I am stumped with the brakes on Tux

Boydsdodge

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Hello, I think I need some input or knowledge help with the brake problem on my Imperial.
1973 Imperial, New Raybestos pads and shoes, rebuilt and restored booster, new master cylinder, then back to the original master, new rear wheel cylinders, new flex lines front rear, all new brake hardware in drums, new NOS calipers.
I have had a hard pedal with slow stop since I brought Tux home. I pulled the booster and had it rebuilt, it failed booster test with vacuum and had plenty of old brake fluid crystallized inside. Also had booster replated.
Installed booster but bad winter, held off on road test till April. Once road tested I still had a hard pedal, so I thought it might be a faulty new offshore master cylinder I had installed with booster. replaced with good working Chrysler master from Imperial.
Still hard slow stopping.
Replaced front calipers that I rebuilt earlier with NOS calipers, I was thinking maybe my old calipers were hanging up.
Still hard pedal and slow stop.
I replaced the pads and shoes with new wheel cylinders and all drum hardware.
Same feel, this time I feel the pads grabbing better, car stops straight as it always has, but it is still a hard pedal slow stop. While sitting at a light waiting for change, the pedal almost feels as if its starting to push back.
I took Imperial out for a 40 min drive on two lane, urban main and side streets.
As I was on the return run I could feel pulsing brake grab on side streets. Not enough to stop the car, but enough to create a pulse slowing pulse in the car. This is new, but may be because new pads and shoes grab better the the asbestos.
Could this be the combination/proportioning valve?
Could the metering valve be stuck?
I have not had this problem before, all the cars I have done over the years, I have had symptoms like this but it was booster, seized calipers, etc...
Running out of time for the big Carlisle drive.
Extra input. Brakes get harder after first few stops, hard from start. I have been bleeding brakes with hose into jug of brake fluid with steading push of pedal until no air and pedal hard.
Thinking I might try another master.
Thanks.
 
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WOT440

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I had similar issue a while back on front drums. If I remember correctly, I swapped out the new off-shore brake hoses, for some OEM hoses. I also swapped out the new off-shore brake cylinders for OEM.
 
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68 4spd Fury

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In what you wrote, you didn't mention the rubber hoses, to each caliper and the one to the rear axle. If they are old they can inhibit fluid return. Another thing is make sure all the brake lines are clear, blow them out with air or keep pumping fluid through until it runs clear. Just some thoughts, good luck!
 

halifaxhops

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Did you adjust the push rod for the master and booster also?
 

pomonamissel

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is it a duel diaphragm ? does the engine run like a vac leak ? i've had rebuilt booster units brake one of the pair of diaphragm was torn , rebuilder said its was from lack of use it failed .
 

Ripinator

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Hello, I think I need some input or knowledge help with the brake problem on my Imperial.
1973 Imperial, New Raybestos pads and shoes, rebuilt and restored booster, new master cylinder, then back to the original master, new rear wheel cylinders, new flex lines front rear, all new brake hardware in drums, new NOS calipers.
I have had a hard pedal with slow stop since I brought Tux home. I pulled the booster and had it rebuilt, it failed booster test with vacuum and had plenty of old brake fluid crystallized inside. Also had booster replated.
Installed booster but bad winter, held off on road test till April. Once road tested I still had a hard pedal, so I thought it might be a faulty new offshore master cylinder I had installed with booster. replaced with good working Chrysler master from Imperial.
Still hard slow stopping.
Replaced front calipers that I rebuilt earlier with NOS calipers, I was thinking maybe my old calipers were hanging up.
Still hard pedal and slow stop.
I replaced the pads and shoes with new wheel cylinders and all drum hardware.
Same feel, this time I feel the pads grabbing better, car stops straight as it always has, but it is still a hard pedal slow stop. While sitting at a light waiting for change, the pedal almost feels as if its starting to push back.
I took Imperial out for a 40 min drive on two lane, urban main and side streets.
As I was on the return run I could feel pulsing brake grab on side streets. Not enough to stop the car, but enough to create a pulse slowing pulse in the car. This is new, but may be because new pads and shoes grab better the the asbestos.
Could this be the combination/proportioning valve?
Could the metering valve be stuck?
I have not had this problem before, all the cars I have done over the years, I have had symptoms like this but it was booster, seized calipers, etc...
Running out of time for the big Carlisle drive.
Extra input. Brakes get harder after first few stops, hard from start. I have been bleeding brakes with hose into jug of brake fluid with steading push of pedal until no air and pedal hard.
Thinking I might try another master.
Thanks.

