Radiator boiling after replacing entire cooling system (including radiator)

[Fishtaco]

UPDATE: Changed to Tridon CA18125 (Correct 18psi Rad cap) and it's helped a lot.... still seems to be super hot, hoses and radiator is too hot to touch after driving. Still boils, but only slightly when I switch off. 100 degrees today also.

EDIT: is my cap the wrong one? I'm using a Tridon Recovery Radiator Cap CA16110. The alternative one they said I could use was a CA18125. I'm in Australia, not sure if you have these brands in US.

My TJ has 65,000km, just bought it, it was running hot when I bought it, weather has been 100 degrees f+ last week .... I replaced all the following with brand new just to be sure:

- Radiator (alum) + new 16psi cap (Switched for 18psi cap which helped)
- Water pump
- Thermostat
- Radiator hoses
- Heater hoses
- Heater core bypassed
- Gave it a good flush, all new coolant

Radiator is boiling, but stops boiling when I push down on radiator cap. Temp gauge shows 100-105 degrees Celsius constant. Mechanic looked at fan clutch and he said it's spinning fine. is it just my cap? Coolant is going into overflow bottle and returning when it cools down. Thanks

43c today in Perth and 41c yesterday my temp gauge did not go over half way both days that's 109 in the shade for our US friends, all Aussie temp is taken in the shade by the way.
TJ,s run really hot under the bonnet (Hood) How hot was it running when you bought it? Hot under the bonnet or temp gauge up Hot? Is your temp gauge going over half now?
Run it with the radiator cap off and look for bubbles even "Effervesce" .
Why did you renew the cooling system?
I was concerned when I bought my TJ a few months ago but discovered that this 4.0 puts out a lot of heat.

 

[JohnJ78]

43c today in Perth and 41c yesterday my temp gauge did not go over half way both days that's 109 in the shade for our US friends, all Aussie temp is taken in the shade by the way.
TJ,s run really hot under the bonnet (Hood) How hot was it running when you bought it? Hot under the bonnet or temp gauge up Hot? Is your temp gauge going over half now?
Run it with the radiator cap off and look for bubbles even "Effervesce" .
Why did you renew the cooling system?
I was concerned when I bought my TJ a few months ago but discovered that this 4.0 puts out a lot of heat.

I'm also in Perth. Temp gauge showed half, maybe a few degrees over today but that's it. It's more the under bonnet heat just seems hotter than any car I've owned. I checked for bubbles when I bought it, nothing at all, still nothing. I've seen bubbles from bad head gasket before on other cars, none of that in my TJ.

I renewed the cooling system because It was hot to touch the bonnet when I test drove it. I assumed blocked/dirty radiator or bad thermostat because coolant looked old and a tad rusty. The low mileage and general condition sold me on the car, easily the best one I've seen.

Higher PSI cap made a difference. I'll get head gasket check next week.

Might have to get one of those hood scoops or some venting. That much heat can't be good for electrical stuff in engine bay.

 

[MrMark52]

You really need to get a scan tool to read the actual temps - don’t trust the idiot gauge on the dash until you’ve confirmed it’s reliability with a scan tool. Either a scan tool with live data capability, or an OBDII dongle that will Bluetooth to your phone to send data (the limited data app is free).

As for heat under the hood - there’s really nothing to insulate the radiant heat from the radiator. At a 210 degrees F, (100C) radiator temperature, that’s pretty darn hot - the radiant heat off the radiator could easily heat the hood to a temp hotter than you could put your hand on for long. Keep in mind, research has shown that you can hold up to 109F (43C) for long periods, hold 131F (55C) for very short periods, and at 149F (65C) you’ll just barely touch it before receiving burns (YMMV).

So, unless you get a thermometer out and actually measure the hood temp, you do t really know if it’s hotter than it should be or not. And, subjective comparing hood temps without knowing the details can be misleading.

Not trying to cook your toast here, it’s just that hard data is important As opposed to subjective assessment on what’s right and what wrong.

TBH - I’ve felt the hood on my 4.0l a few times and thought I could fry eggs and hash browns on it if so inclined in the middle of the day.

If I were you, I would confirm that the fins of the radiator were clean. They may be full of crud that limits air flow which in turn limits under hood cooling. Yours might be running the ragged edge of cooling where it doesn’t overheat, but given a few more degrees of ambient, it might.
Hard data would gives us clues as to whether this might be in your future or not.

 

[Vtx531]

I used a Repco pump, metal impeller, this is the one:

Repco Water Pump - WP4101RP​

• High-quality precision bearings used throughout
• Induction hardened bearing shaft, heat treated using electric current for more consistent hardening and increased strength
• The seals are the latest technology offering superior lubrication, wear, and corrosion resistance
• Silicon Carbide used for the rotary face seal offering superior lubrication and wear resistance compared to ceramic seals
• Sintered Graphite used for stationary face seal offering superior lubrication and corrosion resistance

This is bad - You do not want a metal impeller. When the bearing goes bad, the metal will wear away at your engine block and ruin the close tolerances/fluid dynamics = time for a new engine because replacing the waterpump won’t fix it. Change this out ASAP with Mopar.

