BayArea-Jeeper

Hi Everyone! I'm a newbie to Jeeps and trucks in general. My 91 XJ is running a little past the 210 marker on the stock guage, now from reading here I gather that 210 is normal but mine is a little past that. The weather here in SF is in the cool side so I can imagine the water temp would get too hot on our hot days, so I want to avoid running this temp.

Would a 160 or 180 thermostat be okay? Were can i get a 180? I see 195 is stock.

At what temps does the fan turn on?

My water pump is new and so is the radiator. The motor only has 47k miles and no milky oil or air bubbles from the radiator.

I appreciate the help and thanks in advance.

finneys98xj

get a 180 from napa and u will be fine

BayArea-Jeeper

Thanks Finneys.

93XJLI

run the 195. operating temp is 210-215 for the 4.0.

running a lower tstat wont let the engine run in closed loop correctly. efan turns on at 220.

are you overheating moving or not moving?

BayArea-Jeeper

93xjLI when I kinda get on it hard in starts to move towards the right side of the 210 marker. When I slow down for traffic ahead, it stays there and does not go back to the 210 marker.

220 for the fan to run huh, kinda warm I guess i just have to get use to these temps.

Thanks again.

93XJLI

they run hotter than normal motors, just something different.

96 XJ Sport

I always throw this out there when overheating comes up...check the mechanical fan clutch. Pop the hood with the engine running hot and watch the fan as you shut off the engine. Working fan clutch should stop the fan almost immediately, but if it freewheels, replace it. It did the trick for me after all else had been replaced. I realize that it's not going to be the solution in every situation, but I think it is often overlooked.

xer0

have u checked the condition of your radiator fluid? might need to be changed.

BayArea-Jeeper

Thanks guys! I will certainly check fluid and fan clutch. The radiator was replaced with the motor 47k miles ago.

xer0

but is the fluid the pretty slimer green?

BayArea-Jeeper

xer0 I replaced the thermostat today with a 180...i also bough a 195 just incase. BTW this is by far the easiest t-stat replacement iv'e done. the fluid seems like a pretty fresh 50/50 mix of green coolant and water.

Thanks again.

farmfuel

https://www.cherokeeforum.com/showth...t=cooling+woes

Read this.

I replaced my T-stat with a 180, and the mileage went down a little (I think). This would make sense, because the computer thinks it's cold- and change the injector pulse width. With regard to the computer operating in open/closed loop: The computer does use the CTS to decide when to switch to closed loop, but it also uses the O2 sensor as well. I think the only way to figure out if a 15* difference between T-stats will decide the status between constantly running in open loop or not would be to plug in a scan tool, and monitor the data stream. It will tell you if the computer kicked into closed loop once the CPS tells the computer the water has finally reached operating temp.

I do agree that the fan clutch could be a problem, but I changed mine out, and it didn't help. At least I have piece of mind knowing that it's new.

I think the ultimate decision is in the thread that I cut/pasted above- and to replace the radiator with a 3 row unit. My radiator was just replaced prior to me purchasing it, so I know it's good, I just think the coolant capacity isn't enough.

farmfuel

When my motor starts running warm on the hwy, I turn the cabin temp to HOT, and turn the a/c on. That way the heater core becomes an auxiliary radiator, and the a/c kicks the fan relay on. It won't take that long for it to come back to 210 once you've done the above.

If you get it REAL hot, don't turn it off. Go to a gas station and hose down the radiator with water. The temp rises once you shut it off, and you run the risk of blowing a 10+ year old head gasket.

BayArea-Jeeper

Good points Farmfuel. I am seriously giving the bigger radiator a lot of thought. Thanks for the other tips also.

BuckB91XJ

Bay Area Jeeper - Here is the scoop. I too own a 91 XJ. I learned the har way while living in the cxentral valley of Cali, that my little XJ didn't much like hot weather. I installed a 180 degree T-stat thinking that would do the trick. I ended up installing a CFS 3 core radiator, as well. That did the trick. I know some guys say that it knocks down your mileage a bit. I can only speak for my own experience. With 180 T-stat and 3 core radiator, 4.56 gears, 32" tires and an Auto tranny. I get 20-22 mpg on the highway.