Expansion Tank

[glmoore0001]

The radiator on the 250c doesn't even have a expansion tank hose, and no expansion tank. I have attached a pic and wonder if it would be ok to fit this type of expansion tank on the car.

The tank sits to the left of the battery and is a wedge shaped thing.

I have no idea if they are available for purchase, but it would at least let me be on the lookout for the item. I would prefer to install something like this rather than vent onto the ground.

[Frank Reiner]

Look again; the tank by the battery is for the windshield washers.
The radiator vent hose comes forward & down the right side of the radiator.

[Tomguy]

Welcome to vintage car ownership. In the 60s and 70s, there were no regulations about not pouring animal-killing fluids directly onto pavement. So like Frank said, the picture posted does show the overflow tube, and it's just a tube, right at the neck of the radiator. It's only purpose as designed is to release excessive pressure in the system, either from slight overfills or boiling over to not make a messy engine bay (or perhaps opening the system when the engine is hot and it's pressurized).

You would not want an "Expansion tank" - that indicates a pressurized vessel. What you'd want is a "Coolant recovery tank" that the hose can go into and, with the proper radiator cap with a brass button on its bottom, can allow the coolant to be "Sucked up" back in when cold, so if you are consuming small amounts of coolant you will not be as likely to overheat. There are all types of these bottles for all types of cars that have non-pressurized recovery tanks from XJ Jeep Cherokees to Honda Accords. There may even be Mercedes models from the 90s to today that have this style system, I just haven't experienced them firsthand to know.

[rumb]

Just use an old plastic pop bottle with a hole in the lid the hose goes in. That would catch any liquid. Mount it down low along side the radiator where the current hose goes. You will probably never see anything in it if your cooling system is good.

[glmoore0001]

I remember now the p.o. saying the Electronic ignition controller was mounted where the washer resevoir used to be, which is on the left beside the battery.
I will figure out some type of catch can I guess.

[Idle]

Some Mercedes of that era, some 111s, came with overflow tanks. They were small barrel looking things that mounted, I think, on the firewall or close to it.

Why some had it and some did not is something I don't know. But they show up on Evil Bay now and then.

The ones i have seen were made of both steel and brass. I don't know for sure but I think the brass ones came from early cars and the steel ones came on the later models before Mercedes changed to the plastic tanks.

I know the plastic tanks were available on 107s, so you might check for photos of an SL's engine bay to see how they were mounted.

Another source of these would be Volkswagens from the 80s but I have found they don't hold up as well as the tanks from Mercedes.

Also check out the plumbing on the various tanks. Some have simple in and out with the same hose. Some have other hoses running from them.

[250 Coupe]

Renault’s of the 50’s and 60’s used a glass bottle with the pressure/vacuum relief valve as part of the lid.

I have a universal recovery tank on the truck. It has a number of connections and mounting tabs so it can be mounted horizontally or vertically.

Amazon lists quite a few versions under universal coolant recovery tank.

Michael