Emanuele Ferry23

One more "odd behaviour" on my 1990 C4...

My windscreen washing system includes "intensive wash" reservoir in the trunk, and it works fine. Therefore sprinklers and piping to reservoir are not stuck. Standard reservoir instead doesn't work properly. Sometimes it pumps water correctly to the sprinklers, sometimes I just hear the pump humming, but I get no water.

I checked the piping diagram on Road&Race collection. My idea is that when I get no water to sprinklers, main reservoir pump is just transferring water from main reservoir to intensive reservoir. This may be due (but it's just an hypothesis) to a bad non-return valve which MUST be present (parts 9 and 10 (?) on R&R downloadable diagram).

Any 964-Guru with an idea?

Thanks All

BGLeduc

Check out John Miles site...there is a tech article on the subject. The check valves can in fact fail.

I can say though that in my case, I had similar behavoir, and I got barely a dribble from the nozzles (the fluid was not being pumped from the main to the intensive tank).

I replaced the main pump, and all was well. Given the time it takes to do it, if you have headlight washers, you might want to buy that pump and replace it too while you are at it.

BGL

DaveK

One easy way to check stuck valves - when mine failed, it meant the water from the "normal" tank went to the intensive wash tank - which overflowed out of the breather hole on the cap. So the carpet around there gets nice and wet.

If you use the normal wash while looking at the intensive wash reservoir you will probably see bubbles in the tank as it's being filled up - if it's the one way valves.

HiWind

Blast from the past I know!
But does anyone know how the intensive wash tank is used? is there another switch/trigger for it or does it work off the wiper stalk too?

Aha found the toggle switch right of steering wheel. Can hear the pump trying to make cleaner come out but nothing comes out of windscreen nozzles.

Water does come out when wiper stalk used to try clean windows (right hole only ie of each of the two windscreen nozzle pairs). Is the left hole perhaps for intensive and the right side for normal?

Does one add the OEM P cleaner fluid to this intensive tank ie in the frunk
or the one next to the petrol cap?

my intensive tank also has some black silicony residue inside - boiling water and vinegar haven't been able to clean it off - any idea what that is? Old cleaner liquid gone bad?
Thanks!

jack.pe

For the OP: it is almost certainly the non return valve to the intensive reservoir. Just put a new one in line.

For the post above.. as far as I am aware the holes in each nozzle are fed by the same pipe ... so two of yours must just be blocked.

HiWind

Thanks Jack - will try dig around for the pipes then test all the electrics ...
Ala this thread ...https://rennlist.com/forums/964-foru...er-wiring.html

Harry Apps

One hose to each nozzle, clean the jets with a pin. The intensive clean switch is a small rocker switch located low on the dash between clock and speedo.

HiWind

Thanks Harry - neat how each nozzle swivels like that.
Seems its the non-return L join getting blocked on the intensive
due to the black silicony buildup in the intensive reservoir.
Going to try petrol tomorrow ie to clean it.

Why is there a non-return? What would happen w/o it?

Harry Apps

You have two reservoirs and pumps supplying common nozzles. Each system has two NRVs to stop the fluid "back-flowing" into the other. Take a look at the PET wiper bit and you get a good diagram of how it all works.

HiWind

Doh! Right! Thanks again
Amazingly post-clean the passenger side nozzles are now super strong and can hit the
Garage roof with water lol ... Useful for bikers with bad road manners

stevepaa

You can always plug the line coming form the intensive washer, then add a new line to a rear nozzle and have a rear washer.