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ianc's Avatar
 
Join Date: Dec 2004
Location: Novato, CA
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Windshield Washer Question

Good day Gentlemen,

Perhaps someone could give me some insight to the windshield washers. It seems to me that the way these should work is that you pull the washer switch back, the squirters squirt water on the windshield to lubricate it, then the wipers make 3 or 4 passes, and hey presto, hopefully your windshield is a little cleaner.

The way it works in mine is I pull the wiper switch back, the wipers grind along my unlubricated windshield, and after a bit, the pump manages to fill the supply lines to the squirters enough to dribble a bit of water out. Too late.

The problem is that the water is not staying in the lines, but tends to run back down to the reservoir. Here's a little diagram of the way mine seems to be plumbed:



The pump pushes water up the supply line, but there is a tee in the line that returns back to the reservoir. I assume the function of this is to prevent the positive displacement pump from bursting the lines if there's too much resistance in flow to the squirters for whatever reason. I've replaced the check valves, and even added one just upstream of the pump, but there is nothing to prevent the water in the lines from running back down to the reservoir through the return line. I can see it draining right out after I turn off the pump.

In order to prevent scratching the windshield, water needs to be maintained in the lines all the way up to the squirters, but I can't see a way to do that. A check valve in the return line would of course prevent it from doing its job.

What am I missing here, and why do I seem to be the only one to have this problem? Thanks for any insight,

ianc

Old 04-17-2005, 12:20 PM
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I just replaced my pump and tuned up my washers on a 1980 I didn,t see a return line Perhaps it is for the headlight washers that I never had. Plug the return T and leave one hose loosely attached if you are worried about overpressure. I wouldn,t worry myself as I don,t see any reason for Porsche to install a squiter pump capable of causing pressure damage to the system.
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Old 04-17-2005, 03:28 PM
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What year car? Do you have the intensive cleaning tank on yours? I found when repairing mine I had one bad check valve. That made all the difference. I don’t think they are only check valves but I they allow the system to build pressure then release. If you have the intensive cleaning system you will have 4 check valves and the system sort of loops around.

Craig
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Old 04-17-2005, 03:53 PM
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Ian

My system is identical to your drawing. Maybe the bypass drains the lines to prevent freezing the lines in winter if your ww anti-freeze is too dilute???? Germany is a northern country . . .

Ian
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Old 04-17-2005, 04:36 PM
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Hi gents,

Thanks for the suggestions. I'm almost thinking of something like this configuration now:



The added check valve at the return tee would still let water through back to the reservoir in an over-pressure situation, but the little spring and rubber valve inside might make it act like a pressure relief valve in this circumstance too. Hopefully the force wanting to gravity feed that much water back through the return line will not be enough to cause it to open. The second L-shaped check valve near the reservoir will ensure that the pump has a good feed to start.

Gotta order me a couple of these, but Sonnen sucks for the small stuff...

ianc
Old 04-17-2005, 07:49 PM
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Let us know how it works . . .

Ian
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Old 04-17-2005, 08:01 PM
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There is already a check valve at the foot of the suction tube in the tank on mine. Istill don,t understand why the worry about overpressure on the system . They are only washer hoses operating at only a few PSI and will easily separate and reconnect at all the connections anyway.The rotary pump on mine is not a positive displacement pump like a piston pump would be .

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Last edited by johnsjmc; 04-18-2005 at 01:54 PM..
Old 04-18-2005, 01:51 PM
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