FWC (overflow tank size?)

[Ando]

What size are you guys using for the antifreeze overflow tank? I have a 2.5 quart one that I haven’t yet installed. The auto parts store said it’s for v8 engines. Is that overkill? I wouldn’t mind using a smaller one to save space if possible.

[ndutton]

Mine is 2 quarts, never an issue.

[Ando]

Thx again, Neil. So that brings me to another question and that is, how small can/should I go? I see that there are quart sized ones as well.

[ndutton]

My cooling system has probably twice the capacity as yours due to an 11 gallon water heater located under the V berth with a lengthy 5/8" hose run to and from its internal heat exchanger and my 2 quart recovery tank handles that easily so I expect a 1 quart tank for yours will be fine. However, I'm a big fan of reserve capacity so to that end I recommend installing the largest overflow recovery tank/bottle you can fit comfortably.

[ronstory]

Neil is spot on (as usual ) a quart should be fine... but I also prefer a larger capacity for 'just in case'. The amount of coolant pushed into container is directly related to how much air you have in the cooling system. More air, more gas expansion and more liquid movement.

I have the Indigo thermostat mounted at the high point in the engine and and it has a port that can be used to bleed the system. With the 'reverse flow' in the head I can get most of air out of the engine. With careful placement of the HX and the hose runs you can get nearly all of air out of the system and mine maybe pushes a a cup or so coolant back and forth between hot and cold.

[Ando]

I swapped the 2.5qt to 1.5, which seems like a nice fit.

[Ando]

Does it matter if the tank is above, below or level to the top of the hx?

[ndutton]

Level or roughly so with the HX makes the recovery function less demanding on the negative pressure gradient. Translation in plain English: if the tank is placed well below the level of the HX the cooling engine has to suck harder to get the antifreeze back in.