OK, I've searched this forum over and over and can't find any direct comments about this....


When I first bought my 97 12V last Nov. it would always warm up to around the 180 degree range and stay there no matter what(idle, driving, loaded.) EVen in the middle of Michigan winter it would eventually get there . As far as I know that is where it needs to be. About 4 months after driving I noticed on a trip in June that the temp was sitting just at tick about the 140(lowest reading) mark and might move slightly above there. It would actually go down almost all the way when idling even when it had been running for hours.

I haven't seen the temp gage reach that 180 mark for months now, even towing an 18ft loaded trailer in 90 degree temps.

What's the guilty cause?

 

idk if this is the same problem, but when i got my 24 valve, my temp would never go above 140 either. so i replaced the sending unit. nothing. then i talked to my papaw and he said my thermostat was probably stuck open. replaced it and stays about 190 now give or take a few degrees. hope this helps, try the thermostat!!!

 

That seemed like the most obvious problem, but thought someone on here would have experienced the same prob. Thanks olwhitey.

 

Sounds like the thermostat is stuck open, or partly open. Easy to change. Good time to flush the cooling system and fill with fresh coolant. Add about half a cup of Cascade dishwashing detergent, no don't use some other brand and drive it for a day. Drain it and fill with water, drive for a day and drain, repeat until its clear coming out. Then fill with a 50/50 mix of deionized water and antifreeze. As yours came with green, that's what I'd put back in it.

 

yep its most likely the tstat.Mines done it ever since Ive bought it.Im not worried about it

 

Quite common for the rubber seal on the stat to come off and get stuck holding it open.
I've found just removing the seal entirely and tossing it doesn't effect anything except allowing the stat to close.

 

If your temperature gauge isn't moving much it could be a stuck thermostat. Mine T-Stat was stuck open because the rubber seal had broke and got sucked down into the T-Stat and was holding it open. Pete

 

This is what Infidel is referring to…My 1997 had the same symptoms and this is what I found.

T-Bone
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I have the opposite problem. After a cold start-up i get warm air from the heater maybe 2 minutes later (i dont know for sure, same as it always has though) but then after another 2 or 3 minutes the temp goes right to the red line and only cold air comes from the heater. That is my sending unit right? i have pooped the cap off the rad and i didnt get scalded so its not running hot, just the gauge says so. crappy tire wants $92 for a sending unit and guage, is this a decent price? and is this my problem?

 

My DTD in the warmer day will cycle between about 140 to 180 degrees. It's done that since I bought it in 95. I asked the dealer and was told it was normal. I do recall seeing a TSB regarding this issue. You cal replace it with a with a substitute the TSB recommends or not worry about it. I have the same thermostat since the truck was new.