I do not think the two problems are related. If you already bled the front brake, you should do the same with the rear ones. Make sure you fill up the reservoir as much as you can in order to get fluid to rear brakes.

For door locks vacuum, in my 300E, the motor is under the rear seat. You have to remove the seat to access it.

__________________
Zorin

'88 Benz 420 SEL
'79 Porsche 911SC ('87 Carrera Engine)
'00 BMW 540 Sports Package
'99 Land Rover Discovery

86 300E - Manual (sold)
88 260E (sold)
84 944 (sold)