Engine/Transmission (1994 - 1998) engine runs cold 1998 12 valve

[DAnsel]

temperature gauge shows approximatly 150 degrees! have replaced thermastat & gaskets from cummins. changed jiggle check valve & hose,radiator cap & did pressure & leak test on radiator & flow system (also checked new radiator cap) did not change temperature sending unit but after warm up at running 20 miles checked temperature in radiator & was the same as gauge within a couple of degrees took new tstat out & checked for gasket slippage & tested tstat in hot water. (would be pretty hard to loose or misalign gasket on the 98 tstat housing) all parts from cummins. would appreciate any & all suggestions or help. thxs dansel (1998 12 valve)








1998 12 valve s/b q/c ddt trans lots of eng. mods
dyno 502hp 973 f/t sadly only 17/18 mpg i love it

 

[mweiman]

Does your fan clutch seem to be free? I would think you would hear the fan roaring a little if it was locked up.
Matt

 

[Woodenhead]

Is it pretty cold where you're at? (I don't see a location). Maybe just need a winter front. Sounds like you've done everything right.

 

[DAnsel]

yes the fan clutch works properly according to specs. test by spinning blade by hand & it should spin 4/5 times freely
thxs mweiman i should have said this in my blog

 

[DAnsel]

woodenhead im in southern washington, state & the weather is in its mid 40s. i did make a cardboard front & put in front of the radiator then drove it approximatly 40 miles with no change. i tested the water in the radiator when i returned & it agreed with gauge. it does cool down all the way over night warms up the same next start up the same approx. 150 degree. i think i will take the tstat back out & retest it again in hot water. (i did suspect the gauge at one time guess i will check it out next) i have 390k miles on the truck with the original tstat thats why i started with it & its always ran 180 degrees in hot or cold weather. thxs a lot woodenhead

 

[Woodenhead]

I see. Has it always done this? Or just started recently? When it's warm does the gauge cycle like all the other 12V's?

 

[DAnsel]

woodenhead this is the first time its done this ive never had a heating or cooling problem before. i dont know what you mean by the gauge cycleing in warm weather. its always done the same thing year round winter or summer slow to warm up but always does & has always been at 180 degrees. thx woodenhead dansel

 

[mweiman]

Was the temperature stamped in the thermostat? 180 or 190 degree thermostats is all you typically hear about though.
Matt

 

[DAnsel]

mweiman yes it is stamped 180 bought from cummins. thx dansel

 

[Woodenhead]

woodenhead this is the first time its done this ive never had a heating or cooling problem before. i dont know what you mean by the gauge cycleing in warm weather. its always done the same thing year round winter or summer slow to warm up but always does & has always been at 180 degrees. thx woodenhead dansel

Most 12 valves seam to cycle within the normal range of the gauge as the thermostat opens and closes a bit. It's normal, there are probably 1000posts here from first time owners asking about this.
Was more of a curious question I guess, sorry I don't have more suggestions for your issue. You could swap the sender I guess, they're fairly inexpensive but maybe a pain to get at.

 

[DAnsel]

thxs for your help. im going to change the sending unit just because im running out of ideas. the gauge does cycle i just didnt under stand the question pushing 80 yrs old, the reason i didnt change it already i checked the temp. in the radiator after warm up it agreed with the gauge & your right its a pain to get at. again thxs for the help dansel

 

[DonFitzwater]

Do you have a digital temp gun? If not, find one to borrow and go for a drive and climb a hill to get the engine under load. Check temp at the thermostat pocket when you stop at the top of the hill. It should hold temp near what your tstat is rated at. If it's not, you may have a bad tstat out of the box.

 

[Woodenhead]

thxs for your help. im going to change the sending unit just because im running out of ideas. the gauge does cycle i just didnt under stand the question pushing 80 yrs old, the reason i didnt change it already i checked the temp. in the radiator after warm up it agreed with the gauge & your right its a pain to get at. again thxs for the help dansel

If you were further north I'd gladly give you a hand to change it. I just swapped one into the head for my '98 but the head was on the bench .

 

[DAnsel]

i checked with digital temp gun twice 149.7 & 150.1 i will take it out again & test it in water (i know its a waste of time but ill feel better) then take it back to cummins. the tstat doesnt have the temp rating on the part but its on the cummins box it came in. maybe it wont be the temp sending sensor which was my next step but this agrees with the temp check i took in the radiator. thx dfitzwater dansel

 

[DAnsel]

thxs for the offer maybe some day we will run into each other. thx dansel

 

[NIsaacs]

Use a 190/195 thermostat, the 180 is too cold.

Nick

 

[DAnsel]

thxs nick! ill try anything at this point dansel

 

[DonFitzwater]

Temp guns usually don't lie, that's what I like about them. Quick and easy diagnostic tool.

 

[DAnsel]

thxs nisaacs the thermostat im using from cummins opens at 181 & operates at 203 thxs dansel

 

[DAnsel]

i want to thank every one for there input very much! unfortunately i still have the problem & will keep looking for a fix & when i do will post the solution. again thxs a lot i had a lot of replys dansel