2006 Volvo XC90 Temporary Brake Failure

[maxwelljay]

I have a 2006 XC90 2.5T with 67K miles that runs great. This morning, after a rainy night, i drove about 50 yards and there was a temporary loss of brakes. I pushed down and nothing at all (no ABS, no grinding, etc.) After 3 seconds I got the brakes back and all was normal. This same loss of brakes happened after a car wash 3 weeks ago. I expected it from the carwash, but didn't expect losing the brakes today from just sitting out in the rain overnight. Has anyone else had this problem? Was this just water on the pads/rotors?

[difflock54]

Presumeably the brake pedal travel remains normal when this occurs?
i.e. it doesn't go right to the floor.

[maxwelljay]

When I lost the brakes, the pedal was hard too push, but did go down some (not to the floor).

[difflock54]

Probably is water on the pads / rotors.
Test by running a garden hose down in the cowl vent area and observe where the built in drain outlets actually discharge. They may have outlets under the front wheel arches as opposed to the lower sill board area ?
Given this is a fresh observation you would be wise to have the brakes,especially the power booster checked if it persists.
Also check your brake fluid reservoir is correctly topped up.

[jimmy57]

Turn on ignition but do not start engine . Depress brake several times. You should hear an electric vacuum pump start and run and quit when you stop depressing releasing brake pedal.
When you start the engine and it is cold the engine controls adjust camshaft timing for emissions purposes. This causes the engine to not produce vacuum and the pump must run or you will not have much power brake assist. If you hear the pump and still have hard pedal then more things related to power brake system need inspection.
If the pump is not heard running then the pump system needs to be diagnosed.