A few weeks ago my window washer fluid kept running out. The mechanic told me the tank was cracked. When I took out the tank and filled it, it didn't leak, next I tried the grommets; on around the pump and one covering where the headlamps washer would be if I had the option. I thought it was the small grommet as water was coming out around it(the small grommet has a hole for the pump probe to go in and the pump itself snaps into the side compartment of the plastic washer tank on the outside. I replaced the grommet and even epoxied grommet for a tighter fit. The leak kept coming, from around the back of the grommet. At this point I pulled the hoses off again, there's two that are on top the tank they connect to a coil that cycles antifreeze from the engine through it to heat the washer fluid during the winter so it doesn't freeze. When you disconnect the coil clamp off about 4 inches down each rubber hose or you'll lose and get burned by antifreeze. When I took the tank off and took the pump off I filled the tank keeping my hand over the grommet to not let water out and then I stuck the pump in the hole but kept it up high enough so I could turn it around to see the back. There's an air port so the pump can breath. Water was actually coming out of the port and it shouldn't be; evidently the pump has internal seals that wore out, so the tank and the grommets were fine. Cost of repair less than $50.
Make sure you get VDO pumps, and put the metal heat shield back on the side of the tank. tighten your hose clamps but don't overtighten.

good info. Where did you buy the VDO pump?