Thermostat?

[lukecp]

I am having another thermostat problem with my truck. After i start it up and it runs for about 5 minutes, the temp guage will shoot way up, like to 240-250, then go back down to 215 or so, then back up to 240, and it will eventually go down to about 175, which is what it usually runs at. When it was running around 240, i popped the hood and felt the radiator hoses. The top hose was pressurized, but it was cold to the touch, about the same temp as the outside air. The bottom hose was getting pretty warm, and the heater hoses were pretty hot.

Is my thermostat the problem? I am running a Stant 160 degree stat in the truck. I have had bad luck with Stant themromstats....the last one i had which was rated at 195 degrees had the truck running at about 215 all the time. I put in the 160 degree stat, and it usually runs about 175 degrees. What is a good brand of thermostat to buy?

[crazy longhorn]

It sure sounds like you have a bad thermostat. I am running a robertshaw stat, but you can get a bad one in any brand. if you change it, you might look @ a 180 as a midlde of the road.....if you run tween 185-200 degrees, thats about right. Good luck,crazyL

[jef5150]

first thing id do is take the thermostat "out",,,,,,,run it for a while and see if still does the same thing,,[its only 2 bolts],

[lukecp]

I may take the stat out....but as long as i have it out and have to replace the gasket, why not replace the stat.....

I was thinking of switching to a 180 degree stat anyway, my 160 runs a bit cold during the winter to have my heater work well, and i have to have a good heater, lol

[Class of 69]

I'm with crazy l...stats can drive one nuts!!! They don't seem to be all that consistent, or dependable. Try a different brand, and see what you get. I have a hard time believing a cold engine could hit anywhere near 240 after only five minutes of run time! Are you using the stock electric gauge, or mechanical? The sending units for electric gauges will cause that wild fluctuation also.

[lukecp]

I am using a Sunpro mechanical guage, which is only a week old. I had an old el-cheapo mechanical temp guage, and it sometimes did the same thing. It may be 5 minutes or so, just enough time for me to drive 2 miles @ 35mph to the end of my road and get on the highway.....

[Stocker]

Yup, sounds like a bad thermostat. Toss it in a pan of water on the stove along with your new 180* unit and check with a cooking thermometer . After checking them both, throw away the old one and install the 180!

[Class of 69]

I doubt it's the gauge then...go with the stat.

[jef5150]

i didnt mean take it out 'permanantly'!Just remove it temporarally, run it in the drive way,and see if your temperature gauge still fluxuates.If you still have the "same problem",you can check out other things,you dont need to put a new gasket on just glob some RTV on the housing,your only gonna be running the motor for 20 mins,,,,,,,jeff

[lukecp]

Problem solved....

Appears that last time i put in the thermostat, i put it in upside down. I have done stats before and know better, but i was in a hurry to get the truck running again and wasn't paying attention, lol. I went ahead and installed a Autozone house brand 180 degree stat in it. It said MotoRad on the stat. The truck now keeps between the 180 degree and 195 degree ticks on my temp guage all the time.

Thanks alot for all the help

[Wabash]

DOH!!!!!!!!!!!