hey guys happy 4th!
well i just finished my truck the other day;new radiator,fleetguard coolant and some fuel mods. and i dont yet have a fan shroud because my old one broke. but no overheating though. My temp needle is in the middle when im moving when warmed up but when i stop and idle,doesnt matter how long it actually cools down to the first notch.i just think its weird. is it because i dont have a fan shroud? or maybe fan clutch i have no clue and help appreciated

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oh and sorry forgot to mention this is on the 1st gen

 

Get a Cummins T-stat, about $40. Lol, mine had bipolar issues as well and I got a T-stat (from Cummins) and it's a cool 180 degreez

 

i kno this is old but the tstat was it just put a cummins one in perfect thanks

 

I may be way off, but i have a sneaking suspicion it may be due to the position of the factory temp. sending unit. I noticed that I had the same sort of problem with my factory guage after i put the new rad in, mine will run up to the 3rd line or so, and it seems that every time the 'stat opens(?) the guage takes a dive back to the first line(even going down the road i get this). almost like the stock sending unit is somewhere that makes it sensitive to the cooler incoming charge of water from the rad, and thats what it's reading? I was concerned with this so I bought an aftermarket guage, and being the lazy kinda folk that I am, i just jammed the sender into the water neck up by the top rad hose, this one reads steady, even when the one in the dash is losing its mind..

 

that might be the culprit also i cant really tell you forsure because first i changed the rad and coolant and then noticed the erratic temps then changed the thermostat,sender and an auto meter temp gauge and it was fine.but i put the new sender in stock location also