Cleaning out cooler lines?

[CarsonChris]

I got the A4ld out today. I know to use air to flush the cooler lines but is there a best way to do it? Any tips? The fluid was full of shavings and I don't want that crap getting into the replacement.

 

[adsm08]

I like to use a dipstick tube flush machine. Stick it in the return line and pump about 3 quarts of fluid through backwards.