 

[DrDmoney]

I'm using 350ml per liter Ethylene glycol 50/50 premixed coolant. I live in super hot climate. Radiator specialist recommended lower Ethylene glycol mixture (more water) as it transports heat better. Never gets below 10 degress C here.

Also I did a heater core bypass, I wondered if that would actually have an effect on cooling.

The factory recommended coolant is HOAT, Zerex G-05 is a good alternative to the Mopar stuff.

 

[SkylinesSuck]

This is bad - You do not want a metal impeller. When the bearing goes bad, the metal will wear away at your engine block and ruin the close tolerances/fluid dynamics = time for a new engine because replacing the waterpump won’t fix it. Change this out ASAP with Mopar.

I don't agree with this at all.

 

[Fishtaco]

I'm also in Perth. Temp gauge showed half, maybe a few degrees over today but that's it. It's more the under bonnet heat just seems hotter than any car I've owned. I checked for bubbles when I bought it, nothing at all, still nothing. I've seen bubbles from bad head gasket before on other cars, none of that in my TJ.

I renewed the cooling system because It was hot to touch the bonnet when I test drove it. I assumed blocked/dirty radiator or bad thermostat because coolant looked old and a tad rusty. The low mileage and general condition sold me on the car, easily the best one I've seen.

Higher PSI cap made a difference. I'll get head gasket check next week.

Might have to get one of those hood scoops or some venting. That much heat can't be good for electrical stuff in engine bay.

These things get really hot! the heat really radiates from the hood and its a bit of a shock opening the hood after a drive to see just how hot they seem to get. I have not had a car that throws out this much heat either. Just a fraction past half should be fine, if it was overheating it would show on the gauge and it seems your gauge is working.
I think because of parts availability and servicing costs combined with most aussies being land cruiser fan boys and all say jeeps are shit pots that break down all the time you tend to worry about it not running right as soon as you get it!
Go to "Rockauto website" in USA they deliver most parts within 2 week and still ends up cheaper than local with shipping.
Rockauto is used to shipping parts to Australia and are pretty efficient. Try to buy "Mopar" parts mopar stands for Chrysler Motor Parts, bit more expensive but worth it if you want to keep it.
Too many jeeps in Australia have been "Basterdised" by local mechanics using non genuine parts along with owners who cant afford proper repairs/maintenance because all they want is ARB bumpers a 4inch lift and 33 muddies without the extra expense and changes that goes along with it.
If you fill out your profile members here can see what year/mods/transmition you have and help come fast from those experience in the year and mods.

 

[TJ4Jim]

I'm also in Perth. Temp gauge showed half, maybe a few degrees over today but that's it. It's more the under bonnet heat just seems hotter than any car I've owned. I checked for bubbles when I bought it, nothing at all, still nothing. I've seen bubbles from bad head gasket before on other cars, none of that in my TJ.

I renewed the cooling system because It was hot to touch the bonnet when I test drove it. I assumed blocked/dirty radiator or bad thermostat because coolant looked old and a tad rusty. The low mileage and general condition sold me on the car, easily the best one I've seen.

Higher PSI cap made a difference. I'll get head gasket check next week.

Might have to get one of those hood scoops or some venting. That much heat can't be good for electrical stuff in engine bay.

Pretty sure calling your Jeep a car down under carries the same penalties as North America.

 

[Fishtaco]

Pretty sure calling your Jeep a car down under carries the same penalties as North America.

I cant spell Ve ic al lol

 

[JKP]

This is bad - You do not want a metal impeller. When the bearing goes bad, the metal will wear away at your engine block and ruin the close tolerances/fluid dynamics = time for a new engine because replacing the waterpump won’t fix it. Change this out ASAP with Mopar.

This is not true. MOPAR impellers were just like the one you have depending on the yr.

My 92 has the steel one, my 06 has the plastic one. They both work.

 

[Fishtaco]

Bit off topic I had a metal impeller seize into its housing once (not a jeep) I thought I seize the motor it stopped it dead! I had to cut off the fan belt to get it off the road.

 

[Goatman]

Under hood temps do not indicate an overheating engine. You can put all the vents and ports in the hood and inner fenders and that won't change engine temp. It is controlled by the thermostat (and blockages) only. Assuming the water pump is doing its job. Plastic or metal impeller shouldn't matter, as long as the impeller is pushing the water. Even with half of the impeller worn away there should be enough flow to prevent overheating.

