I have a 1989 F-800 with the Lucas Girling brake system. The line that comes out of the hydromax into the Hydraulic relay is building up too much pressure I believe. I put a new line on it that was rated at 315 PSI and it started to bubble out of the side like it was about to blow. I then went back to the park store and got a higher rated psi hydraulic hose. After running for 15 minutes with the parking brake on it, blew the line off. Since it's a stronger line a normal hose clamp would not hold it. I went and got a better hose clamp put on it and it appears to be holding now but still believe it is building up too much pressure. I've took off all the lines and made sure none were stopped up or collapsing. Then made sure the electric pump wasn't running while the engine was running. I'm stumped. The brakes will pump off back Brakes when the emergency brake is off but it is making a constant straining or whistling nose when the E brake is off. If you press the brake hard the sound will stop until you let your foot off the brake. If you put the parking brake back on the whistling sound will stop. I might add that this truck has been sitting for 7 years. I've had to change the 2 back parking cylinders due to leaking but they are fixed now. Everything is working properly except the brake issue. Any ideas?