Front Disc Brakes oddity

[Auggie]

I was checking my brakes because they are spongy at best and even though I had bled the lines thinking the last person to work on the brakes had not done this, they still had to go to the floor to stop the Bronk.  The front brakes have had a conversion to discs, but when looking at the calipers, they look odd.  I have attached pics for your viewing pleasure.  I could not find the usual 2 bolt attachment from the rear of the calipers....as a matter of fact, there was nothing i could find holding the calipers in place other than pressure.  I could not however move them off the rotor....any info from the vast knowledgeable majority?

I also found the rear drum pads to be in pieces so that is the project O' the day...........any responses to the disc brakes would be appreciated.

 

[Bully Bob]

'76-'77 came with discs.   Someone may have stuck an older D-44 under there with a conversion.

However.., that looks stock.  2 pics are too close-up for a good view.

Turn the wheel & a straight-on shot of the back side (backing plate) may help.

 

[Auggie]

Hey Bully,

Here is the what I think you wanted.  Also, there is a "tee" on top of the front axle that has a hose running down from the master cylinder/booster, the two front steel brake lines, and another hose that is running up to the front left fender.....it is not connected to anything...just tucked in behind some wires.  Any ideas if this is supposed to be connected anywhere?  I thought maybe a vacuum hose for some function that helps with the braking?????

I replaced the shoes on the rear today and the brakes are still a bit spongy, but much better than they were.  I think maybe the booster is not functioning properly....maybe something to do with that hose.

 

[Bully Bob]

BTW.., I noticed that brake/caliper set-up is on '76 thru '79 Bronco.

Near as I can tell.., there's a lip that tucks under the caliper mounting bracket and that

single bolt on the other side IS the only lock-down bolt.

(the bolt & the lip have some oil  in their areas in these pics)

The Tee includes the 2 metal brake hard lines. 

The hose is just a "air vent" for the differental..., nothing to do with the brakes.

Any hose coming from the booster should go to the intake manifold. It's usually a larger

hose.., almost the size of a garden hose.  Any pics of that situation..?

If you have "good hearing" you can listen for a booster leak.  With your head up under the dash..,

see if you hear a "hissss" coming from the rubber boot area where the brake rod goes thru the firewall.

(engine runn'n)

However.., mushy pedal would more likely be air in the lines or a failing Master cylinder.

Master cylinders can leak internally (fluid by-pass) with no external signs.

 

[Auggie]

Thanks Bully.

Is there any way to test for a failing Master Cylinder?  I also need to check the front pads on the disc brakes to make sure they are still good.  But the way the brakes mush on me feels like air in lines, but I have bled the lines until I am about to add another full master cylinder of fluid....not getting any air out of lines and brakes do pump hard, just sponge up when trying to stop and do not force the shoes/pads on to the rotors ( at least that is what it feels like)

 

[Bully Bob]

Way back when.., folks put Chevy disc brake set-ups on their Broncos.  

Maybe that's what's on there...,  I can't tell.

There has to be a way to get the calipers off.

You could jack the front end up, spin a wheel & have someone press the brake.

It should stop spinning suddenly.

Know of no way to test M/C except taking it apart & view the guts.

(cylinder wall., cups, etc.)

Sometimes the cyl. wall will rust in spots & chew away at the cups.

 

[Bully Bob]

Looked in my Chevy book.  Chev. used Delco & Bendix calipers.

Yours looks like the Bendix.  One bolt with a locking clip.

If you go to auto parts store.., they can show you one.  Looks pretty simple actually.

 

[Auggie]

Thanks...looks like a Labor day project!

 

[Rons beast]

Hey Auggie,

The first pic shows me a lot of the caliper piston exposed.  There should be a pad between the piston and rotor and I don't see it.  The wrong pad could be on there.

also that one bolt that holds the caliper slide "wedge" in should be flat on the slide. It looks loose or not positioned correctly...or that caliper is incorrect for the application.

If there was a problem with vacuum to the booster the pedal would feel hard, but difficult to stop the vehicle. 

Another possibility is if the brakes were bled by pumping, the fluid could be foamed. Try gravity bleeding.

In any event the rears have to be corrected first and adjusted correctly to eliminate that as a possibility. 

Good Luck

 

[Bully Bob]

GOOD catch Ron...!!!!  Absolutely correct....!

I kept look'n at that but it didn't dawn on me.., couldn't get my head around it.

The fact that the piston seal is showing is  big problem.

