I have a '75 car and the screenwash system looks original . However I no longer have a full size spare tyre mounted to act as a pressure reservoir for the wash bottle.
The bottle has a short rubber hose with a valve fitted ( looks like standard tyre pressure valve that a pump can connect to

So to pressurise the bottle I tried a bicycle pump with a car tyre inflator adapter , and checked result with a tyre pressure gauge - zero pressure .
Dont have a drivers handbook , have a Haynes manual but that does not cover what I need ..

What pressure is it safe to have on the wash bottle ?

Will the wash system still work with unpressurised bottle ?

What should I dismantle and check ?

PS stlll getting wash water onto screen through the screen nozzle jets but flow not strong

OK , I have now done the search to see previous threads on the windscreen washer system! Some horror stories about failed tubing and getting wet laps !

It looks like I have a modified pressurising tube with an end connection that connects to a tyre pump and not to the tyre valve itself .

Also , the reason why a tyre pressure gauge shows zero pressure when connected to this is because there is no back pressure , you need over 28psi back pressure to overcome a non return valve in the reservoir cap and connect hydraulically to the washer reservoir.

I might try connecting my foot pump that has a pressure gauge fitted next time I pressurise the reservoir , rather that a simple hand held bicycle pump

So as it is working and not leaking I will leave it alone . I took it for an annual UK ' Ministry of Transport' inspection yesterday and a working wash-wipe system is needed otherwise the car fails . It worked for that so will try to keep it that way by not using it otherwise !

Pics would help to see what you have. There should be a short piece of tubing from the fill cap on the pressure bottle that ends with a female threaded fitting to accept a standard schrader (tire) valve. That should connect to a long hose that has a male schrader valve that connects to the short hose on one end, and a female fitting to screw onto the valve on the spare tire. The connection on the short hose lets you refill the spare tire without having to dig it out of the trunk. It sounds like someone might have swapped the valve fitting on the short hose to the bottle to allow pressurizing the bottle directly,

The max pressure for the system is ~42-43 psi. I don't think you are going to get good results just pressurizing the bottle without the spare tire connected. It won't hold enough volume. Remember that gas compresses, but liquid doesn't. So when the bottled is full of fluid, there isn't much volume of compressible air and you'll only get a few squirts before the pressure drops. If you can't use a spare, your best bet is to convert the system to electric. A lot of people do that anyway, but that spare tire system is so ridiculously German that I like it

http://www.914world.com/specs/tech_el_washer.php

i'm with bbrock on the original system being so stoopid, its .....just got to be kept.
but sane and rational minds get rid of it. i've kept it. draw your own conclusions about state of mind.

but you got to go right through it, all the hoses to get it back up to speed.
sounds like your missing the line that goes from the short bit off the bottle to the spare tyre. ......and if the hose blows off the steering column - its worse than looking like you pissed your pants because no one has a bladder that big. happened to me about 30 years ago. while i was driving on the freeway. you just got to keep driving and let it finish. the water is cold too. not nice. i can't remember being a baby, but i'm sure it was a more comforting experience doing the real thing.

the original method for ensuring the hoses stay on is fool proof as long as the hoses and rubber bits are all in good unperished condition. a short length of rubber sleeve is used which goes around the hoses where they fit over nipple connections. it can all be remade using replacement sections of hose, including the sleeves. i rebuilt the lot. no pissed pants so far....touch wood. and i have discovered its also stopping at around 28 lbs pressure and not flattening the spare. so i got it all to work again. lots of cleaning out the valves with air guns and soaking in warm water. i also had to replace all the back flow valves in the hoses to the washer jets. you can buy those back flow valves still from porsche.

as i discovered after 31 years of oblivious ownership, thanks to bbrock, you can pump up your spare tyre by disconnecting the two hoses up near the bottle there rather than drag your spare tyre out. boy am i a dumbo. thats the point of why its got the valve and connection up near where you fill the gas tank.

bbrock might be correct about tyre volume making it work, but..........VW did have a version where only the bottle was pressurised. think that was on kombi vans. not sure how that worked. but the bottle was different shape. a slightly different version of the cap and hose is involved.

