With the nice people on this board, I was able to locate the check valve and fixed mine.

It's very difficult to get to the check valve. In fact, you can't see it without a mirror. It's between the upper and lower rigth-hand-side radiator hoses. Yes, follow the hose from reservoir and you'll notice it disappears into that area.

(1) You'll need to unplug the right-hand size spray hose from the headlight wiper (to give you some room to remove the check valve)

(2) Unclipping the check valve from the bumper(?) is no easy job (it took me quite sometimes to study it upside down with a mirrored image. I ended up holding the clip open with my right hand (from the front of the car) and pull the hose toward rear of the car using my left hand. It's an easy job from this point on.

If I have to do it again, it'll probably take me 10 minutes only. But it took me about 2 hours and a lot of bruised up knuckles and I almost gave up.

Good luck!

You can buy a new valve. But I'm cheap. I just opened it up, cleaned it up (the problem is always the broken piece of rubber in there), remove the spring, and super glued the the otherpiece upside down so that the tiny hole on top is completely blocked. I'm confident that this fix will work for the lifetime.

I believe the rubber is there only to prevent back-flow of the fluid (or other junk). I think the engineers worry too much. Why can't they just make it like my Buick where there's no nut to tighten or check valve to replace?