On newer Vectras 02- there is a filter which gets blocked, especially if you use screen washer fluid!!.
If yours is a newer car, the washer bottle sits in front of the passenger side front wheel.
Turn steering to max right.
Using a torx drive remove the 3 or 4 bolts that hold the wheel arch liner to the front of the wheel arch.
You will see the washer bottle.
Lift the motor up, its just interference fit.
You will see what looks like a black washer on the bottle where the motor came out of.
Caution: when you carry out the next step, all of the water thats in the bottle will come out!!!
Gently prise this up with a flat bladed screwdriver, its abot 2 cm long into the bottle.
This is a micro filter, just wash in clean water and all the gunge will come off.
Rebuild
Les Jones, January 2008