Brake Issues...

[sentrek]

Could use some input.
Finally got my sons 99 1500 back up and running after a new engine install and was having some brake issues, actually the brake issues started before we replaced the motor, but anyway, I replaced the pads, rotors, calipers and master cylinder, and the wheel speed sensor. I bench bleed the master cylinder before install per the instructions and i though were were good, pedal was solid, abs light went out, but as soon as went to pull out of the garage for a test spin the pedal went back to the floor. Any idea what to look at next? I could not find evidence of a leaking line or anything anywhere. I bleed the brakes after installing everything as well. Kinda at a loss.

 

[diymirage]

How far did you drive once you pulled out of the garage?

When you replace pads you back the piston back up into the caliper
This leaves a gap between the piston and the new pads

It takes a few pumps to push the piston back out and get it to where the pedal feels right

 

[sentrek]

I drove it for few miles because we did a lot of other work to it. The pedal gets solid when it's not running but goes to the floor when you start it. Based on what I am reading it sounds like a booster issue.

 

[Mojo88]

I'm betting you still have air in system.................. bleeding brakes properly can be kinda tricky. It's easy to have a lot of air trapped somewhere in the system.

I always use a MOTIVE pressure bleeder, that makes the process a lot easier and more efficient, plus I can do it by myself. If you're bleeding manually (with a helper pumping the brake pedal) it takes a fair bit of concentration and good synchronization between the two people to do it right.

 

[Daw14]

Might be air in the abs , if you go in reverse and slam the brakes ,this may take care of it . This will need to be done several times. I would follow with another system bleed furthest wheel from master cylinder to the closest , RR - LR- RF - LF .

The reverse deal may do the trick if not , you will need a scanner that can do the job .

I may be way off but this should get more responses.

 

[diymirage]

I drove it for few miles because we did a lot of other work to it. The pedal gets solid when it's not arunning but goes to the floor when you start it. Based on what I am reading it sounds like a booster issue.

Yes sir, what I was thinking of is a one time deal and it self resolved

Definitely should not be there after a few miles

 

[sentrek]

I dont know, I am definitely no expert but I have replaced many brakes in my days and haven't run into the issue of the pedal being solid and then as soon as you start it that it goes to the floor. Before I replaced anything I did notice the fluid was very low. I filled it back up and bleed them but it didn't help anything. When I pulled the master cylinder there was obvious signs that it was leaking into the booster. I am thinking the brake fluid probably damaged the booster at this point. After I replaced everything I did have a helper with bleeding the brakes and I feel like I bled the **** out of them.

 

[Daw14]

After rereading I’m gonna say that master is no good ,it sucks there’s so many new parts that turn out to be garbage.

I dont know, I am definitely no expert but I have replaced many brakes in my days and haven't run into the issue of the pedal being solid and then as soon as you start it that it goes to the floor. Before I replaced anything I did notice the fluid was very low. I filled it back up and bleed them but it didn't help anything. When I pulled the master cylinder there was obvious signs that it was leaking into the booster. I am thinking the brake fluid probably damaged the booster at this point. After I replaced everything I did have a helper with bleeding the brakes and I feel like I bled the **** out of them.

 

[diymirage]

After rereading I’m gonna say that master is no good ,it sucks there’s so many new parts that turn out to be garbage.

I could see an issue with the piston not lining up, or the holes being off

You step on the brake and the fluid just circulates back into the reservoir

 

[sentrek]

So I had my wife in the truck pumping the brakes while I was looking for leaks and the was a lot of fluid noise around the master and booster. But still they get solid until you start the engine. I paid extra for a dorman master thinking dorman made quality parts.

 

[Mojo88]

So I had my wife in the truck pumping the brakes while I was looking for leaks and the was a lot of fluid noise around the master and booster. But still they get solid until you start the engine. I paid extra for a dorman master thinking dorman made quality parts.

I owned two service stations back in 70's and 80's. We did brake jobs every day. This is a very common symptom of air in system. Pedal gets hard with engine off, because booster is not making any pressure. Engine starts, and now booster is activated, applying MUCH more pressure to M/C and pedal drops.

Typically a bad M/C will get a good pedal at first, then slowly drop to floor as you hold pressure on it, due to fluid slowly bypassing the inner seals.

Anyway, I still say air in system. Occam's Razor and all that.

 

[sentrek]

Alright, thanks for all the input, I am going to try a brake bleeder kit before I replace anymore parts.