Brakes "65"

[jhuebner]

Installed new booster, dual master cyl, flex hoses, rebuilt calipers ( seals pistons ) .......with engine off pumped brakes pedal does not go hard, with car running have the same pedal feel as when off, with vehicle on jack stands and in gear have to push pedal to floor to stop, was not able to check if front brake calipers are doing anything.......any thoughts, push rod length, bad master cylinder. ......

[Joe Johnston]

Sounds like air in the system so, lets start with the 3 obvious questions.

1-did you bleed master cylinder?
2-did you bleed each wheel cylinder?
3-have you checked for leaks?

If you have done the above, re-bleed the master then the wheel cylinders again.

[jhuebner]

1. Bled M/C on vehicle, installed 2 hoses placed open end in reservoirs pumped till no bubbles
2. Bled brakes with a pressure bleeder also the bottle method more than 2 liters worth trying to get them to work
3. No leaks detected
4.The M/C check valve is from the old M/C the new one was damaged in the mail
5. Does M/C push rod length remain .990-.995 with the Mustang M/C and a Midland booster screw type the old one was the crimp style

[simplyconnected]

1. Bled M/C on vehicle, installed 2 hoses placed open end in reservoirs pumped till no bubbles
2. Bled brakes with a pressure bleeder also the bottle method more than 2 liters worth trying to get them to work
3. No leaks detected
4.The M/C check valve is from the old M/C the new one was damaged in the mail
5. Does M/C push rod length remain .990-.995 with the Mustang M/C and a Midland booster screw type the old one was the crimp style

1-3, ok
4. The brake system has no check valve because brake fluid must travel in both directions. Your system may have a combination proportioning valve and maybe a residual valve.
5. Master cylinders do not have a pushrod. Some may have a spacer but boosters and brake pedals have push rods.

New master cylinders are all different so you need to adjust the booster output rod so there is nearly zero play in it. The last adjustment will be your brake pedal rod.

Be sure all your bolts are tight. Any flexing will detract from your pedal feel. That is why your booster is directly bolted to the brake pedal support bracket. - Dave

[jopizz]

The brake system has no check valve because brake fluid must travel in both directions. Your system may have a combination proportioning valve and maybe a residual valve.

I believe he's talking about the vacuum check valve on the booster.

[jhuebner]

Looked over the brake lines once again seemed ok........took the MC off the booster there was a very small amount of break fluid where the MC goes into the booster I also had the shop manual and was looking at the booster disassembled fig 28 page 2-24 and it shows a front seal the booster on the car does not have it also the original booster I took off the car is.missing the seal as well is the seal necessary........if so does anyone have a source for one, can't find one on the web.........also got a new proportioning valve the one on the car seems to be the original and is pretty corroded

[simplyconnected]

You probably have TWO problems. The M/C should not leak brake fluid and the booster should not leak vacuum. You probably have brake fluid inside your booster. As it fills up, all that vacuum area will be gone and finally brake fluid will go out the booster's check valve and into your engine, causing periodic white smoke. - Dave

[jopizz]

It would help to know exactly what booster you have. There are a number of different Midland style boosters. Some had a spacer along with a gasket. The gasket however has nothing to do with your fluid leak as Dave pointed out. If the master cylinder is leaking it's from the seal around the piston.

John

[jhuebner]

The booster that's on the car now is the type with the band and with the spacer between booster and MC.......the original one is the Bendix

[jopizz]

Some boosters have a seal, some don't. I'm not sure what purpose it serves. If vacuum is leaking between the booster and the master cylinder then the diaphragm is bad. Vacuum should never come out the front of the booster. As for your leak I would bench test the master cylinder. Mount it in a vise or something stationary. Use flexible bleed hoses or bent brake lines and connect the outlet ports back into the reservoir. Fill with fluid and push on the piston. If fluid comes out the back then you have a bad seal.

John

[jhuebner]

If I get some time this weekend will do the bench bleed also have a new vacuum check valve, and a proportioning valve still had originals on the car, my brake calipers are missing the splash shields, do they also retain the brake pads?

[simplyconnected]

Splash shields are optional. Some 'grab' the air and cool the rotors as your car moves. I guess they help keep water off the rotors as well. Most of my driving is in dry weather.

I run with no splash shields on the Galaxie and it has never presented an issue. - Dave

[jhuebner]

Finally had time to work / finish brakes, new booster, M/C, proporting valve, rebuilt calipers, flex hoses front & back hard lines, and rear cylinders. ....yes they work....now I just need one washer nozzle tip and the car is ready for inspection