205 Six Runs Hot

[Hair]

71 GMC 250 str8 six
New radiator, new water pump, new 160 degree thermostat, new antifreeze, and added a mech temp gauge. I have the dummy light sensor in the thermostat housing and the gage sensor in the side of the head. Fan shroud is present, stock non clutch fan. I haven't driven the truck yet, I just got it half way back together and the engine running. Sitting in the garage idling @ 70 degrees it runs 205 to 210 constant. I'm thinking that is too hot.

Could it be that the 160 thermostat is to low and opening too soon not allowing the water time to cool in the radiator? Reackon I should try a 180?

At what temperature does the dummy light come on? If the dummy light is supposed to come on by 205 to 210 then maybe my new gage is bad.

I also thought about swapping the locations of the dummy sensor and the gage sensor and seeing if I get a different reading.

Maybe this temperature is normal for a six cylinder???

Any ideas / suggestions?

[68gmsee]

First, make sure the truck is in good mechanical condition -that is check to make sure you don't have head gasket leaking.

I would then replace thermostat with a higher one or the one that is recommended for the truck. IIRC mine is a 180. Also, make sure you have the correct pressure of radiator cap installed for your engine. I believe there are two 14# and 18#.

One thing I did to cure my overheating problems was to install an overflow tube. Then I installed a radiator cap that shows the temp and verified it's accuracy. I monitored it last summer and now stays at about 185-190.

[cdowns]

did you check the gauge b4 installing for accuracy?

the routing of the line for a mechanical gauge can affect readings especially if routed near exhast and other heat producing things