One of the difficult things when working on old cars is finding the right parts. Even when they’re available, its not immediately obvious what is correct. Since I’ve had the engine running, I’ve noticed cooling water leaking out of the radiator’s cap. Although the cap looked good, I decided to order up a new one and see what came. The new part wasn’t what I was expecting, but makes perfect sense. These pictures show what was on the radiator on the left, and the new part (A 000 501 19 15) on the right.
The issue is the way the expansion tank, which is unique to the sedans, is connected to the radiator. There is a small hose running from the tank to the overflow connection on the radiator. This means that any pressurized water in the expansion tank was pushed out of the radiator’s cap above the rubber seal. The new cap seals at the top of the radiator, closing the system and allowing pressure to build. The cap that is on the expansion tank is more like the one on the left (although its a larger size) and uses a spring to hold pressure in the system up to a point.
So, another minor problem solved!