My buddy (no not me) was low on coolant and added 1 reservoir of concentrated antifreeze which was gobbled up and then refilled it again with the concentrate.

Obviously he has to find the leak but is there any harm of having the concentrated liquid in the system?

 

Harm - probably not. The mix ratio could vary depending on your location. I would have refilled it the second time using distilled water since 50/50 is the "typical" ratio that is good to around -35 to -40F.

 

"It's also not a good idea to use straight antifreeze in your car's radiator, even if you do live in a freezing cold climate. Straight water actually does a better job of getting rid of the heat in your car's engine than antifreeze!"

http://www.autohub360.com/index.php/...ng-enough-409/

p.s. btw my 79 runs best on a 20% solution. If it is HIGHER the engine temp goes UP . . . . small cooling system and it NEEDS the water.