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Thermostat modification


DrP

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Recently a local 63 Riv owner came by and suggested when installing a new thermostat to drill a single 1/8" hole in the peripheral of the thermostat. He works for a major antique auto restorer in our area. He says this allows a little bit of water to circulate when the thermostat is closed and makes the engine run better and warm up faster. Any comments about this theory? I have my 1/8" bit ready. Dale

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I've done that in the past. Not so much to let a little water through but to allow trapped air pockets to escape to the radiator. With the tiny hole in the peripheral of the thermostat, and with the car parked in the driveway or better yet on a grade with the nose up, the air will eventually find it's way to the thermostat and get out over night. Burp! Xcuse me.

Ed

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I've done that in the past. Not so much to let a little water through but to allow trapped air pockets to escape to the radiator. With the tiny hole in the peripheral of the thermostat, and with the car parked in the driveway or better yet on a grade with the nose up, the air will eventually find it's way to the thermostat and get out over night. Burp! Xcuse me.

Ed

Ed is correct regarding an air bleed. Over the years I have encountered many heavy duty diesel thermostats with such an air bleed. I cant see how the hole would allow a faster warmup?? I would think it would be just the opposite or have very little effect.

Tom Mooney

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Yep, worked Hd diesels for 40 years, most thermostats now have a "jiggle pin" which will allow air to go thru the bleed hole until coolant pressure hits it and forces it closed. It remains closed under pressure of coolant flow and only opens when air bubble hits it when thermostat is closed. We didn't have problems filling the system. They have a minimum fill rate spec so that it purges air and fills reasonably quick. The reasons for this are obvious.

Failsafe thermostats that I have seen latch in the open position after severe overheat/overtravel. That usually results in running cold.

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Hello Everyone

I can remember in the days gone by, when thermostats came standard with the air bleed/jiggle pin holes in them. The hole was always placed towards the radiaitor and while never explained, it must have been for the reasons which Ed, Tom and John have said. Are we reinventing the wheel? Does anyone here remember the days when guys whom raced cars, would take the termostat out and fit a "swirl plate" in its place and this initially gave the engine a flow restriction when cold but also prevented overheating issues when hot?

Take care

John

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