Won’t work with out the tire providing 40-45 psi to the system. It was designed not to drain the spare if pressure got too low. The full size spare is a safety feature that basically provides an internal bumper that helps to protect you in an accident.
I use rain-x in my Porsche’s and never purposely squirt water on my cars. If the windshield is dirty, mixing the dirt with water and then rubbing on the glass isn’t good.

there is definitely a version not involving the spare tyre.
but its not on the 914.
i'll see if i can dig it up.
i think it may have been on some bugs, but not sure. and for sure on kombis.
it predates the 70s.
but you might be right, it may not have worked too well and they went back to powering off spare tyre. if i remember right, my mother's 64 aus spec bug never had windscreen washers, and the wipers were a joke, so its all academic when it comes to vw windscreen cleaning technology. rain x would just stomp on their afrika korps mechanism.

its possible the germans were forced to invent this crazy system when windscreen washers became part of design regulations.

many years ago i drove my 914 into the driveway of an old german architectural photographer in perth. to get some negs for an exhibition. he waltzed out and opened with, Ja, ve had zoze in afrika. a whole afternoon of rommel stories ensued before we got to the negs. another story. he didn't have a bad word for kubel wagens. he was apparently part of rommel's wildly mobile afrika korps command group. he'd be dead now. he drove a merc, stuttgart taxi variety.

he loved rommel - who wouldn't. he sounded like a real human being.
i doubt he needed his windscreen cleaned.

here you go.

http://1967beetle.com/windshield-washer-system/

the early system with directly pressurised bottle.
it used to sit in the spare wheel, for spatial efficiency, but was not connected to spare wheel. you pumped up both when you checked them each time you filled up with fuel.

i don't think early aus spec beetles (made in australia at that time) had this. more a european spec thing. i might be wrong but i think that early aus assembled/made type 3s had it---- fancier cars, which is where i might have seen it along the way and remembered it. my 72 squareback had the tyre deflater option.

phased out in 67 - spare tyre powered version came after that and is in 914s.

Thanks for this.I figured the bottle would be larger than the 914 version, but it is not. I don't see a fill line. I would think filling only half full with liquid would work best to have enough volume of compressible air to get more than just a few cleanings out of it.

I went through my system and replaced the hoses and the cap. It holds pressure, but the washers are permanently on and can only be stopped by releasing the pressure.

That is caused by a stuck valve on the wiper switch. I bought a replacement valve here: https://www2.cip1.com/ProductDetails.asp?Pr...111%2D953%2D553 Following a great tip from @wonkipop I swapped the little plastic plunger stick from my old valve into the new one to avoid a problem he had with the plunger bending and jamming up the valve. So far, so good.

I have run into problems with the hose that 914Rubber sells leaking when the system is pressurized. You are supposed to put the hose ends in hot water just before pushing onto the fitting so they take a "set," but even using boiling water, mine popped off when the system was pressurized to the max 42 psi. Adding tight fitting shrink tube over the fittings to replicate the reinforcing bands worked to hold and seal the hoses downstream of the bottle that are filled with liquid all the time, but the hose from the spare tire to bottle leak slowly so I have a flat spare after a couple days. I have confirmed that air is seeping out of the hose at the fitting so I now have OEM hose on order from Volkswagen.

Thanks for the tip

Seems like you could rig a 2-liter soda bottle in place of the tire as a pressure reservoir...

yep, its bastard of a job bbrock. i got blisters and burnt the skin off my finger tips doing it. its literally got to be boiling water to do it. i also used the rubber sleeve technique on the stoopid valve on the steering column as well. its holding up. another way you could do the steering column valve connector is with a zip tie. i probably should have done that there as it would have been a lot easier.

the valve at the spare tyre (tire for you yanks) also caused my tyre to empty initially, but i sorted it with lots of warm water soaking and cleaning. there was tiny sand particles in there that were causing the deflation of the tyre, so it was leaking air out regardless of what the bottle valve commanded from the russian front.

as a further tip, the back flow valves will also screw up under combat conditions.
i think the way it works is the early washers which are chrome have the valve incorporated and the later (74 on ?) washer jets which are black use a back flow valve in line in the feed tubes. i have the later jets. you can still buy the back flow valves and you can get them from porsche, not expensive, standard 911 f&ck up part. but if they are stuffed i think the jets won't work at all.

i went right through the system, but i still lost the war. its just such a joke system i laugh every time it dribbles at the windscreen. all part of the joy of reliving the 70s.

not a bad idea...............its a wonder werner von braun got the saturn V to work - more than likely a few sensible americans stepped in on behalf of neil, buzz and mike?

Better would be a portable air canister designed to inflate bicycle tires. The ride air canister holds up to 200psi, is the size of a bicycle water bottle, weighs 1 lb, uses a schrader/car tire valve and cost $35-40


.https://www.bikemag.com/gear/accessories/tools/review-sks-rideair-refillable-air-canister/