Difference between radiator cap and header tank / expansion tank cap?

Question

I know this may sound silly, but on my Dad's car there is a header tank / expansion tank cap and a radiator cap on, well, the radiator. On my corsa B car, thereis no radiator cap on the radiator and only a cap on the header / expansion tank.

If you google radioator cap, it comes up with the majority that most would think of as radiator caps. If you google corsa b radiator cap, it comes up with the yellow header tank / overflow / expansion tank cap.

With that said, can someone tell me if I just don't have a cap on the actuall radiator on me car? Or is it somewhere? Can they have just a header / expansion tank cap?

I am wondering if my header tank / expansion tank cap acts like a radiator cap on some cars. If so, how would that work?

Cheers

Answer 1

With that said, can someone tell me if I just don't have a cap on the actuall radiator on me car? Or is it somewhere? Can they have just a header / expansion tank cap? YES THEY CAN AND THAT IS MOST COMMONLY THE WAY IT IS DONE NOW



I am wondering if my header tank / expansion tank cap acts like a radiator cap on some cars. If so, how would that work? YES IT DOES IN THAT IT WILL ALLOW ANY EXCESS COOLANT TO PASS ITS RELIEF VALVE IF THERE IS SUFFICIENT PRESSURE TO VEN TO THE OUTSIDE

Answer 2

Expansion Tank Cap

Answer 3

If a car has both a cap on the radiator and the overflow/expansion tank, the cap on the radiator is a pressure releasing one which is set usually to 15psi. If there is only a cap on the overflow/expansion tank, that one is a pressure cap. On cars with a radiator cap, the overflow/expansion tank doesn't need to be pressurized. It is vented to atmosphere.

Answer 4

in the old days, radiator caps had a spring loaded seal to release excess pressure.

then along came the header/expansion tank, the radiator cap became a fixed seal cap, and the header tank got the pressure relieving cap.

Eventually, the radiator lost its cap, as it served little purpose.

Think of it as Lamarckian evolution in action..

Answer 5

The radiator must have a *pressure cap from the dealer of the car. The radiator pressure cap raises the boiling point of the coolant to 265 degrees F when a 50/50 mixture if antifreeze from the dealer of the car is used and 50% distilled water. The radiator cap had two valves. One for pressure when the engine is up to operating temperature. A small one on the center of the cap which opens as the engine cools to allow the coolant in the plastic reserve tank to return to the engine.

Answer 6

I once had a car whose coolant recovery tube broke loose from the radiator filler. You might want to check for cracks, breaks, or foreign matter allowing coolant past the cap.

Answer 7

They are both caps. One at least has to have a spring incorporated to release excess pressure.