The MC is OK.

Not the brake pad wear sensors, the one that looks at front / rear brake hydraulic pressure and triggers a light if there is an imbalance.

Diagnose, don't randomly throw parts at the car.

Install the fittings that come with the master. Route the hoses back into the reservoir, move the piston in & out until the air is gone from the hoses.

Mount MC in car. Connect brake lines per usual. Bleed system. I have a power bleeder made from a bug sprayer. It works fine. Hose is long enough that I can do the Quad Cab, 8' bed Dodge by myself.

You know what, i'll give you the whole story. Once I finished the brake and bearing job, I attached the power bleeder to the master cylinder. I pumped to 10 psi, fluid began leaking from the fluid reservoir cap, spraying and peeing. Then immediately after the reservoir sensor caps bursted and shot fluid everywhere.


Ever since then it's been poor brakes.


Needless to say, i'm never using that thing again.

I have a Motive power bleeder and it works well.

Things to look out for before using:

Make sure that the level sensor caps are in good shape and not loose or cracked. I have Girling on my '89 W124 and they don't last long before they are cracked and need to be replaced. Maybe the ones that I've been getting from the Dealer are old stock?

Check the cap seal that comes with the bleeder. Mine changed shape after a few years and turned into an oval. I use a seal from a spare OE cap and now it seals properly.

Fill the reservoir up to the maximum level before hooking up the bleeder making sure that the rear chamber is full as well. I put a mirror in the back so you can monitor the level in the rear chamber. On some reservoirs it is hard to tell if the rear is full.

It would be nice if a quick disconnect would have been used in the design of the bleeder. Also a schrader valve on the container would make bleeding off of the pressure easier.

The same test is in a lot of service Manuals and the typical Chilton and Haynes Manuals.

The power bleeder didn't cause your low brakes. While the reservoir isn't pressure rated and could leak, the rest of the system runs around 1,000 PSI so there is no way 10 psi caused damage.

Saying " Ever since then it's been poor brakes. " and apparently ignoring the other parts you changed indicate you have no idea how a braking system works.

I foresee you getting another MC, installing it , bleeding the brakes over and over with no improvement , demanding the parts seller send a new one to replace the "defective" one they sold you.

Turned the car on,
While the car was on, I bled from the right rear, to left rear, to front right, to front left.
Kept bleeding all four lines until there was a nice long solid stream of brake fluid.
And I made sure the reservoir was ALWAYS above the minimum line.
Took the car for a spin, and the brake pedal is still a slush box and the pedal makes that distinctive airy sound when I engage the brakes.

Also had the sensors re installed...and no warning lights came about when the engine was on.

While the car is off, when I press my foot on the brake pedal, it doesn't "give out" and depress to the floor. However, given enough force it can slowly be pushed down with the pedal itself having a good bit of resistance.
I can push it down an eighth or a quarter of an inch and it will hold at that interval, I can push down another eighth or quarter of an inch and it will still hold. The only problem is that when the car is off, that pedal is supposed to feel like a brick wall IIRC, there shouldn't be ANY movement in the pedal when I put my foot on it.

And if I leave the pedal at it's initial position OR push down a small interval and THEN turn the engine on, the pedal will then "give out" and depress to the floor accordingly.
And the airy slushy pedal comes back.
Once I turn the engine off, I can pump the brakes and the airyness goes away, the pedal begins to build resistance and firm up, but it can still be pushed down with some force like a mentioned earlier.

So that's basically where I'm at. What's next?

Also, when I first began to crawl under the car and start bleeding the brakes in the very beginning, I forgot to mention that I instructed my brother NOT to press down all the way to the floor before we begin bleeding the brakes. Once I finished bleeding all the brakes I asked him, "What did you let the pedal do while I was bleeding?"
He responded, "Well, I pushed on the pedal, it would hold resistance for a bit... and it kind of just sank to the floor." That "sinking" feeling had to be me loosening the bleeder screw on the caliper, allowing the fluid to pass trough the line.

In other words, the pedal was being pushed to the floor...through the entire process. He also said he was "kinda pushing on the pedal hard" while I was bleeding. These two things...pushing the pedal to the floor, and pushing the pedal hard can almost certainly blow out the MC if I am not mistaken. So now it's self evident, I get it, I screwed this job up big time.

I should have instructed him to "(Do not) not let the pedal depress to the floor while I bleed the brakes....That there will be some resistance while bleeding, and that the pedal will 'try' to depress on it's own into the floor, DON'T let it do that. And DON'T press hard. Press nice, slow, and distanced pumps."

