Fluctuating temp gauge

[bcwoods]

I have a 93 silverado 2wd with 286,000 kms. I bought this vehicle in nov 2002 and it runs fantastic. This is also my first diesel and it will not be my last just by the performance i am getting. My one concern is the temperature changes. Under normal driving around town the temp stays at consistent 70 to 80 degrees C. On long pulls or towing my boat it climbs to 90-100 C. but never hot.
But as soon as i go down hill the temp will drop to 50c or lower.
Is this normal. I have been told that I should be running a constant temperature. In the winter the truck runs 50 to 60c
I have never had to add coolant since the day I bought it.
Any comments or resolutions if required.

[catmandoo]

god i hate centigrade anyway 100c is 212f so i wouldn't think anything of it, some guys on here are talking running up to 230- 240 degrees on hard pulls guess it depends on how you're gonna use it if your pulling trailers all the time you might think about cooling system upgrades dual t-stats and ho waterpump but if not don't worry about it

[bcwoods]

what about the temperature dropping low to 40c on the down hill runs. In BC we have lots of hills and I do not seem to have a problem with over heating just the drop in temp.

[richard7]

In cold temperature like -20C, if the diesel engine has very little load, like idling, the engine doesn't produce enough heat to maintain the normal operating temperature of 195F (90C).

But if you are going down the road, maintaining a normal load on the engine, it should maintain the temperature as set by the thermostat. If you go down a long hill without asking any power to the engine, the temperature may drop if it is cold enough outside.

Unlike gas engines, diesel engines are very efficient at idle (part load), but that means it burns very little fuel too!

[bcwoods]

thanks for the input. I understand the cold temp part but i live in Kelowna,BC and the temp this summer has been +32c (86+F) and the operating temp is 80C (180F) but down the hills (over 2 miles) the temp drops to the 40C-50C(105F-125F) range. I am not sure if this is normal

[pgoldstein]

BC,
Sounds to me like maybe you have a thermostat that is not closing all of the way. This would allow some water to circulate all of the time, and if you are not under a load run cold. I had the same problem on my 97 and a couple of new thermostats fix it.

Good luck,

[MM9135]

pgoldstein, I see you live near me, but that is not why I am posting.

I have a 1996 6.5L express van. I purchsed a new thermostat but chickened out when it came time to replace it.
You said that you had purchased a couple of thermostats. Are there more than one? I assumed that the stat was located under the housing of the upper radiator hose connection like a gas engine. Am I correct? On this Express van getting to the bottom bolts would take a magican. My engine runs 165 unless I am pulling the hill at Floyd Knobs on a hot day and then it might get to 195. Should I have it replaced for running too cool? I am under the impression that a diesel should run at it's designed temp or it will smoke black???? :confused: Thanks for any help. I am still learning diesels.