2001 XC70 Why Check Valve Before The Wiper Holes?

[Oka]

Hello folks. Need some education on the need for a check valve at the "T" hoses to the headlight washers.
The line comes out of the pump to a "T". The straight line goes to the windshield and the right-angled line goes to another "T" check valve that splits to the two headlight wipers.

Why a check valve and why not just a "T" connector? The fluid pressure there won't be that much for fluid to flow back to need a 'checking' process.

[abscate]

Is there a check valve on the windshield line ? If nit, I would guess they got switched by PO

Otherwise, its quirky swede engineering, or a nice way to give you a spare check valve.

[shiloh51933]

Hello folks. Need some education on the need for a check valve at the "T" hoses to the headlight washers.
The line comes out of the pump to a "T". The straight line goes to the windshield and the right-angled line goes to another "T" check valve that splits to the two headlight wipers.

Why a check valve and why not just a "T" connector? The fluid pressure there won't be that much for fluid to flow back to need a 'checking' process.

I would think they placed a check valve there because headlight squirts are lower than washer fluid reservoir, they would probably gravity bleed out until either fluid is out or at same height. I would also say that it's probably a one way check valve to keep fluid right there at the ready to squirt when command is given, otherwise it would take a minute for washer fluid to get there. There are "T" style check valves and built in check valves for windshield squirters

[draser]

Do the headlight squirters work off the same switch, or separate switch?

[Oka]

Is there a check valve on the windshield line ? If nit, I would guess they got switched by PO

Otherwise, its quirky swede engineering, or a nice way to give you a spare check valve.

Nope! The hose comes from the pump, to a "T". The direct line goes to the windshield and the perpendicular one goes to the check valve which goes to the headlight wipers.

[Oka]

Do the headlight squirters work off the same switch, or separate switch?

The headlight squirters has their own switch on the steering column but from the same pump with the windshield washer.

[abscate]

It would sense for the windshield hose to have a check valve, preventing run back, but the headlight hose to have a pressure valve - requiring positive pressure on the valve to open, to prevent gravity draining of the headlight washer. Are the part numbers on the two valves identical or could they be different?

[draser]

Then it sounds like you'll need a check valve so you won't have windshield and headlights sprayed at the same time.

[Oka]

It would sense for the windshield hose to have a check valve, preventing run back, but the headlight hose to have a pressure valve - requiring positive pressure on the valve to open, to prevent gravity draining of the headlight washer. Are the part numbers on the two valves identical or could they be different?

No, there is only one check valve which is located just about one foot and half from the fluid pump.
The line goes from one pump to a "T". The straight direction on the "T" goes to the windshield and the perpendicular line then goes to the "T" check valve splits to both head light wipers.

[benrk]

There is no seperate switch for the headlight washers, they come on with the windshield washers & the reservoir sits in the bumper below the right headlight (on left hand drive vehicles anyways) no gravity drain possible.
The idea of having check valves to prevent the entire line from draining back into the reservoir sounds most plausible to me, I haven't yet tried on my Volvo, but on other cars it took quite a while for the windshield washers to start squirting again after completely draining & refilling the reservoir.