Rocinante

Need your sage advice please!

I have just completely rebuilt my rear calipers in my '82, and made the mistake of letting the fluid drain out of the rear brake hoses. I initially vacuum-bled my rear brakes, and when that didn't work, I attempted a traditional brake bleed (having someone pump the brake pedal while I opened the bleed valve), Now I have absolutely no pressure at the petal, and consequently no stopping power. I suspect I may have ended up tearing the seal in the master cylinder due to excessive brake pedal travel while bleeding, but I'm not sure. I have attached some photos of the master cylinder/brake booster from my 82 (sorry for poor camera angles), and even though it is dry now, you can see that some fluid has leaked passed seal connecting the brake booster to the master cylinder, and as there is trail of surface rust that has removed the paint from the booster.

Correct me if I'm wrong, but I believe my next steps are:

- remove the master cylinder and bench bleed
-check the brake booster to see if it is leaking/if there is any brake fluid inside (I just bought a borescope for this)

Some questions...

I've seen some videos in which you can bleed the master cylinder on the car (with a master cylinder bleed kit), and Cardone and others make a large syringe with the claim (and a supporting video) that it can be used for bleeding while still installed. Will this work instead?

Replace the seal between the brake booster and the MC?

If the master cylinder needs a rebuild, do I just need a kit after having the MC honed at a machine shop?

Phoenix Systems makes a reverse brake bleeder, where you pump clean fluid if from the caliper, resulting in the air being forced in the direction it already wants to go (up, and out the master cylinder). Wouldn't this in effect end up bleeding the master cylinder as well?

Tools required in addition to my basic set would be a flare wrench set? Regular length or the "stubby" versions?
Will any part of this process interfere with my clutch?

Thanks for reading. Ultimately, I'd like to have all the tools and parts I need before I get started so that I don't spend wasted time waiting for shipping!

The Forgotten On

As soon as you remove the reservoir you will have to bleed the clutch. But seeing the condition of that hose you may as well replace it and the master cylinder while you're in there.

You most likely have finally killed the seals in the master as it gets corroded in the part you don't normally use and it eats up the seal as you've noted.

I would send your master to whitepost to have it sleeved, it'll probably outlast the car after that https://whitepost.com/brake-sleeving...ding-services/

Mrmerlin

do yourself a favor,
buy a new ATE booster,
and ATE master cylinder,
they are available.

Use DC111 on all the rubber parts to stop corrosion. ,
and use ATE brake fluid since they made the parts ,
also add on the 4 SS flex lines,
and your brakes should be trouble free for the next 20 years or more

NOTE you will find out the MC is not made to be taken apart,
and this is so easy to do.
Nicking the center piston will create a leak into the booster so your cost cutting can actually cost you a plenty in time wasted,
and damaged parts that now have to be replaced.

Please listen to my advice it has been hard won and very costly in some circumstances,
it has taken me many years of fixing 928s to learn this,
sometimes with a paying customer footing the bill to do it two even three times.

Do it right the first time , dont cut corners with the brakes ,
brand new parts are available for relatively fair money,
and once your brakes feel great again you will soon forget that they work so well.

since you have a clutch replace the master and slave and blue hose and release arm bush and get a new Greg Brown flex hose for the slave dont forget to mod the MC to 75mm piston length and cut off 2 winds of the spring

Jason89s4

1. Listen (read) to MrMerlin.
2. If you are working on brake lines, invest in proper flare nut wrenches. (I’ve not yet seen the need for stubby. Although stubby comes in handy taking MC off) However I have seen a bad situation turn worse using “regular “ instead of flare on brake fittings.
3. I have had great success with Motive pressure bleeder. No need to fill it with fluid, just use it as pressure and watch the fluid level between each corner bled. Makes one man jobs easy.
I’m also a fan of Speedbleeder bleed valves, but only install in the calipers if you make sure and tell any future owner they are in place. No reverse bleeding will work once installed.
4. Ditto on while you have things bled install SS brake lines. For a little more than 100 bucks, it’s a great investment.
5. If you bleed the clutch slave cylinder there is good advice here about how to pull and pump the slave, but you’ll have to search that. ( not in a place now to find it)
You’ll be stopping in no time!
-Jason