brake bleeding issues after axle rebuild

[TSJ]

Background: 1994 with ABS and rear discs. 280k on the odometer. I just wrapped up rebuilding the front and rear axles.

I have replaced all the calipers with new Napa remans and new factory toyota rubber lines. I believe the area where I screwed myself was leaving the old lines attached when I traded in the cores and waiting a week to finish the axles.

So where I am at now, the brakes go to the floor with no building of pressure. When following the bleeding procedure of RR, LR, LSPV, RF, LF, I was able to get clear fluid through the RR and LR, but the LSPV was mainly air with some fluid. I tried the fronts to see about clearing the LSPV last. Both fronts had no fluid at all. I had the wife pumping with one of the bleeder screws completely out and no fluid.

I think my first course of action is to crack the MC lines to make sure its functioning. Other than that I think the ABS module maybe be the culprit.

If any of you sages have some guidance I would appreciate it!

 

[Timpanogos Slim]

Are you certain that you did not tear the diaphragm in the brake booster when you were bleeding the brakes?

That was the resolution to my brake saga a couple years ago. Regular vacuum leak testing didn't turn this up because it held vacuum until the pedal was partially pressed.

Centric reman required no shenanigans and has been working very well.

The master cylinder can also be rendered inoperable by pumping too hard when bleeding the brakes. It is believed that this happens when the pistons are forced past their normal range of travel, causing the seal to drag against either an edge that has worn into the cylinder or a bunch of crud that gets trapped under the seal. This has been known to happen even with freshly installed reman master cylinders bought straight from the dealer - has even happened to cdan himself.

During my brake saga i bought one of the brand new Aisin master cylinders on ebay that are complete with a new reservoir with sensor. I'm pretty sure it came in an Advics box.

 

[ajax1]

So did you let he master go dry then ? If so you need to bleed that first

 

[inkpot]

So where I am at now, the brakes go to the floor with no building of pressure. When following the bleeding procedure of RR, LR, LSPV, RF, LF, I was able to get clear fluid through the RR and LR, but the LSPV was mainly air with some fluid. I tried the fronts to see about clearing the LSPV last. Both fronts had no fluid at all. I had the wife pumping with one of the bleeder screws completely out and no fluid.

So, yu do realize that you have to close off the bleeder valve, or cover the open hole with your finger before the brake pedal is released to raise back up?

 

[TSJ]

So did you let he master go dry then ? If so you need to bleed that first

Strangely enough I don't think the master ran out. The lines and calipers definitely cleared out, but there was still fluid in the MC.

So, yu do realize that you have to close off the bleeder valve, or cover the open hole with your finger before the brake pedal is released to raise back up?

Yes even with system closed I don't have any pressure build up and MC level doesn't change.

This morning I cracked each of the top abs module lines and pressed the pedal. I had fluid with each stroke. Not sure if that means it's functioning completely. I am going to build a pressure bleeder and see if anything improves.

 

[Pin_Head]

You have to close the bleeder valve or at least put your finger over the hole when the pedal is let up to make sure that the bubbles and fluid goes one way: out. There is no point in just sucking it back and forth.

 

[TSJ]

You have to close the bleeder valve or at least put your finger over the hole when the pedal is let up to make sure that the bubbles and fluid goes one way: out. There is no point in just sucking it back and forth.

I get that. We did the typical 2 person pump and open/close the caliper bleeders. It worked fine for the two rear calipers. Mainly air for lspv, and nothing but air for the front calipers.

 

[TSJ]

Is there a bleeder for the abs module?

 

[DARKNESS]

The LSPV is also a bypass valve that can cut the front brakes out of the system if they develop a major leak. The fact that neither front brake is getting any fluid suggests the LSPV is involved. I would guess that it's gone bad and needs to be replaced but perhaps it just doesn't function right until you've bled it all the way. Whatever the case, I'd focus on it.

 

[Pin_Head]

The front half of the MC may not be pumping. Try opening the bleeders on the front and gravity bleeding it and if there is no flow, open the front line on the MC and pump it to prime it.

 

[Timpanogos Slim]

The method my friend who wrenches for a living taught me was to secure a bottle to catch brake fluid somewhere above the caliper. Tie it to a shock or something. And then run a hose from the bleeder nipple up into the bottle.

This should assure that there is always a column of fluid on top of the bleeder.

I also used the "speedbleeder" check valve bleeders. I'm not certain that the check valve helped. Those fancy bleeders also have a waxy thread sealant on them, which makes a ton of sense IMHO, and that also may have helped.

 

[TSJ]

Just to update, I built a power bleeder based on Firedog's instructions. Hooking it up to the system I was able the bleed the LSPV and both front calipers. I went ahead bled the system a second time.

Then the test, I got in the cab and the pedal is firm!

I feel like it's a bit rear biased for my liking so I'll adjust LSPV mounting. Other than that, all is well on the brake front.