nikuk

Drove my wifes 95 ZJ 4.0 the other day and then asked her how long the heats been lukewarm. Apparently it'd been a few weeks, but we had 0 - 15* F weather so she assumed that was it. However I noticed the gauge never got over what would be ~160*.

Spent $10 on a 195* stat, popped it in and flushed the heater core extensively while i was at it. The radiator had been done ~18 months ago, and the water pump ~24 months ago.

After I buttoned her up, revved her a while and topped off the coolant... the gauge still barely got to what should be ~180*; I checked a few points on the motor with my cheapo laser thermometer and got nothing higher than 176*. This was after the truck sat in the garage at 55* for a couple hours as well, so I discounted the weather.

Any thoughts?

Also, the old tstat was NOT stuck open when I pulled it out, though I did not boil it to check operation. Also, MPG is down to about 10-11 (tune up summer 2013), and the HVAC was a bit warmer but never hot like it used to be.

Thanks,

Nick

dave1123

Hello from Syracuse! I don't think this will be much help, but my WJ 4.0 has been doing the same thing. A little history first. In the 2 years I've owned it, the temp NEVER got more than one needle width above or below the center mark, either in winter or summer. One night I was out delivering newspapers in -5* temps and I noticed a lot of steam coming up around the front. I sometimes get a little from the grill when snow gets in the radiator and the fan isn't running, but I noticed the guage was about 2 needle widths above the center. I checked under the hood and found a pinhole in my heater hose spraying coolant around. I loosened the cap and drove home. I cut the hose off about 3" and put it back on, topping off the coolant. It hasn't gotten above 180* since then, unless I sit and idle for awhile. The temp comes right up on a cold start like the thermostat is working, but it never really gets warm. There is no air in the system but the heater doesn't get hot like it used to.The system is clean and the coolant was changed last September.

I've been told to try a 210* stat, but haven't done it yet. I don't know what stat is in it now. I think the stat is working but opening too wide and not closing enough to maintain a normal running temp. I'm living with it until the air gets a little warmer because I don't have a garage. I may take it to my buddy's shop.

So basically I'm saying your problem is not unique. I hope this gives you some insight and isn't just another story.

nikuk

Its funny (in an aggravating way) how finicky these things can be. I appreciate the reference. I know that when I drove her for a few days in fall she was running snuggly at 200. I took her out and beat the he'll out of her this morning and she onlyspiked to 180* twice.

Also, the clutch fan spins easily the whole while I was doing the t stat.

dave1123

Here's how things have progressed in the automotive world. My first car was a 1937 Dodge. The only thermostat in that was the driver! There was a window shade in front of the radiator controlled by a chain to the dash. You had to watch the temp guage and adjust the shade yourself! I put a thermostat housing from a 54 Dodge in it myself.

Oh, and it had no heater!