Interesting Thermostat To Purge Air From System

[NoNeck]

OK, I know we have argued over whether to drill an 1/8" hole in the thermostat to allow trapped air to escape from the cooling system. Some say "NO" and some say "I Always Do". Well, I put this 68 year old brain to work remembering what an old Auto Parts guy told me around 1971. My 1966 SS 396 Chevelle started overheating after I changed the thermostat.

He explained to me that even though the parts books (no computers back then) called for this particular Stant thermostat, it was not the BEST CHOICE. He went on to explain that most of the earlier thermostats utilized a "Air Bleed" design to help eliminate pockets of air in the cooling system. Later designs were going away from the Air Bleeds for one reason... closed systems. Basically, the newer cars featured coolant recovery tanks which helped bleed off trapped air more efficiently.

I guess what I am saying is that maybe if your truck has coolant recovery tanks you really don't need the bleed hole? But if you have the old fashioned system with just the overflow tube maybe you do need a bleed hole?

Just food for thought. Just so happened that I bought 6 of those thermostats from him back in 1971. After cleaning out my garage yesterday, I found the last one stashed away inside an old box of junk. The original Stant box is long gone and I forget the part number, but here is a picture of what the thermostat looks like. You will notice the bleed valve (red arrow) as seen from the top and bottom.

POP