My 99 tj 5 speed 4.0 overheats but only at highway speeds. I have 35inch m/t’s and 4.88 gears on a rear Dana 44. I have the largest racing radiator that will fit in the Jeep currently in there( 3 row made of brass). All new hoses. New thermostat. Heavy duty fan/ water pump. Heavy duty 3 speed fan clutch. At this point I’m just looking for a solution that doesn’t involve cutting into my hood for vents. I was researching around and some said that it may be a bad crank pulley but I’m not so sure. Any ideas?
Overheating at high speeds
- Thread starter Emil
- Start date
What radiator is it? Personally I tend to think it's a mistake to put anything other than the OEM Mopar radiator in a TJ. A very high percentage of overheating problems on this forum can usually be traced back to an aftermarket radiator. More rows ≠ better cooling.
Fan clutch is irrelevant at higher speeds, so my guess is either your radiator is bad or your water pump is. Once again, with the water pump, you should be using OEM—what brand did you use?
Fan clutch is irrelevant at higher speeds, so my guess is either your radiator is bad or your water pump is. Once again, with the water pump, you should be using OEM—what brand did you use?
More rows does not necessarily or even usually mean better cooling. In fact, Jeep even went from a 2-row to a 1-row radiator in the early TJ days that cooled better.
And in fact again, we really haven't found a reasonably priced radiator that cools better than the OE Mopar radiator. Even for those of us who wheel in hot desert conditions. My bet is if you replaced your aftermarket 3-row radiator with the OE (1-row) Mopar, which has an all aluminum core, your cooling issues would absolutely disappear.
The OE design has proven impossible to beat where the TJ is concerned.
And in fact again, we really haven't found a reasonably priced radiator that cools better than the OE Mopar radiator. Even for those of us who wheel in hot desert conditions. My bet is if you replaced your aftermarket 3-row radiator with the OE (1-row) Mopar, which has an all aluminum core, your cooling issues would absolutely disappear.
The OE design has proven impossible to beat where the TJ is concerned.
The rad is CSF and the rest of the parts I’m not 100% but I know they come from quality oem manufacturers. (I’m lucky enough to have a father that has owned an auto parts warehouse the last for the last 20 years specializing in oem spec parts)I’ve had these issues before I put in the parts when I bought it from the previous owner. It had a mopar radiator when I bought it originally and it blew up one day when I wasn’t paying too much attention to the gauges. So I got it towed and swapped in a duralast rad from autozone just to get it running again and that gave me the same problems too so that was when I decided to do an overhaul on everything.
OEM replacement does not mean it's the actual OEM brand, I'd replace it with an actual Mopar.
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