Coolant Drain Plug - The 1947 - Present Chevrolet & GMC Truck Message Board Network

44SAA · 11-09-2022, 11:25 AM

Howdy- is the nut shown above the “2” and 12 o’clock from “S” the coolant drain plug?” Thank you

**kwmech** · 11-09-2022, 11:57 AM

YES it is. Use a 6 point socket as it will be very tight. When it comes out, more than likely it will not drain due to sediment and a crusty like gunk. You may have to shove a small screw driver up in the hole and wiggle it around to get it moving. Always nice to have an arm and elbow full of coolant

44SAA · 11-09-2022, 12:07 PM

Thanks KW- if I’m not bleeding or covered in fluid, something miraculous occurred. Shoving a water hose down the thermostat hole help bust up crud?
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Dead Parrot · 11-09-2022, 01:12 PM

It is A coolant drain plug. There should be a matching one on the other side if you have a V8. You need to remove both to drain all the old stuff out.

Better idea for moving crud out is forcing a cut garden hose over one of the heater hose nipples on the intake. Good use for a dead garden hose. Leave the t-stat and housing in place and let stuff come out the radiator opening.

When finished with the flush, re-drain and fill with either 50/50 or pure antifreeze diluted with distilled water(usually the lower cost option).

44SAA · 11-09-2022, 01:41 PM

Thanks Parrot. Bought new rad and it’s not hooked up yet. Figure it’s smart to flush w/o contaminating new rad
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**kwmech** · 11-09-2022, 05:56 PM

Have a drain pan ready, it will dump at least a gallon per side

44SAA · 11-09-2022, 06:18 PM

Yanked one out- couldn’t get the other. Gonna quit while I’m ahead.

Dead Parrot · 11-09-2022, 07:12 PM

IIRC - they are 3/8" pipe thread. If you damaged the one you got out, should be easy to find a replacement at a hardware/plumbing store. I think some older ones were 1/2" thread with a 3/8 square drive.

**kwmech** · 11-09-2022, 08:59 PM

1/4'' pipe thread and 9/16'' hex. If replacing, use brass and don't crank it down as hard

GRADYS Performance · 11-21-2022, 01:27 PM

The time and effort required to remove BOTH plugs and get out what you do not want in the new radiator will be well spent.

11-09-2022, 11:25 AM	#1
44SAA Registered User Join Date: Apr 2017 Location: Fort Worth Posts: 111	Coolant Drain Plug Howdy- is the nut shown above the “2” and 12 o’clock from “S” the coolant drain plug?” Thank you Attached Images Last edited by 44SAA; 11-09-2022 at 11:27 AM. Reason: Pic

11-09-2022, 11:57 AM	#2
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,388	Re: Coolant Drain Plug YES it is. Use a 6 point socket as it will be very tight. When it comes out, more than likely it will not drain due to sediment and a crusty like gunk. You may have to shove a small screw driver up in the hole and wiggle it around to get it moving. Always nice to have an arm and elbow full of coolant

11-09-2022, 12:07 PM	#3
44SAA Registered User Join Date: Apr 2017 Location: Fort Worth Posts: 111	Re: Coolant Drain Plug Thanks KW- if I’m not bleeding or covered in fluid, something miraculous occurred. Shoving a water hose down the thermostat hole help bust up crud? Posted via Mobile Device

11-09-2022, 01:12 PM	#4
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,472	Re: Coolant Drain Plug It is A coolant drain plug. There should be a matching one on the other side if you have a V8. You need to remove both to drain all the old stuff out. Better idea for moving crud out is forcing a cut garden hose over one of the heater hose nipples on the intake. Good use for a dead garden hose. Leave the t-stat and housing in place and let stuff come out the radiator opening. When finished with the flush, re-drain and fill with either 50/50 or pure antifreeze diluted with distilled water(usually the lower cost option).

11-09-2022, 01:41 PM	#5
44SAA Registered User Join Date: Apr 2017 Location: Fort Worth Posts: 111	Re: Coolant Drain Plug Thanks Parrot. Bought new rad and it’s not hooked up yet. Figure it’s smart to flush w/o contaminating new rad Posted via Mobile Device

11-09-2022, 05:56 PM	#6
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,388	Re: Coolant Drain Plug Have a drain pan ready, it will dump at least a gallon per side

11-09-2022, 06:18 PM	#7
44SAA Registered User Join Date: Apr 2017 Location: Fort Worth Posts: 111	Re: Coolant Drain Plug Yanked one out- couldn’t get the other. Gonna quit while I’m ahead.

11-09-2022, 07:12 PM	#8
Dead Parrot Registered User Join Date: Aug 2012 Location: Oklahoma City, OK Posts: 2,472	Re: Coolant Drain Plug IIRC - they are 3/8" pipe thread. If you damaged the one you got out, should be easy to find a replacement at a hardware/plumbing store. I think some older ones were 1/2" thread with a 3/8 square drive.

11-09-2022, 08:59 PM	#9
kwmech Senior Member Join Date: Mar 2003 Location: Colfax-California Posts: 8,388	Re: Coolant Drain Plug 1/4'' pipe thread and 9/16'' hex. If replacing, use brass and don't crank it down as hard

11-21-2022, 01:27 PM	#10
GRADYS Performance Registered User Join Date: Dec 2013 Location: Columbus, Oh Posts: 366	Re: Coolant Drain Plug The time and effort required to remove BOTH plugs and get out what you do not want in the new radiator will be well spent.



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