Is it normal for a car with no overflow to dump a bit of antifreeze after a day
The upchuck will stop happening once the coolant volume is no longer excessive. Filling the radiator right up to the filler neck ring when cold means there's nowhere for the fluid to go once it's hot — except onto the ground. If you don't want to add a tank — universal add-on tanks are readily available — then let the fluid find its level and don't add coolant just because the level is an inch or so below the filler neck ring when cold.
Radiator caps are more complicated than they might seem. A cap for a recovery system has two rubber seals: One on the face of the main valve, which seals against the lower flange ring of the radiator neck, and another larger one just under the cap's underside, which seals against the upper flange ring of the radiator neck. The upper ring's seal against the upper flange means that when the system cools down and coolant volume in the radiator decreases, the resultant suction is channeled via the open centre valve through the overflow tube, which draws coolant from the reserve tank back into the radiator.
A cap intended for a non-recovery system has only the lower seal, no upper seal. When the system cools and volume decreases, the centre valve opens and admits air to the system.
There's no problem using a dual-seal cap without a recovery tank, but a recovery tank won't be of any use if your radiator cap hasn't got the upper ring in addition to the lower one.
There are two kinds of centre valve. Chrysler's rad caps had the free-hanging valve clear on up into the early '90s, at which point the spring-loaded type began appearing on Mopars.
The difference between free-hanging and spring-loaded centre valve isn't whether the cooling system has a recovery tank or not. Rather, it's to do with the design of the cooling system: Partial-pressure (free-hanging valve) vs. full-pressure (spring-loaded valve).
In a partial-pressure system, the cooling system does not become pressurised until the system becomes sufficiently hot that the coolant and/or steam wants to rush out of the filler neck. At that point, the coolant trying to flow out of the radiator closes the cap's centre valve, and system pressure builds. It continues to do so until the cap's pressure rating is reached, at which point the cap's main valvespring is compressed and coolant flows out of the filler neck via the overflow tube.
A full-pressure system begins building pressure as soon as the coolant begins to heat up, and retains it long after coolant outflow would cease to push closed a free-hanging centre valve. This can offer increased protection against localised boiling in the system, which can be necessary in engines prone to such. However, the cost is greatly increased physical stress on the entire cooling system -- hose junctions, seals, solder joints in the radiator and heater core, etc.
So, leaving aside the pressure rating differences, and the physical differences (shape, size, length of centre stem, etc.) there are four different types of cap:
With lower ring only, with free-hanging centre valve (Partial-pressure, open system)
With lower and upper ring, with free-hanging centre valve (Partial-pressure, coolant recovery system)
With lower ring only, with spring-loaded centre valve (Full-pressure, open system)
With lower and upper ring, with spring-loaded centre valve (Full-pressure, coolant recovery system).
I run my cooling systems unpressurised (a 4-pound cap) in conjunction with waterless coolant which is costly but good (my comments here, here, and here for discussion and here for the company's website. Not only is it more effective at extracting heat from engine metal because there's no localised boiling, but the lack of system pressure means much less stress on every gasket, seal, hose, the radiator, the heater core, the heater valve, etc.
The upchuck will stop happening once the coolant volume is no longer excessive. Filling the radiator right up to the filler neck ring when cold means there's nowhere for the fluid to go once it's hot — except onto the ground. If you don't want to add a tank — universal add-on tanks are readily available — then let the fluid find its level and don't add coolant just because the level is an inch or so below the filler neck ring when cold.
Radiator caps are more complicated than they might seem. A cap for a recovery system has two rubber seals: One on the face of the main valve, which seals against the lower flange ring of the radiator neck, and another larger one just under the cap's underside, which seals against the upper flange ring of the radiator neck. The upper ring's seal against the upper flange means that when the system cools down and coolant volume in the radiator decreases, the resultant suction is channeled via the open centre valve through the overflow tube, which draws coolant from the reserve tank back into the radiator.
A cap intended for a non-recovery system has only the lower seal, no upper seal. When the system cools and volume decreases, the centre valve opens and admits air to the system.
There's no problem using a dual-seal cap without a recovery tank, but a recovery tank won't be of any use if your radiator cap hasn't got the upper ring in addition to the lower one.
There are two kinds of centre valve. Chrysler's rad caps had the free-hanging valve clear on up into the early '90s, at which point the spring-loaded type began appearing on Mopars.
The difference between free-hanging and spring-loaded centre valve isn't whether the cooling system has a recovery tank or not. Rather, it's to do with the design of the cooling system: Partial-pressure (free-hanging valve) vs. full-pressure (spring-loaded valve).
In a partial-pressure system, the cooling system does not become pressurised until the system becomes sufficiently hot that the coolant and/or steam wants to rush out of the filler neck. At that point, the coolant trying to flow out of the radiator closes the cap's centre valve, and system pressure builds. It continues to do so until the cap's pressure rating is reached, at which point the cap's main valvespring is compressed and coolant flows out of the filler neck via the overflow tube.
A full-pressure system begins building pressure as soon as the coolant begins to heat up, and retains it long after coolant outflow would cease to push closed a free-hanging centre valve. This can offer increased protection against localised boiling in the system, which can be necessary in engines prone to such. However, the cost is greatly increased physical stress on the entire cooling system -- hose junctions, seals, solder joints in the radiator and heater core, etc.
So, leaving aside the pressure rating differences, and the physical differences (shape, size, length of centre stem, etc.) there are four different types of cap:
With lower ring only, with free-hanging centre valve (Partial-pressure, open system)
With lower and upper ring, with free-hanging centre valve (Partial-pressure, coolant recovery system)
With lower ring only, with spring-loaded centre valve (Full-pressure, open system)
With lower and upper ring, with spring-loaded centre valve (Full-pressure, coolant recovery system).
I run my cooling systems unpressurised (a 4-pound cap) in conjunction with waterless coolant which is costly but good (my comments here, here, and here for discussion and here for the company's website. Not only is it more effective at extracting heat from engine metal because there's no localised boiling, but the lack of system pressure means much less stress on every gasket, seal, hose, the radiator, the heater core, the heater valve, etc.
