Radiator boiling after replacing entire cooling system (including radiator)

J

JohnJ78

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Australia
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
 
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Is it really boiling or do you just hear a pressure leak due to a poor seal between the radiator and cap? Did you use a 50/50 mix of water to coolant?

It is normal for some coolant to go into the overflow bottle as it expands due to heat and be sucked back in when cool.
 
TWiG01 said:
What Thermostat is in it? What coolant?
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Tridon TT1-195 Thermostat. I checked it was functioning before I installed it by putting it in boiling water.
Repco Green Coolant Premix 50/50 - Premium grade coolant
Used a razor blade to prepare surfaces for gaskets, and gasket glue. Water pump is a repco one.
 
JKP said:
Sounds like a bad rad cap.

Normal operating temp is approx 210 F.
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??

Did you mean bad thermostat? Because he just replaced that and even checked it before he installed it.


OP---how much effort did you put into bleeding air from the system?
 
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Rad cap.

He stated that when he pressed on the rad cap it stopped boiling..

A weak rad cap won't hold pressure allowing the coolant to boil.
 
SkylinesSuck said:
??

Did you mean bad thermostat? Because he just replaced that and even checked it before he installed it.


OP---how much effort did you put into bleeding air from the system?
Click to expand...

Squeezed hoses a couple of times, topped up coolant after a minute or so. So yeah, not very much. My mechanical knowledge is limited.
 
What engine do you have (fill out your vehicle details in your profile)?

If it's the 4.0, the cap you used is 16PSI and should be 18. It's possible that the 2PSI is allowing the fluid to boil at a lower temperature. Can you get a Stant products there? If so, try the 10234.
 
RMETeeJay said:
What engine do you have (fill out your vehicle details in your profile)?

If it's the 4.0, the cap you used is 16PSI and should be 18. It's possible that the 2PSI is allowing the fluid to boil at a lower temperature. Can you get a Stant products there? If so, try the 10234.
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That must be it, thanks. Auto store told me this one was 18 PSI but no markings on it. I will grab the other one instead. Good work.
 
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2 psi will definitely make a difference in boiling point. Reconnect heater core will also add a bit extra cooling. It is a small radiator after all. Air pockets can be a real pain to deal with. 4.0 not known for air pockets as a major issue, but park nose first up a steep hill and let the hot coolant cycle for a minute or 2. Then turn around, nose down on the hill and cycle 1-2 minutes. Should be no more air.
If the fan clutch isn't right then you can have overheating regardless of everything else being right.
 
Goatman said:
2 psi will definitely make a difference in boiling point. Reconnect heater core will also add a bit extra cooling. It is a small radiator after all. Air pockets can be a real pain to deal with. 4.0 not known for air pockets as a major issue, but park nose first up a steep hill and let the hot coolant cycle for a minute or 2. Then turn around, nose down on the hill and cycle 1-2 minutes. Should be no more air.
If the fan clutch isn't right then you can have overheating regardless of everything else being right.
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Thanks. Useful info. I disconnected heater core as I presumed it would leak eventually and I live where its hot all year. I'll see how the 18psi cap goes.
 
A cracked head or bad head gasket can also cause boil over (combustion pressure escapes into the coolant system).

To test, have a compression check run on the engine. Depending on how bad the crack or leak is, you will also see what appears to be boil over before the engine has even had a chance to get hot, regardless of cap pressure rating (typically over 100 psi).
See the FSM for testing procedure.
 
Check the water pump again. Remove it and inspect. Aftermarket waterpumps are notrious for being pieces of crap that fail within couple hundred miles of replacement. Then get a mopar unit and you should be all fixed.

I bet you replaced the waterpump with aftermarket and the fins broke off or impeller disconnected from the shaft.
 
Vtx531 said:
Check the water pump again. Remove it and inspect. Aftermarket waterpumps are notrious for being pieces of crap that fail within couple hundred miles of replacement. Then get a mopar unit and you should be all fixed.

I bet you replaced the waterpump with aftermarket and the fins broke off or impeller disconnected from the shaft.
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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
A9430250-2.jpg
 
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.
 
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