Rick's Free Auto Repair Advice

How to do a coolant drain and fill

Perform a coolant drain and fill at home

It’s hard to do a full coolant flush at home (see why here). But it is a bit easier to do a coolant drain and refill yourself. Here’s how.

Ignore the recommendation to drain coolant from the radiator drain

The old plastic drains break and leak

In the old days metal radiator contained broken radiator drain petcockbrass drain petcocks. But modern radiators have plastic side tanks and plastic drains. The drain sits unused for almost 10 years before you decide to open the drain. I guarantee that once you open the drain and try to close it, it will leak, or crack, or simply disintegrate.

If you’re married to the idea of using the radiator drain, do yourself a favor and buy a replacement drain from the auto parts store BEFORE you open the old one on your radiator. They’re cheap. At the very least, be prepared to install a new O-ring on your old radiator drain valve.

replacement radiator drain valve

Replacement radiator drain valve


No shop ever drains the cooling system through the radiator drain!

Remove the lower radiator hose to drain out as much coolant as possible

Disconnecting the lower radiator hose will quickly drain both the radiator and a portion of the engine. But it won’t drain the entire engine. To do that, you’ll have to remove the block drain plugs— and many late model engines don’t come with block drain plugs.

So resign yourself to the fact that no matter how much coolant comes out, you’re still going to have some old coolant left in the engine. The only way to get it all out is to do a full coolant flush and fill which requires special equipment.

Capture the old coolant and recycle it

It’s illegal to drain old coolant into the street and storm sewers. Worse than that, it kills wildlife and pollutes rivers and streams. Don’t be one of those people!

Refill the cooling system

Reconnect the lower radiator hose and secure with the hose clamp. Then refill the system and bleed air pockets.

©, 2023 Rick Muscoplat

Posted on by Rick Muscoplat

Custom Wordpress Website created by Wizzy Wig Web Design, Minneapolis MN