Thermostat

[Mr_D]

Our ISC has always run about 185° even when new and still runs that temp. This is with my VMSpc monitoring it.

[two sailors]

Even after replacing the TSTAT the temp would run about 170 deg. traveling on flat roads but would go to 200 pulling long hills.
I replaced my radiator fan control yesterday and engine temp is back to the 93c / 199f mark! And the fan doesn't spin at low temps. On the flats the temp stays at 199f. So I guess a fan running at the wrong time can hold the engine temp below the TSTAT setting.

On a ILS 400 The part no. is 1090385, Saur-Danfos. About $425 from NW dist.
__________________

[dons2346]

Quote:

Originally Posted by two sailors Even after replacing the TSTAT the temp would run about 170 deg. traveling on flat roads but would go to 200 pulling long hills. I replaced my radiator fan control yesterday and engine temp is back to the 93c / 199f mark! And the fan doesn't spin at low temps. On the flats the temp stays at 199f. So I guess a fan running at the wrong time can hold the engine temp below the TSTAT setting. On a ILS 400 The part no. is 1090385, Saur-Danfos. About $425 from NW dist. __________________

To all of you that said I didn't know what I was talking about......your apology is accepted.

[rhm]

I wonder if that's my issue, too. My 350 ISC always runs cold and I don't get any heat up front.

Quote:

Originally Posted by FleetMan If those low temperatures are constant, it sounds like your thermostat is stuck in the full open position. Ideally a diesel engine should run in the 195 degree temperature range. On my digital radout, I can monitor mine as it cycles.

[two sailors]

Check to see if the fan is turning enough to move air through the radiator when the engine is dead cold. What ever type of fan control you have, electric or hydraulic, it could be engaged when it shouldn't. The temp on mine would run at 170,s except when pulling a hill then it would go to 200. Now it hardly fluctuates around the 195-200 mark.

[dons2346]

Quote:

Originally Posted by rhm I wonder if that's my issue, too. My 350 ISC always runs cold and I don't get any heat up front.

See post #33

[spike45]

Quote:

Originally Posted by two sailors Even after replacing the TSTAT the temp would run about 170 deg. traveling on flat roads but would go to 200 pulling long hills. I replaced my radiator fan control yesterday and engine temp is back to the 93c / 199f mark! And the fan doesn't spin at low temps. On the flats the temp stays at 199f. So I guess a fan running at the wrong time can hold the engine temp below the TSTAT setting. On a ILS 400 The part no. is 1090385, Saur-Danfos. About $425 from NW dist. __________________

First, what is the function of any thermostat in an engine? Answer: to maintain MINIMUM operating temperature.

Second, what controls temperatures above the thermostat control temperature? Answer: your right foot and a hill, i.e. engine load.

Having the fan run all time time can only affect engine temperature by blowing air onto the engine and cooling the block and head and the coolant therein. If the thermostat you installed was marked "185" that would be the 'crack open' temp when it just begins to open. Fully open at about 10 degrees above that +/-. With the fan blowing and the jacket temp gauge indicating 170F, the thermostat did not need to open much if any. And this is more so when the air temperatures are cool to cold. In another century when I was a Caterpillar tech person, we had some machines that could not maintain more than minimum temp requirements in Winter as the fan blowing on the engine cooled it to the point that the thermostat did not open and still the engine could maintain the required minimum temp.

[two sailors]

I asked Cummins shop if there was a choice of tstat temps. They say only one, 180. I put the old tstat in a pot of water and brought it to a boil checking the water temp as it increased. Around 165 or so it began to open letting water pass through.
My conclusion was; If the fan runs near full speed all the time, there is enough air drawn through the radiator to hold the temp below the full open tstat temp.
I have watched the temp. fluctuate between 170 and 200 since I bought the coach, thinking that it was how it was supposed to be. After replacing the fan control, the temp gauge barely moves from 195. I only have the Actia analog gauges so I can't give exact temp. numbers.
I am not a diesel mechanic but thats my story and I'm sticken to it.

[spike45]

Quote:

Originally Posted by two sailors I asked Cummins shop if there was a choice of tstat temps. They say only one, 180. I put the old tstat in a pot of water and brought it to a boil checking the water temp as it increased. Around 165 or so it began to open letting water pass through. My conclusion was; If the fan runs near full speed all the time, there is enough air drawn through the radiator to hold the temp below the full open tstat temp. I have watched the temp. fluctuate between 170 and 200 since I bought the coach, thinking that it was how it was supposed to be. After replacing the fan control, the temp gauge barely moves from 195. I only have the Actia analog gauges so I can't give exact temp. numbers. I am not a diesel mechanic but thats my story and I'm sticken to it.

A 180 T-stat should begin to open (crack) at 180 and be fully open at 10+ degrees....like 195! You did the right thing to put it into hot water and watch the temperature at which it cracks and when it is fully open. Also do that in reverse to see when it closes. Opening and closing temps are not always the same. You are working with an old technology in that the sensing bulb has a wax that expands as it warms and contracts....that is the power that opens the valve with the spring pushing it shut.