-----There's no pad in there..!!

I posted this website showing Oreilly product (GM) earlier, but it didn't stick.

http://www.oreillyauto.com/site/c/detail/OBH3/184166/03345.oap?year=1996&make=GMC&model=C3500%2BPickup%2BRWD&vi=5008618&ck=Search_brake+caliper_5008618_4748&keyword=brake+caliper

Jeffs Bronco Graveyard is showing this/your caliper as "stock"  '76-'77 (This is a good sign)

http://shop.broncograveyard.com/Front-Brake-Parts-Disk/products/1679/

The "new" more modern disc "kits" for EB's have the two bolts on the back-side holding

the calipers in place.

 

[Auggie]

Okay...you guys are great......who wants to come to St. Augustine for vacation and work on a Bronco!!!!???? hahahaha!

So I guess I will remove the calipers and check for pads...which probably are NOT there...(wonder why I was having trouble stopping?)

Thanks for the eagle eyes. Will update after Holiday weekend as I am sure part of it will be under the Bronk.  BTW, what piston are you referring to?  In the first set of pictures?

Thanks again.

 

[Bully Bob]

You barely see the black rubber seal/piston thru that hole in the top of caliper (1st pic)

Please do let us know your results/progress...!  It's good for our egos to know if we're worthwhile... B)

 

[Auggie]

Great....got it.

 

[Auggie]

Well after all the good advice I replaced the front calipers, pads, rear brake wheel cylinders, master cylinder and then went thru the "bench bleed" process.  I have bled the brakes and need to run them thru one more time since I used the "one man bleed system". ( Little bottle with a magnet on it and tubing to go over bleed *****) but I need to get my able assistant to help me bleed them properly today to make sure all air is out of the lines......brake pedal pushes to floor once, then firms up...obviously still air in the lines somewhere.

Thanks again for all the advice.

 

[Bully Bob]

Also, adjust the rear shoes 'til they rub on the drum a bit, while spinning the wheel.

Too far away will cause long pedal travel as well as need for pumping.

Actually the one man bleeders work great as long as there a little fluid in the bottle

to cover the bottom of the bottle tube.  (this eliminates air being sucked up when pedal is released)

In some cases.., the bench bleed doesn't always get all the air out., but that's the least

of the possibilities.

 

[Auggie]

Hey Bully,

Well I adjusted the shoes, double checked the MasterBC for air bubbles, bled each of the tires 3 more cycles each ( starting with the RR and working from back to front....still have spongy pedal and the brakes just do not want to stop on that first push...pumping gets it done...2-3 pumps stops the Bronk.  The truck slows when first push, but as pedal drops to floor no more braking power until it is pumped.  Any more ideas?  Really stumping me.  There are no leaks anywhere...performing all work in garage with clean,pristine floor.

Help!

 

[Bully Bob]

Well.., after reading that.., from my "steel=trap" of a memory comes another common issue.

That is the length of the "adjustable" rod that goes from the brake pedal arm, thru the firewall,

to the booster &/or master cylinder.

If it's set too long or too short.., it won't allow the master cylinder the proper stroke.

I'd have to read-up to find the way to adjust.

If you can't find it.., I'll dig out my book.

OOPS..!!   Check that.., I think it was the Land Cruisers that were (push-rod) adjustable.

If all 4 wheel cyl. & calipers are oozing nothing but fluid..., then the prob. has to be in the

Master cylinder.

Once pumped up.., the pedal should be solid i.e. no pedal drop with constant pressure.

 

[Auggie]

I guess it is not out of the realm of possibility that I recv'd a bad cylinder.....what about the proportioning valve?  I see that located down below on the frame on the driver's side.......is that a possible problem that could cause the spongies?  Of course I have not replaced that  :/

 

[Bully Bob]

The porp. valves rarely fail.  Suppose they could get plugged with crud..?

M/C has two reservoirs. Both need to be fully loaded.

You could try having someone pump the pedal 'til it's hard., then you pop the cap off

the M/C  & with the pressure still on the pedal, check to see if there's fluid movment

in the reservoir(s) Assuming the pedal is slowly moving downward with the pressure.

Careful.., re-pumping the pedal could squirt fluid in your face.

If the pedal stays hard, and there's no fluid movement, it's likely the M/C is good.

Where did you get the M/C..?  New or re-built..?

BTW.., were there pads missing.... both sides..?

Are the new calipers grabbing & releasing normally..?