+1 on the pump up the pressure test

John and I had just got the 300TD system together, we put the tester on it and it was slowly bleeding down.

Looked under car saw a steady drip looks like from the evap drain. Oh no.

upon closer inspection it turned out to be the aux water pump (it's on the driver side under the washer tank on a 87 300TD).

We had just replaced the aux pump with one from a p-n-p. We took the housing off to check the condition of the impeller. When we put it together the o ring was not in the right spot.

Put it back together right and she is all good now. I was sweating it thinking I would be tearing out the dash again.

__________________
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