1972 chevy 1/2ton pickup overheating, not sure why?

[chevman51]

I had started in the driveway and it was 40 degrees outside and the gauge was climbing. I drove it done the road and the gauge kept climbing so i shut the truck off and let it cool, turned around and went back home. Why would you stay with a 180 t stat? I'm getting a fan shroud but I have never had my other pickup without a shroud get this hot, so that makes me think there is more of a problem.

[joes50pu]

Bubbles in the water is a bad sign. Looks like you have a head gasket problem. To find out which cylinder is leaking into the water you pull the sparkplugs and apply air into the cylinder one at a time with tool designed to thread into the sparkplug and the other end hooks up to shop air. When you find the bad area, the bubbles will start appearing at the radiator cap area.

[lovnthe70]

If your gauge is climbing that quickly i doubt the shroud is your only culprit, i would still get one but it is not the only thing wrong. I would do like someone above posted and make sure your temp gauge is working (they have digital gauges you just point and click to verify the temp, check the temp in your block) if your gauge is wrong you might not have a problem at all. I would stick with the 180 t-stat because changing to a lower temp t-stat is not going to fix your problem and your engine needs to run at a higher temp to be efficient(you also live somewhere cold 40 deg!! ) I live in Arizona and we are at 105 some days and i still run a 180. Then cycle the air out of your system, get a new cap and a new t-stat and like the other guys said make sure it works before you put it in by testing it on your stove and drill holes in it. Then do a pressure test and verify that you are holding pressure.