The 1947 - Present Chevrolet & GMC Truck Message Board Network - View Single Post - T-stat to drill a hole or not to drill a hole?

NoNeck · 05-09-2018, 02:16 PM

The coolant should not flow until the thermostat opens. That's it's job... to regulate engine temperature. It doesn't help cool. It stops flow to keep things warm in a properly functioning and sized cooling system.

I sometimes drill a 1/8" hole in them. But not all the time either. It only helps when filling the cooling system after it has been drained. The objective is to not have any air trapped in the heads or block after the system has been run and cycled. Especially if it's a coolant recovering type system where the coolant is drawn back into it while things cool down.

Whatever you do, don't drill a series of 2 or 3 holes. That would simply weaken the effect of having a thermostat in the first place. It would take forever to get warm air to the heater on a cold winter day.

Bottom line, a single 1/8" hole drilled at 12 o'clock on a quality stat helps to eliminate dreaded air pockets.

POP

05-09-2018, 02:16 PM	#45
NoNeck Registered User Join Date: Jan 2011 Location: Chattanooga, TN Posts: 1,106	Re: T-stat to drill a hole or not to drill a hole? The coolant should not flow until the thermostat opens. That's it's job... to regulate engine temperature. It doesn't help cool. It stops flow to keep things warm in a properly functioning and sized cooling system. I sometimes drill a 1/8" hole in them. But not all the time either. It only helps when filling the cooling system after it has been drained. The objective is to not have any air trapped in the heads or block after the system has been run and cycled. Especially if it's a coolant recovering type system where the coolant is drawn back into it while things cool down. Whatever you do, don't drill a series of 2 or 3 holes. That would simply weaken the effect of having a thermostat in the first place. It would take forever to get warm air to the heater on a cold winter day. Bottom line, a single 1/8" hole drilled at 12 o'clock on a quality stat helps to eliminate dreaded air pockets. POP __________________ 2016 RAM Laramie HEMI 1966 Fairlane GT/A, 390/335 HP If it costs you a dollar to make a friend, KEEP THE DOLLAR. If it costs you a friend to make a dollar, KEEP THE FRIEND.