Coolant: Overflow vs. Expansion tank

[MB750]

I've never owned a vehicle with an overflow tank as opposed to an expansion tank.

Firstly, are there any pitfalls to this system? I like the idea of a self-regulating coolant level with the expansion tank, even though technically my current system is purged. When I filled the coolant I did have the upper radiator air bleed open until coolant started dripping out, but I still feel like there's some air in the furthest upper reaches of the radiator.

If I wanted to switch to an expansion tank, does anyone have any suggestions why they did and what they used?

Thanks.

[OB6]

I don't know that it's an either/or question (not that you're suggesting it is). I'm using both, but it's for an LS3 which may have different requirements than your engine.

[MB750]

I've seen some systems that use both. The expansion tank is the highest point of the coolant system and it's basically also the fill point, and the overflow tank is filled when/if the expansion tank gets too full.

[BEAR-AvHistory]

I've seen some systems that use both. The expansion tank is the highest point of the coolant system and it's basically also the fill point, and the overflow tank is filled when/if the expansion tank gets too full.

Some tanks have both a cylinder head & top of radiator inlets.

https://thefactoryfiveforum.com/attachment.php?attachmentid=202022&d=1721414949

System self purges the engine & does not loose coolant. In 8 years have not added coolant between fluid changes.

A replacement unit the same as the FFR one but with a very large tank still dumped coolant on the floor. Made the change & was good to go. Old tank is still in the car but not connected found no point in removing it.

[CraigS]

The problem w/ expansion tanks is location. It is very difficult to get an expansion tank and it's filler cap to be the highest point in the cooling system. Overflow tanks take care of the problem easily. If your system has been working fine I don't know if I'd change it. But, if you ever have a reason to, for instance, move your tank to get room for something else, I'd change in a heartbeat. I used the Canton 2qt tank w/ a sight tube and it was so easy. Remove the temp sensor or heater hose from the intake. Fill the system til coolant comes out of the intake fitting. Reinstall what was in the intake. Install the pressure cap and never remove it. Fill the overflow tank maybe 3/4. Start the engine and let it warm fully (top rad hose has been hot for several minutes). Shut it down and monitor the tank level so it doesn't go dry as it cools. Once cool, fill it to 2/3 and drive it. Hey warming it in the garage is boring and I think that some extra rpms can be a good thing so I usually plan a short drive. You will note that, each time you need to top up, it will take less coolant. At this point I am not ready to head to Cali but I am ready to drive on normal local trips to breakfast or lunch w/ a qt or 2 of coolant in the trunk. I watch it for 2-3 more drives and then it's done. What I really like is you never need to open the pressure cap, it is all done at the tank.

[Rebostar]

CraigS has some really good points. One of which is why on my 427W I went with an FE expansion tank modified to fit the Windsor motor. Also has the benafit of having the nastalgia 427 FE look.

207981
On the run stand

207982
In the car

[MB750]

CraigS has some really good points. One of which is why on my 427W I went with an FE expansion tank modified to fit the Windsor motor. Also has the benafit of having the nastalgia 427 FE look.

207981
On the run stand

207982
In the car

That was exactly the type of affair I was thinking about.

I've only put 26 miles on my car thus far, and the cooling system is clearly working, so I'm not going to reinvent the wheel. But if I ever have a desire to make changes for some reason it's good to have solutions to potential problems, just in case. There's a good half a foot above my current radiator cap, which is located in the vicinity of your expansion tank right after the thermostat outlet.