How cold is too cold?

87 4.0. Weather is cool where I'm at now, right around 10-30* or so. After a 20 minute trip the temp guage only reads about 125* max or so after that time after running highway speeds. Heater works fine. I seem to remember it running warmer last year. What temperature should it be warming up to and staying at? Could the thermostat be stuck open? Coolant is dirty but that shouldn't actually cause it to run cooler right?

Thanks for any help given.

I would tend to think dirty coolant would make it run hot. It should run around 210 when fully warmed up. If the heat works I wouldn't suspect thermostat. How long does it take the heat to get warm?

Not to steal your thread but, I have a similar problem in that the coolant temperature takes a long time to warm up and sits between the 1/4 mark and 1/2 (210) mark when fully warm. I thought for sure it was a bad thermostat so I replaced it over the weekend, but it had no effect at all. I'm using a 195 thermostat from Checker, if that matters and I've researched enough to know that sometimes the non-oem thermostats can be crushed by the housing elbow, but the old one that came out wasn't stuck open and didn't have any visible damage to it. Any suggestions? Oh, and the heater works fine as long as the coolant temperature gauge is reading above the 1/4 mark.

i to have the same problem. no clue what is going on. seems to still be running fine. gas mileage might be suffering though

my 89 limited has been doing the same thing... pretty much since i have had it, a little over a year now. I have replaced thermo with 195 and still no luck, even when temps were higher in late late summer. heat works fine, i was thinking maybe a shot sender for the gauge? how can i tell if that is it? are there ranges for the readings off of the gauge and block sender?
thanks

I'd say it's definitely too cold. Running too cold may not be as bad as too hot for the short term...but in the long run can be bad.

Try blocking part of your grill. I had a TJ that would not run hot enough in the winter (even here in Florida) and would tape up about half the grill with 'duck' tape and it would run right up to temps...had to play around to make sure I had enough but not to much tape. It;s easy, cheap, and if the weather warms up you just peel it off.

First, I would make sure you are running that cold. If you have a good balanced 195 thermostat then I would not be too concerned. Also, take a reading with an infared thermometer; it will be more accurate than the gauge on the dash.

043500 said:

Try blocking part of your grill. I had a TJ that would not run hot enough in the winter (even here in Florida) and would tape up about half the grill with 'duck' tape and it would run right up to temps.

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LOL, man try running in Winnipeg! I've been fighting this cold problem since I got my jeep. And my gas mileage suffers BAD from short cold trips.

What I do to help.

1) Use an electric block heater. (required by law on new car sales in Manitoba) you can also get electric oil pan heaters. This will start you out at a warmer state, meaning less time to warm up.

2) block most of the grill. if you run a tranny cooler, leave the space over the tranny cooler open. I've seen several burnt out vehicles started by overheating transmissions form trying to get unstuck form snow.
For mine I use a 1/4 inch piece of hardboard cut to fiton the inside of the grill, and wired on. Paint it black and you'll never even see it. This will alow your jeep to warm up to a higher point.

3) I'm told replacing your clutch rad ran with electric helps. Personally I'm more tursting of the stock clutch fan working in the deep cold. (electric can freeze and burn out)

4) In Winnipeg, park facing south. This keeps the engine downwind for the prevailing wind. Also alows more sun to warm the cabin.

5) beyond -25'C (-20'F) it will be very hard for the engine to keep warm at speed.

6) at -40'C (-40'F) and below just give up on trying to get to opperating temperature and be happy that a jeep produces enough heat to warm the cabin.

7) not fun but works, don't run heat to the cabin and the engine will warm faster and keep hotter.

I put a 180 thermostat in my 87, and its pretty good about actually staying at 180 degrees. Is this too cold? Should I have put a 190 or 210 in?

karter74 said:

Is this too cold?

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Yes. The factory uses a 195 for a reason.

Been in the high 20ies here in the am heading to work. within a few miles mine is heading up to 210 mark. it actually seems to run a little hotter on cold days?

Mine will heat up till the 195 when the thermostat opens then the temp drops dramatically. Then continues up and down. Even just sitting still. The electric fan never comes on.

A cold thermostat isn't necessarily a bad thing for engines. Modern, emissions-controlled engines use a hotter thermostat not because an internal combustion engine (in general terms) was designed to run at that temperature, but because emissions are lessened (and gas mileage improved, to a degree) by running hotter. A hotter engine requires less fuel to combust the mixture. So, while a 160 degree stat theoretically allows an engine to make more power, it's not necessarily helpful on a factory computer-controlled vehicle because it's been programmed to operate at the higher temperature. If anything, you'd just see a reduction in fuel efficiency. If the ECM has been modified to take advantage of cooler engine temperatures, then a power gain may be realized. If the computer has not been properly tuned, running a cooler thermostat usually doesn't help (unless the engine doesn't use a computer).

Sorry to get off on a tangent, but to provide some insight to your problem...

My YJ displayed your exact symptoms when I first purchased it. The temperature gauge barely moved from the first notch past 100 degrees, even after an hour of driving (40 degree ambient air temperature -- shouldn't do that). Then, for a while, the needle would constantly show that I was overheating. There were no unusual mechanical problems, aside from a very small radiator leak which was purely by coincidence. I replaced the gauge sending unit and it's been fine ever since. Not sure about the location on the I6 motors, but on my L4 it was in the very back of the engine (head or block, I don't remember) almost up against the firewall. Make sure you've got the new unit in hand, ready to go in, as soon as you pull the old one -- coolant will want to squirt out of the hole because the system is under slight pressure (even when cold; I think it's something related to the fluid dynamics of the cooling system).

You actually CAN check to see if a sending unit is bad by submerging the "sensor" end in a glass of hot or cold water. Attach a multimeter to the terminals and measure resistance. As the temperature changes, the resistance should change in a linear manner. The upper and lower limits of the sensor depend on its design, so I don't know the exact numbers in ohms.

The gauge can also be checked by doing the process in reverse -- power on the ignition and place various resistors across the terminal connectors. The gauge should respond accordingly. I wouldn't do it without knowing what the gauge is designed to operate from, because you might end up pegging the needle and causing damage.

One more note--on mine, the electic cooling fan ran all the time. It was a bad temp sensor switch in the radiator. See my previous thread (http://www.naxja.org/forum/showthread.php?t=34708). Just a thought.