Not sure how much smaller you can go

Overflow tank has a reserve of coolant in case of the leak, and as coolant heats up and expands in the engine it flows out of radiator and into the overflow tank, the hotter the coolant the more it expands so the more coolant flows out to the tank.

As engine/coolant cools down that coolant is sucked back into the radiator via the smaller valve in center of rad cap

So in the summer months or if pulling a load more coolant should flow out.


The overflow tank needs to be self purging of air and not sealed
The hose needs to be at the bottom of the tank, so if any air comes in it will bubble to the top and then at cool down coolant will be sucked back in to replace the air


You could change to a Degas system, thats what was run in the old days and now used on many engines
No overflow tank
There is a reservoir tank with a 16psi cap, radiator has a sealed cap no valves, reservoir tank MUST BE the high point of cooling system so any air left in the system will end up in this reservoir
The reservoir has some coolant and then air at the top
The coolant expands into the reservoir pressurizing the air inside at 16psi it lets some air out

In the old days the radiator tops were bigger and that was the reservoir tank, you always left air in the top of the radiator so the coolant could expand, if engine over heated coolant would come out or if you overfilled it

 

 

Just one hose from rad cap port to the bottom of the bottle
Some tanks have a hole in the bottom for this, I prefer the kind that has the hose that comes in from the top and goes almost to the bottom of the tank
As the tank gets used it WILL get debris in the bottom, as warm coolant comes in it can push the debris out of the way, but as engine cools off, when it comes time to suck coolant back in this debris will clog the passage.
If the hose sits just above bottom of the tank then it won't get clogged

Bottle must be vented, open to the outside air pressure


Set your current reservoir at cold line , then fill it to HOT line measuring the amount of fluid you need to add, then double that to get new bottle size

 

 

Can't think of any reason why not

 

 

No restriction on the level of the reservoir, its not gravity dependent.
It should have enough suction as coolant cools down to pull it up from bottom of rad level
You may want to put a clamp on the hose at rad cab, if it doesn't have one, for the suction to work it can't have an air leak or it will suck in air if the coolant is too hard to lift from sitting lower
Other limitation is upper and lower rad hose hardness, if the larger hoses are soft then they will start to collapse when pressure in rad drops below -1psi, if that starts to happen then there is no suction until they stop collapsing, its a balance of how hard it is to lift the coolant vs the hardness of the larger hoses

Yes, hit the wrecking yards, many vehicles use washer fluid reservoirs with long necks that sit low down in the front of engine bay, or rad support
And it will come with 12v motor, get the electrical connector with it, also connector for low level if it has that sensor

Google: Dorman 603-106
or Dorman 603-403

There are all kinds of shapes and sizes

 

 

For the overflow, yes
I prefer the ones with hose coming in at the top but extending down to the bottom inside the tank, less likely to be clogged by debris in the tank
But bib at the bottom is fine if that's whats available

And vented cap for sure, or holes in the cap, lol

Wrecking yard will have literally thousands of these in different shapes and sizes

 

 

You need a pump for washer fluid, but you could use an in-line pump like this: So could use same type of reservoir for both

Yes, moving or changing these is popular when adding a battery, don't recall seeing many how-to's about it though

I would hit wrecking yards for cars and have a look around, there are many ideas out there