billkoboldt Report post Posted September 25, 2012 Where is the drain plug on a 8.1 Chevy? Is it that white nylon plug on the lower left side of the radiator with what looks like a 1/4 in. square in it? If so, does it come all the way out and can it be reused if does come all the way out? I don't see your basic petcock that radiators used to have. Or would it be easier to just take the lower hose off and let it drain? Share this post Link to post Share on other sites
Kevin510 Report post Posted September 28, 2012 Instead of messing with a plastic drain plug, I would recomend pulling the radiator hose and then let the engine run with the heater on and get up to temp to allow thethermostat to open and the remaining fluid in the system to be pumped out. If you just open the drain valve you are not getting all of the old fluid out, just the stuff that was in the radiator. Just my 2 cents. Share this post Link to post Share on other sites
cmarq Report post Posted September 29, 2012 My 2003 8.1 has a large allen plug on the left side of the block. This will drain everything including whats in the block. It is a large plug. We are away so I can't give you the size, I got a socet style allen wrench at NAPA. Share this post Link to post Share on other sites
ClayL Report post Posted September 29, 2012 The white nylon gadget is the drain plug. The square part of a 1/4 ratchet (1/4 inch as I recall) or a ratchet extension is used to turn it. It either turns 1/4 or 1/2 turn. You can tell when you hit the stop. I think it is 1/2 turn. There are two recessed head 8 mm drain plugs on the sides of the engine block that need to be removed. The plugs are between and a little below the next to last and last sparkplug towards the back. One on each side. Altogether I got about 5 1/2 gallons of coolant out. On mine the radiator cap was a bear to get back on. I ended up taking the air horn (two screws) off so I could get leverage enough to replace it. Share this post Link to post Share on other sites
