Despite my best efforts, my brakes still don't feel right. I've been working on cars and brakes since my teens and now at over 50 years old, I simply am out of ideas as to how to improve these things.

My problem is that it seems that my pedal has to move further (is lower) than normal before the brakes come on and even when they do, they don't feel as hard and firm as I would expect. I've done a search and didnt' find any thing specific to this type of problem. The brakes work and stop the car, they just don't seem to be firm and I doubt I could lock up the brakes and the pedal seems to need to be depressed more than I would expect.

So far I have installed/tried:
1. new front pads, rotors, brake lines (Russell SS braided)

2. new rear drums, shoes, all new brake hardware and Russell line to the rear

3. new master cylinder- yes I did bench bleed this puppy. I made sure the cylinder was absolutely level and locked in a vise. I tapped the housing to dislodge any air bubbles and kept bleeding it until all the bubbles were out and continued even after the fluid was bubble free.

4. Bleeding- wow here's where the fun really started. I've gravity bled them, pressure bled them at a professional shop, pressure bled them an home with a pressure bleeding kit, regravity bled them, did the old fashioned method (open valve, depress pedal, close valve, let pedal come back up) and since I've had so much fun bleeding the heck out of them, I even installed Russell speed bleeders just so I could enjoy this fun all by myself and bled them again! The amount of fluid bled through this system is measured in quarts... I've lost tack of how many quart containers I've gone through. Trust me when I say, there is no air in these lines!

5. Adjusted the rear brakes so there is a light drag. I know that the pedal will be low if they are loose.

6. All lines have been inspected and are in good shape and tight.


I've done a ton of brake jobs over my life and have never encountered anything like this before. Anyone else ever run up against this? Maybe this is just a characteristic of this type of vehicle? I've heard at a local shop that many customers with these cars have had similar problems, but I find that hard to believe. I have never heard of a proportioning valve/metering block going bad, but it's just about the only thing in the system that hasn't been replaced. Any suggestions are deeply appreciated. Thanks in advance.

Brad
The perplexed one

 

If the flex lines have never been replaced, or are at least 5+ years old, that might be the problem. Just because they look good on the outside and don't leak, doesn't mean they are good. I replaced mine, 3 lines total for my year and the front brakes improved dramatically. Also, it's a good idea to check all the vacuum lines and the brake booster itself. I know leaving a certain vacuum line off caused my brakes to become full manual brakes. Not exactly your problem, but there's more to the brakes than just the calipers/pads/lines/master cylinder.

 

The flex lines are new as of a few months ago. I'll check the vacuume lines again, but I had checked them earlier. Thanks for the reply. This one has me really stumped. I've never had such trouble getting a decent pedal feel on a car before. I appreciate the suggestions, thanks!
Brad

 

I don't know all that much about them, but what about your proportioning valve? Has that been checked? Just another suggestion since the lines are new.

 

Well here is my 2cents. I have seen this but it was about 15 years ago and the problem was exactly what you described. I am not saying this is what is wrong with your car but it is a possibility.

I had a customers car that we replaced the master cylinder on. The bore size on the master was 1/16" larger which made the pedal much lower. It looked exactly like the master that we took off the car but had a different size bore. If your really trying to fix your car, I would pull off the master cylinder and measure the bore size with a set of calipers. Go to one of the local auto parts places and have them look up in the BOOK not on the computer and see what the bore size should be. I have also read about this in service books. Usually it is when a rebuilt master is used.

Good luck and let us know.

 

Hmmmm... that is very interesting! I had never thought of that! The master is a brand new unit that they did look up on the computer. I am wondering if they could have sold me one with the wrong bore diameter. I'll have to check my factory service manual and see if it has a bore specified in it. The only thing that I have ever run into that feels like this is air in the lines, but I will guarantee that there is no way that is true in this case. I've done way too many brake jobs over the last 30+ years. It has to be something else and the brake master cylinder bore diameter being wrong may just be the solution. Thank you very much for the advice and I will be checking that on my next day off!

Brad