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hey everyone Im Cody Im building an 85 gmc s15 its lowered smoothed out , blacked out, riding on some 20" wire rims. I am SOOOOOO close to having my truck on the road. Ive recently replaced both wheel cylinders and one rotten line. I was bleeding the brakes today and the passenger side had tons of pressure while the driver side was ok but not matched to the passenger. No leaks or anything the fluid level was good yet the parking brake light kept coming on. It would go away as we were pumping then when it sat for a minute the light came back. In the process of bleeding the brakes the wheel cylinder I JUST installed blew apart, not sure if that has anything to do with my issue or just my crappy luck. Any guidance is really appreciated I just want to drive my truck!! haha
 

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You replaced both rear wheel cylinders and when bleeding one flows well and the other no so much?

I don't know why that would be, it's a solid metal line between them.

If a new wheel cylinder blows, it's because the shoes were not assembled so that the shoe rests in the wheel cylinder piston. You step on the brakes and the piston moves out but becasue the shoe is not there to stop it, it pops out. That or the brakes are soooo out of adjustment that the wheel cylinder piston pops out. The piston doesn't need to pop out completely, just enough that the seal catches the outer bore of the cylinder.

A brake warning light that won't go out after bleeding means that you were too rough when bleeding and caused the shuttle valve in the proportioning valve to move over and block off a circuit, front or rear. This also means that you can no longer bleed that circuit because the shuttle valve has now closed it off. This shuttle valve is a safety device that when it senses more pressure in the front or rear circuit, it closes of the side with low or no pressure to preserve the remaining brakes. In order to reset this valve you need to now create more pressure in the circuit that had the low pressure. So while bleeding the rear brakes if you hit the brake pedal hard when their was still air in the circuit the shuttle valve would move over and block off the rear brakes and turn the light on. To reset you need to create a "leak" on the front circuit and apply some pressure to the brakes to move the shuttle valve to the middle. Too much pressure and the valve will move past its center position and go to the other side. I crack a line open at the MC on the circuit had have somebody punch the brake pedal once sharply, while the ignition is on. If you get it right the light will go out. It's an art to hit it just right and sometimes you need to play with this for several minutes before you get it.
 
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