Brake pedal goes to the floor after new shoes

[SUBURBAN5]

Here's amazon

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[97c1500ext]

Adjusted the drums as far as i could then Ran through the full bleed process, mc then wheels in the pattern and theyre nice and tight now. As tight as brakes get on this truck anyway. Thanks for the help everyone

 

[pressureangle]

If they're working well, great! I was going to ask the basic and embarrassing question, "are the shoes on backwards?" Getting the long shoe on the leading side causes both poor performance and jerky/locking with no control, and adjustment just doesn't work.

 

[SUBURBAN5]

Good job. Glad you found it

 

[Schurkey]

they are the dreaded 10in drums in the rear

I was going to ask the basic and embarrassing question, "are the shoes on backwards?" Getting the long shoe on the leading side causes both poor performance and jerky/locking with no control, and adjustment just doesn't work.

But with the craptastic 254mm (10 inch) leading/trailing shoe drums, all four rear shoes are identical.

 

[Russ B]

This may be off base. Presuming all was well before you started on the back brakes, not sure how the MC had anything to do with it. So I am thinking the problem is at the back brakes. I would be inclined to think the wheel cylinders were shot. As the brakes wear the cups in the WCs get pushed outward. When you redo the brakes they get pushed back into their original inward position. Combined with age and accumulated dirt, they may not seal. Cheap fix is to just change them.

 

[Russ B]

I did not read all the posts, so missed that you redid the front calipers as well. Any chance you forgot to install the copper washers at the calipers? In fact if you did, possible the new ones did not seat enough. I have had to reuse the old ones as the new ones would not seal. My very first break job over 50 years ago I did not know about those washers. Very upset wife spent several hours pushing on the brake pedal to no avail. Ended up getting car towed to dealer just to install the washers on the calipers. To this day wife does not like helping on brake jobs just because of that.

 

[Hotcorner]

Glad you fixed the problem. Did you bleed the module with a scan tool?

 

[Russ B]

Not sure I get your logic of jacking up the the rear wheels. Seems to me that would prevent master from getting all the air out. Need to have vehicle level to bleed. MC is usually highest point in the brake system. Not all MC are level so have to take that into consideration.

Not sure this applies, but my first brake job in the 1970's I could not get a pedal. After hours of bleeding wife was ready for divorce. Ended up having car (Chevette) towed to dealer. I had dropped the copper washer to the wheel cylinders.

When in doubt, takes two people. With vehicle totally up on jackstands, one hits the brakes and other checks each wheel for brake action. Do it with engine on and then off. To bleed you may have to put teflon on the bleeder threads to get a good seal. Also put clear plastic line on the bleeder and route it upwards to allow air bubbles to move and not return. Also can gravity bleed that way, just leave bleeder cracked.

Booster is always suspect when all else fails. With engine off, foot on brake, turn on engine and see if pedal falls. If it does, booser is working.

Bleeding MC is as much art as science. I do it off the car, but you can do on the car. Use plastic fittings and tubes to route fluid back to MC until all air is out. If that does not work put plugs in MC and see if it holds pedal.

 

[Schurkey]

Not sure I get your logic of jacking up the the rear wheels. Seems to me that would prevent master from getting all the air out. Need to have vehicle level to bleed. MC is usually highest point in the brake system. Not all MC are level so have to take that into consideration.

Most all master cylinders are tipped "UP" in front. Brake tubing generally screws into the side of the cylinder, not the top.

If there's a small air bubble in the master cylinder, it'll never come out the brake tubing. It'll be trapped all the way forward, and above the brake tubing. Best way to get rid of it is to lower the front of the master so the bubble goes to the rear, then tickle the piston(s) until the bubble releases into the reservoir via the ports between cylinder and reservoir.

When in doubt, takes two people.

Not an option when working alone.

I gravity bleed for work at or near the wheel cylinders, and pressure bleed for major work or work at or near the master cylinder.

To bleed you may have to put teflon on the bleeder threads to get a good seal.

Yes...but only if you're vacuum-bleeding. No need when pushing the fluid out the bleeder.

Booster is always suspect when all else fails. With engine off, foot on brake, turn on engine and see if pedal falls. If it does, booser is working.

Well...if the vacuum was depleted when you start, sure--the pedal should drop some. If the booster still had a proper vacuum reserve, the pedal won't drop much if at all.

But that doesn't mean there's nothing wrong with the booster. I've seen boosters that pass all the "typical" tests--hold vacuum, pedal drops when vacuum is applied, no audible leakage when the pedal is pushed--but they still had no or reduced "assist", so the brakes were more like manual brakes than power brakes.

Bleeding MC is as much art as science. I do it off the car, but you can do on the car. Use plastic fittings and tubes to route fluid back to MC until all air is out. If that does not work put plugs in MC and see if it holds pedal.

Bleeding the master cylinder "on the bench" takes more time and effort than most folks realize.