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Problem: dragging brakes. I am looking for springs to install on the shaft of Van's brake master cylinder shafts to ensure the brake pedals retract relieving any pressure on the master cylinders after application.
Someone told me Van's old brakes had an external spring on the master cylinders. Can any one help??

I wouldn't think that this was necessary. If you have problems with brakes dragging due to the pedals not retracting I would think that there would be a bigger problem such as geometry or sticking cylinders. Alternatively the pistons in the calipers could be binding which is also a bad thing.

The problem is most likely in the master cylinder geometry. Be sure the master cylinder is mounted in such a way that no side load exists on it's piston rod. Most master cylinders are designed with some kind of mechanism to relieve pressure from the system when the cylinder returns to the top of it's stroke. If anything prevents the cylinder from returning to the top of it's stroke, such as side load on the rod or incorrect distance between the base mount and the rod mount, it cannot relieve pressure. If it can't do that, temperature changes on a hot day might lock up your brakes.
I had the brakes on our Cessna 120 start dragging after I had been on a beach in Washington State. Salt water had started bad corrosion in the caliper bores. I cleaned them up and reassembled the brakes and they were OK. Years later they started leaking fluid at the calipers. I sat the calipers up in a vertical milling machine and bar bored them to .020 oversize, then machined new pistons for them. That was about 15 years ago. they are still working fine.

Bobby S