Did I overfill my radiator reservoir???

Chs tank is they're with a lil pump next to it . It's like a thermos. No need to slam overflow tank . Pour slowly in to filler neck . It'll take over four minutes to fully fill. That's how slow it goes in . Fill overflow tank to whit plastic you see just below tank lid neck . See the tube on side of o flow tank?

 

you fill that overflow tank just halfway, not all the way to the top. When the radiator gets pressurized some of the coolant from the radiator gets pushed into the radiator cap and goes into that overflow tank. If your overflow tank is full already (when cold) then it will dump the excess to the overflow hose that drains down in the center of the blower fan assembly. When it is cooling the coolant in the overflow tank is sucked back into the radiator.

 

The fluid expands when it is hot. I don't recall the exact amount, but somewhere between 5% and 10%. If the expansion tank is already full to the top, where is that extra volume going to go?

As mentioned two posts up, fill it half way. In fact, take a Sharpie and put a mark there, so you can check the tank once and a while when it has been off for a while. If the level drops well below the mark then fluid is going out somewhere. Always do this on flat ground, or at least on the exact same spot, because the level will change when the car is tilted. The level can be up or down slightly from day to day depending on temperature or slight changes in tilt (if not always parked in exactly the same place). Don't worry about those little changes.

Also if you ever have to do any work on the coolant loop that half way mark will make it easy to know when all the bubbles are finally out of the system. After burping most of the air (involved process on this car), drive it for a day, fill to center mark next morning. Do that for a couple of days and all the air will be out.