WARNING: This page is about a different car, the 2003 Suzuki XL-7 and 2003 Suzuki Grand Vitara. However, it is still accessible from the selected car via links, so may be relevant.
Check sliding surfaces of each part for wear and damage. If any defect is found, replace pump assembly.
Fig 1: Checking Pump Body, Cover, Side Plate & Shaft Sliding Surfaces Of For Wear & Damage