I have a '97 Seville STS that had both the left and right rear brake lines fail. I had to replace both lines in the fuel/brake line harness assembly directly under the left rear passenger seat, close to where the brake proportioner valve for the left rear caliper is located, as well as the lines that travel between the two rear wheels; so basically the entire rear brake line assembly. I was having some difficulty bleeding out all of the air in the system, so I did a little research and this is what I found that helped me get all the air out of the system. (BTW I performed most of the repair solo, including the bleeding; but having a second pair of hands would have made the job a bit easier/faster)
**NOTE** If the master cylinder has air in it, than it must be bled first before moving on to anything else in the system.
- Inspect master cylinder reservoir tank for any debris that may have collected in there paying close attention to the main feed port. Mine was gummed up with all kinds of garbage. I used a vacuum pump to drain any remaining fluid left in the tank, and to get out as much of the dirt and grime that had accumulated as possible. Once drained I used my air hose to blow out the remainder (cover opening with a rag before blowing it out) then I used a clean rag to finish wiping it out and to wipe off the outside of the tank.
- Replaced all bleeder valves and wrapped new threads with PTFE [Teflon] tape to ensure a good seal around the caliper housing threads, so as not to suck air while trying to bleed them. (Mine were rusted up beyond salvaging. If able to loosen without rounding off the valves, they should be fine, but I still recommend PTFE tape to ensure a good seal while bleeding)
- Recommended bleeding Sequence:
1st=Left Front
2nd=Right Front
3rd=Left Rear
4th=Right Rear
- Fill reservoir with fresh, unopened DOT 3 brake fluid. Brake fluid absorbs water over time so any fluid that has been sitting, unless still sealed in original container, will absorb water over time, ruining the fluid and increasing the likelihood of having to replace more lines down the road from internal corrosion and higher than normal line pressure caused from the degradation of the fluid; especially on older lines. (don't be cheap)
- With engine off, apply brakes 10-12 times to ensure that any vacuum still left in the system is removed.
**DO NOT** quickly pump breaks in short succession. That can cause the secondary master cylinder piston to engage and travel down the bore, causing the primary piston to have to travel that much further before any kind of pressure can be built up in the primary break circuit, making it very difficult to bleed the brakes after that.
- I use the vacuum pump method to bleed my breaks, but any method works. If attaching clear lines to the end of the bleeder valve, coat the end of the valve with any sort of grease you have available to unsure an air tight seal at the union. This makes identifying any air you see in the clear line leading from the bleeder valve to your holding tank easily distinguishable as air in the line, not air getting sucked in from around a poor seal. If need be, use a small hose clamp or some tie wire twisted around the union to ensure a good seal where there may be some doubt or to prevent accidentally knocking the hose off while loosening/tightening the valve. Bleed until there are no more bubbles present in the line, and then tighten the bleeder valve back up and move on to the next valve.
- After the last line has been bled to satisfaction, check brake pedal for firmness. If the action is still spongy, repeat the bleeding process from the first valve again, going in sequence.
** If concerned, the torque specs. for the bleeder valves are as follows: **
10 ft. lbs., 115 inch lbs. or 13 Nm
**IMPORTANT**
During the bleed, keep the master cylinder reservoir topped off as frequently as possible. Allowing the reservoir to drain below the minimum fluid level line can result in air getting back into the system, requiring you to start all over again from the beginning.
Hopefully that helps. It really just boils down to taking your time and making sure everything is in good working order and that you don't allow more air into the system as you bleed it. If all else fails, get a scan tool and try that. If you still can't figure it out after that, brakes may be out of your depth and you may want to consider taking it in to a local garage to have them look at it. Swallowing some pride is a better alternative to swallowing the bumper of the person in front of you :devil:
