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

[rsavage]

I would. Once you overheat a stat, it has been my experience that they no longer work as they should - it might be one of the reasons why with it out it doesn't overheat. If your radiator is new it should hold the pressure so I see no reason to get a lower pressure cap as that will only make it easier to boil. I would get a shroud, a new 160 stat, make sure the timing isn't too advanced, and not idle it in the driveway for long periods of time, as you are not going to move enough air to keep it cool.

[mrein3]

You're dealing with WAY too many variables here. This is what I would do in your situation.

#1 I'd get the proper shroud and a 7-blade factory fan and new fan clutch.
#2 I'd run a 192 degree thermostat.
#3 I'd change out that thermostat and burp the system. I would not start that engine again until I'm burping it with #1 and #2 complete.

To burp it fill the radiator to the brim, leave the cap off, put a catch pan under the cap area of the truck and start it. As the truck warms up you'll notice flow then no flow as cold antifreeze from the radiator is exchanged with hot from the engine. When you notice a good, constant flow, top it off and put the cap on.

The system is now burped - you removed all the air from the coolant system.

NOW if you overheat you need to worry because except for a new radiator, your truck is now functioning on the coolant front the way the General intended it to.

Let us know what it is doing after you get the right parts on there.

[mdwilf]

Lots of good input here. I would look down in the radiator, see if the ends of the cores are clean or crudy. If crudy, fill the rad with vinegar & let it set a few days.

Before I did too much work, I'd verify the gauge, sender & wire are good & that the gauge & sender are compatible. Shroud will make a huge difference, but I've run several without it.

When it starts showing hot, turn on your heat & see if it feels unusually hot. If you get caught out in an overheating vehicle, turn the heat on full blast, this may save your motor. You'd be surprised at how much you can cool a motor down this way.

Be wary of the cheap aftermarket temp gauges, I've had several that were inaccurate.

[mightyatom]

Did you replace the temperature sendor ? I had a similar issue after I replaced it with a new one from Kragen/O'reily's, the gauge kept saying it was overheating but it was not. Once I ordered an NOS temperature sendor from Classic Parts it fixed the issue. Below is the thread.

http://67-72chevytrucks.com/vboard/s...d.php?t=393670

Jay