Troubleshooting brakes i need some help

[B RON CO]

Hi, so I understand you put a new master cylinder on your old power brake booster. You are aware of the push rod to master cylinder adjustment. Did you know that many master cylinders for the same car have a different piston depth? When I put a dual piston, disc brake master on my 66 to replace the original, the new part had a deep piston and I needed to use a 1/4 drive short socket to use as a spacer.
Can you compare the piston depth on the old mc to the new one? You do not have to remove the brake lines, just loosen the nuts and slide it forward to look at the piston
Check that before doing anything else.
By the way, you only say the calipers are on correctly, you are not saying "I see the bleeder screws up top". Calipers are made left and right side. They will definitely bolt on to the wrong side and be upside down. They are mirror images of each other. It is easy to mix them up.
Good luck

 

[TheBuckinBronco]

Hi, so I understand you put a new master cylinder on your old power brake booster. You are aware of the push rod to master cylinder adjustment. Did you know that many master cylinders for the same car have a different piston depth? When I put a dual piston, disc brake master on my 66 to replace the original, the new part had a deep piston and I needed to use a 1/4 drive short socket to use as a spacer.
Can you compare the piston depth on the old mc to the new one? You do not have to remove the brake lines, just loosen the nuts and slide it forward to look at the piston
Check that before doing anything else.

Thats for the suggestion. Ill look at it

 

[rmcmillan]

I am having the same issue. Just bought a new proportioning valve and brake hoses from Toms's Bronco Parts. I already had front disk brakes from a 76 model Bronco and was not having any issues with braking until I replaced the proportioning valve and hoses. No pedal. Checked the rod length on the brake booster and have put on two new master cylinders without any success. I also purchased the proportioning valve tool from Tom's to keep the proportioning valve centered. I have tried bleeding the brakes by the two person method and after putting on second master cylinder, I used a vacuum pump to bleed. Still no pedal. I spoke with a tech at Toms' and he seems to think that air is still in the lines or calipers may be sticking. It will be two weeks before I will be back to where my Bronco is. May try bypassing the proportioning valve just to see if it may be defective. Been very frustrating.

 

[Broncobowsher]

No, the calipers are installed correctly. In fact i think this set can only be installed one way

There is a HUGE problem. They can be installed wrong.

You have yet to actually tell us that the bleeders are actually at the 12 o'clock position. If you put the left caliper on the right side it will fit perfect. The line will hook up perfect. But there is an air bubble behind the piston in the caliper that you can't get out because the bleeder is below the bubble. The caliper being on the other side takes the bleeder from the top (the 12 o'clock position) and puts it near bottom.

Stop arguing that you installed them correctly and go look at them. Where is the bleeder? It is a very common mistake to put them on the wrong side. I've seen very good technicians that do this stuff for a living make this mistake. The home wrench is very capable of doing the same thing.

 

[TheBuckinBronco]

There is a HUGE problem. They can be installed wrong.

You have yet to actually tell us that the bleeders are actually at the 12 o'clock position. If you put the left caliper on the right side it will fit perfect. The line will hook up perfect. But there is an air bubble behind the piston in the caliper that you can't get out because the bleeder is below the bubble. The caliper being on the other side takes the bleeder from the top (the 12 o'clock position) and puts it near bottom.

Stop arguing that you installed them correctly and go look at them. Where is the bleeder? It is a very common mistake to put them on the wrong side. I've seen very good technicians that do this stuff for a living make this mistake. The home wrench is very capable of doing the same thing.

I figured i got the point across by saying they were installed correctly. THE BLEEDER IS IN THE CORRECT PLACE

 

[Broncobowsher]

OK, the bleeder is on top. Got it.

To be fair, a lot of people think they installed stuff correctly when they didn't. I (we?) were reading it as you got the knuckle clearance and the caliper bolted up. The hose and pads all fit right. To many people this is a part installed correctly. The little detail of the bleeder on the bottom because the calipers swapped sides is overlooked. It's not just calipers that get installed backwards that cause issues, cooling fans have been put on backwards way more times than you could imagine. (If you want the fan to work right, the concave side of the blade needs to face the engine).

Do you still have rubber lines from the frame to the axles? If you do a trick to isolate stuff is to pinch off the rubber line. Needle nose vice grips are good for this. This can help narrow down if you need to be looking at the calipers as an issue, or if it is upstream in the master cylinder area.

Speaking of calipers and clearancing the knuckles, do you still have a good air gap between the caliper and the knuckle after you bleed the brakes and drove it? Because if the caliper touches the knuckle at all the front braking power gets cut and you get long stroke (only the inner pad working and the stroke is flexing the rotor).

 

[TheBuckinBronco]

Hi, so I understand you put a new master cylinder on your old power brake booster. You are aware of the push rod to master cylinder adjustment. Did you know that many master cylinders for the same car have a different piston depth? When I put a dual piston, disc brake master on my 66 to replace the original, the new part had a deep piston and I needed to use a 1/4 drive short socket to use as a spacer.
Can you compare the piston depth on the old mc to the new one? You do not have to remove the brake lines, just loosen the nuts and slide it forward to look at the piston
Check that before doing anything else.

THIS WAS IT! the fronts lock up now on pavement i brought out the adjustment and the brakes worked like a charm! Thank you