This really sounds like a booster problem. Also, the pulsing you experience indicates that perhaps the push rod from the master cylinder to the booster is not set correctly. I think it is almost a black art to get that damned rod adjusted right. The FSM may help. . .
 

Boydsdodge

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I agree on it sounds like a booster problem. I have backed the the push rod off to double check that it had clearance.
Thanks
 

Big_John

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Thinking about it, I would try this... Start the car and pump up the brakes so they get hard and while holding the brake pedal down (obviously you'll need help) and then go crack one of the front bleeders and see if the pedal drops. If it drops, that brake hose (on that side) is probably OK. Do the other front and then the back. Since there's only one hose in the back, you'll probably only need to crack one side.

This should verify the hoses and lines are good.
 

Boydsdodge

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is it a duel diaphragm ? does the engine run like a vac leak ? i've had rebuilt booster units brake one of the pair of diaphragm was torn , rebuilder said its was from lack of use it failed .
That is what I was thinking, maybe only one diaphragm doing the work. with my vacuum pump connected, the booster will hold 20" with out a drop until I touch the pedal.
It does take almost a minute for the vacuum to rebuild. But it is a small pump.
 

Big_John

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While this guy's elevator doesn't go to the top, and I would never buy from him, he does have some good videos with good info. Worth watching to maybe get an idea of what to check.






 

1970cat

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when bleeding, does the pedal push hard or drop easily without the car running? i've had proportioning valves stick to where i could force fluid through with the pedal but it took a lot more effort than it should have.
 

thethee

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Sorry if this is too obvious, but have you checked vacuum reading at the booster line?
 

Boydsdodge

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When this first started I went through all the connections and hoses, all checked out well. Then when my cruise control stopped working, I did find that the cruise control servo had a full vacuum leak. shaped put servo this week. test drive, same as before. Scratching my head, I started going through the vacuum points on engine booster. Booster holds well with 22" vacuum, holds until I release. Then I removed the 11/32" vacuum hose from engine, plugged end and hooked up vacuum pump, I leaks. I couldn't see it at first but found it. Right in the crease from where the corbin clamp sits was a split a third of the hose. I am waiting on replies from couple parts stores now to get new hose picked up. I hope this is it. The hose would pull vacuum on the car when hooked to gauge, but I am thinking that when brakes are used it leaks enough to not allow booster to refill fast enough.
I will post results.
 

Boydsdodge

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My parts store is ordering in for noon, I had to buy the roll of 25'.
If anyone is in need of 11/32" vacuum hose, I will have stock.
Store doesn't want to stock old car parts.
 

Boydsdodge

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Uncross your fingers.
Went for test drive, things are getting worse. Rear brakes are staying loaded, smoking on return to garage after 20 min drive. wheels off ground I can barely turn. loosened master to see if I was as stupid as I am starting to feel. no difference. Loosened rear brake line at master to see if it was holding pressure. no change. tried parking brake, locks tight, released parking brake, very tight wheels.
Still hard pedal.
I took temps when I returned, right rear 205 deg, left rear 195 deg. Fronts 150, all temps taken between lug nuts on wheel.
I didn't think the crack in hose was going to be the cause.
 

thethee

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Damn.. but it does provide new insight in your problem I'm sure. Could it be that your hard pedal is not a lack of booster function but more an overactive brake system if you know what I mean?

Could it be as simple as a problem with the brake self adjusters? The rears shouldn't get hotter than the front since front should handle most of the braking, that I know.
 
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