Where to put engine coolant expansion tank

[preserved_killick]

Hey Guys,

I need to move my coolant expansion tank, there's just no room to have it mounted next to the engine. The spot I'm thinking of, is on the other side of a plywood wall putting it under a counter.

My question is this, does the expansion tank need to be higher than the engine's heat exchanger? I'm wondering if siphoning would be an issue. ie Would the coolant siphon into the expansion tank and just fill it up, lowering the coolant in the heat exchanger. What goes on inside that heat exchanger cap (radiator cap)? Can it prevent siphoning? If so, then how does it draw the coolant back?

My guess is that it needs to be higher than the heat exchanger, can someone please tell me otherwise???

-Jeff

[bcooke]

Otherwise.

Is your expansion tank in your car higher than the radiator?

What goes on inside that heat exchanger cap (radiator cap)

There is a spring loaded valve in that cap. When the pressure in the exchanger gets above a certain point, the valve opens and allows fluid to flow out of the system and into the expansion tank. If the pressure drops too low the valve opens and the low pressure draws the extra coolant into the system. (okay, the higher pressure outside the system pushes the extra coolant into the relatively lower pressure system)

[Tom Young]

Hey Guys,

I need to move my coolant expansion tank, there's just no room to have it mounted next to the engine. The spot I'm thinking of, is on the other side of a plywood wall putting it under a counter.

My question is this, does the expansion tank need to be higher than the engine's heat exchanger? I'm wondering if siphoning would be an issue. ie Would the coolant siphon into the expansion tank and just fill it up, lowering the coolant in the heat exchanger. What goes on inside that heat exchanger cap (radiator cap)? Can it prevent siphoning? If so, then how does it draw the coolant back?

My guess is that it needs to be higher than the heat exchanger, can someone please tell me otherwise???

-Jeff

Like Britton says, location shouldn't matter. Keep in mind, as the engines coolant heats up, like any liquid, it expands. If the system is full and you have no expansion tank, it will blow off the excess through the radiator cap with a pressure release of 10 or so pounds.

Your expansion tank allows the heat expanded coolant the required space it needs. The expansion tanks usually have a tight plastic top but that top will allow a pound or two of pressure to pass. As long as the coolant that will enter the expansion tank when it heats up has space, it will simply build a pound of two of pressure inside.

When the engine cools down, that pressure and some vacuum created in the cooling system, will draw the coolant out of the expansion tank. The low pressure valve Britton mentions allows this back and forth flow.

My engine works directly through the engines coolant loop and taps a small hose to the expansion tank located 6 feet away in a cockpit locker. The expansion tank is high above the engine so in fact drains completely when the engine cools down but still works on the vacuum

It's a good idea to be sure the expansion system is working(filling when hot, draining when cold). It's a good indicator of small leaks or other problems in the cooling loop.

[preserved_killick]

Thanks Guys,

I looked in my car, and the expansion tank is about the same level as the radiator. Funny, we've got two new cars, and every new car I get things look less and less familiar.

One concern is trapped air, if there's an air bubble in the coolant system, I'd rather it be in the expansion tank, set just a bit higher than the heat exchanger.

I think that I'll put the expansion tank nearby in a cockpit locker. It'll be at a good height and I can easily take a look from time to time.

Thanks for your input.