Interesting radiator cap

[JHZR2]

So I wanted to drain and refill my 81 MB 240D. Pulled the cap, drained the radiator, but look at the cap. What seems to me to be what should be the larger, outer gasket on a cap, in this instance, is a flexible copper-based disc.

Never seen one like this:

 

[Chris142]

Does the car use an overflow bottle?

If the tube goes to the ground then you don't need the upper seal. If it goes to a bottle then you need the upper seal.

BTW your lower rubber is swelled out past the metal flange. You need a new cap anyway.

 

[JustinH]

Looks like it has a thermostat on the bottle cap, I know thats not the truth, but thats what it looks like.

 

[Steve S]

Chris you are on top of it as usuall!!!

 

[George7941]

Vehicles that do not have a recovery tank do not have the upper gasket.

I bought a Mazda B2000 new in 1982 and it did not have a coolant recovery tank. I bought a new aftermarket universal recovery tank(I think the brand was INTERTEC) and mounted it in the engine compartment. I cut a round gasket from sheet rubber and put it on the cap and the recovery tank worked well for the fourteen years I had the truck.

BTW why does the rad core appear so yellow? It must be the lighting. Congratulations on a super clean looking cooling system. Are you using G-05?

 

[JHZR2]

No recovery bottle, and the cap may well be from 1981. It holds pressure fine and doesn't leak coolant.

The coolant in there is MB coolant, which is a yellowish-orange. All original in there, though the coolant has been regularly changed, of course.

My biggest issue is that at all the parts sites, the cap they show has dual gaskets. Would this be acceptable for use in my system, which doesnt have an overflow bottle?

 

[George7941]

The second gasket is only to maintain the vacuum when the coolant is cooling down and to prevent coolant spilling, in systems with recovery tanks.

It should be fine to use in your car with no recovery tank. Of course you always have the option of removing the second gasket and have a setup similar to the original cap.

 

[Chris142]

Yes you can use the cap with both gaskets. No problem and no reason to remove the upper seal. Just screw it on and forget about it.