On this '95 E320 wagon I found the coolant recovery tank cracked and leaking. Unlike other cars, this tank is under radiator pressure and exposed to hot coolant. It is made from Polyethylene and cracks under pressure with age. On other cars the coolant recovery tank is not under pressure: The pressure cap is on the radiator, the tank only catches expanding coolant. On my W113 the tank is also under pressure, but it is made from brass. Are there other Mercedes models that have a metal tank I could fit? Can the plastic tank be repaired? Anyone else having the same problem? Any good ideas?

 

I just replaced mine about a month ago, they are innexpensive and quite easy to do. They are using the same materials today, so I am guessing that the problems just come with age.

If you are looking for a local supplier of parts at great prices try www.mercedessource.com I used to work there and they have some of the best prices I can find anywhere.

 

Engineering error???? this is a 12 year old tank exposed to 300 Degree heat for the last 12 years,,,you should call Mercedes Benz and thank the engineers for making such a good piece of plastic...You have a nice selection of cars but up until the W124 they are rudementary,the perfection on the
w124 will never be allowed again in our lifetime...Even the almightly AMG cars of today do not have the build quality of the W124..

 

To add -- many manufacturers, including the American ones, are increasingly switching to pressurized plastic overflow tanks. Get used to it. Brass is incredibly expensive nowadays.

 

Would you care to add that this observation is purely subjective & personal?
From an engineering perspective however: Polyethylene is a very good material for many applications. A pressurized tank containing hot coolant is not one of them. Proof of this observation is the failure of this part. As I pointed out in my earlier post, When the tank is not pressurized and merely an overflow tank and doesn't get very hot, then Polyethylene is a very good choice. Mercedes, of course, knew this. On my '69 280 SL the pressurized tank is metal. But plastic is much cheaper and lasts as long as the first owner statistically keeps the car. I can buy a new tank for $32. So what am I complaining about? I can also check the coolant level visually and because the tank gets dirty after so many years, it's easier to throw it away than to clean it. It's a design philosophy thing and you have correctly observed that the older cars have "built quality". The new designs are built to be cheap and to be replaced after use. When an engine goes bad, it is replaced by a new engine rather than rebuilt. Easy, and no liability by the rebuilder. Same thing for other components. Systems become modular. If the clock fails, you must replace the entire instrument panel. Cars have become an appliance like a microwave or a lightbulb. You may have noticed that some people cherish old cars/motorcyles and spend a lot of money on restauration, far more that it would cost them to buy a new model. And many people admire these old classics. It has been said that men are primarily motivated by ego and I admit that it deeply satisfying to fix something that was claimed "unrepairable"

 

I, too, am an engineer of sorts. For what it's worth, these tanks have a very low rate of failure. The pressure is only about 1 bar and polyethylene is actually pretty stable. IMO, MB made a good call with this tank. Now if they could make the AC evaporator last that long...

 

It will always be a battle of cost against function. Perhaps you could fabricate your own replacement?

 

Ok Guys - I give in! I see that at the mercedessource.com they list the tank for $32 and I just ordered one. Thank you myfirstbenz for pointing out that supplier! I was wrong to complain!

 

For the cost it seams reasonable especially after twelve years

 

Couldn't agree more....just about any new production vehicle uses a similar style, albeit with more modern compounds.

Would rather have a "plastic" product that is inert to the coolant, then worry about a "lifetime" metal container that secretly is contributing to rust in my cooling system !!!

 

Yeah, mine is the same spec thick plastic. They indeed are high-pressure. The neck is reinforced with metal around the cap seal also rated in lbs.

I'd just get a new plastic tank, mine is 12 years old and original. That's a pretty good life span.

There is a method to "weld" poly-plastics gooing the crack with a soldering iron. Great for no pressure applications not your Boiler Tank though.

 

Yeah, I talked to my friendly, local plastic fabricator about welding: He said:
" Buy a new tank. The cracking indicates that it has become old & brittle. If we weld, it'll just crack somewhere else or where it has been welded".