Cooling system: Does it circulate the coolant in the resevoir?

Hey guys, long time listener, first time caller. Just curious, I added straight (undiluted) antifreeze to my radiator after replacing the water pump and thermostat.('97 Chevy Express 3500 5.7L) I assumed I would need at least 2 gallons, but I noticed it getting close to the top so I stopped with about 1/8 of the coolant left in the jug. I ended up putting maybe 1-2 cups of water in the radiator before it was full, so I just poured the rest of the water into the resevior, making the mixture in the radiator far from 50/50. My thinking was that the water in the resevoir would circulate through and it would all mix together and everything would be fine. Then I started doubting that theory because the resevior tank is NOT pressurized, so why would it? Is this bad? Will it all eventually mix together?

Or am I just crazy?

Thanks for any and all help!

Welcome fellow Iowan!

As you suspect, the water in the reservoir will not readily mix with that in the radiator. However, as the coolant heats up and expands it will flow in to the reservoir, then as it cools coolant will be pulled from the reservoir. So after several long-ish drives you may end up getting all the water and lightly diluted anti-freeze mixed together. In the summer it's probably less of an issue if you aren't experiencing overheating, but as winter approaches you will want to have the freeze protection point of the coolant in the radiator tested.

-Rod

It will mix eventually. As stated, just check it with a hydrometer before it gets cold out.