On the vacuum pipe between the brake servo and the vacuum pmp I have a small non return valve. There is a small brown pipe (3mm) leading from this to somewhere in the bowels of the car. Does anyone know what this does cos ive just broken it!!!!
Many thanks

The original vacuum pipe was black with white plastic nipples that support various vacuum systems. Not knowing what body its hard to guess. Presuming you have a 123 body. The lines coming from the nipples are green: A/C, brown: shut-off function, yellow: door locks, black: early cruise control. Also black lines go to trans control on 80 and newer models.

If the line involved is the trans control the nipple has a very important oriface size and you should replace the vacuum pipe. The others can be variously fixed.

Its an 88 300d 6 cylinder. 124 chassis.