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overheated & boiled over

I bought the metal radiator thinking it would be more resilient. So I got back from telluride, no shroud still. I did notice open running high rpm up i70 would keep it above 210 unless I was coasting down hill or 2300 and down for rpm.
I flashed build once where the heat sensor shoots on the check gauges light. I kept her under 4000rpm after that.

I'll try the shroud as it needs replacing anyway. 99s use a 195 thermostat but would a 180 be a problem and not allow proper cooling?
 
Pretty sure the 180 thermostat only keeps it from warming up as fast, which might increase wear as lubricants (unless high flow synthetics) and engine parts reach operating temperature. It does nothing to keep it cooler once it reaches operating temperature. At operating temperature (fully open) its up to the radiator to remove excess heat.

http://www.tuneruniversity.com/blog/2012/04/low-temp-thermostats-whats-the-advantage/
 
So far with the new shroud i havent had a temp over 210 though it will easily reach 210 which im not worried about. I have not driven in as hot of temps either. lately we havent seen 90+ degrees.

My xj did come with the tow package and the radiator has what i think is transmission lines as well, or is this my power steering? theres also a smaller like radiator on the bottom right in front of the CSF radiator. I think thats for power steering?

My last long road trip before replacing the shroud temps stayed above 210 a little and the days were in the 90s. It flashed boiled the heat sensor once up I-70 and i was giving it hell. 4000rpm +

What i havent had a repeat of is the first boil over where i could hear coolant in the block boiling. The cooling system is now all fairly new down to the shroud lol so I hope like hell its solved.
 
Mine seems to stay a hair under, at, or a hair over the 210 mark...depending on the ambient temp.

After I replaced the all metal 3 core with the OEM, as a test, I put my foot into it and did a 1800ft elevation gain in 6.5 miles on a 100 degree afternoon. The temp needle got to right before the first line above the 210 mark (just a reference point), but never overheated. With the 3 core I couldn't make it 2/3rds of the way on a 85 degree day before the red light and buzzer went off and the needle shot to the highest mark.

I have a transmission cooler that sits in front of the radiator and is almost the full width of the radiator. The smaller radiator in front of the transmission cooler is the A/C condenser.
 
That is a transmission cooler for towing. Towing can over heat the T-fluid, and raise the radiator temp some as well. The lines to the radiator are also for the transmission, to warm up the transmission fluid faster in cold weather, the extra mini radiator is for cooling when towing...

4x4JeePmaNthINg said:
So far with the new shroud i havent had a temp over 210 though it will easily reach 210 which im not worried about. I have not driven in as hot of temps either. lately we havent seen 90+ degrees.

My xj did come with the tow package and the radiator has what i think is transmission lines as well, or is this my power steering? theres also a smaller like radiator on the bottom right in front of the CSF radiator. I think thats for power steering?

My last long road trip before replacing the shroud temps stayed above 210 a little and the days were in the 90s. It flashed boiled the heat sensor once up I-70 and i was giving it hell. 4000rpm +

What i havent had a repeat of is the first boil over where i could hear coolant in the block boiling. The cooling system is now all fairly new down to the shroud lol so I hope like hell its solved.
Click to expand...
 
im getting mixed answers so far.

its a 99 xj and automatic. If im correct the radiator has a transmission line in it. I have no full length secondary cooler.

the smaller cooler is maybe 16" long and 3" tall? the jeep does have the up-country tow package so im confused as to if this is an additional tranny cooler?

All A/C condensors ive looked up seem rather large and more sizable to the radiator itself?

thank you for all your help!
 
4x4JeePmaNthINg said:
im getting mixed answers so far.

its a 99 xj and automatic. If im correct the radiator has a transmission line in it. YES I have no full length secondary cooler. He was talking about the AC condenser.

the smaller cooler is maybe 16" long and 3" tall? the jeep does have the up-country tow package so im confused as to if this is an additional tranny cooler?

Yes it is a secondary Tranny cooler.

All A/C condensors ive looked up seem rather large and more sizable to the radiator itself?

thank you for all your help!
Click to expand...
 
4x4JeePmaNthINg said:
well not much help on here, but if someone is reading this ive replaced the electric fan and the mechanical fan clutch. I went for a test drive up to the same trail and it didnt boil over, but it did go above 210. I checked my oil level and it was at add.

Other than a faulty temperature sensor or the radiator cap im at a loss for the high temp. Its only hot going when i travel into the mountains. Typically the engine is working harder going up hill. Down hill its stays cool.....:dunno: I can drive around town all day and never see a difference.

I tried driving with the ac on and off thinking maybe a pulley seized or the ac clutch was gone but everything seems to be working.
Click to expand...

How much over 210? How steep of a trail?

While in heavy sand or a steep trail an XJ will usually run ~210 or higher, somewhere below the red zone, even with a HD radiator and trans cooler.

One method used to keep the coolant ~210 and lower while in more extreme, stressful conditions is to install an aux. fan manual over-ride switch and turn the aux fan on before reaching more extreme road conditions.

The PCM turns on the aux. fan when coolant temperatures become very hot, on my jeep it's 218 degF. = ON 210 degF = OFF. The coolant never has a chance to cools down. Often the dash temp gauge will stay at 210 and higher until after more extreme conditions no longer exist.

One method I use for more precise CTS readings is to use a OBDII scanner with live readout. (Only works with OBDII Jeeps).
 
Last edited:
Anony please correct me if im wrong but the aux fan will turn on with the A/C on yes? So the a/c could be used as an aux fan switch youll just be getting could air too right?
 
It will but it will also generate heat at the condenser so you're pulling the heat from that through the radiator as well. Probably not enough to matter unless you're already at the tipping point. This may send you over.
Also, when I run AC, the fan isn't constant. Only turns on when needed.
 
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