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jeep runs to cold, im stumped!

dellstopjeep

dellstopjeep

NAXJA Forum User
Location
KUNA, ID
when i bought my 1991 xj with the 4.0 i was told it had a 180 thermostat. it ran at about 160 and never over 170 to 175. i replaced my coolant sensor when i failed but then it was fine. then after being told my gas mileage is crap because im not gettin proper fuel mixture due to temperature and heater not bein as hot as i like i decided to throw in a factory thermostat. the install went fine and now i am runnin at 140 and no hotter than 155. im stumped! jeep runs fine just not hot enough! and i air in cab is a bit cooler, still warm just not obviouslywhat it should be. any ideas?????
 
is it s 195 degree stat? thats what the 4.0 came with from the factory
 
195* is factory, correct.

No way motor could stay at 155 with a 195 tstat. The thermostat would stay closed unit 195, allowing the cool water thru then.

For it to stay at 155, the motor would somehow have this bulging fire going on inside, and never heating up.

I would replace the factory gauge with an aftermarket. just had to do the same to my xj on turkey day. Replaced temp sender, factory gauge would still give me crazy readings, installed aftermarket gauge (obviously still w/new sensor) and now I can actually tell how I'm running.

$20. cheap insurance.

And your gas mileage CAn be from running too cold, but it's most likely because it's a jeep.
 
I have a 88 and it runs at 150-160 but i have it set up with vents and fans to be that way. It used to run at 200. The heat is great inside even at 150 and the gas millage is great at some where between 24 and 27 miles to the gallon.
 
boomer1 said:
I have a 88 and it runs at 150-160 but i have it set up with vents and fans to be that way. It used to run at 200. The heat is great inside even at 150 and the gas millage is great at some where between 24 and 27 miles to the gallon.
Click to expand...

Something about that just doesn't sound right....especially the 24-27mpg part...:dunno:
 
99XJSPORT06 said:
Something about that just doesn't sound right....especially the 24-27mpg part...:dunno:
Click to expand...
It isn't right. Not only is running the 4.0 at that temp bad, but there's no way he's getting 24-27 MPG.
 
I got that type of mileage with the 2.5L, not the 4.0L.

Running that cold does not get hot enough to get rid of the moisture in the crankcase/oil. Non-synthetic oil contains sulphur. Sulphur + water + time = H2SO4 = sulphuric acid. This is one of the main failure contributors to bearing wear and sludge buildup. The problem isn't as bad with synthetics, but it still doesn't go away.
 
I suggest using infared to test temps.

I went through the same thing on my 87. To low, changed the sender, then to high. Added VDO gauge after infared confirmed a problem.

Don
 
so general consensus is my gauge failed. where do you stick the sensor for aftermarket gauges? the heat thing is what makes me think the gauge is working though because its not as hot since this happened. it happened at the exact same time. what could cause that seperate issue then? the temp gauge does start at zero and then works its way up to 140 150 after proper amount of time to warm up.
 
Mine would work its way from the bottom up as well, it could most definitely be this.

If it IS running that cold, I would make sure you have a thermostat, and honestly, ive never even imagined my jeep or any jeep running TOO COLD.

Truth be told, anyone i know whos said their jeep runs that cold, puts in a real gauge, and sees the light, lol
 
You sold me some tires last night, thanks by the way.

After talking to you last night I started thinking about my own gas mileage, and the 180 thermostat in mine. I think I'm gonna go back to a 195 for the Winter.

It seems to me the gauge is probably fine, especially since you said the heater isn't performing like it should.

My best suggestion is one of two things.

1. parts counter guy grabbed the wrong thermostat, or it was packaged wrong, and you got another 180 or maybe a 160.
2. its a defect. its sticking open. maybe you just got a bad egg.

either way my best suggestion is to run to a napa and buy another 195, try one more time.
 
Have you felt the upper and lower radiator hoses? Does one feel hotter then the other? Are you sure you purged all air out of cooling system? Did you install the thermostat with the bleed ball at the top?
 
i am gonna go try another one definitly.
two questions? what and how do you purge air out of cooling system and the bleeder ball, what is this?
 
theres a little bleeder thing on the top of the thermostat, looks like a little rivet or something. its on the flat part.

personally I always put a radiator flush kit in the top of the upper heater hose, makes bleeding air out way easy
 
but i did jsut check and my upper radiator hose is hot while the bottom is warm. its not a huge difference in temperature but noticeable. and i cut my hand on the aux fan haha
 
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