Radiator caps work differently in his world.

[pfarber]

See, its just not me.... everyone is getting in on it!

http://www.g503.com/forums/viewtopic.php?f=4&t=187068

MB/GPW RADIATOR CAPS DO WEAR OUT

Postby Ben Dover » Fri Jul 08, 2011 7:04 pm
Take a peek at your OEM MB/GPW AC Radiator Cap and also the later replacements, you will observe a thin Brass Disk that is the seal between the top of the cap and top of the radiator filler neck. In time these are known to develop cracks resulting in ability to maintain pressure. The OEM AC and Replacement AC lifespan of the brass seal has averaged 15 tears on my MB.

Smackdown in 3.. 2.. 1..

(Poster is not identified (not me) but the link is above.)

Hmm....I think we need to learn a bit more about how the radiator cap works. If the gasket in the NECK of the radiator is between the CAP and the Inner ledge of the neck then that is where the pressure seal is created, if my understanding of the radiator cap is correct, then it is the EXPANSION of the coolant (not the temperature) to the 4 lb+ threshhold the opens the cap/gasket/neck and allows coolant to rise higher in the neck of the radiator. The thin brass disc has sealed the CAP to the TOP of the radiator and thus the expanding coolant has only the overflow tube available to expand into.

So I am of the opinion the the PRESSURE in the radiator and in the cap is not created by the brass disc, but by the gasket down further.

Therefore if your brass disc has a crack in it, the PRESSURE seal of the cap is not effected since that is a function of the gasket, the lower part of the cap and the ledge down in the radiator itself. If there is a crack in it, the worst that would happen is the possibility that when the pressure in your fadiator exceeds the 4 lb cap, the coolant will not only have the option to escape via the overflow tube, but it MIGHT also escape between the cap and the edge of the radiator where the brass disc is mounted.

The point being....the brass disc has nothing to do with actual SEAL the gasket provides between radiator neck and cap. If it is not what seals the system, then it is not what maintains the pressure in the system.