 

[MrMark52]

Under hood temps do not indicate an overheating engine. You can put all the vents and ports in the hood and inner fenders and that won't change engine temp. It is controlled by the thermostat (and blockages) only. Assuming the water pump is doing its job. Plastic or metal impeller shouldn't matter, as long as the impeller is pushing the water. Even with half of the impeller worn away there should be enough flow to prevent overheating.

I mostly agree with you - but I look at it a bit different (but to @JohnJ78 as well) -

If you were to put a contact temperature probe on various points of the engine block or head, an engine running at design temp will or should read within a few degrees of that design temperature.

But the under-hood temperature can vary based on the amount of cooler air that can or will be driven under the hood (the thermostat will modulate to control coolant flow to insure the engine continues to run at design temperature).
Does that mean one needs to add air scoops to improve under-hood cooling - I would say "No" unless you know what your doing. You could easily mess up the air flow through the radiator, not to mention have an impact on the already low fuel mileage.

I'm sure Jeep Engineers tested all of this before releasing the design for production. That doesn't mean there might not still be issues (take my 1990 Chevrolet 454 motorhome with it's exhaust manifold issues for example), but as long as your running right at 210F (~99C), then unless there is fire under the hood somewhere, all should be well.
If the hood temperature still bother the OP, then maybe they should get some insulation - just being careful that they don't create more problems with the under-hood aerodynamics.

 

[JohnJ78]

Radiator boiled again badly today. Coolant was down for some reason, boiled madly for 10 minutes after turning the car off. Coolant everywhere. Need more ideas what could possibly be wrong with my TJ. I did a TeeKay test which did not show bad head gasket. I'm stumped. I've been driving it daily quite a bit and its been fine. Was 100 degree day again today.

Should I replace thermostat with a high flow one?

Also: I have 2 massive spotlights in front of the radiator.... could this be preventing air flow to the radiator? I think they are 10 inch spot lights.

I'm seriously thinking TJ's are not good in hot climates.

 

[SkylinesSuck]

Plenty of people run TJ's in very hot climates with no issues, so I don't think that's it. List for us again the parts you have replaced so far please.

 

[Goatman]

It just sounds like the compression gasses getting pushed into the cooling system. Try removing the big lights, but so many TJs drive around with big winches, bars, and big lights and don't overheat. So if it isn't some type of head gasket leak then the fan seems next on the list.
Without back reading, did you boil the thermostat with a thermometer on the stove to be sure it opens at the right temp? And are you positive it is installed in the right direction?

 

[Vtx531]

Soooo Im guessing you didn’t pull the new water pump to check the impeller is still functioning...

And it wasn’t boiling over when you bought it before you did the work to the cooling system, correct?

 

[MrMark52]

Radiator boiled again badly today. Coolant was down for some reason, boiled madly for 10 minutes after turning the car off. Coolant everywhere. Need more ideas what could possibly be wrong with my TJ. I did a TeeKay test which did not show bad head gasket. I'm stumped. I've been driving it daily quite a bit and its been fine. Was 100 degree day again today.

Should I replace thermostat with a high flow one?

Also: I have 2 massive spotlights in front of the radiator.... could this be preventing air flow to the radiator? I think they are 10 inch spot lights.

I'm seriously thinking TJ's are not good in hot climates.

You are running with a radiator cap aren’t you?

From a cold start, how quickly does the engine warm up to operating temperature, and then does the temperature just continue climbing?

I’m not sure what a “TeeKay“ test is, but one sure way to find a blown head gasket, especially for a vehicle that is boiling as you are saying, is to start the engine cold - and as it’s warming up but before it’s hot, pop the radiator cap (assuming you have one). Listen for the release of any air pressure as you open the cap.
You could also smell the coolant to see if has an exhaust odor to it.

I also suspect that if the water pump impeller has an issue, that you would not feel much warming of the hoses going to the heater core (from a cold start) when the temperature is turned all the way to hot.

I also agree that you may have a fan clutch issue.

 

[DrDmoney]

Radiator boiled again badly today. Coolant was down for some reason, boiled madly for 10 minutes after turning the car off. Coolant everywhere. Need more ideas what could possibly be wrong with my TJ. I did a TeeKay test which did not show bad head gasket. I'm stumped. I've been driving it daily quite a bit and its been fine. Was 100 degree day again today.

Should I replace thermostat with a high flow one?

Also: I have 2 massive spotlights in front of the radiator.... could this be preventing air flow to the radiator? I think they are 10 inch spot lights.

I'm seriously thinking TJ's are not good in hot climates.

The spotlights shouldn’t be an issue the clutch fan will pull the air that it needs if it’s operating properly and the shroud is in place, a fan doesn’t do much above 35 mph vehicle speed. Did the system get “burped” of all the air?

 

[Zorba]

My uneducated guess is either fan clutch, or a bad/wrong water pump impeller. I'll be interested to see what it ends up being!