Coolant leak - bad reservoir?
 

I have a slow coolant leak as evidenced by spots on my garage floor. It may be coming from around the tank but its hard to verify. Is the tank or nearby hose or connection a common point of failure?

Here are some pics. Clearly there is evidence of coolant around the tank, but it is all dried up.


https://cimg0.ibsrv.net/gimg/www.mbw...40e19d2c9e.jpg
https://cimg1.ibsrv.net/gimg/www.mbw...d4790d3634.jpg
https://cimg2.ibsrv.net/gimg/www.mbw...ab774dd8f0.jpg
https://cimg3.ibsrv.net/gimg/www.mbw...a8fdb827c6.jpg

My E63s has been running perfect except one hiccup with the coolant leak. I had my reservoir and pipes replaced and it was not covered under warranty which really sucks.

Bring it back to Mercedes to get it checked.

Last year I rested my arm on that hose going to the reservoir by accident and it snapped in half lol.

I had a bad reservoir on my old ML63

It’s a common problem. Mine was replaced under warranty.

I had to do the main radiator hose, popped off while driving and all coolant drained out.

Why is your coolant green BTW? Shouldn't it be blue?

Does anyone know the part number for the reservoir tank and how hard it is to change out? I have noticed a pin size hole in the tank.

Common to split at the seem
like yours appears to have done. Easy to change

Same thing here. Though magically my dealer never saw a problem with it until after my warranty expired. 🙄

While this appears to be a tank leak, mine was leaking around the reservoir cap. You could see dried precipitate around and down the sides of the fill. Wiped it all down, pulled the cap, cleaned the gasket really well and put back. No leaks since.

same here. if the reservoir isnt the issue, I would check that. its fairly easy to spot from under the car.

Video showing a hairline leak in the bottle


Easy enough to fix.... the part is under $100
Pressurizing the system as shown above will help identify the leak.

Man for $100 I’d try some crazy glue first! Sad, my Toyota’s never had these sorts of issues. WTF Mercedes are you really that desperate to nickel and dime us? You can make a 600hp super motor that lasts over 100k miles but you can’t design a simple plastic reservoir that doesn’t split and leak?? Homer Simpson could design a better one...

it’s an expansion tank under constant pressure. Toyota is just overflow

I agree with the sentiment. I had the same issue with the reservoir failure at 70K miles in M156. The main issue seems to be heat in the engine compartment. The M157 is worse with turbos baking rubber and plastic elements under the hood. Brittle and fragile wiring harness, disintegrating intake ducts, leaky sensors, etc. Some owners open the hood when garaged to mitigate... The successor M177/178 appears better in this respect with the Hot-V design and shielding. Oh well.

Mine had 2 miniscule pin holes in the side closest to the engine.
MY 2016 , 50000KM.
Replaced under warranty

Coolant leaking
 

I'm driving c63 amg 2008 .Coolant is leaking at the back of the reservoir not on a cap,sometimes when the idling you see coolant under car. What could be the problem?

These tanks are a molded 2 piece design. So over time the glue and seals loosen up due to age, heat, and pressure causing leaks. Buy a new tank, fill coolant and bleed air.

You may have answered your own question.

Mine was leaking too. Purchased a new cap and tank. MB must have known something about this as the new tank has a different part #. Looks the same as the old one.

Oh no - the (German) hot V engines are much, much worse. Anything in the valley is being baked and breaks very easily.
ItalianJoe (who if I recall correctly was working at a dealer) confirmed this. And since all plastic becomes very brittle in there, you break more pieces than you intend when you try to fix the broken part.

And I am part of the hood club, have done that to all my cars for the last 10 years and it does make a difference.

I was trying to fix/replace the coolant overflow hose on my gl450 (2013) and the hose that it plugs into broke!! I cannot find the part number for that hose. Here is a picture (from this post) of the hose circled in blue. Anyone know what part I need to buy?
https://cimg4.ibsrv.net/gimg/www.mbw...e09606c9a8.jpg
What part # is this hose?

I just replaced it his on my car as well. I have to look for the part number but when replacing be careful when removing the hose. At the end of that hose it is connected to another plastic piece that is easily cracked as well. It would be best to remove it along with hose which is held in place by a torx bolt.