Ironfistt

My wife has a very slow coolant leak in her 2014 ML350. Every 1-2 months the warning light comes on and I top off the reservoir. Looking around the engine bay, I think I found where it maybe occurring (pics below). Can someone confirm this is a coolant line? If so, is there some gasket or oring that needs to be replaced to get rid of the leak? Lastly, any other common areas I should check for leaks?

thanks!

CaliBenzDriver

that could well be it! Your pictures shows deposits and wetness...

This coolant line carries the heat exchanged with the engine oil to thermostat.
I am going to guess you should change your oil more often to keep better qualities.

Try 4 or 5kMi "approved oil" service. Old oil makes the engine extra hot. Also your wife may drive too gently to trigger piston coolers limited to above 3500.RPM.

The CAP of the expansion tank can leak coolant out due to high pressures.

kalali

Check the coolant hose that go into firewall behind oil dipstick. I have similar problem, very slow leak. Top off and 3,4 months later Coolant light come on. Last time i see some wetness on that area, Turn out the plastic connector was degraded, breaking apart when touch.

Ironfistt

If that is the leak, any idea if there’s an oring or some other gasket I need to get?

the wife does drive pretty gently and I’ve been changing the oil myself when the service light comes on. I guess I can change more often but I don’t think it’s going to help given it’s already leaking.

Lastly, I’m fairly certain the cap isn’t leaking

thanks!

Ironfistt

I’ll try to check it in the morning when I have some daylight

CaliBenzDriver

Unfortunately MB does not sell this O-Ring separately, only complete pipe down to oil exchanger.

I just got down searching for this seal.

Ironfistt

you don’t by chance have a part number do you? I guess worst case I can pull the oring, measure it and get a new one from McMaster.

Ironfistt

I checked and luckily that looks fine. Looks like a pita to get to