2005 s60 R brake pedal hard to push only when driving slow

[dna316]

Hi all,

So I have had this problem for about a year now. The car will "loose brakes" from time to time. It used to happen only once every 2 months or so, now it happens 1 to 2 times a month, While pulling out of the drive way mostly. A few times I was pulling into the parking spot at a local grocery store and the brake pedal gets really hard to push, I can still stop but its really hard to push the brake pedal.

Thankfully it has never done this at speed, only when going really slow. I thought maybe it was only when I first started the car but no thats not the case, it will do it after driving for a while also. Thankfully it only does it as slow speeds.
Im hoping its a module or relay... Any thoughts on what to check for??

Thanks in advance

[rmmagow]

Power brakes are run via engine vacuum. The power brake vacuum unit has a fairly biggish line leading to a source of vacuum. It might be leaking/cracked. You should eventually get some kind of lean running engine code at some point. The power brake unit itself may be failing. Get it looked at as this can eventually affect your brakes all the time. Good test, car off, press hard on the brake pedal a few times to bleed off vacuum, press hard and hold the pedal down and start the engine. The brake pedal should drop down some, few inches as the vacuum comes back. If not, you need to look for air leaks etc. Have it checked out.

[jimmy57]

That car has an electric vacuum pump to assure adequate vacuum for brake booster. The switches do have issues and the pumps can fail (usually due to switch sticking and keeping pump on too long).
Turn on ignition w/o starting engine. Pump brake pedal. By third brake pedal push the pump should run and is loud enough to be heard.