Windshield washer connections

[Geoman]

Might be a silly question, but would someone explain to me how the two tubes that enter into the windshield washer fluid reservoir relate to each other? I understand how the one tube directs water to the pump when the pump is activated. And the output port/tube from the pump moves water through a 3-way connector on the reservoir cap and then to the sprayers.

My specific question is what is the purpose of the "extra" port/tube on the 3-way connector that goes back into the reservoir? I ask this because I'm redoing the system and when I checked out whether the 3-way connector was clear, it appears that there is NO connection in the fitting between that "port" and the two other openings. Is it a check valve?

[curtisr]

If the 'T' you're referring to is No. 15 in the diagram below it's, I imagine, for the headlight washers found on the 924, 944, etc front Euro bumper. Which, by the way, looks a lot better than the NA spec'd one. And then there's the rear bumper...



Hope this helps.

[Geoman]

Thanks for the reply. The connection I'm referring to is on top of the reservoir tank. See arrow in picture. Why have a third port that enters the reservoir tank? Especially when that third port appears to be blocked off? If it shouldn't be blocked off, then wouldn't that reduce the pressure of the water reaching the sprayers? The washer pump isn't that powerful.

[vintageant]

Geoman - did you ever figure this out? I have exactly the same question!

[onZedge]

OK.

I deal with boiler feed pump systems (among other things) and continuous run pumps always have a recirculation line, with a calibrated orifice fitting, piped back to the feed tank. This is done to ensure a minimum flow through the pump at all times to prevent a dead-headed pump from generating too much heat that would damage seals, and in extreme cases, overheat the pump casing to the point of catastrophic failure.

Relating this concept to the Porsche windshield washer system, the part of the TEE that plugs into the reservoir cap has an orifice restriction to prevent the pump from dead-heading.

This seems like overkill in my opinion as the windshield washer pump only runs dead-headed for very short periods of time.

[vintageant]

Thanks, but as Geoman suggested, wouldn't that actually reduce the pressure being sent to the washer nozzles? Surely some, if not most, fluid is being squirted right back into the reservoir?
My system is set up without this return hose to the reservoir. With a hose connected to the out nozzle of the pump, over the side of the fender, the pump works and water is squirted onto the road. Testing the hose to the washer nozzles with compressed air, there is good air stream from all 4 washer nozzles. Connecting all without that secondary return to the reservoir and the pump whirs away, but no water emerges from the washer nozzles. Physics was never my strong suit!

[acavallo17]

resurrecting this thread - having the same issue. working pump, working when just the pump and hose attached. nothing making to the nozzles. did anyone figure this out?

[originalowner]

The "recirculation" tube, the one going down from the tee, is there in case the nozzles or line are frozen or plugged and no washer fluid can go through them. This prevents the positive displacement pump from hydraulically locking and the motor burning up while you hold the washer lever in the on position wondering why nothing is spraying. Also, it makes it easier for the pump to prime should there be fluid between the tee and the nozzles, which is unlikely. The tube goes down to the fluid to help prevent loss of prime given that the check valves in the system are absolute crap.

[Peter Graham]

Originally Posted by onZedge

OK.
Relating this concept to the Porsche windshield washer system, the part of the TEE that plugs into the reservoir cap has an orifice restriction to prevent the pump from dead-heading.

Makes sense (and agree: overkill).

Originally Posted by acavallo17

resurrecting this thread - having the same issue. working pump, working when just the pump and hose attached. nothing making to the nozzles. did anyone figure this out?

The bypass restriction is missing, allowing all pumped fluid to recirculate to the tank: you need to introduce a restriction/restricting orifice to the return tube. When I bought our 951 and subsequently replaced all the washer lines, I found a zip tie was used to clamp/reduce diameter of the return tube. The amount of the [restriction] fluid bypass will determine how much washer fluid pressure the nozzles see.

Interesting that none of the three PETS I have show the return tube attached to the tee fitting.

Peter

[acavallo17]

Originally Posted by originalowner

The "recirculation" tube, the one going down from the tee, is there in case the nozzles or line are frozen or plugged and no washer fluid can go through them. This prevents the positive displacement pump from hydraulically locking and the motor burning up while you hold the washer lever in the on position wondering why nothing is spraying. Also, it makes it easier for the pump to prime should there be fluid between the tee and the nozzles, which is unlikely. The tube goes down to the fluid to help prevent loss of prime given that the check valves in the system are absolute crap.

ah, makes sense and that hose from the 'T' wasn't there originally either. i'll attach something there and drop it into the tank and retest. thanks for clarifying that, i might take pics of all this if i can get it to work so it's here as a reference in general. thank you!

[acavallo17]

Originally Posted by Peter Graham

Makes sense (and agree: overkill).



The bypass restriction is missing, allowing all pumped fluid to recirculate to the tank: you need to introduce a restriction/restricting orifice to the return tube. When I bought our 951 and subsequently replaced all the washer lines, I found a zip tie was used to clamp/reduce diameter of the return tube. The amount of the [restriction] fluid bypass will determine how much washer fluid pressure the nozzles see.

Interesting that none of the three PETS I have show the return tube attached to the tee fitting.

Peter

more good info and i will be retesting with a hose attached to the 'T' will also check the diameter of the tubing. it was encouraging and frustrating at the same time as we had the motor working and then almost spraying to back to nothing once attached. if we do get it set up and working, pics will be taken so there will be a reference as well. thanks for your info, it helps a lot!