Sudden Loss of Brakes, No Fluid Loss...

[threewood]

Kind of pissed. 62 Belvedere 4 wheel manual drum brakes. Master cylinder is less than 1100 miles old, new or rebuilt wheel cylinders on all corners. Fresh fluid during install.

Driving to work, on the brakes at 4 to 5 stops. Go to brake next time and pedal goes to floor. Use e brake to get it stopped, turn it around and limp it back to the garage. Very light traffic thank God. Expect to see something ruptured or leaking....nope. nada. All 4 corners dry as a bone, m.c. dry in engine compartment, nothing leaking in the interior.

Sooooo, I am about 90% positive it it the ACDelco Chinese master cylinder. But the other 10% of me thinks maybe the brakes weren't bled all the way? Only rubber line not replaced 1100 miles ago was the line to the rear different distribution block. Going to get home this afternoon and swap out the rubber line and bleed the brakes again. Also check again for fluid leaks. Speed bleeders on all corners as well.

What do you think? I already ordered a m.c. rebuild kit as the frickin bore should be good. Driven it those 1100 miles without an issue l, firm pedal, panic stopping not an issue either...until today.

Does ACDelco warranty their products? Did I mention I am pissed lol

Edit: it is an AC DELCO professional mc. Brand new, $62.00 from Amazon Aug 10, 2015. Engine fired up in October at some point....so 4 months use and dead. My apologies to Raybestos

 

[Johnny Mac]

If the fluid is still in the MC...and the pedal goes right to the floor. I believe you appear to already know it can only be a seal in the MC letting the fluid basically remain stationary while the piston moves fore and aft. Unless a blown wheel cylinder can displace enough fluid in the same fashion, but i doubt it.

And yes, i'd be talking to the place i bought it. I wouldn't have bothered with a seal kit. With as "cheap" as new ones are...I'd probably have one in the mail already....more than likely at THEIR cost.

 

[Glenwood]

yikes! You're lucky the traffic was light. I'm betting the mc is the problem. Even if you have 'some' air still in the lines, you should still have some braking power. I've had bad mc's in the past but never that severe. Once a front brake hose decided to blow while pulling the boat out of the water. That was an interesting ride home! Even with a blown line, I still had a little brake power left, but I tended to slip it into neutral to take the drive off the rear wheels which helped.

Good luck!

 

[moparsteve636]

Might I suggest since you're changing the mc why not go to a dual mc! Much safer setup and it won't cost much more!

 

[threewood]

Might I suggest since you're changing the mc why not go to a dual mc! Much safer setup and it won't cost much more!

I'm listening. ...

So, I would need new dual mc, new distribution block up front, new lines for front or rear or front and rear?

- - - Updated - - -

And yes, i'd be talking to the place i bought it. I wouldn't have bothered with a seal kit. With as "cheap" as new ones are...I'd probably have one in the mail already....more than likely at THEIR cost.

New m.c. was $60ish, rebuilt is $40ish. Raybestos rebuild kit was $4.00 on Amazon plus a cylinder hone for $10. The body has to be good unless there is some weird void in the bore. I think I will contact Raybestos when I do a little more investigation on the system.

 

[threewood]

Came home and everything is dry. Checked the rubber hoses, no bulging. Under the mc, on the frame rail, looks like some fluid splattered from under the cap but it didn't look recent with dirt stuck to the rail. With hand pressure, the pedal feels like it might have some resistance but not alot.

 

[shorty64]

Most likely you'll find either a cut pressure cup lip or an inverted lip, ie the lip rolled the wrong way.
The first can happen if there is a burr by the compensating hole and/or damaged during assembly. The latter if the bore is too big, seal too small, etc.
Most remote is possibility of poorly made seal itself (lowest bid, etc).

Good luck and please let us know what you find.

 

[704spdbzzz]

Just a word of caution. ....synthetic fluid will burn your paint. Silicone brake uid is an option I went for. Already went through the BS with a bad mc

 

[Glenwood]

Just a word of caution. ....synthetic fluid will burn your paint. Silicone brake uid is an option I went for. Already went through the BS with a bad mc

That's good info, never hear of silicone bf.

 

[threewood]

Update: Pulled the master cylinder this evening and.......I couldn't find a thing wrong with it. And believe me I tried. Both cup seals were perfect, spring was good, bore was clean and smooth. And the casting and internal parts are made in the USA which is good to know.

Now, what I did notice is that when the pedal is pressed there is some odd springing noises coming from up front and maybe a clunk or two. Could just be the drum brake hardware. The pedal hits a hard spot 3/4 of the way down then bumps through it. When I bench bled the mc it was smooth through out its range. So I guess I will pull the front wheels and have a look see. Tomorrow since I am beat

 

[MarPar]

could it be that the wheel cylinders wept onto the drums?

 

[threewood]

could it be that the wheel cylinders wept onto the drums?

Well, I honestly don't know. Car has been sitting for a few days and I have been hitting the brakes enough that I should see fluid on the backing plate, wheel or ground. But everything is dry. No fluid loss. I am leaning to something mechanical at the moment (broke, misaligned, etc) that could allow the wheel cylinders extra movement without popping the pistons out. I'm at work now but will dig into it when I get home.

 

[dangina]

For peace of mind you should still upgrade to the dual, just as cheap, better piece of mind, and marpar said, I'd check the wheel cylinders in the drums

 

[threewood]

This is going to sound stupid, but here it is. Pass side front brake adjuster fell out. I pulled the drum and the adjuster tip hit the floor and the body was jammed in sideways. Greased the nub, re installed it. Adjusted for a bit of rub when turning. Checked out everything else in the wheel and I have brakes again!

I am guessing it was out of adjustment to begin with and without it the brake shoes just slid down the drum. No leakage on the wheel cylinder which I rebuilt 6 months ago. Crazy lol.

Thanks all for your help

 

[resq302]

Glad to hear it was an easy fix ! Also glad you found it before you had a really bad sorry following this one !

 

[miller]

Good find, threewood. At least your brakes are acting right, again.

 

[coloradodave]

You were pumping the brakes with the brake shoe uninstalled and it didn't blow the cup and seal out of the cylinder? Better check the line to that wheel. Hydraulic pressure should have blown fluid all over that drum...

 

[bm02tj]

On a lot of units there is a stop for the piston so it will not blow out
That wheel cylinder needs to be checked
This goes to show it is good to double check your self for safety

 

[khryslerkid]

Make sure to check it again after a few miles.

I remember finding the wrong adjuster on a car once. The adjuster was for the opposite side of the car. Each time you hit the brake it would loosen up instead of tightening, result would be what you discribed. They have a "R" or "L" on the end where the cap goes on.

Just a thought...

 

[resq302]

ah, yes, excellent info KryslerKid!