Engine/Transmission (1994 - 1998) Problem with water temp running to cold...

[JBlackwell]

Well, I need someone to double check me on this, but my water temp guage won't go up to about 150*. My buddy put the new thermostat and gaskets in it when we put the new head on. You think some trash or the inner seal might have it hung open? I am gong to pull the thermostat back out this weekend I guess. Cummins Southern Plains has another new stat and inner & outer seals coming again since it is only $30 or so... . I will use them later if I don't need them now.



But have a question on the temp guage... is it accurate? I didn't know if I ought to buy an aftermarket electric water temp guage or not. I checked the plug-in on the back of the head and the connection was good.



Any opinions?



Justin

 

[swhalen]

Hi Justin:

i made a similar post about a week ago and got no replies... . so i will relay my experience for better or worse. changed coolant and hoses (94ctd), put back old thermostat which used to cycle continuously from 140 to 180. after slapping it all back together, pegged at about 155 and stayed rock solid. drained some coolant and put in new stat. same thing. tested old stat on stove with thermometer. worked fine. drained some coolant, put back old stat. same thing. put a piece of cardboard in front of radiator, drove around for several miles. same thing, even though it was 95-100 degrees outside. called the dealer who suggested i had air in the system. drained her dry, hecked the jiggle pin (worked freely) and filled slowly. still came up to 155 and stayed there, 200 miles later no difference. warmed her up and shot the tstat housiing with an infrared thermometer. read 180. shot the block and it read 180 to 185. ground the sensor. checked out ok. took it to the dealer who said the gauge was ok. i think the oem cummins stat is a 180, so who knows what's up. guess i am just going to live with it as the engine seems to be at the correct temp. so, before you become an expert at draining/refilling like i did, try to round up an infrared thermometer and check the temp of the block and tstat housing. also, check the # of the stat you get from cummins. the old # is 3928499. it has been superceded by 3802968, but this is reputed to run cold. i always get the oem stat. hope my long winded response helps. steve whalen

 

[JBlackwell]

OK, thanks. I have an infrared thermometer and I will keep it with me and check from time to time.



Thanks,

Justin

 

[bmoeller]

Steve, did you put a socket on the temp sensor, and wiggle it back and forth a few times? May not be making a good ground.

 

[JBlackwell]

Steve, did you put a socket on the temp sensor, and wiggle it back and forth a few times? May not be making a good ground.

I read about that in a past TDR issue last night. A guy had the same problem and changes the thermostat and nothing. Then pulled the sensor out on the back of the head and took the teflon tape off that he had put on there before and put it back in and it worked prefect then.



I will be trying that this evening.



Justin

 

[JWilkinson]

A bad overflow valve caused mine to run cold.

 

[JBlackwell]

A bad overflow valve caused mine to run cold.

Hmm, didn't know an overflow valve could cause a problem like that. I just replaced mine. I think my water temp is up, so it is looking towards the sender as the problem. I recorded 170*+ on the water neck with a infrared thermometer gun... ...



Justin

 

[HBrunton]

I believe the reason for the thermostat update was to remedy a customer complaint of the temp guage fluctuating between 180 (normal) and around 140. engine would warm up, t-stat would open and temp guage would go down. It is hard to get these engines to 190-200 degrees without working them considerably. the cooling system on em is huge compared to some other 6B applications. The only thing that I can think of is check your connectoins for any looseness or corroded connection that may cause too much resistance giving you a different reading than you are used to seeing on your guage.

on a different note, I got into quite a discussion one time with a person who had toasted a engine in a tractor. It had been overheated, he refused to believe this because his guage never read hot. A temp sender needs coolant flowing around it to read, if there is no coolant in the system, the guage will always read cold,no matter how hot the surrounding areas are. Just my $. 02 worth. A infrared heat gun is a good tooll to have and they sure have came down in price since I bought mine a few years ago. a lot cleaner way of checking for a mis-firing cylinder than cracking a injector line, just shoot it at every exhaust port and the cool one is the bad one, on the big engines there are no injector lines to loosen. Also great for the new HPCR engines.

 

[wildwestdiesel]

same on the sensor. if your gauge is reading correctly and you got water in there be glad you wont burn up espessially with a cranked motor. cooling is the biggest prob i have with the 1 +2 gen trucks when i,m towing. two things that worked the best for a leadfoot like me is to let the animal breath with exhaust and turbo mods and to give it a drink with water inj. !