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View Full Version : 98 grand cherokee limited 5.9 seems to run hot



clkid
August 25th, 2018, 09:31 PM
Really planned to hit some trails with the group this summer using a 98 grand Cherokee limited with a 5.9. Ever since I bought this Jeep it seemed to me it ran on the warm side, as in the 190 to 230 range. At least that is what the after market temp gauge was giving me as a reading. At about 230 this thing starts to boil and ghat ain't good. The original temp gauge stop working two weeks after obtaining the Jeep. Between the temp control devices that are in the upper and lower radiator hoses, the relays, and the electric fan, there seems to be no end to problems. Electric fan stopped so replaced that, then the sending units in the radiator hoses malfunctioned, so those were replaced with some but not total success. Fan runs on high speed, kicking in at 187 to 190, with temp going to 195 or sometimes 200 if you are working the engine on a grade. Low speed never has worked but relay has not been replaced. Last weekend went up to Long Draw Res on a shake down run and the radiator developed a major leak. Replaced the radiator and am thinking about going to a 160 degree thermostat, it has a 180 in it now. I think some of the problem my be air flow restriction from the winch on the front. There is a after market tranny cooler in front of the air conditioning unit and the radiator. Information on the internet indicates this thing is suppose to run in the 210 range, but that sound dam high to me.Oh, and radiator is a new 18 pound cap. Call me a paranoid old man, but I'm not sure I trust this thing on the trails. Anyone out there have any suggestions or had experience with a 5.9 MoPar???? Would going to a mechanical fan and junking the electric fan have any merit???

xaza
August 25th, 2018, 10:04 PM
The fan system is a PITA. Different sensors to control different speeds with combination of 3 relays if I remember correctly. Finding replacement sensors is like pulling teeth. 180 degree is already cooler than stock, stock is 195 IIRC. Another website that might provide you some answers on these is speedfreaks.com. It is a very slow site now, but guys are still checking in occasionally. All my Jeeps have run right around 210, that is normal for them. If you are able to hold steady at around 200 then I would say you are doing good. There are other after market fans you can try and make work but I think you are better off with electric over mechanical on something that will be spending long periods of time revving at low speeds.

Spieg
August 26th, 2018, 01:26 AM
Agree 205-210 is pretty normal operating temp (230 is too high). I know some people that bypassed sensors so the fan runs on high all the time (a bit noisy at times but never have to worry about multiple sensors/relays going out on you). Switching to a mechanical fan may be an option if you have room for it behind the radiator.