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Low Engine Temps

Blue XJ

Blue XJ

NAXJA Forum User
Location
Sterling Heights, Michigan
I've noticed lately that when its cold out the engine temp goes down as my speed goes up. I put a stroker in about 4000 miles ago, a new radiator, waterpump and thermostat at the same time. About 300 miles ago I put in a new heater core and another thermostat.

If I let the jeep idle for 5- 10 minutes, the heat blows out hot and the engine temp is about 190ish, once I start driving the engine temp goes down to about 160 and the the heat stops blowing out warm. If I sit at a stop light the temp goes up to about 180 - 190, then once I start moving its back down to 160 - 170ish and the heat goes away again.

Is this possibly an air bubble in the cooling system? Its a 90 with the closed system, I've tried burping it many times. I don't think its the thermostat, its done this with 3 different 195* ones now
 
I would love to have a low temp problem but, not bad enough to live where you live.
I do think it is an air blockage problem but I think it is where your temp sending unit is located. try removing it and see if air is trapped under it.
Mine is to 210 by the time I reach 2 miles down the road and never cools that low. I had a heck of a time burping the system when I changed the radiator about 18mos ago.
 
You have a thermostat that is stuck open.
 
old_man said:
You have a thermostat that is stuck open.
Click to expand...


Blue XJ said:
I don't think its the thermostat, its done this with 3 different 195* ones now
Click to expand...




So the last 3 thermostats that I have bought have all been stuck open? They have been closed when I take them out to replace them.
 
Blue XJ said:
So the last 3 thermostats that I have bought have all been stuck open? They have been closed when I take them out to replace them.
Click to expand...

The only way the engine isn't gonna come up to temp is a stuck or missing thermostat.

overly cold temps might make it run a little cooler, but not by much.
 
Try a new cap?

That fixed my low temp. problem. I hadn't noticed it was leaking a little bit. A new $5 cap from NAPA made all the difference in the world.

HTH.

Hale
 
i had the same problem with my 90 XJ when i first got it, i had to put a peice of cardboard in front of the rad. but just dont cover the entire the whole thing(i know thats basic but i just have to say it)
-Keep Jeepin
 
Jason-RJR said:
The only way the engine isn't gonna come up to temp is a stuck or missing thermostat.

overly cold temps might make it run a little cooler, but not by much.
Click to expand...


Well, put in thermostat number 4 today, heated up to about 200ish heat blew out nice and hot. Drove it to work tonight, engine temp wouldn't go over 175ish, 1/3 of the way between the second line and the 210 line, and the heat is ony blowing luke warm now.


I'll try the cap, it seems to hold pressure when the temp was nice and hot, then I loosened it to add more coolant, not sure if there was pressure after that or not.
 
Pardon my thoughts but a new one installed upside down won't work. May not be possible to install wrong, just a thought. After thinking about it, that should cause it to run hot. Getting OLD! I should get my brain in gear before full speed ahead with the typing fingers.
 
Last edited:
langer1 said:
Upside down and you will boil over real quick.
Click to expand...

Maybe I'm missing something, or are just confused.

Do you mean upsidedown or backwards?

Upsidedown, meaning that the hole is at the bottom.
Backwards, meaning that it was installed with the spring facing out of the block.

Hale
 
I have the same problem on my 89. I thought the t-stat was stuck open and replaced it today. Still no change. At idle it acts like it is going to running temp, but at speed it drops to about 160....also no heat. I think the heater core is clogged, but don't see how that would make the temp stay so low. I am going to flush the heater core next and see if that helps.

Anyone got any more ideas???????
 
Jess said:
I have the same problem on my 89. I thought the t-stat was stuck open and replaced it today. Still no change. At idle it acts like it is going to running temp, but at speed it drops to about 160....also no heat. I think the heater core is clogged, but don't see how that would make the temp stay so low. I am going to flush the heater core next and see if that helps.

Anyone got any more ideas???????
Click to expand...

Cap?

:dunno:
 
I just replaced the thermostat in my '91 with a 180 Degree one, and now my temp rarely goes up to 210. Stays around 170-190. Hmm...
 
Upside down, backwards, spring away from eng, all meaning the same, anyway it was a stupid idea as I mentioned in the post, clearly not thinking before posting. To save face, I should have deleted the post, But a little humor helps in a situation where there's no clear answer. Since it's a closed system, I'm leaning toward the cap also.
 
Man, I wish my XJ ran cold. Sucker overheats something fierce in temps above 80 degrees. I have a new aftermarket rad and water pump in the garage awaiting time to install them (before Summer certainly) that should take care of the problem.


All the advice in this thread is good. I'd start with a new rad cap, then a small piece of cardboard in front of the rad if it still won't run at proper temp.

Good luck!
 
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