V40 intermittent brake problem

The service dept must be staffed with morons. I had exactly the same thing happen with my 01 S40 and it was a leaky vacuum hose to the booster or the device that maintains a vacuum for the booster. What happens is the leak bleeds off the vacuum overnight (at least that's how it was in my case) so in the morning - no power brakes. Letting the engine run for a while before taking off will get the system working again. Since this is a slow leak, it is unlikely that it will fail suddenly. Since this is Volvo, the fix wasn't as simple as a mere hose replacement but rather some vacuum brake system assemby. I might be wrong about this as I don't have the repair ticket available right now but there may be a Volvo Technical Service Bulletin on this.

I think that you've solved the mystery! I now realize that it happens if I start driving immediately after starting the engine. Hopefully now I could reproduce it at the dealership.

I am surprised that Volvo service didn't know this. Car is still under warranty and they are probably not too keen on doing repairs. It's just too bad that their profit considerations taking over the safety concerns.

Thanks.

I take my S40 to an independent shop and he didn't have any problem identifying the problem. You'll probably need to leave it overnight so they can see for themselves what's wrong. I took the precaution of putting a note in plain view that the power brakes don't work just so the tech doesn't drive it into a wall expecting it to stop normally!