SiRed91

Mine runs on the first quater mark of the guage. Solid. After replacing the thermostat.

I put a 180 in it, but from feeling the air when as hot as it gets, it's on the cool sid of hot.
94 4.0 stock motor and electronics.

jpmarine6786

Should be 195 thermostat. If it's at the first mark that kinda cool, your heater may be a clogged heater core.

sycoglitch

Change that out to a 195 stat. Why did you out a 180 in??

SiRed91

Because its 200k+ and runs hot while wheeling. I dont need to hear rookie remarks about "meant to run at 210" or higher lol if thats what anyone wants to say. I just need to know when or if the 4.0 obd1 system will run substatialy richer or not and at what temps. Any engine tuners here that know the fuel maps?
Gotta do the radiator anyhow, so the water pump is getting done too. My system flows freely. Nothing is plugged up. Bht the freeze here did in my 250k radiator. I suspect a slightly worn pump impeller too.

shadowman

The engineers who designed the vehicle, designed it to run at 195 degrees. This was done to ensure the engine emissions systems operate effectively, the oil gets hot enough to 'burn off' unwanted contaminates(moisture and any unburnt fuel that may wash past the rings) and adequate heat is available for the cabin. In my experience (20+ years of owning and working on Jeeps) the emission equipped Jeeps, they tend to run much better and get slightly better mileage with a 195 degree thermostat. The computer doesn't even go into open loop (using the sensors to monitor and modify operating parameters) until the engine gets to operating temperature (in this case 195 degrees), it will stay in closed loop and operate off of its preprogrammed parameters (usually a very rich fuel mixture and a very conservative timing setting).
Now I'm sure there are many different opinions and someone out there will swear that I'm a complete idiot, but as an engineer and a former auto tech that's just my humble opinion.

neverenuff

shadowman you are right on the money. It is not a "rookie remark" to say that is how the system was designed. That is how it works,some folks just don't want to understand and accept it. The computer thinks the engine is still in warm up mode. so the answer to the question is that any temperature below full warm up will cause suffering gas mileage.

LittleRed94

Sorry to interupt the thread but then what should I do?
I'm always on the first mark as well, but I have a 195 thermostate and my heats always hot hot hot. If it's an issue to run that cool that worries me because mines never even touched the 190 mark.

Jimbo Slice

Before jumping to any conclusions, grab an Infrared thermometer and check your temp at the thermostat housing. It's possible your gauge is off.

jpmarine6786

If you're running hot while wheeling there's a problem with the cooling system. What do you mean hot, what temp?The computer wants the temp to be 195 and will keep it rich until it gets above that. No way around that. Don't ask for help then say our help is wrong because it's "rookie". 210 is the highest it should ever get with a properly maintained cooling system.

kgm

I believe the motor goes out of their fuel-rich loop @ 90F or so. I remember a thread a year or two where someone ran their scanner tool along side the temp gauge. Lower engine temps will cause other issues but its not in "warm up mode" AFAIK. Anyone care to corroborate? I thought it was CCKen or someone else with the know how.

Do still believe a 180F will end up with some smaller longer term issues due to the engine not running at its full temp.

toasterknight

If you use a more accurate gauge than the dash gauge it actually fluctuates a lot and a bit higher than that. Mine will do swings between 210 and 215 all day down the highway having its upswings going up hills. When you push it hard the coolant will go higher. The electric fan turns on at 217. Mind you during all of this the gauge hasn't moved a wiggle. By the time the gauge moves the engine is closer to 220-225.

jpmarine6786

The only time I have ever seen mine go above 210 was in hot rush hour traffic not moving in 90 degree weather with the AC on high. It got to between 210 and the next mark on the gauge. Even going up I-70 W in the mountains in 2nd doing 4000+ RPMs to hold 60mph didn't make my temp move. It was probably 70 out and I was at 4000+ for about 5 mins.

toasterknight

Running sand does it for me according the the dash gauge. I dont count on it though. It's sluggish and terribly innacurate.

mschi772

Fine, you don't want to run so hot. The thing is: a 180 deg stat won't change that. Those of us with 195 degree stats are not running at 195 degrees, are we? Nope, our engines level off at 200-210, and with a 180 deg stat, yours still will, too.

The thermostat merely sets the minimum running temperature of an engine. That's it. It's the cooling system that sets the maximum temp of the engine, and assuming your water pump and radiator are in proper condition, it's specifically the fan clutch (or switch if you have an electric fan) that sets the maximum temp of the engine.

If you do force your engine to run cooler, your computer may never move out of its preset closed loop settings because it never reaches a temp required to do so. Your fuel efficiency may suffer. Your spark plugs may foul. Carbon deposits may increase. Moisture bits that accumulate every night from condensation in your oil won't burn/boil off as quickly. Your oil itself won't be hot enough to be performing optimally.

shadowman

^^^Very well said! As many have stated the dash gauge can be horribly inaccurate. My '92 is at operating temp (verified with an infrared temp gun) when the gauge has just passed the first quarter of its sweep while my '99 is at operating temp (again verified by infrared) just past the middle of the gauge. I usually do not worry about the temp until the electric fan kicks on, then it's time to back off a little. As others have stated, as long as the cooling system is in good shape (it must be maintained just like the other systems of your Jeep) you should not have any problems. If it has been a while since it was serviced, no time like the present! A little quality time on maintenance now will save you a lot of heartache (and money) later.