Last time with Mazda i used Hella UP28, SC-VP-Hella-UP28-Vacuum-Pump-Technical-Information auxilliary vacuum pump a lot of cars use to assisst with brake servo. It was not meant to be in permanent operation, it needs a vacuum switch and check valve. Also Peugeot 406 has larger brake cylinder bellows that pump must evacuate.
I decided to get a larger Hella UP30 vacuum pump. It is fully capable to assist Pug cylinder and provides powered braking 3 times before evacuating.
I used 30A relay to trigger pump operation according to this schematic.
I made a small mount so pump is suspended on its rubber mounts. I decided to mount it inside the central tunnel for easy acces in case replacement would be neccessary. It is after all a part of a critical system.
To the system i added one check valve. It fights the outside pressure and keeps the “vacuum in”. I tried different check valves and i decided that here are the best/easiest to use variants. I use 10mm hose that fits directly to the cylinder bellows.
I installed Volvo XC90 switch P/N 30645383 or 31400608.
Connector is Bosch of some variant…
One line goes to GND and the other one connects to the relay which is powered by fused 12V on the other side.
It has 3 ports. Each port has its own non-return valve. Two ports (1, 2 from leftmost going CCW) were setup for underpressure flow and one (3) is setup for overpressure flow. This lets me connect the hose directly to 1 and 3 with one port (2) in the air.
You can see the 1 port is connected to the pump with 3 port going to the cylinder booster.
For the hose i used blue gas hose since it has double sleeves.
Volvo vacuum switch is definitely worth using. Not only it has a good reliable sensor it also has one way valves built in. Essentially it is a plug and play item. I highly recommend it.