I have just replaced all hoses and made my windshield washer system work, using the air pressure from spare tire. I realize I could have replaced windshield washer with the electric pump kit, but I liked the idea of going back to the original system. The one problem that I have is that the spare tire loses too much air pressure. It will go down until almost flat.

My understanding is that there is a “shut off valve” that limits how low tire pressure can be reduced (29 psi, I think). My question is, where is this valve located? My guess is that it’s in the reservoir cap.

My apology if this has already been discussed in another thread, but I did a search and could not find info.
Thanks
PDXBob
1975 914

Click to view attachment

I also have a strange affinity for the pressure fed system but have had similar problems. It is the ONLY thing I don't have working after my resto. I replaced all the hoses, but I cannot find a hose that can hold the pressure between the spare tire and the bottle. Try spraying all of the fittings from your spare tire to the bottle with soapy water and see if any of yours are seeping air. Mine were slowly seeping so after about 3 days, my spare tire was flat. Note that the check valve to keep the tire from going flat is in the cap for the bottle, so any leakage before the cap will result in a flat tire. I've had no problems with leaks downstream of the water bottle; only the run from the tire to bottle. That's probably because downstream of the bottle is filled with liquid that seals better.

My main leak was the screw-on fitting to the schrader valve on the tire. I replaced that with this one from amazon. That fixed the main leak but air was still slowly seeping around the hoses at all fittings. The hose I bought is supposed to heat set by soaking in hot water before installing. I even tried boiling water, but the hose is just too soft to hold 42 psi. The factory installed rubber bands at the fittings to reinforce them, but they are NLA. I tried heat shrink instead, but no luck. I also bought a length of OEM hose from Volkswagen but instead of the 2m length in the product description, it came as a short 2 ft. piece that was worthless to me. That's when I got frustrated and set the project aside.

I'd like to find the proper hose that fits tight on the fittings and can withstand the pressure, but so far have had no luck. There is a website that lists some sources, but they are out of date and I haven't been able to source the same hose. I guess the other option is to figure out some kind of clamp to squeeze the hose tight to the barb fittings. Simple twisted wire might work, but would look like

I don't think this helps you any, but that's where I am in my quest to get the quirky washer mechanism functioning again.

Thanks to both of you for the helpful responses. I think I’ll replace the reservoir cap and then continue to hunt for leaks. I know kind of futile, but a pretty simple project- for once!
PDXBob

Mine did this as well, I fill the spare then put the hose on the tire valve then take it off the tire and the pressure in the bottle lasts months without being connected to the tire
zac

Please let me know where you find the cap.

Not sure this is exactly the same, but if they used a VW part this most likely is it.
I don't have one to compare to the picture,

Click to view attachment

I think the one in Gandalf’s picture is the correct one. I think I’ll buy and see if this solves the problem.
PDXBob

The tube assembly posted above doesn't appear nearly long enough to serve in the 914 spare tire position.

That's an intermediate connector. Yes?

It connects (at least on a 914) to another schrader valve near the bottle which, in turn, is connected to the tire. I think the purpose is to let you re-inflate the spare tire without having to pull the frunk floor board out (and whatever luggage is on it). I haven't been able to find a length of that correct hose long enough to reach from the intermediate connector to the tire.

I think I'll try some of these to clamp the hose I have onto the fittings. Not CW, but hopefully will function while looking like they might belong there.
https://www.amazon.com/gp/product/B0892NW4V...RVLL3&psc=1