Any advice would be appreciated. 1999 TJ with 6-cylinder. My old radiator cracked. Mopar OEM no longer available, so I bought a CSF 2576 radiator for a replacement. I used Prestone flush (and rinsed, of course). I'm using Zerex G05 coolant (and 50% distilled water), like I always do. It ran too hot after I installed the new radiator and I've been throwing parts at it. I have now changed: thermostat (Mopar 195F, I drilled a 1/8" hole and put the hole at the top), water pump (genuine Mopar at $300), and radiator cap (Mopar 18-lb). It's still running too hot. I also did a cheap combustion gas leak check (with indicator fluid)--negative (so I don't think there is a head problem--plus, I see no gases bubbling up when the cap is off). I have owned this Jeep since 2005 and it's had multiple radiators--it has never run over 210F on the dash temperature gauge, but it's running much hotter now and will overheat. I checked with my cheap laser thermometer--it really is getting hot. It does fine at idle and slow speed--it's only overheating at highway speeds (so I don't think it's a fan clutch problem). Once it gets hot, it will eventually cool back down at idle (but it takes a long time and it helps to open the hood and run the dash heater). The temperature gauge is not wildly fluctuating, like you might expect if there was trapped air in the cooling system. Any advice? I'm thinking about trying a different radiator, but I don't know which one to try.
TJ running hot
- Thread starter MBK
- Start date
CSF or Koyorad radiator. Robert Shaw thermostat from Flowkooler.
I'm sorry--are you asking? It is a CSF 2576 that I just installed and is running hot.
Have you verified the temperature using an ODB reader/scanner and an IR gun to the thermostat housing?
-Mac
-Mac
I have verified it with my IR gun--it really is getting hot.
Are you sure you burped all the air out? With the cap off do you see good flow in the rad?
At hwy speeds, there is enough air flow that the fan is not needed. The fact it cools at idle indicates the fan clutch is working.
Verified the belt is tight?
Verify belt routing.
I have had that rad in my YJ for 20 yrs or so, it has always cooled it fine in the GA heat with AC on.
At hwy speeds, there is enough air flow that the fan is not needed. The fact it cools at idle indicates the fan clutch is working.
Verified the belt is tight?
Verify belt routing.
I have had that rad in my YJ for 20 yrs or so, it has always cooled it fine in the GA heat with AC on.
Thanks for telling me about your experience with the CSF 2576. I agree (and did note so in my original post) that it's probably not the fan clutch. Belt is tight and routing is fine. Do you have any advice for better burping? Though the temperature gauge is not wildly fluctuating (as it does sometimes when there is air in the system), I cannot rule out that there could still be air in the system.
Is it down on power? Maybe a clogged cat?
Are your O2 voltages trending below .9v? Fuel trims under 10 percent?
-Mac
Are your O2 voltages trending below .9v? Fuel trims under 10 percent?
-Mac
Use your IR thermometer to check input and output sides of your cats, they may be restricting your exhaust flow under load.
Let it run with the cap off until you see good flow, blip the throttle some, elevating the front a little helps.
I got one of these to avoid splatter and keep the rad full
Emphasis on elevating the front end to better force the air out. If you just run it on flat ground after filling you may still have some air in there.
I backed mine into the ramp for my driveway which was good enough to get my front end angled upward to burp mine after flushing my cooling system.
Power seems okay. I don't have a catalytic converter. I'm not sure about O2 voltages or fuel trims--is that something I can check on OBD2 scanner? Thanks.
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Have you checked the line to and from the heater core? The reason I ask is that I had the same problem with a brand new MOPAR water pump. Turns out that the plastic impeller must have been cracked around the shaft. I looked at it and spun it up before installation and it must have broken off of the shaft when I cranked it up. It was new so I had every confidence that the problem was somewhere else. I even thought that I might have left a rag in my engine block from when I flushed it. The lines going to and from the heater core never got hot so that tipped me off that the new water pump was bad. I took it back off and sure enough that was it. Broken impeller. I replaced with a FlowKooler and everything's been good ever since. Hope that helps.
Thanks for your help. In my case, I don't think that is the problem, because I have already replaced the water pump (the old one looked fine when I took it off, but at that point I was just throwing parts at the Jeep), and the temperature was about the same with both water pumps.
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