GM front disc brake retro issues

[salineriverman]

Recently purchased a front disc brake kit for my 71 bronco and finally got it installed. To my disgust brakes are really poor. Mechanic installed a larger MC but didn’t install a proportional valve.
He also did brake job on rear drum brakes and all new stainless brake lines.
I talked with vendor today and got a proportional mounting kit and valve on the way. Hoping this will solve issue.
Saw where gladkin used a MC for a 74 f-250 with dual pistons and 1.25” bore on his 76 bronco - anyone know if it will work on a 71 bronco?
Any help would be appreciated - My mechanic got too busy at work so I now have it at home.
Thanks in advance for your help.

 

[Pa PITT]

Sailner--------. Ok now you on an old item ...We all did 20 years ago.
SO What I'm saying a lot of my information is old stuff.
.......... For the next guy reading your post it would help if you can tell us what you believe is bad in your new brake set up.
.............................
........ SO HERE I go in telling you what I think may be wrong...
IT Doesn't need a Bigger M/C ... Basically needs a smaller cyl.
The 1.25cyl doesn't put up as much pressure as does One of the 15/16 ...
One of the old members on here. years ago explained this situation. Now I've had to change my M/C ABOUT 3 TIMES Over the last 15 years ... When I did my install. I'd gathered up all the parts & put my brakes on...
So when I installed mine My stock 1972 Bronco M/C was still on my Bronco ... So I like to fix only one item at a time .
SO WHEN I got my disk on & fluid running to them .. & I took it for it's 1st drive I was very impressed at the fact I had good brakes . Really good brakes .
SO For the next several weeks I began to ask the gain here ... What M/C I NEEDED TO PUT ON MY BRONCO.
The old man explained it ... If it's stopping good stay where your at .. SO I DID .
LATER SEVERAL other members put on their brakes & Had bad brakes .
Then he told us the big bore cyl weren't what we wanted .
..... SO I'M Going to say just put on any of the Bronco cylinders & you'll be fine.
... M/C used to be cheap like 20.00 exchange . Maybe their 35.00 now but I'll bet their not that bad.
So if the M/C WILL BOLT UP .& If your line will mount up on the sides of your cyl. Then i'LL BET YOU HAVE
better brakes ..
....... Now there are lots of other problems So if you can describe you brake problem .. You may have other issues .
Like I had to grind more off my calipers to get the complete travel
on my rotors .
so let us know the issues ... & You may have to send me a P'M Because I spend most of my time on the off topic section nowAdays .

 

[WILDHORSES]

You may have other issues . Like I had to grind more off my calipers to get the complete travel on my rotors .

I have found this to be the most common problem with these kits. Easy to diagnose. Stick your head over the top of the tire and look down to see if there is good clearance between the caliper and the knuckle. I don't know how many times we hear something like " the caliper bolted right on so I thought I did not need to grind the knuckle"..... Start there, it cost $0.00.

Jim

 

[salineriverman]

I have found this to be the most common problem with these kits. Easy to diagnose. Stick your head over the top of the tire and look down to see if there is good clearance between the caliper and the knuckle. I don't know how many times we hear something like " the caliper bolted right on so I thought I did not need to grind the knuckle"..... Start there, it cost $0.00.

Jim

Thanks for info- He ground a lot off but I’ll doublecheck and see - will let you know -

 

[pcf_mark]

Can you describe the problem in more detail? The pedal is low, it has low grab and takes a long time to stop, pedal is spongy, veers when I stop, lock ups rear wheels?

Also can you list the parts used in detail? Brake booster, disc kit, m/c etc. Sorry but a prop valve is not going to do anything to solve your problem unless you have one end locking up while the other is not.

I feel bad you probably spent real $$ getting it done. I am sure we can help you get it sorted. This upgrade is absolutely worth the time to sort out. After EFI this is my best upgrade.

 

[salineriverman]

Can you describe the problem in more detail? The pedal is low, it has low grab and takes a long time to stop, pedal is spongy, veers when I stop, lock ups rear wheels?

Also can you list the parts used in detail? Brake booster, disc kit, m/c etc. Sorry but a prop valve is not going to do anything to solve your problem unless you have one end locking up while the other is not.

