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Squishy Brakes After Replacing Rear Shoes

whitefish

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whitefish Enthusiast

whitefish

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I replaced my front disc/pads last weekend and did the drums/shoes this weekend. I had no problems when I replaced the front brakes, drove it all week. But after replacing the rear ones, my brake pedal is squishy and heads for the floor.

 

I checked my rear shoes, as snakedoctor mentions here and they're fine and seem to be in adjustment:

http://www.gm-trucks.com/forums/index.php?showtopic=134344

 

The only thing I think of is one of the pistons on one of the slave cylinders popped off when I was putting the shoes on one side. Abit of brake fluid leaked out, maybe 1/4 to 1/3 of a cup. The reservoir on the master cylinder is still full. So, did I get air in the lines by doing this? Would this cause my soft brakes?

 

Thanks - Fish

dlewis1111 Senior Enthusiast

dlewis1111

Posted
Posted
I replaced my front disc/pads last weekend and did the drums/shoes this weekend. I had no problems when I replaced the front brakes, drove it all week. But after replacing the rear ones, my brake pedal is squishy and heads for the floor.

 

I checked my rear shoes, as snakedoctor mentions here and they're fine and seem to be in adjustment:

http://www.gm-trucks.com/forums/index.php?showtopic=134344

 

The only thing I think of is one of the pistons on one of the slave cylinders popped off when I was putting the shoes on one side. Abit of brake fluid leaked out, maybe 1/4 to 1/3 of a cup. The reservoir on the master cylinder is still full. So, did I get air in the lines by doing this? Would this cause my soft brakes?

 

Thanks - Fish

 

If fluid leaked out, then air probably took its place. Time to bleed.

nickvrebel Senior Enthusiast

nickvrebel

Posted
Posted

you definitely have air in the line. Your symptoms point straight to that and the fact you had fluid come out means air went in. bleed them.

whitefish Enthusiast

whitefish

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Ok thanks guys. I wanted to change out the brake fluid anyways. When bleeding the brakes, is there anything special you have to do with an ABS system?

whitefish Enthusiast

whitefish

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I did a google search and found a bunch of info on brake bleeds and GM ABS. I think I'll try the pressure bleeder from Motive and poor mans cycling of the ABS module (gravel road).

whitefish Enthusiast

whitefish

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Quick question - if the antilock system hasn't been activated since I got air in the lines, would there be air in the antilock module? In other words, would i have to purge the antilock module if its isolated from the rest of the system until activated.

Doug_Scott Senior Enthusiast

Doug_Scott

Posted
Posted
Quick question - if the antilock system hasn't been activated since I got air in the lines, would there be air in the antilock module? In other words, would i have to purge the antilock module if its isolated from the rest of the system until activated.

 

Not likely. Chances are very good that you only need to bleed the wheel the lost the fluid, if a very small amount leaked out.

whitefish Enthusiast

whitefish

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Not likely. Chances are very good that you only need to bleed the wheel the lost the fluid, if a very small amount leaked out.

 

Thanks Doug - thats what I thought. I'll give it a try and see if it makes a difference. I suppose I can't make it worse.

jblakeney Senior Enthusiast

jblakeney

Posted
Posted

Yup, AIR in the line. Bleed brakes.

 

passengers rear

drivers rear

passengers front

drivers front

 

Sounds like a good time to flush the old brake fluid out tooooo. As it probably was brown which means the fluid has water in it. Causing rust in the system.

 

Jbo

whitefish Enthusiast

whitefish

Posted
  • Author
Posted
Yup, AIR in the line. Bleed brakes.

 

passengers rear

drivers rear

passengers front

drivers front

 

Sounds like a good time to flush the old brake fluid out tooooo. As it probably was brown which means the fluid has water in it. Causing rust in the system.

 

Jbo

 

Actually, it was greenish colored. Not sure if thats what it looks like new.

jblakeney Senior Enthusiast

jblakeney

Posted
Posted
Yup, AIR in the line. Bleed brakes.

 

passengers rear

drivers rear

passengers front

drivers front

 

Sounds like a good time to flush the old brake fluid out tooooo. As it probably was brown which means the fluid has water in it. Causing rust in the system.

 

Jbo

 

Actually, it was greenish colored. Not sure if thats what it looks like new.

 

 

Ya flush it..... Never seen green brake fluid......

 

Jbo

jblakeney Senior Enthusiast

jblakeney

Posted
Posted
Yup, AIR in the line. Bleed brakes.

 

passengers rear

drivers rear

passengers front

drivers front

 

Sounds like a good time to flush the old brake fluid out tooooo. As it probably was brown which means the fluid has water in it. Causing rust in the system.

 

Jbo

 

Actually, it was greenish colored. Not sure if thats what it looks like new.

 

 

Ya flush it..... Never seen green brake fluid......

 

Jbo

whitefish Enthusiast

whitefish

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yup - usually clear. Gonna try this weekend with the one man bottle (no vacuum pump) method.

 

I picked up a BIG jug of Prestone DOT 3 just in case.

whitefish Enthusiast

whitefish

Posted
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Bled the brakes this weekend and long story short, it worked! Brakes are nice and firm again.

 

I used this method, with some modifications:

 

 

 

- I had my wife pump the brakes while I held the hose on the bled screws to make sure air didn't get past the hose and screw

- I added a little grease around the bleed hose to ensure an air tight seal as well as on the bleed screw base

- while I was holding the hose on the bleed screw, I made sort of a small "J trap" to keep fluid against the screw at all times. Otherwise brake fluid just flowed down the hose, leaving air next to the bleed screw. Don't know in the end if this made any difference, but theoretically it did.

 

All in all, it worked great. I haven't tried the ABS out yet to see if there are any problems, but the ABS system did its checks at start up (did this twice) and the ABS light went off so good so far. I plan on taking the truck on a gravel road to trigger the ABS to see if there was any air trapped in the module. My theory is that since the air got in at the drum slave cylinder and the ABS hasn't been activated, there should be no reason for air to be in the ABS module. We'll see if the theory holds up. :)

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