Can u fill coolant resorvoir above hot full mark?

[edwardh1]

Why do radiator overflow bottles have such a large capacity above the hot mark?
My 99 infiniti, and my 200 Toyota - you can put 2 cups of coolant above the full hot mark and still have room.

What gives- some of the dexcool articles say to fill above the hot full mark?
Should you?
why not?

 

[pidster]

It's an expansion tank. The hotter the coolant temp, the higher the level will rise. If you're below the cold mark, and the temp drops really low into the negatives, you can suck air into the cooling system. If you fill above the hot mark, and coolant temp rises quite high, it will overflow and basically puke some coolant out onto the ground. In most conditions you can over or under fill and nothing will happen. But there is really no advantage to this that I can see, unless its leaking from somewhere else, then I'd keep it right full.

 

[GMBoy]

Originally Posted By: pidster
It's an expansion tank. The hotter the coolant temp, the higher the level will rise. If you're below the cold mark, and the temp drops really low into the negatives, you can suck air into the cooling system. If you fill above the hot mark, and coolant temp rises quite high, it will overflow and basically puke some coolant out onto the ground. In most conditions you can over or under fill and nothing will happen. But there is really no advantage to this that I can see, unless its leaking from somewhere else, then I'd keep it right full.



Very well said. Exactly right. I can't add anymore. Did I say, good job?

 

[dwendt44]

Depends on the engine/model.
I've done just that on a couple of vehicles.
The 'room' provided is enough for even most extreme conditions.
Hot soak after shut down for example.
If you check a few minutes after a AC on run on a very hot day, you'll see how high the coolant gets and know if you have room to spare.
My 2¢

 

[Spector]

I keep all of mine to the full Hot mark when the engine is cold. If you check the container when hot you will see the max expansion and if you want to add more to that later when cool you can approximate how much you can add to bring the level up a little. The outside temp will also make a diff, a 100 degree day in summer will place more coolant into the container then in the winter.

 

[eljefino]

It's a good way for mechanics to get it right the first time after a coolant service when there's an engine style that stubbornly releases air bubbles days or weeks later. The worst that can happen is some gets lost; hopefully scattered enough cats don't get it.

 

[mechtech2]

Additionally, cars take turns. The puke tank caps are designed by the guy who made the space shuttle seals that leaked.
So having extra room keeps coolant inside.