Alright so I've thrown a bunch of parts at this 2001 XJ sport that I rescued. However now that it is hitting 100* outside the thing is overheating.

Conditions. AC on temp gauge reading normal 210-220* both times has happened at traffic lights the dash will chime and check gauges lights up followed immediately by the temp gauge jumping over into orange 240-250*.

Work done was installed all new AC components which are working good nice cool air. I also while I had the front end apart replaced the original water pump. My electronic fan appears to be functional and does kick with ac as well as temp.

I'm at a loss right now. When I first got it together this winter I installed a cheap autozone duralast radiator #A1193 which has worked in tandem with all other parts until now. Its hard to narrow down since ive replaced other parts along the way combined with now its actually getting hot outside.

a couple days ago was the first overheat, since then i replaced thermostat with premium napa one as well as a new housing. And then refilled rad/and added coolant at the thermostat housing as well to avoid air pockets. Drove around all day with ac on at good temps even low speed mild offroad. Then hopped on i10 and it warmed up with mt driving over 70* but maintained about 220-230 about 1 notch from orange on the gauges. Then as soon as i pulled off the highway the second red light i hit it jumped into red and was boiling and dripping form the coolant overflow bottle.

Onyk thing original in the cooling system at this point is the fan clutch and e fan but both seemed to be working. Later tonight i will install a new fan clutch just to see if that helps but im feeling like maybe this radiator just is not capable of handling the engine and outside temps. I do have the fan shroud installed as a side note.

What do yall think? Time to replace radiator with better quality or more row?

 

I was in a similar boat. Had replaced water pump, put in a colder thermostat, flushed several times, recently had replaced my ac evap core, heater core, and blower motor. I replaced the radiator and it has run fine ever since. Easy work too. No stubborn bolts or anything. Straightforward process

 

I'm about to install the new fan clutch, if that does not do it I will buy a nicer radiator and flush the whole system really well. Should not be overheating with this setup unless the water pump from napa is garbage but it looked pretty good before install...

 

To add to what's already been discussed above, it seems over time these cast iron engines can develop a good coating of rust inside the water jacket that insulates the coolant from the engine. When flushing the engine, use something like Thermocure to dissolve that layer of rust.

The main problem is the Cherokee radiator is a bit on the small side, so it's taxed pretty hard when idling with the AC on in hot weather. The radiator is also pretty short since it sits entirely above the bumper, so the cooling fans aren't particularly big either.

 

I will try this as well before I decide to pursue a nee radiator since mine is only about 5 months old.

 

And not to insult your intelligence, but when you mention you flushed the cooling system, did you take the garden hose and flush out with lots of water the block in both directions via the heater hose connections to the thermostat housing and water pump as well as from the lower radiator hose? Did you also flush the heater core in both directions before putting the new radiator in?

 

this is my first project vehicle so its not taken as an insult . I've just redone the entire heating and ac system so its got a brand new heater core. Previously i had flushed it a couple times both the old core and the radiator. I didnt really do the block but i never had cooling issues before. This is the first under my ownership that it's gotten hot. I just replaced the water pump as well same time and heating and ac so I'm curious as to why now it's not running cool. The old water pump looked oem and was nice and rusted. I will go out tonight and flush the block really good once the neighbors aren't watching... and refill with more coolant if autozone has some rust flush stuff I'll give that a shot too. To verify the heat works great (too good) and the lines are all pressurized when hot.

When the vehicle overheats the upper rad hose has almost no pressure in it but the overflow bottle will be boiling to the brim or spitting up. As soon as it cools down it sucks the fluid back into the radiator/engine and pressurizes again.

 

You may need to check for a cracked head if you're talking about the 2001 Cherokee. Also, check out these vid's for tips

 

Okay, are you ready for this?

Performed a flush with a inline t fitting from autozone. Ran water for probably 20+ mins with engine on and off till clear and then drained the entire system at the radiator drain plug.

Jeep is staying below 210 now except at idlewith will sit right on 210 but I noticed something odd about my alt output. When I move my fan blower speed past low I can watch the alt output on dash lower and noticed it was actually stealing power from the radiator e-fan! This could be a big reason for the overheat as I had ac on both times. I'm thinking time for a new alternator now to see if that helps with some additional output. Otherwise it looks like possibly the blower motor I got from rockauto is using way too much juice compared to the original blower motor.

I did also notice my coolant reservoir was bubbling while the engine ran but it was not overflowing or higher than when I refilled it prior to driving. I'll be bummed if the head gasket is toast/cracked head because I just replaced the head 5 months ago and had it running again after it sat for 4-5 years with the previous owner.

I will update more on the cooling side once ive let yhe vehicle cool enough to reflush i added some rust/rad cleaner to the system and filled with water to get everything flowing and flushed depending on how much crud comes out I may do this several times but already I'm seeing about 10-25* cooler on the dash compared to pre flush.


*edit 2
Re checked coolant for bubbling in reservoir it only did it so far when op temp was just about or at 210 on dash when I turned heater on max temp dropped a bit and the bubbling went away. Hopefully this was just air trapped or hot water boiling off from the system with the flush... fingers crossed.

 

Could have been the air
However, do an exhaust leak test at the radiator with a test kit. Mine only leaked at operating temp..

 

Just wanted to provide a final update in case anyone has this problem or similar.

After flushing the whole cooling system and burping the radiator for probably 30 mins i was able to get all the air pockets out and have been driving around with no issues, have done several trips already and totalled over 500 miles. There has also not been any more bubbles at the reservoir after all the burping was completed.

I did get a new alternator but have yet to install it but even with fan on max and the alternator struggling with output the temps have not gone up to anything dangerous.

Thanks for all the help and advice.

I did not do a exhaust test yet (I'm scared) but can do it in the future, for now the seeable problem is fixed.