As I mentioned a few days ago, I built a pressure bleeder for $20 worth of Lowes parts. Today, I used it and it worked! I put it on and pumped it up to around 15psi, cranked up one corner of the car, pulled the wheel, turned the bleeder valve and - viola! - crappy brake fluid came out.

Now that it's all changed out, the pedal feel is still soggy as hell. Plus: the fluid that I drained was a yellow/tan. Based on a couple other threads I found, it sounds like it's time for a new master cylinder?

It looks like a new one runs $250 or more. Summit Racing carries a remanufactured master cylinder. Does anyone have experience with them?

Also, I found this guide for doing the job. Is that pretty much it, or is there a better reference I can use?

Thanks for the help!

 

Where you careful not to run the fluid out of the res and put air into the system?

 

Affirmative. I ran fluid though until I could see the color change as the new fluid came out, and the reservoir was overfull when I pulled the cap.

 

Get in the car (do not start the engine) and firmly press and fully release the brake pedal 12 - 15 times. Release the pedal, and sit there for a few minutes. Press the pedal - Firm? Soft? How high?

Hold the pedal down with moderate pressure, and start the engine - the pedal should sink and get softer. Release it and wait a couple of minutes. Press the pedal - Firm? Soft? How high? It is normal for it to now be softer and lower...

 

Before starting the car, the pedal is firm and high. After starting, it is very soft and all the way down. I've driven it around the block and I can't 'panic stop'. That is: I can't lock up the wheels.

 

You probably still have air as that is normally the cause of sponginess. I had a heck of a time getting mine bled. The bias valve kept messing with me.

When my MC went it would start to grab then fade to the floor with no braking. It was fine for "soft" stops but would fail on "panic" stops; then it got worse and worse. MC failure is usually rust and pitting causing seal damage/blow by and a complete loss of pedal rather than sponginess.

 

Sounds to me too like air in the system.

Was it good before?
Did you bleed the MC too?
This should always be done first I think.

 

Okay, no, I didn't bleed the MC. Found this post:I'll give it a try.

 

This car is notorious for trapping air. Bleed the master, your symptoms, although similar in some ways to master problems, sound more like trapped air.
You may have to bleed the whole system again.

 

If this is an old MC and you dont have any improvement after a rebleed replace the MC
Dont buy a rebuilt part get new,
Roger has great prices
Use ATE fluid Roger has it

 

Thanks, Stan.

 

Shawn--

What year is your car? (it's acceptable to put that info in your signature, btw )

On my '89 with ABS, I somehow got air in the system, just enough for a slightly low pedal that wasn't as firm as it should be. I suspect that air was lingering in the ABS pump but no way to confirm. I did several fluid replacements with a pressure bleeder eerily similar to the one you made, just ten years older than yours. I tried benchbleeding the master cylinder, normal pedal bleeding with an assistant, all to no avail. Pedal was "OK" but not excellent. Nicole had a similar issue on her later car, with actions up to and including new master cylinder not helping. She found a place that did something different AFA bleeding technique to restore hers, so I had some confidence that I could get mine "right" with different bleeding technique.

Fast-forward to a Pm brake-system refurb a year or two ago. It included caliper rebuilds, new hoses, etc. As part of the new hoses install, I ended up opening each section of the plumbing system, and drawing vacuum on the section at the high end of the line. Then pushed fluid through from low end to high end, ending at the ABS and then the master cylinder. It took the best part of an afternoon to replace all the parts including the hoses and caliper rebuilds, and do the two-step vacuum-and-bleed on each section. Results are excellent from that effort, with high hard pedal and excellent feel. Some of that is likely the result of the new brake hoses, but getting all the air out was really the key.


We've used that pressure bleeder on lots of cars here for fluid-flush clinics with no problems. Just one time I accidentally let the bleeder go low on fluid level or otherwise got the MC reservoir low, and ended up going to those slightly greater lengths to get all the air out.

For the vacuum, I started with a MityVac-style of pump but graduated to an air eductor type when I saw that the hand pump didn't pull that hard. The three-stage eductor I have pulled about 28" indicated (at ~1200' AMSL), and was used instead of the AC system PD pump in deference to the possibility of aspirating brake fluid into the pump; the PD pump wouldn't handle the liquid well. Vacuum causes any air bubbles to expand in the liquid, making them easier to draw to the top. Once the air was out, pushing fluid from the bottom (caliper) ends of each circuit finished the job.

 

Thanks for sharing.

It's an '82.

I'm definitely going to keep pursuing air in the system before spending money. Unfortunately, it's snapped cold here again (20s today), and my garage is detached and unheated. Looking at the weather, it will be a few days until I get back out there.

 

Well, it's been a few years Shawn, what was the verdict?