Thanks for the great post. It really helped
I wanted to add my experience so that others can benefit just as I did. (Proceed at your own risk, no responsibilities are taken here)
Problem: Car is leaking the windshield fluid overnight when the Prestone Windshield De-Icer Washer Fluid gallon is used. I didn't even know where to start. But one at a time. I read on other threads that the water pump might leak at the weep hole (a small opening on the pump for atmospheric pressure regulation) or it might be the tank itself has a hole so I cleaned up the area and left it over night with new gallon of Prestone De-Icer and the next day I found the fluid on the garage floor sitting there mocking me. I knew it was not leaking from there because the fluid I used is yellow and no yellow line came from mentioned areas. I said it has to be the washer that the water pumps plugs into is either leaking from the water pump insert or the from the washers contact with the tank, so I put some Teflon tape(a lot of Teflon tape--Teflon tape is a white tape that is used to seal up water leakage in a pipe used by plumbers) around the water pump insert and on the washer insert as well and forcefully inserted the washer into the tank and super glued it just to make sure no leaker and then I inserted the water pump with the Teflon on it into the washer. ( please make sure not to put Teflon tape on the opening of the water pump because it will block and kill the pump very quickly not to mention you will not get any water on your windshield).
anyway, after doing that and leaving the car all night with a new Prestone De-Icer and the next day I found it on the garage floor sitting there mocking me again (I had to leave it over night because its a slow process of water leakage). afterwards I was just frustrated then while working I noticed that a previously clean area was somewhat wet so I followed the barely wet line and found the problem it was a stincken hose that connected the windshield line from the car to the pump, and over time of seven years it seems to have been enlarged, so every time I hooked and unhooked the pump I was making it worse so I just cut a piece of the hose( not too much or you will run out) and inserted it into the pump and left it overnight and viola the problem was solved.
New Problem: next day the tank was full and no leaks whatsoever. But when every I told my girlfriend to press the lever to get the pump going I hear the pump working but no water is coming out. So after chewing on the problem for little while I remembered (being an engineer and all) that air must have gotten into the pump and cavitation is occurring. What happens is water is sucked in but cannot leave or it leaves very slowly due to the existing of air bubbles that the pump is spinning instead of water so need to clear this problem.
Solution: while the pump is attached to a full tank and all electrical wiring is attached unhook the hose from the pump line (you know the hose that connects the cars windshield washer to the pump) insert a hose of similar dimension and have it pointing away from the engine tell a friend or preferably a girlfriend to pull the lever to get the pump going. At first pressure will be little and little water will come out but after a second the waster bubbles will come out along with a strong jet of water, now you have no water bubble that can cause cavation. Carefully unplug the hose from the pump. Place your hands on the pump hole then put the cars windshield washer line quickly into the pump. And you are done. Everything should work.
Now you might ask now wait why not just connect the cars line in the first place and just press the lever to get the pump going, you would think that I the pump will take water from the tank and expel the bubbles through the washer jets, but actually the pressure restriction inside the hose of the car is much greater than the pump can overcome ( this only true when water bubbles are present ) so that's why you had to do the separate hose to allow for true atmospheric pressure to help the pump expel the bubbles and operate at pristine order.
Finally after 3 days without any problems, i left my car over night and the problem came back with all of the fluid on the ground. So i went and bought a autozone pump and conected the red and blue wire to the brown BMW wire and the other wire of the pump to the black BMW wire. the pump worked but it was not as powerful as the BMW one made by Siemens VDO so i returned it and will bought the original one from BAVAUTO for 37.95.
Last edited by almoula; 12-30-2008 at 10:24 AM.