Hello fellow volvoites.....
We just got a 2003 S40 with 45k miles.....
looks pretty clean...
maybe needs a tuneup AND....
sometimes the brake pedal is hard to press!
We replaced the brake booster pump.....$65 item... (SCSN Power Brake Booster Vacuum Pump Assembly Part#20804130 20939309)
though that might fix it...guess not...
what else could it be?

 

The booster pump does most of the work after a cold start - once the engine gets up to speed it produces enough vacuum...
does the pedal turn normal after a few miles of driving? any noises when pressing the pedal (like air leaking in the booster diaphram?)

If I recall correctly there's also a check valve in one of the vacuum lines to the booster from the engine and aux pump which may be in play here..

 

hello, thanks for replying!
#1-well...let's see.....good question - does the pedal turn normal after a few miles of driving?.........I need to confirm this...
right now...my wife is scared to drive it because the pedal is hard when shes backing up the car and she has to press the pedal kinda hard for her.
#2 - no real noises on the pedal...
#3 - Aux pump?...another pump? ...is there another pump?.......I think I have seen this check valve thingy - maybe this part is the problem - see below:

 

aux pump = the vacuum pump. its job is to maintain sufficient vacuum when the engine doesn't. You can hear it on a cold start. Try this - first start in the morning, start the car and listen to the idle. You may hear a subtle "vrrrt vrrrt" sound (like a few seconds on, then off then on again). That's the vaccuum pump. When my car had a hard pedal at start up, it was the part in your pic...

 

thanks for replying!...
so I will buy that switch thing...!

 

It would make a lot of sense to check that the engine is actually making sufficient vacuum itself, without the help of the booster pump (I read that the car "needs a tune-up", which could point to a vacuum leak). The auxiliary pump should make sufficient vacuum, but there could be a bad vacuum line and/or valve in the system that allows the vacuum leak to affect the vacuum getting to the brake master cylinder booster. Listen REALLY close for a vacuum leak (they can be hard to find - I like to use a piece of hose to my ear to localize the sound). Better, get a high-spec scanner (I recommend the Torque (free) or Torque Pro (cheap) app and a $10-15 Bluetooth "dongle", which will let you monitor the vacuum and dozens of other valuable things, not to mention read and reset OBD codes, and create a custom "dashboard" that is really handy).

 

interesting!!!!