2017 GLS550 Coolant Leak

[rpaoness]

Pretty significant coolant leak from somewhere near the drivers side bellhousing. I refilled coolant yesterday due a low coolant alarm, and it was down enough to alarm again with only about 30 miles on it. There was coolant on the ground near the drivers door hinge. I looked under the hood and saw no evidence so far of a leak topside. I put it on the lift but haven't been able to pull off the undercladding to get a look at it yet.

[kevm14]

If it's like the w212 there may be a heater hose plastic fitting that goes into the firewall.

[rpaoness]

Pulled the undercladding and still can't seem to find any reasonable source of the leak. There's a ton of heat shielding around the driver's side cat that makes it hard to trace the dripping. Both plastic fittings for what I assume is the heater core seem to be fine/dry. I need to get a pressure test cap that fits the benz overflow tank to assist in troubleshooting. Nothing from my kit seems to fit at all.

[kevm14]

I have this and one of them fit: https://ebay.us/m/DYCws6

[rpaoness]

I wonder where the cap overflow hose dumps out:
https://mbworld.org/forums/gle-class-w1 ... light.html

[kevm14]

It dumps under the tank. If you remove the cap you'll see a passage that just runs under the tank. Is your tank on the back? I did new tanks on mine and had to run a Gates cap (on both cars) to get it to stop leaking.

[rpaoness]

The tank is in the drivers front headlight area. It's a real bummer the kit you linked is out of stock.

[rpaoness]

This one appears to be available:
https://www.ebay.com/itm/127481775797?_ ... 1506.m1851

[kevm14]

Unlikely source of bell housing coolant then ...

[rpaoness]

Unlikely source of bell housing coolant then ...

That was just the region of the floor it was hitting. Looks like it was coming off the backside of the body-mounted cat heat shielding somewhere in that area.