I spent some time working with the brakes today, and found that I have an intermittent combination valve (distribution+proportioning in one assembly). I first noticed that the brake warning light was staying on some of the time, but not all the time. I checked the wiring and the switch operation and both were OK. I then removed the proportioning valve and disassembled it. The shuttle was fitting tight and did not slide very easily, which may explain the intermittent brake light.
So I plan to replace this valve, but want to find out what everybody’s experience is with these brake parts - are you using the OEM distribution block with the separate proportioning valve? Many people complain about these, and even WCCC recommends the adjustable Wilwood version for the PV. Or are you using a combination valve?
Thanks Cougar Bill - I agree with you, and want to keep the car as original as possible, but there is a big quality variation in repro parts so I like to keep my options open.
You’re almost always better off to refurb original stuff than to trust repops.
Or go to the aftermarket adjustable pv. I’ve put a lot of those on restomods and hot rods including twitchy Cobra replicas to resolve the pv issues.
Threads like this make me glad I ditched the power brakes and factory proportioning valve and went with manual brakes from wilwood. Troubleshooting is simple, and The brake work fantastic.
Which booster do you have? I’m most familiar with the Midland type. It requires the push rod extends .98" (1inch is close enough). If the push rod is not extended enough then the brakes never develop the pressure you need. Maybe as a test you could extend the push rod and see how it effects the brakes.
Mine is a Bendix that was rebuilt by Booster Exchange. I assume they set the push rod length, but it would probably be a good idea to verify - thanks for the suggestion.
I still have not resolved this issue - I still have a brake pedal that goes to the floor with the engine on, fairly firm with engine off. Here is a summary of what I have done, many based on your suggestions:
Replaced pads and rotors, verified calipers are on correct side
Rear brakes replaced by PO, appear OK, adjusted them for a slight drag.
Replaced master cylinder (old one had rust)
Booster rebuilt by Booster Exchange (2 times)
Replaced Dist/Prop valve with correct type (PO had a generic version that was frozen)
Flushed all brake lines
Bench bled MC
Bled entire system 3 times. I removed the switch from the distribution block and replaced with the correct bolt to prevent the shuttle from moving during bleed.
Confirmed booster rod length and gap was correct
Verified vacuum at booster (18 inHg)
Verified no leaks in system
Verified booster check valve is OK
Checked all hoses for any signs of collapse.
All the brakes appear to be working, ie with the brakes applied I cannot turn the wheels, but I still do not trust them.
Given that your car has probably been through several owners, you can’t assume anything about whether it has the correct components in the brake system, or anywhere else for that matter. All it takes is one idiot, or even one improperly identified replacement part to mess things up.
I think it is time to measure the bores on both calipers, both wheel cylinders, and the master cylinder. The service manual tells you what the sizes are supposed to be. It sounds like you may have one or more oversized wheel components or an undersized master cylinder.
I don’t know if there are different brake pedals between power and manual brakes on your Cougar. Check that you have the power brake pedal in there. If you have a manual pedal arm, it should have a higher pedal ratio than the power pedal arm has. That will cause you to go closer to the floor for a given amount of brake pressure than you would have with a power arm.
Brake Issue Solved. It ended up being multiple problems: leaking wheel cylinder, mismatched booster and master cylinder (the booster rod has a flat adjusting screw, but the bore of the master cylinder was concave, which caused the rod to bind and bend), but the major issue was that the calipers were reversed and could not be fully bled. I did not think that was an issue at first, because they were labeled and reinstalled the same way they came off, and the bleeders were pointed up, but not back. Interestingly, the PO had just changed the calipers, but never test drove it before it was sold. Like many of you have said, don’t trust the PO! All is fine now, at least with brakes. Thanks for all your help.
Yes, thanks. I think I explained why the calipers were reversed (they were reinstalled in the same positions that they were removed from), so the lesson learned is to always double the check the POs work.
Well meaning but misinformed. They put the calipers in upside down. Current product design would have engineered in a fail safe to keep the parts from so easily being mis installed.
Band aid fixes. The car overheats. So instead of replacing the radiator they buy fans thermostats and new alternators. And the car still over heats because it needs a new radiator.
Short cuts. Power steering leaks. So they remove the entire assembly.
Hot Rod horse power adders. Big cam, stock heads, headers, intake and carb. No improvement in performance, but terrible idle, less torque, and no power brakes.
Add, rear brakes assembled incorrectly. Wrong shoes (swapped front to rear), spring inserted on wrong locations (holes), cable not in guide cause spring wont let it seat, so cable runs behind the guide.
Because that how it was done , so I “just “ redid it, using the pic i took pic on my phone