The hard pumping, and pedal being depressed into the floor while bleeding had to screw up the MC.

I'm going to check for leaks just for the sake of checking for leaks. But the brake fluid level has been constant. But it does not hurt to rule out any variables.

The FSM requires that if I take my current master cylinder and bench bleed it, then I will HAVE to replace the seal between the MC and brake booster. Which happens to be a simple o-ring. (I have a spare, new and unused o-ring)

I'll go about it as followed.
1.Bench Bleed MC
2.Bleed calipers starting from rear right.
3.Check for leaks or wet spots at each caliper and brake line.
4.Check for leaks or wetspots between the brake fluid reservoir and MC. I'm pretty sure there are two rubber rings that sit between these components. It is where brake fluid from the reservoir is allowed to travel into the MC. (Is it even possible for air to get in, or leaks to occur there?)
5. Check for leaks between the MC and the brake booster. There is an o-ring in that area too I believe has to be vacuum tight.

This has to do more about step 4. I'm wondering if air can get into the system where the green boxes are in this picture here?
Like I mentioned earlier, I bled the lines to find NO AIR. But I'm worried the seals might have been destroyed while I was using the pressure bleeder. Because this picture came from a website where they claim if your sensor caps and seals are bad and you attempt a pressure bleed, you will have brake fluid piss out all of the rubber cracks....which happened to me.

https://d3nevzfk7ii3be.cloudfront.ne...GDoc5B3.medium

If you installed a new master cylinder, it should have come with new grommets to install the reservoir onto the MC (green boxes). The rubber caps (red boxes) are just vents. If that's an actual picture of your car, they need replaced.

It's not a picture of my car, but it looks pretty much identical to that one. And I think that's why the power bleeder made such a mess. So I ordered new reservoir caps to replace the cracked ones.

I haven't installed the master cylinder yet.
I'll go through one more final preliminary check probably Sunday evening, attempting to rule out all other variables before concluding the master cylinder is bad.

In fact, the new MC is on it's way and will be here tomorrow, it comes with new grommets an o-ring to slip between the MC and brake booster and two new hex nuts. Hopefully the problem is something stupid like air or a bad brake hose, or a leak somewhere so I can send it back, but that's unlikely sense the brake hose is new, I have not been losing fluid, and I can't find any leaks on the calipers or around the MC, and I've been bleeding straight fluid from all four calipers as well.

I'll update the thread and let you all know if the MC is the problem....I highly suspect it is...since my brother did the two cardinal sins of brake bleeding...pushing the pedal hard, and pushing the pedal to the floor while bleeding the calipers.

I'll try to bed the pads against the rotor and see if that helps tomorrow.
Then check to see if the pads are actually sitting flat against the disk.

Also if I lightly and slowly press the brake pedal with the engine on, with a constant light force...it will sink to the floor.
I'll try to drive on a rough road and try the pedal sink test when I apply the brakes.
I'll be adding this light pedal force test and rough road test to my preliminary brake check before resorting to installing the MC.
If you guys have any other tips to check what could be wrong with my squishy brakes let me now.

I'll go through each procedure and see which tests the car fails and passes, then ask you guys what the verdict could possibly be.

So now it will be
1.Bench Bleed MC
2.Bleed calipers starting from rear right.
3.Check for leaks or wet spots at each caliper and brake line.
4.Check for leaks or wetspots between the brake fluid reservoir and MC.
5. Check for leaks between the MC and the brake booster.
6.Attempt to bed brake pads against rotor, then pull wheel and check
7.Lightly press foot on pedal and see if it sinks to the floor, with modulation as well. (Do I do this with engine on or off? I'm guessing on)
8.Try the same thing while driving on a slightly rough road while braking lightly and see if the pedal falls to the floor as well.

Subscribed just to see how it turns out .

I never use more than 5# with a pressure bleeder because what you experienced, is what always happens .

Pedal sinking under soft pressure normally means master is kaput .

ANNNNNNNNNNNND brakes work. Car off, pedal feels like a wall. Car turns on, pedal doesn't sink to the floor.

Panic breaking, tires nearly brake traction.

So 97 SL320, you can eat your words.

Only problem is now my hood tongue latch SHATTERED as I closed the hood...another thing to fix.

Here's proof. Here's the raw photo https://farm5.staticflickr.com/4423/36438768391_7820be2554_o.jpg
Men don't bench bleed master cylinders for no good reason.

Bench/Pre Bleeding
 

Nice ~ where did you get those bleeder pipes ? .

When I had my Shop I always had to keep some made up from old pipes cut off a junker .