Are you actually refilling the cooling system or just topping it off. If just topping it off, the plastic resevoir would be correct. If you need to refill it (after draining for example) you will need to go directly into the radiator.
That's my problem.
I didn't really get the reaction of the 2 people that replied previously.
My resorvoir tank is full.
I kept topping it off since the previous owner said it had a slow leak somewhere in the area of the water pump.
But the tank never got less and I kept overheating.
Now I popped the rad cap and notice my rad is damn near empty!
The overheating isn't quite as bad now.
But I have to keep refilling with coolant.
I bet I have a leak somewhere in the rad.
It's time for you to find the leak and repair the problem. Once complete, you gill the radiator with distilled water and coolant and bleed the air bubbles. THEN go about filling your resevoir to the COLD line and keep an eye on its progress for a while to ensure all is well.
Ya..Hot Full and Hot cold.
I never filled it up all the way.
Well I just filled the rad with plain water (yesterday I used a 50/50 mix).
The car did not overheat one bit.
Actually the temp was below the half-way mark.
Well, fill it with water and let it heat up a to operating temp (or even let it overheat a bit by running in fast idle in a controlled setting) then shut the engine. The water will boil and you'll see mad steam shooting from the problem area. Then you can plug the leak, flush the system and fill it back up with regular coolant.
DO NOT use radiator sealer. It will pork your radiator good. It plugs the leak and everything else too. I had to replace a leakfixed radiator after 1 bottle since it didnt radiate very well after the inside was coated with aluminum flakes.