[glgrumpy]

Are they leaking or just weak pressure?? Sometimes bypass valves can get gunky and sticky and not seat, thusly letting pressure slip by and not working correct. That valve is usually under an acorn nut/cap and can come off easy. Have to watch for the spring and any little contact pieces that will want to come out when cap is realeased. O-rings or seals on it maybe too, but many times just a tapered pin that sets into a machined hole, all polished and smooth of course. If yours are leaking, then tear-down to new seals is needed. The idea of twin valves and a "Joystick" might be good if mounted out in air, not enclosed in a body. If you had to have rebuilt by someone else, bet new valves would cost about same as having shop do your old ones.

 

[glgrumpy]

That bolt is the item you turn to change the pressure you wish to release at. Usually a locknut or some resistance to keep in place. Only way to check pressure after adjust is put back together and use gauge in system, then tear all down again and re-adjust if not right. Spring strength also involved in this.

 

[glgrumpy]

Is there NO hole in the inner works to screw that bolt into then?? Is there a brand on the valve? Might have to see if any manuals maybe on-line.