You can save even more money if you pull the T-valve apart. Under the red cap there is a small spring and a rubber disk.

I had one with a disk with a hole in it, and another where the disk had turned to goo.

At ozbrick there is instructions on repairing the T-valve with a piece of dishwashing glove. I repaired both of mine and my wife did not even notice the missing glove material.

Both repairs have been working for more than a year.
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3 8s & 2 7s 725,000 miles total