Bad Power Brake Booster?

[Hikin Mike]

The car is a 68 Coronet with drum brakes. I added a power brake booster about 25 years ago. Car hasn't been registered since 2005 due to my mobility issues. My legs can't bend and my brake pedal is very high so I'm not able to drive it safely. I'm trying to figure out how to lower the pedal. I haven't modified anything yet.

So lately, when I pull the car out of the garage the brakes are barely stopping it. Decided to pull the wheels and check for leaky wheel cylinders. Everything was fine, so I tried to bleed them. Got pressure on all 4 wheels but now the car won't stop.

Does it sound like a booster failure? Or do I continue to try and bleed them again?

 

[The Rebel]

Possible vacuum leak?

 

[Hikin Mike]

Possible vacuum leak?

Don't think so.

The car is on jack stands and my wife just pressed the brakes, engine off (battery out of the car) and I can spin the wheels.

 

[Bad B-rad]

Are drums adjusted correctly?

 

[Hikin Mike]

I did have to back out the adjusters to get the drums off. I THINK I have them adjusted correctly. The fronts spin about a turn (wheels off) until they stop.

 

[69L48Z27]

With your foot on the brake pedal, lightly. Start the car, of the pedal drops a little then your booster is working.

Who knows if your wheel cylinders are still working 100%. Also you could have rust on the drums.

 

[Hikin Mike]

With your foot on the brake pedal, lightly. Start the car, of the pedal drops a little then your booster is working.

Did that yesterday and there was no change, that's why I think it's bad. My only concern is when I bled them yesterday they held. Not great but they held.

Who knows if your wheel cylinders are still working 100%. Also you could have rust on the drums.

I didn't look at the drums.

 

[Bad B-rad]

So no change in brake feel when off to running?
Have you checked vacuum lines to booster?

Could also be the master, internal leakage.
Sorry I cant be more help, Good luck!!!

 

[Hikin Mike]

So no change in brake feel when off to running?
Have you checked vacuum lines to booster?

Could also be the master, internal leakage.
Sorry I cant be more help, Good luck!!!

Thanks! I'll re-verify in the morning.

When I added the booster 25 years ago, I removed the brake firewall plate because it won't fit. I now have the correct plate so I installed it recently. Seems like after I did that, everything went to pot. So tomorrow I'm going to do some checking and see if something got moved or something.

 

[Hikin Mike]

Removed the master cylinder from the booster and looks like I'm missing the adjustment on the rod.

Quite possibly it fell out the last time I had it apart and never noticed.

Anybody have an extra I can purchase?

 

[Bad B-rad]

If you cant find the just the adjuster/or a new rod, then I have a complete master and booster from a 67 Charger, but I bet shipping from NY to CA, would suck.

 

[Hikin Mike]

If you cant find the just the adjuster/or a new rod, then I have a complete master and booster from a 67 Charger, but I bet shipping from NY to CA, would suck.

Thanks. I'm looking at just buying a booster at the local auto part store. I'm not 100% sure the booster I have is correct. I did this 25+ years ago and I can't remember where or how I got it. Suck getting old.

This is what I have now. Does it "look" correct?

 

[Bad B-rad]

Mine was removed from a perfectly fine 67 Charger that was being upgraded to power disc brakes from aftermarket kit, It looks a touch different.
Mine has the double hump master, I think the cap is held on with a bolt not the bail arms.
I also think my booster in crimped together.
When it cools down I will go into my shop its in the loft, and its 89 degrees out so that means like a million degrees up there now, LOL!!

I am fairly sure the master I have looks like this

 

[Hikin Mike]

I understand about being hot. It's been in the high 90 for awhile. I do any work before noon.

I've seen both the bailing arms and the double hump as being "correct" or maybe suitable at the auto part store's website. Looking at @JimKueneman Coronet, his has the humps.

Thanks again.

 

[Bad B-rad]

I THINK it just depends on where the car was at built, some got Bendix, some Midlan ross.
I can do some home work, and let you know for sure.
But I think you are right, both are considered correct.

 

[Bad B-rad]

The master you have looks to be from a 1971.
I am not saying it wont work, I was just looking threw my books and it looks like in 1968, it claims only one master cylinder was used P/N 2808599, and it is the one I posted a photo of.("S" clamp held double hump)
The style you have was used on power drums in 1971, and has a slightly larger piston.

I am not saying your set up wont work, just that is was not used from Mopar on drum brakes in 1968

 

[Don Frelier]

The car is on jack stands and my wife just pressed the brakes, engine off (battery out of the car) and I can spin the wheels.

This is a good first check.
NO - you shouldn't be able to turn any wheels by hand even with the car off using moderate pressure on the pedal with power brakes.
I would say something isn't right. When you bled the brakes pedal pushes blew out fluid accordingly?

 

[Hikin Mike]

The master you have looks to be from a 1971.
I am not saying it wont work, I was just looking threw my books and it looks like in 1968, it claims only one master cylinder was used P/N 2808599, and it is the one I posted a photo of.("S" clamp held double hump)
The style you have was used on power drums in 1971, and has a slightly larger piston.

I am not saying your set up wont work, just that is was not used from Mopar on drum brakes in 1968

Funny that I didn't see you picture until now. It has worked for 20 years. The only reason I'm looking into it more is because I can't drive it because the brake pedal is extremely high and I can't bend my knees. Jim verified my pedal is too high. I re-installed that brake plate which seems to have helped, but in the process I think part of the adjustment fell off. Don't know how, but it's missing.

 

[Hikin Mike]

When you bled the brakes pedal pushes blew out fluid accordingly?

Yes. I think it's because I'm missing part of the adjustment rod. See few replies above this.

 

[Ron H]

If the booster rod is missing the adj tip (if it had an adj one) this won't engage the MC as you know. If it was gone you never should a had brake engagement and the tip should be somewhere...maybe where you separated the booster from the MC. Who knows could be laying down in the engine bay. There's a critical adj gap btw the booster rod and MC and if it's a factory unit you can look up the spec's, mine being a conversion though, requires a .20 gap. Mopar I think has a larger gap and also think might vary by system mfg. There's also a pedal ratio factor btw power and manual brakes that influences pedal height. If this is an untouched factory setup (well sounds like possibly not) that shouldn't be a factor. The pedal should set around 1.5" or so higher than the gas pedal normally. If it's way high then the rod attaching to the booster rod thru the firewall could be checked...I had to shorten mine due to excessive height; but again I have a power disk brake conversion from manual brakes. A tip could be fabricated by the correct size/thread bolt and grinding down the bolt end to mate the radius on the MC piston and add a jam nut for locking it in place as an interim measure until finding a correct tip. This would be something I'd do to see if this solves the problem...