Over the past month, I have replaced my master cylinder twice, brake booster, brake lines, drums, shoes, calipers, and pads on my 96 Jimmy. I did this all due to symptoms or wear.

Now, I've replaced the lines today because my old ones seemed to collapse on themselves. Now that parts fine, brakes work great, but its as if the pedal continues to slowly sink down once i've come to a stop. I cannot find a leak anywhere.

I did have to remove the junction that connects the abs and regular lines to the master cylinder in order to get the brake booster out and in. I'm wondering if I've got air in my abs system and thats whats going on here. I'm thinking this because the sinking pedal feeling didn't happen until after I purposely locked up the brakes and activated the abs.

My step dad has been working on cars and motorcycles for probably 40 years, and he's telling me its just more air in the system and I'll be able to fix this by re-bleeding. Whats your take? The pedal and brakes feel great until it slows down and the pedal starts very slowly sinking.

 

After doing some digging around, i'm going to go buy a vacuum pump tomorrow and bleed the brakes again without pumping the pedal. I'm going to attempt to run all the air out of the abs before I do a regular bleed. Then I'll test drive it and see how it goes.

If anyone else has any better methods please let me know

 

No mention of year, but with rear drums, it must be 1997 or older. Try a gravity bleed first. Search the forum or Google for details, but basically remove the master cylinder cover, make sure the reservoir is full, and open each bleeder, one at a time. Let each one drip until no bubbles are seen exiting the bleeder valve, (usually up to 10 minutes per wheel). Do not pump the pedal during this procedure, and do not allow the reservoir to run low.

 

Thanks Captain, it is a 1996 you're right. I am going to give gravity bleeding a go tonight and see where it gets me. I bought a mityvac to speed up the process a bit, we'll see how it goes.

 

Shouldn't need the mityvac, it should start on its own or there's a problem.

 

well, I am going to gravity bleed it first, then I may use the mityvac if I need to in the end. Do you leave the car running when your gravity bleeding, or does it matter?

 

Engine off, master cyl cover removed, reservoir kept full during the bleed, do not pump the pedal.

 

Thanks Captain, I should be able to get time to do this within the next day or so. Works been crazy. Hope it all goes well, thank you.

 

So I finally got a chance to work on my truck today. I'm in houston, so we're getting hit with some pretty crappy weather right now. After waiting through the entire weekend for some dry weather, we just went for it and spent about 3.5 hours in the rain gravity bleeding under a pop up canopy. After I gravity bled every wheel for about 15-20 minutes, we gave it a regular bleed and the brakes feel great now. I believe I got all or atleast most of it out of the ABS module, I hope so anyways. We'll see in the next few days of driving it.

Thanks again for all the advice. Now I can get back to things I really want to do to my truck, like finishing the body work and laying a nice gun metal paint job down.

 

Glad you have brakes again, and thanks for posting back.