STERLING STINGER Posted October 12, 2011 Share Posted October 12, 2011 i recently had to replace my thermostat housing and i didnt have a new thermostat to put in. therefore, i took it out, leaving it out. i see that the engines running very cool....around 120 or less...... i see i have less heat than usual also my question is, will this hurt my engine if i leave it? thanks, Paul Link to comment Share on other sites More sharing options...
acfortier Posted October 12, 2011 Share Posted October 12, 2011 The reason why thermostats are in an engine is because it has an optimal running temperature. You WANT your engine to heat up quick, which is why the thermostat is there, because, again, the engine performs optimally at a certain temperature, which is controlled by the thermostat. I'd put one back in quick.. Link to comment Share on other sites More sharing options...
Backdraft Posted October 12, 2011 Share Posted October 12, 2011 Gonna burn more gas leaving it like that. Truck will stay in warm up mode (open loop?) Link to comment Share on other sites More sharing options...
Donkey Posted October 12, 2011 Share Posted October 12, 2011 Running an engine to cool will hurt it, jeeps normally stock run a 195 degree thermostat at least my wrangler 4.0 does. I dropped in a 180 degree which just slight brings it off the 210 temp it normally runs giving me a little piece of mind. When I really work the motor it will still get to 210 but drop back off when I'm done. I like running the jeep a little cooler then 210 but I'm not making a big jump from stock. Link to comment Share on other sites More sharing options...
STERLING STINGER Posted October 12, 2011 Author Share Posted October 12, 2011 Thank you. Iwill get one right now. Link to comment Share on other sites More sharing options...
Eagle Posted October 12, 2011 Share Posted October 12, 2011 i recently had to replace my thermostat housing and i didnt have a new thermostat to put in.therefore, i took it out, leaving it out. i see that the engines running very cool....around 120 or less...... i see i have less heat than usual also my question is, will this hurt my engine if i leave it? thanks, Paul Yep. If the engine can't get up to an operating temperature of at least 165 to 170 degrees, the ECU will never switch out of "open loop" (or warm-up) mode. That means you will ALWAYS be running based on a hard-coded, overly-rich fuel mixture. Your fuel economy will suck, and you may end up fouling the catalytic converter due to excess unburned hydrocarbons. Link to comment Share on other sites More sharing options...
STERLING STINGER Posted October 12, 2011 Author Share Posted October 12, 2011 Cool thanks. I just got a 195* thermostat. Ill install it at work tomorrow when i get paid to do it. Lol Link to comment Share on other sites More sharing options...
HOrnbrod Posted October 13, 2011 Share Posted October 13, 2011 If the engine can't get up to an operating temperature of at least 165 to 170 degrees, the ECU will never switch out of "open loop" (or warm-up) mode. That means you will ALWAYS be running based on a hard-coded, overly-rich fuel mixture. Your fuel economy will suck, and you may end up fouling the catalytic converter due to excess unburned hydrocarbons. Not true for HOs. If you have an A/F meter installed it's easy to see. After about two minutes max of idling even on the coldest mornings you can see the switch from open to closed loop on the meter. And the dash temp gauge had barely moved. These meters are wired directly to the O2 sensor output (both the wide and narrow band meters) and the O2 sensor doesn't operate until the ECU sees closed loop operation. I have an A/F meter on my 91, and also had one on my previous 96 and 01 XJs. They were all the same. This is not to say I recommend a lower temp thermostat (or no thermostat) than the factory 195* at all. 200*-215* is the most efficient operating range for the 4.0s and they should all have the 195* stat to maintain that operating temp. Link to comment Share on other sites More sharing options...
STERLING STINGER Posted October 13, 2011 Author Share Posted October 13, 2011 Wow I do love to learn.... Thank you Link to comment Share on other sites More sharing options...
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