JPX Posted October 6, 2016 Share Posted October 6, 2016 While inspecting my 96 Legacy's brakes, I discovered that the right rear caliper was not functioning. The slide bolts are in good condition and sufficiently lubed. The piston is fine as well because I could push it smoothly back in the caliper bore easily AFTER I opened the bleeder screw to relieve the pressure. When I tried to bleed the caliper from the reservoir with my power bleeder modification (different post!), I could not force any fluid to that caliper. The rear left caliper bled fine. Troubleshooting so far: - Caliper is clear - can push fluid (and air) through both the bleeder screw hole AND the hose connection. - Rear brake hose is clear - disconnected from the hard line in the rear wheel well and fluid/air flows freely through it both ways. - Hard brake line from rear wheel well to the proportioning valve is clear. When I removed the hard line from the valve, the trapped fluid immediately drained of the rear brake hose. Testing the proportioning valve: - I could readily blow compressed air through the ports for the left side caliper. - I could NOT get any air to flow through the ports for the right side caliper. - Conclusion so far is the valve is not working. Upon disassembling the valve cover, pieces of some type of gasket fell out with some black colored brake fluid. The main gasket for the valve cover was intact and in good shape (probably would have brake fluid leak in engine bay if this particular gasket was bad). I can't find any information about how this particular valve is constructed to operates. It appears that gasket debris was located UNDER the spring. Further, the spring is pressing on one of the plunger buttons - but it is not touching the other button at all. My next step is to remove the spring retaining bolt and seeing what the plungers look like. Anyone have more ideas on how to proceed? (other than the obvious buy a new proportioning valve) Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted October 6, 2016 Share Posted October 6, 2016 It should probably be on both. My guess is something caused port in the the right plunger to clog, pressure built too high and caused it to push the spring off. Proportion valves are actually very simple, it's just impossible to get parts to rebuild them. Take it apart and see what you find, but you'll still have to replace it. Good news is, junkyard is a good option since those almost never fail. Quote Link to comment Share on other sites More sharing options...
JPX Posted October 7, 2016 Author Share Posted October 7, 2016 A friend of mine was cruising Pick N Pull today and grabbed a newer model proportioning valve (without the brass cap). I've installed this to the car today and it seems to be workable. Fluid flows happily through both the left and right channels, I took off the spring from the original valve. The plungers could be moved by hand. But without the mysterious "whatever goes between the two plungers under the spring" part, it is worthless. I am in the middle of bleeding the rest of the system and changing out the pads. Then we'll see how the newer valve works with the system. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted October 7, 2016 Share Posted October 7, 2016 Any idea what model that new valve came from? Different models had different pressure split points, so you may get more or less pressure to the rear brakes. It can be an advantage if you know you want more rear braking pressure. But could also cause easier rear wheel lockup, and subsequent intrusion by the ABS system. Quote Link to comment Share on other sites More sharing options...
JPX Posted October 7, 2016 Author Share Posted October 7, 2016 The new proportioning valve is from a 97 Legacy wagon. I don't have any documentation on the 96 Legacy sedan or the 97 Legacy wagon's valve's pressure points. When I jammed on the brakes during the testing, the ABS kicked in predictably and the car stopped straight and promptly. I could not discern any excessive bias to the rears. Quote Link to comment Share on other sites More sharing options...
JPX Posted October 8, 2016 Author Share Posted October 8, 2016 Here are photos of the 96 brake proportioning valve partially disassembled.....the big spring under the cap is removed with a 12mm nut and a lot of pressure on the spring (similar to taking apart rocker arm springs on heads). Use a small screwdriver to pry out the small circlip. Still wondering what the assembly looks like with the spring mounted properly to address both plungers. Quote Link to comment Share on other sites More sharing options...
Fairtax4me Posted October 8, 2016 Share Posted October 8, 2016 (edited) Split point pressure on 2.2 engine models: Disc brake (w/ABS): 427 psi Drum brake (w/oABS) : 533 psi 2.5 engine models with disc brakes(w/ABS): 533 psi Reduction ratio 0.3:1 for all. These are the same for 95-99 Legacy. Per FSM specs. I'm not sure if there is a difference in the number of or placement of ports on ABS vs Non-ABS proportion valves, so not sure if those are interchangeable. Could you tell if the ports in either of the needle valves were clogged? Edited October 8, 2016 by Fairtax4me Quote Link to comment Share on other sites More sharing options...
JPX Posted October 11, 2016 Author Share Posted October 11, 2016 Both ports were clear. After repositioning the plungers manually without the big spring, it was possible to drive compressed air through each port-set. The tiny plungers at the tips were both fine. Have gone about 80 miles so far and the brake bias seems to be okay. Quote Link to comment Share on other sites More sharing options...
Recommended Posts
Join the conversation
You can post now and register later. If you have an account, sign in now to post with your account.