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So it looks like I have a leaking coolant reservoir. I just bought this car, just over 100 miles into it now. The cap feels like it's missing a gasket or something when I try and tighten the cap. Just checking to see if the cap should have a rubber gasket or something? It feels "tight" and I don't wanna be the schmuck that brings in his car to see that "I just need to tighten down on it"
I have the same issue when I drive the car very hard. I will sometimes get what appears to be small dried up coolant spots around that reservoir and cap. My guess is the O ring is old or failed, but it looks new still. I should probably order a new cap but has not been urgent since it does it very infrequently.
hmm... I haven't been driving my car "hard". Been following the sticker recommendation for my car of keeping it below 4500 and 85 mph for the first 1000 mile break in period. It has been unseasonably warmer here lately, but we're talking low to mid 80's.
Anyways, called my SA and also showed him the pictures. He said I can get it checked in but it might be in for "a couple of weeks". Yikes... just for a leaking reservoir?
hmm... I haven't been driving my car "hard". Been following the sticker recommendation for my car of keeping it below 4500 and 85 mph for the first 1000 mile break in period. It has been unseasonably warmer here lately, but we're talking low to mid 80's.
Anyways, called my SA and also showed him the pictures. He said I can get it checked in but it might be in for "a couple of weeks". Yikes... just for a leaking reservoir?
You're on warranty. Drive it to the Mercedes service department, show the service manager the dried leaked coolant and they should order a new cap for you on the spot (there is a good chance they may have a new one at the garage) at no cost to you. This isn't a work intensive problem – its obvious its leaking.
My guess is that the coolant was slightly overfilled by the dealership you bought the car from. Clean off the residue and drive it for a few days to see if it happens again.
The cap should just screw into place without much effort. It won't feel "tight" when you screw it in all the way.
Most people don't realize it, but the reservoir cap is also a valve/vent that bleeds off excess pressure if the pressure within the cooing circuit gets too high. This usually happens if the car is run really hard (temperature gets high) and/or if the coolant level is overfilled. It can also happen if the circuit was not properly bled of any air bubbles after it's been filled.
I'm willing to be that the coolant level was overfilled from the factory or at the dealership. Nothing to worry about at all except for the mess it can make under the hood. You'll still want the dealership to take a look at it to make sure there isn't anything else wrong.
When cold the correct coolant level should be at the point where in the coolant resevoir the upper plastic inside tube (black) meets the lower inside tube (white.)
Update: went to another dealership, drove up to service and showed them what Chino posted... Tech told me the FL cars already have the newest cap. So he just open the cap a bit since it was still hot, vented some of the coolant, and then rinsed out the engine bay near the radiator. I came back home and new coolant is still seeping out... guess I have to wait for it to boil out some more?
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