1991 cherokee briarwood 4.0 auto

so i had a 180 theromostat in, read that was a really bad thing to do so a week ago i put in a falsafe 195 and threw in a new lower hose. it was fine all week but today driving about 45mins on the highway i stopped for gas and after i started drinving again i noticed temp gauge was barely above 100 and at idle would climb just below the next notch about 155 and its been like that since. after about 3 more hours of driving. I pinched off lower hose and added more coolent. it took about a quart and then let it run with rad. cap off and put in another quart or so. and that did nothing. figured i had air in system or something. now im thinkin falsafe failed and is now stuck open. heat comes out pretty hot too. not like normal but its hot. any ideas whats wrong?

 

well it sounds like the t-stat failed and is open all the way. could check it with a lasor temp gun if you had one.

 

I would say samething t-stat is hung open. I'm driving my Jeep right now without t-stat & it does samething my old 1 wouldn't open so I bypassed it for now but will be putting new thermostat in.

 

what temp u run at without a thermo?

 

is it that bad to run a 180 T-stat? i have one in mine now....

 

Motor just likes 195 to 210 range better. Its is the optimum temp range for mpg and power

 

Been running a 180F t-stat in our '98 XJ over 3 mos now.....heater works great, XJ runs like a top, mid-teens mpg in town and low 20's hwy. Coolant temp has little to do with system going into "closed loop" since the O2 sensor is a heated unit.

 

imagine how well it would run at the temp it was designed to.

 

It had a 195F t-stat when we bought it.......zero, zip, nada difference in the way it runs after installing the 180F t-stat, other than a little cooler.

 

yea i think mine is like that too. it came with a 195 and my dad wanted it to run a little cooler so he put the 180 in. there was very little difference between the two. even with the 195 my jeep never warmed up to 210*, not even on the highway. the only time i ever hit a little above 210 was with the 180 t stat going up the grapevine with it floored.

 

We have the idiot lights on our '98 XJ but also have a ScanGauge plugged into the ALDL port. Never saw 210F on the ScanGauge when the 195F t-stat was in.

 

I am thinking I might run a 180 t-stat in mine. I kind of like the idea of it running a little cooler. My 01 runs just a little above 210 on the highway and in stop and go it runs a little warmer causing the fan to have to kick on more often than I would like. I drive more stop and go traffic every day and rarely above 45mph. I think 180 would fit my type of driving better. I dont mean to highjack your thread just thought these other comments fit my situation.

chefeagles... the only thing that throws me off is the fact that your heat blows hot. I had a T-stat stuck open on a truck I owned and it would barely blow any warm air at all. You might want to check your actual temp and see if your guage is failing.

 

your clutch fan is probably shot...my jeep ran the same till i replaced mine now just under 210 is where it runs...

 

A point of a thermostats is to allow the water to stay in the radiator longer and have time to cool......

So one would think if it was "hung" Open it would run hotter....but not overheat.

 

Thermostats stay closed until they hit there set temp then open, so they don't hold the water in the radiator longer to cool. They open when the water in the block hit the temp and then open to let the cooler water from the radiator in. That's why temp goes up when in traffic, no air flow to cool water in radiator.