ‘em off! But if the condenser coil isn’t clean, your engine heat will rise while your A/C cooling will suffer.
And disconnecting the heater core decreases the coolant cooling capacity - not that you would want heating inside the Jeep when the Ambient is as hot as you say.

Just my $.02 worth.

Noted. Will give a/c condenser a clean out, and reconnect heater core and see what happens. thanks

 

[MrMark52]

Do you have the coolant overflow bottle on this Jeep? If not, therein may lay your problem.

Coolant expands as gets hot. It has to have a place to go, and it goes out the overflow tube under the radiator cap hen it does. That overflow should be connected to a hose which goes to an overflow bottle. When an engine is heated to operating temperature and then turned off - they will pump a little more fluid out, but then as the engine cools, the coolant shrinks and what was punched into the coolant tank is drawn back into the radiator.

If you don’t have a coolant tank installed, you will lose coolant - there is no way around it. It will quit losing coolant at some point, but by then you could start running hot and the problem exasperates itself.

Do you have a coolant tank on the radiator as described above, and does it have coolant in it up to the “Fill Cold” mark when the engine is cool?

 

[Fishtaco]

Plastic top radiator. I took my cap off the original radiator just for a look see and it was a Muva Ferka to get back on downward pressure speaking maybe try the gasket as you suggested?
Not sure Repco parts are the best choice for a TJ given even in the US their aftermarket parts dont seem to cut it!
TJ Tis a labour of love