Ok back to the facts

- Brakes were worked on 700 mi ago. What was done exactly?

- Which components in the brake system were replaced during this work effort?

- Any evidence of leaking fluid - at the wheels, under body? Brake fluid leaves an oily mark.

- Did your son notice the BRAKE light coming on? It should have activated as the fluid was declining. Unless it was voided all at once when the failure occurred.

- Are the rubber brake hoses at each wheel original?

On my 1998 E300 someone was ham handed replacing the rubber hoses at some point in the past. When I went to change the brake hoses about 2 years ago (proactive replacement), the union nut on the hose end of the brake line was seized to the brake hose fitting. I had to get a replacement steel line from the JY. Fortunately it was the left front so it was easy to change.

I wonder if something like that happened and the tech uttered the famous last words ‘it’ll be fine’...

__________________
The OM 642/722.9 powered family
Still going strong
2014 ML350 Bluetec (wife's DD)
2013 E350 Bluetec (my DD)

both my kids cars went to junkyard in 2023
2008 ML320 CDI (Older son’s DD) fatal transmission failure, water soaked/fried rear SAM, numerous other issues, just too far gone to save (165k miles)
2008 E320 Bluetec (Younger son's DD) injector failed open and diluted oil with diesel, spun main bearings (240k miles)

1998 E300DT sold to TimFreeh
1987 300TD sold to vstech