Underheating??

Ok I cant figure this one out.. I just recently got my jeep 71 V6 t14 100% on the road ......pausing for applause....... anyway I installed a sunpro mech temp gauge and it seems that while driving I cant keep the jeep above 120 deg. at Idle I run 160. I had to block the radiator while idling to get the to 180 I have no Ideas.. I have never had a problem getting a jeep hot before..

 

maybe the thermostat is broken the right way. could it be it broke and is locked in the open position?

 

Only if it came defective I just added one last weekend. The previous owners had removed it at somepoint..

 

What brand of gauge? I have had those cheapy chinese gauges not work right, even new out of the box. One little kink in that tubing will cause a problem too (ask me how I know)

 

Would almost have to be the thermostat. Remove it, and for giggles drop it into a pot of water on the stove. Bonus if you have a thermometer in there as well. It should be fully open by 190 if it is a 180. Replace it.
-Hill

 

Its a sunpro mech gauge "retro edition" acually it is my 2nd gauge in the last week I thought the first one was bad. But now I think it was fine I just didnt wait 10 min to see the needle move..

 

The only answer, assuming a good gauge, is the thermostat stuck open, although a HUGE radiator may never warm up. I have a 1979 Blazer that had a 4 core radiator and a stock 350 that never had good heater output in the winter. Drove it like that for 2 years always blaming it on the "big" radiator. Then one day out of the blue I realized it was probably the thermostat, sure enough when I pulled it, it was obviously stuck open. Replaced it and enjoyed a kicka$$ heater. My experience is that thermostats are one of those items it is better to spend a little more and get the premium ones, or at least go with the recommendation of an experienced parts counter guy as to a brand. Also it seems they can last 10 years or 10 months, so I don't replace them regularly, but keep an eye open for sudden changes to the temp gauge "habits". Getting real hot and then suddenly cooling down can be a t-stat stuck closed and opening as it gets really hot. A gauge that suddenly doesn't come up to normal in the normal amount of time is a t-stat stuck open.
Only other thing I can think of for a engine running cool is it is missing on one or more cylinders (no air/fuel explosion= no heat!), but I think you would notice that!

 

It also matters where your temp gauge-end is screwed into the intake. Where's yours screwed in?

On my '71, I have it screwed in the back right side, and yes I too get the "underheating" feeling just by looking at the gauge despite proper function of the gauge & thermo. If it's screwed into the front of the intake, you might get drastic changes in temp gauge readings as soon as the thermostat opens up. HTH.
-Alan

 

Thermostat might be in the wrong way, or could be "cocked" to one side, not sitting squarely in the housing allowing coolant to pass all the time. I actually had mine like that the first time.

Stan

 

Thanks guys I'll go through a new t-stat in later and keep you posted..