Brake issues, here we go again

[dpuckett]

I have been battling a brake issue with the pickup in my signature since I bought it back from my step dad 3 years ago. Pedal has always been kind of mushy but not horrible or unsafe. Yesterday, it crossed the line. After a yellow light turning d about 3 seconds before I anticipated, I ended up coming to rest in the middle of the intersection. The pedal eventually ended up on the floor, or darn close, and the rears kind of locked up, but not really. Fronts never did lock. After driving it 200 MO today in my shoeing rounds, I began checking things out.
A little background.

Master cylinder is a new Bendix from Rock Auto (ca 2010).
Wheel cylinders were new at the same time. Bendix 1"
Calipers are NAPA remains.
It got new pads and shoes all around, as well as drums about a year ago.
ALL new hoses up front, rear still has the original.
RWAL has been completely bypassed, so that is definitely not an issue.

I plugged the outlet ports on the MC and the pedal was firm and high, just like it should be under normal driving.
Hooked up the line to the rear. Pedal sank maybe 1/16" more than before. Well within the range of acceptable.
Plugged the port to the rear again, and hooked up the line to the front. Mushy pedal, eventually fell to the floor. This tells me to look on the front end.
Removed a tire and caliper. Can't move the cylinder in the caliper with a prybar or hammer. Pushing the pedal with the pad removed nets no noticeable movement of the cylinder. This tells me the caliper is bad. Am I on the right track here? Is there anywhere else I need to look?
Thanks,
Dan

[ellis93]

Sounds like your headed right to me. id probably have someone mash the pedal while I watch the brake lines for any kind of rubber bulge. That'll give a soggy pedal

[PToombs]

If you step on the pedal with the calper off and the piston doesn't move, it's seized solid and junk. If the truck stops straight and doesn't pull, you need to buy 2 of them, because obviously the other side is seized also.

[Diesel]

You're on the right track but I find it hard to believe that two reman calipers are bad. I've had a reman blow out seals on me. I get the feeling it could be your master. The sinking pedal to the floor makes me think there has to be fluid going somewhere it should be. How does the booster look?

[bmoeller]

I've had 8 bad reman wheel cylinders in a row before, for the same friggin' truck! ALL of them leaked out of the box!! Dayton wheels and NO dolly or help. NAPA and Carquest was tired of seeing me come in with them, so I swapped guts between 4, for the last 2 I needed, til I got'em to stop leaking. Took a GD week to do the work, and my back was killing me. Was ready to roll the f-in' truck (C-60 Chevy grain truck) to the middle of the driveway and light it on fire!

[cougar]

Just wondering if you tried centering the proportioning valve?

[Hansen01]

After you do the calipers, i didnt see a new booster in your list of brake parts, i know that it helped mine out quite a bit

[dpuckett]

Cougar- how does one center the prop valve?
Forgot about the booster. It is new-ish. Has been replaced once under warranty, and gives plenty of assist.



Thanks for the ideas, guys

[dpuckett]

Update.
Replaced calipers. Bled with the help of my wife. No air, coming out the bleeders, but I now have a SUPER low, mushy pedal, but at least it stops straight. I am ready to pull the engine and tranny and dump it in the river at this point. IF I knew of someone to take it to, I would gladly pay to get it stopping again. Only problem is, it's 20 years old, and most mechanics don't know what a vacuum assist disc/drum pedal is supposed to feel like, hence my problem........

I cant help feeling that I am missing something incredibly simple here. Should we have bled all 4 wheels, even though nothing inn the rear half of the system was touched? FSM is no help- it shows the set up like my 91 had. Is the little aluminum box just below the master my proportioning valve? Has a single wire going to it.

[CumminsPower59]

Is the little aluminum box just below the master my proportioning valve? Has a single wire going to it.

Yup!

[lazyjoe]

I was in the same boat you were in. For years my brakes were SO, SO. Mushy, and sometimes would go to the floor. Bypassed the abs, and were GREAT. About 7 months later, started acting the same. Could'nt find anything wrong. Lost them all together one day. Looked under truck. Brake fluid all over the front end. Ended up being the rubber line that goes from the frame, to the axel, ( in my case ). Replaced it, and good again. I know how it is. VERY, VERY, frustrating . Don't give up, you'll get it.

[cmann250]

I replaced rubber lines on a whim and it helped a alot. They didn' look bad, but for some reason new ones helped. That's the last place the fluid can hide. Also my FSM tells me how to center the proportioning valve, but mine's in the frame rail. I doubt it's the same

[KurtzN1]

Update.
Replaced calipers. Bled with the help of my wife. No air, coming out the bleeders, but I now have a SUPER low, mushy pedal, but at least it stops straight. I am ready to pull the engine and tranny and dump it in the river at this point. IF I knew of someone to take it to, I would gladly pay to get it stopping again. Only problem is, it's 20 years old, and most mechanics don't know what a vacuum assist disc/drum pedal is supposed to feel like, hence my problem........

I cant help feeling that I am missing something incredibly simple here. Should we have bled all 4 wheels, even though nothing inn the rear half of the system was touched? FSM is no help- it shows the set up like my 91 had. Is the little aluminum box just below the master my proportioning valve? Has a single wire going to it.

Yes, definitely bleed all 4 wheels. I assume you swapped the front calipers, which requires removing the brake lines from them. If you opened up the lines to any exposure to air, it will dilute into the entire system, doesn't matter if you only did the front or even just one side. Bleed all 4 corners, starting from the furthest corner from the MC.

[ellis93]

Are the rears still adjusted up? Reckon they might have backed off?

[little doug]

I'm not sure what a ca2010 is , but you should have a 11775 master on your truck. I would do as mentioned and replace the front rubber line first (cheapest,easiest,safest),but I suspect you have a bad master. If the bore is bad in the middle,you can have a firm pedal up top,but loose fluid past the cup as it starts moving.Of course be sure to bench bleed the new master before you install it. That's my 2 cents.

Doug