I feel bad you probably spent real $$ getting it done. I am sure we can help you get it sorted. This upgrade is absolutely worth the time to sort out. After EFI this is my best upgrade.

I purchased the kit from WHorse - still using the old H block - put new drum brakes on back - new MC - all new brake lines- I looked and there is plenty of clearance where mechanic ground knuckles down. Brake pedal is really firm and doesn’t bleed down . I got the proportional valve kit in this evening so hopefully I can get it mounted and on in the next couple of days. I believe the only brakes I have are the rear and they’re barely working. My neighbor is going to help me try and figure it out.
I really don’t think the front is working at all. We’ll pull the wheels off so we can see and go from there. I had a 76 that had good brakes but my brother always had bad brakes on this bronco. Mechanic also installed new Milemarker hubs and wheel bearings. Thanks for suggestions -

 

[pcf_mark]

Put it on jack stands and apply the brakes to see if each wheel is holding by trying to spin the tires. It should be impossible to turn a tire by hand. If you suspect the front try to bleed some fluid out of them. If you get fluid and the pedal is high and firm hydraulically you are ok, but there is a mechanical issue like the caliper hitting something. If you do not get fluid then there is a kink or blockage between the master cylinder and the caliper.

 

[stevew]

Put it on jack stands and apply the brakes to see if each wheel is holding by trying to spin the tires. It should be impossible to turn a tire by hand. If you suspect the front try to bleed some fluid out of them. If you get fluid and the pedal is high and firm hydraulically you are ok, but there is a mechanical issue like the caliper hitting something. If you do not get fluid then there is a kink or blockage between the master cylinder and the caliper.

Make sure the calipers are not upside down , bleeders UP ! Common mistake ....

 

[salineriverman]

We p

Make sure the calipers are not upside down , bleeders UP ! Common mistake ...

We put it on jack stands and pulled front tires off so we could see better. Disc pads already rubbing and front hard to spin. Applied pressure on pedal and held firm - did find a leak or seep on old return line but it was very small - ordered new lines - we also tried bleeding brakes on driver's side and very little fluid came out but brake pedal did go down slowly.
When driving Bronco brakes are almost non-existentant - actually have to gear down to stop. Plans are to replace seeping line when it arrives and rebleed brakes to see if this helped but I am skeptical - I suspect something mechanical but we'll see , my neighbor is more mechanical than me - He was an offshore mechanic so hopefully we'll figure it out.
Thanks for you guys help .

 

[Apogee]

Low brake torque like you describe could be caused by several things, so be methodical and you'll sort it out. Like the guys have asked for above, post up the specifics, as they do matter. New master cylinder is great, but without a bore size it doesn't mean much. Booster...factory or aftermarket, and if the latter, what size? Speaking of the booster, have you tested that it's functioning properly? If not, I'd suggest warming up the rig, shutting it off and then pumping the brake pedal several times to evacuate any vacuum from the booster. Apply the brakes moderately firmly and then start the engine...the pedal should drop noticeably, at least an inch if things are sized and working properly. If it does not, then either the booster is bad or your vacuum levels are too low to support vacuum accessories (or both). Most guys run pretty mild (RV type) cams in their EB's and save the wild stuff for their Mustangs, but you never know.

There are a bunch of other things to look at, but that's where I'd start given the information provided thus far.

Tobin

 

[Cooter_76]

Have you checked the brake imbalance thingymabober on the H-block?

 

[salineriverman]

Have you checked the brake imbalance thingymabober on the H-block?

Success!!!! We found one of the rubber lines had a small leak and replaced it and then found the brake warning lite had gotten too hot and had a leak where it connects to H block . Rebled brakes and now working good. Drove it to camp 20 miles away to meet up with my buddy who has a 71 Bronco and talked for about a hour. Got back in and starter went out. Got to install a new starter today. Got to get my heater going next - replacing all hoses and possibly doing upsize to fan and motor. Then on to replacing door gaskets and seals around glass tailgate and top. Thanks again for all of the advice.

 

[Pa PITT]

ok I came back tonight to check on you Because this is too good a Brake set-up to not work correctly.
Glad you got the issue found.

... ENJOY.