Is it OK to step on brake pedal with drum removed?

Dibbons

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If the drum is removed (nothing else) will the wheel cylinder expand too much (and maybe come apart) if one steps on the brake pedal with the drum off? After 3 years in storage, I find the left rear wheel is free wheeling when pressing on the brake pedal (this is after completely bleeding the brake system). Trying to figure out the problem on this 8 3/4 differential a previous owner swapped into a '65 A Body.

left rear brake.JPG
 

4406bbl

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Sure, half a stroke or so to see if it moves.

I guess I better add if you overdo it it will come apart, later backing plates had stops to prevent this, but I do not know what you have.
 
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kiwigtx

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What might happen is if there is a 'lip' on the wheel cylinder bore, the rubber seal will pass over it and create more damage than with the drum on.
Check for leaking first, and then proceed carefully ....have an assistant gently press the pedal while you watch what happens.
 

mr. b

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have a helper put screwdrivers on both brake shoes and backing plate then press the brake pedal easy you will see the shoes move
 

69a100

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I did this once and it made a mess. It popped the rubber boot and sent a piston flying and puked brake fluid everywhere. You can tie a loose wire around it to prevent that from happening while still allowing the cylinder to do it job of moving in or out. Good Luck
 

toolmanmike

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Sure you can. Go ahead and do it and report back to us with the results. You probably won't like what happens though.
 

Dibbons

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Did you get any air/fluid out of that wheel cylinder when you bled it?
Yes.

Just found this interesting info on the internet:

"The wheel cylinder can become seized:

Over time these may becoming rusty or filled with dirt which is usually a result from failing boots. Wheel cylinder has both a front and rear piston, therefore two in total. Either one or both pistons can become seized. To determine if the wheel cylinder faulty, you should be able to push the pads inward from one side to the other if the pistons aren’t bottomed out. If not, then have a second person, being extremely careful, lightly depress the brake pedal. Do not got too far as you do risk pushing the piston out completely. In order to remove the drum, the automatic adjust can be backed off through the small hole in the backing plate. If that fails, then you may need to cut the hold down spring pins on the backing plate or remove the wheel cylinder completely. As for repairing the issue, you can rebuild the wheel cylinder yourself, have someone rebuild the unit for you, or purchase a new replacement."

My situation now: I found on the right rear (which stops the wheel OK) I can press in on the wheel cylinder by pressing inward on the brake shoes. On the problem side (left rear) I cannot budge the wheel cylinder inwards at all. This cylinder must be locked up/seized nice and tight. Needs to come off for a replacement or rebuild. The differential is a later 489 8 3/4 (not the original 7 1/4). I don't know how many different wheel cylinder versions come on these differentials. I do know the brake drums are 10 inch and fit this A '65 ABody (Barracuda).

489 differential 1.JPG
 
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LowBikeMike

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Its possible the rubber hose that connects the hard lines has clogged or collapsed and only passes fluid when there is no restriction at the wheel cylinder (bleeder open). If you press the pedal slowly with a helper watching the shoes for movement and don't overboard you should be fine. I'm betting on a collapsed hose though
 

MoparLeo

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Not complicated. Just plan on replacing both wheel cylinders and possibly the flexible diff hose. When sitting they just gum up, rust and corrode. Just like the cooling system. If you don't keep the fluid clean aand flowing everything will eventually seize up.
Less time and safer to just do it right.
Brake system is the most important system on your car. Doesn't matter how fast or cool looking it is. Everything can change with one pump of the pedal...
 

69a100

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If you suspect one is bad, you might as well just replace the both of them as I'm sure the other one isn't far behind. The same goes for the fronts even if you haven't looked at them yet, do 'em all and feel confident! Good Luck
 

YY1

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I've tapped out a stuck piston with a wood dowel and hammer, then lightly sanded out any ridge in the bore with a brake cylinder hone.
The piston usually doesn't get a ridge but you can check and lightly sand that as well.
 

Don Frelier

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I would definitely replace the flexible line down to the rear axle if it's original as well as the rear wheel cylinders from what you describe.
Flush a couple volumes of the master cylinder through everything.
 

Dibbons

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Thank you, the rubber lines have been replaced when I first purchased the vehicle and renewed the brakes the first time. Wheel cylinders are already shipped from Rock Auto (hope they fit).
 
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