Fox Brake booster keeps failing.

Kid wita 5oh · Jul 19, 2023

Have you replaced the check valve with each new booster?

93CalypsoConvert · Jul 19, 2023

Yes. I even tried a second in-line check valve

General karthief · Jul 19, 2023

Maybe find a different brand booster?

93CalypsoConvert · Jul 19, 2023

Can anyone recommend a good replacement? Or even an upgrade?

General karthief · Jul 19, 2023

Have you looked on Rockauto?

93CalypsoConvert · Jul 19, 2023

Yes. I have the Cardone one

Shakerhood · Jul 22, 2023

93CalypsoConvert said:
From the tree labeled BB

I know its grasping at straws, but did you check the vacuum tree to make sure it is free of any cracks?

AeroCoupe · Jul 23, 2023

Would be easier to just get a vacuum gauge and put it on the car and see what it does or build smoke machine and check for leaks.

93CalypsoConvert · Jul 23, 2023

Tree and manifold vacuum are nearly identical. No leaks as far as I know.

mikestang63 · Jul 24, 2023

Only thing I can think of is you may have a bad soft line, seal, wheel cylinder and when it gets hot the line expands to the point your pedal sinks

93CalypsoConvert · Jul 24, 2023

I thought that too but it must be the booster since the MC can be unbolted and my brake pedal still won't return.
Unless the booster relies on the spring pressure in the master cylinder.

AeroCoupe · Jul 24, 2023

Boosters are typically constructed with a return spring that returns the brake pedal to the original position. Vacuum just reduced the effort that it takes to overcome the spring pressure. So once the vacuum is removed and there is no pressure on the brake pedal rod then the booster diaphragm should return to the orignal position.

Mustang5L5 · Jul 25, 2023

93CalypsoConvert said:
I thought that too but it must be the booster since the MC can be unbolted and my brake pedal still won't return.

Binding in the pedal/ pedal assembly?

With the pedal bound, can you unclip the booster rod from the pedal and see what is free? Pedal or booster?

I'm suspicious that you've gotten multiple boosters in a row with the same issue. Needs to be something that has remained with the car after changing all the parts that you have.

limp · Jul 25, 2023

Mustang5L5 said:
Binding in the pedal/ pedal assembly?

With the pedal bound, can you unclip the booster rod from the pedal and see what is free? Pedal or booster?

I'm suspicious that you've gotten multiple boosters in a row with the same issue. Needs to be something that has remained with the car after changing all the parts that you have.

Good thought here.... The bushings in the pedal assembly could be worn out...

93CalypsoConvert · Jul 30, 2023

It is the booster itself which is consistently failing. MC can be removed and the pedal can be disconnected

85GTStangGuy · Jul 30, 2023

93CalypsoConvert said:
...... Pushrod is adjustable, and is adjusted......

Might be worth double checking that...

limp said:
Good thought here.... The bushings in the pedal assembly could be worn out...

Previously....

93CalypsoConvert said:
Just checked. No bushings.

Mustang5L5 · Jul 31, 2023

That's just strange that you are having multiple boosters fail for the same issue. Have they both been Cardone remans?

93CalypsoConvert · Aug 1, 2023

Both new Cardones. They have lifetime warranty but its far too late to get a refund. I might try spraying some lubricant into the pedal side of the booster. Any ideas what type I should use? I know some oils are bad for seals.

Mustang5L5 · Aug 1, 2023

Silicone lubricant would be best. Petroleum based will make rubber swell.

88FoxLX5.0 · Nov 30, 2023

Hello! Any updates on this? Having the exact same issue under same circumstances. Once MC is unhooked, the brake pedal is still stuck down an inch or so… On my second (reman) Cardone 5.0 booster from RockAuto. Pedal is free and not binding

Fox Brake booster keeps failing.

Kid wita 5oh

I'm definitely not in the original hole

93CalypsoConvert

Active Member

General karthief

wonder how much it would cost to ship you a pair

93CalypsoConvert

Active Member

General karthief

wonder how much it would cost to ship you a pair

93CalypsoConvert

Active Member

Shakerhood

AeroCoupe

lube between the nut and the face. I know my lubes

93CalypsoConvert

Active Member

mikestang63

93CalypsoConvert

Active Member

AeroCoupe

lube between the nut and the face. I know my lubes

Mustang5L5

That is…until I whipped out my Bissell

limp

wrap a little cheese around it and its a done

93CalypsoConvert

Active Member

85GTStangGuy

Mustang5L5

That is…until I whipped out my Bissell

93CalypsoConvert

Active Member

Mustang5L5

That is…until I whipped out my Bissell

88FoxLX5.0

New Member

Similar threads

Fox Brake booster keeps failing.

I'm definitely not in the original hole

Active Member

wonder how much it would cost to ship you a pair

Active Member

wonder how much it would cost to ship you a pair

Active Member

lube between the nut and the face. I know my lubes

Active Member

Active Member

lube between the nut and the face. I know my lubes

That is…until I whipped out my Bissell

wrap a little cheese around it and its a done

Active Member

That is…until I whipped out my Bissell

Active Member

That is…until I whipped out my Bissell

New Member

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