SatiricalHen

I'm going to assume yours is a 97 since you said you bought it new in 97. My 99 has the temp sender in the thermostat housing go bad and send the computer wacky number and it wouldn't run very great. Replaced it and it read correctly. Also on my Cherokee the heater core was clogged which meant I had no heat. I flush it back and forth every winter to clean it all out, seems to clog up every year. On my Comanche when I first got it the cooling system was full of crud and the thermostat had rusted out. Since there was no thermostat it never got over 160 and I didn't have good heat.

dave1123

The thermostat's purpose is to restrict coolant flow until the engine reaches operating temperature, then open to permit flow thru the radiator, closing again if the engine drops below set temp. If you're running too cold, the thermostat isn't working properly. Normally the stat will open after about 10 minutes or less and the engine temp will go down a bit, then come back up. A good thermostat will gradually open to not allow the temp to drop suddenly, but act in a "throttling" sort of way. Stant Superstats were designed to work this way.

When the thermostat is closed, the only coolant flow is thru the heater core as a bypass so the engine doesn't overheat before it opens. The engine MUST reach 195* for the PCM (ECU) to go into closed loop mode and start controlling mixtures. Otherwise it's operating on preprogramed settings, usually too rich.

I think the whole problem here is the thermostat. You've got too much flow otherwise it would be overheating. As far as the heater is concerned, it could be plugged and not giving you any heat, but the engine should still be running at temp. Just my opinion however.

dave1123

Just a funny thing. My 1937 Dodge flathead 6 didn't have a thermostat. It had a window shade in front of the radiator hooked to a bead chain in a tube going to the dash with a bracket where you could hook the chain to control the engine temp! This was the last one built by the Dodge Brothers before they sold to Chrysler.

It didn't have a heater either! I installed a heater from a Crosley. Just a box with a core in it and a fan with doors you could adjust to send heat wherever you wanted. My defroster was a small fan mounted on the steering column.