Take the pad off the bottom of your hood. You just need to turn the fastners 90 degrees to remove them. Try not to drop them. Having a helper is VERY handy.

Where the hose splits from one to two there is a tee with a check valve in it.

Try the washer to see where it is leaking. If the leak is in the check valve, it is probably a bad check valve.

You can remove the check valve and take it apart - the only things in there are a small spring and a round rubber flap. Usually the flap is torn or has melted into a gooey substance.

If the flap is bad you can fashion a flap out of thin rubber, I used a piece of dishwashing glove as suggested at ozbrick, and the valve will probably work great.

My washers worked better than they ever had.
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2 8s & 2 7s 600,000 miles total