Thread: Runs too cold.

My thoughts is that it contributed to the bad mileage. I havnt run my MPG numbers yet since I dropped the new stat in but it just does seem to be peppier , more efficient and I don't blow quite as much smoke out the tail pipe.

wow so yeah i replaced the thermostat and now my truck runs about 190 and feels a lot better. hopefully i will get good mpg now!!!!! my truck has been getting 13 mpg terrible i know but i thoguht it was becuase a bad injection pump. so i replaced that becaus it was bad anyway and also put an airdog 2 on there. but do you think running at 145 has been the whole raeason that i have been getting bad milage?

Do you have your radiator blocked off? Yes, these trucks run cold when not worked. When I had my 2000, I ended up replacing the thermostat. If you do that, only buy a original Cummins part, expensive but they work.

Diesel engines are more efficient when warmed up to the proper temp. Everything is seated properly and the fuel/air is being compressed and burned properly. It's also easier on parts to have the engine all warm and cozy.

you said 99 but below says 98.5. but anyway. if you have never replaced the thermostat or dont know if it has I would for safe measure. normally there is a 180 or 190 degree one. but if your going up and down I-5 up by like shasta with cold temps I can see a little colder but shouldnt be moving the needle drastic. check with the thermostat and go from there.

When coasting downhill you are burning NO fuelat all. The engine is just pumping air through. So, it has to cool down some.

yes true. at no throttle coasting theres no fuel injected at all. but with low cylinder temp when you do inject fuel it is not a complete burn you will eventually glaze the cylinder wall. which will be bad. burning oil, loss of compression.......you just dont want that.

This thread caught my eye. Mine's always run cold like that. I replaced the tstat and it performs the same. Either mine just runs cold or the sending unit or gauge is off. Brad

190-200 on my truck is normal.

Quote: Originally Posted by jrv15 ok im scared now... my truck usually runs just above the 145 mark all the time. is this bad????? throw a new thermostat in and all should be golden, usually if they run cols the thermostats opens too soon, engine is more efficent when up in the 180-190 range. mine runs 190+ all the time except in extreme cold temps does it cool down,