LPSV Bypass Problems (1 Viewer)

[1973Guppie]

Looking for help on what I might have overlooked. Just spent the last few days replacing both front calipers, rear calipers and all pads, ebrake and front pads. I removed the lspv and used the stock front tee that was taken off the drivers side. I removed all the rear lspv stuff and arm, the lower line I broke off in the rear and the front, removed the front 2 port T and bracket, removed the 3 port bracket at the master cylinder. I then routed the rear line of the master direct to the abs unit where it was connected to the 3 port unit on the master cylinder.

Bled the brakes and everything went well. Got lots of air out and bled each corner till there was no more air bubbles. I did the pass rear, pass driver, pass front, drivers front. The only odd thing I noticed is that the front drivers rebuilt caliper had a 8mm bleed port on it which I have never seen, they have always been 10mm. I also got some milky white fluid coming out of the pass side front caliper. I am guessing this was maybe something like oil in the caliper from the rebuild process.

When I went to test drive it the brakes are now worse than before all of this work. Brake pedal goes straight to the floor. The brakes still "work" but are very soft and spongy and is overall not safe to drive. I see no leaks whatsover and I am not losing any fluid.

Any thoughts? I tried to "activate" the abs unit by going over a speed bump and slamming on the brakes but it did not work as the brakes are not strong enough to even activate the abs. I am wondering if opening the port on the abs unit has introduced air into it that I now must get out? I have never unhooked or messed with the abs unit at all.

I know others will say ditch the abs all together but for now I want to try and make it work if possible but am open to deleting it if the unit is worn out or broken as I don't want to spend big $$ to get it working again. But if I can get it working by a simple procedure that would be good.

Any help from other that have been here before is appreciated.

 

[nukegoat]

No proportioning valve at all means you will be pushing more fluid through the lines as the rear brakes are now more 'active' than before, for lack of a more layman's description. This, in turn, makes the pedal feel softer and mushier.

Imagine having bigger calipers... same thing. More fluid needed, will feel softer. Combined with the possibility that your lspv may have been letting virtually no fluid to the rear calipers and you may have had an artificially firm pedal prior.

That, or air in the circuit still, possibly combined with the aforementioned, or head gasket.

 

[1973Guppie]

No proportioning valve at all means you will be pushing more fluid through the lines as the rear brakes are now more 'active' than before, for lack of a more layman's description. This, in turn, makes the pedal feel softer and mushier.

Imagine having bigger calipers... same thing. More fluid needed, will feel softer. Combined with the possibility that your lspv may have been letting virtually no fluid to the rear calipers and you may have had an artificially firm pedal prior.

That, or air in the circuit still, possibly combined with the aforementioned, or head gasket.

no way this is a normal brake pedal, something is definetly wrong. I am guessing somehow there has to be air in the system still, although no idea how as like I said when I bled it I got no air from all four corners.

 

[nukegoat]

no way this is a normal brake pedal, something is definetly wrong. I am guessing somehow there has to be air in the system still, although no idea how as like I said when I bled it I got no air from all four corners.

@Tools R Us

 

[1973Guppie]

No proportioning valve at all means you will be pushing more fluid through the lines as the rear brakes are now more 'active' than before, for lack of a more layman's description. This, in turn, makes the pedal feel softer and mushier.

Imagine having bigger calipers... same thing. More fluid needed, will feel softer. Combined with the possibility that your lspv may have been letting virtually no fluid to the rear calipers and you may have had an artificially firm pedal prior.

That, or air in the circuit still, possibly combined with the aforementioned, or head gasket.

your point on the rear lspv is valid, I don't think there was any fluid going to the rears, my rear pads were virtually brand new. IMO the rear lspv was just not working at all and not allowing any fluid to go to the rear brakes. I was happy with how the front bracket fit up perfectly into the area where the lspv was though, one bolt and a few slight bends and it all came together. Just have to figure out why the pedal is so soft now. Going to look again in the morning to make sure there is no fluid leaking anywhere.

 

[ppc]

You may have damaged the master cylinder during the bleeding process if you pushed the brake pedal beyond its normal stopping position.

 

[Notch]

They kind of suck to bleed compared to other vehicles. Stand on the pedal as hard as you can to check for leaks. Get the ABS going with some hard stops on gravel. Bleed, repeat until it works.

 

[bajaphile]

Are you using a power bleeder or doing this manually?

Since you removed the LSPV I'm assuming you must just have a big ol air pocket in the lines somewhere, yes?

I know you're familiar with mechanic work.. reading about bleeding the 80s has made me scared to do brake work involving fluid!

 

[2fpower]

If it bled well at all four corners, I don't think your master is bad. I am going to guess air in the line of the ABS also. On my son's rig, I had to cycle the abs 4 or five times then rebleed. I did this 4 times before it started getting better.

Same as you said, totally unsafe to drive. I just drove across a field and slammed on the brakes. At first it did not engage much like you said, but you could hear it going some.

 

[2fpower]

With all the rerouting of lines, you may want to post up a pic of how you hooked it up.

 

[Red Merle]

I deleted the ABS because I was having a similar issue. Once I did that, the brakes became amazing(at least as amazing as they can be for such a large truck).

 

[beachboyy]

I deleted the ABS because I was having a similar issue. Once I did that, the brakes became amazing(at least as amazing as they can be for such a large truck).

This is what I did also. Deleted the ABS and the truck has never stopped Better.

 

[1973Guppie]

You may have damaged the master cylinder during the bleeding process if you pushed the brake pedal beyond its normal stopping position.

really? I have never heard of this happening. I usually just use the pump method and it works fine. The MC is original I think so it is old.

 

[1973Guppie]

Are you using a power bleeder or doing this manually?

Since you removed the LSPV I'm assuming you must just have a big ol air pocket in the lines somewhere, yes?

I know you're familiar with mechanic work.. reading about bleeding the 80s has made me scared to do brake work involving fluid!

I don't know but logic would say no I don't have an air pocket. I bled the brakes manual with the help of my lovely wife pumping on the brakes. She knows what she is doing as she has done it a million times for me. I bled each corner until no air was coming out at all, just clean fluid.

 

[1973Guppie]

If it bled well at all four corners, I don't think your master is bad. I am going to guess air in the line of the ABS also. On my son's rig, I had to cycle the abs 4 or five times then rebleed. I did this 4 times before it started getting better.

Same as you said, totally unsafe to drive. I just drove across a field and slammed on the brakes. At first it did not engage much like you said, but you could hear it going some.

I think I agree with you. This makes sense logically. Brakes have never felt this way and this is the first time I have ever opened the abs system by disconnecting a line. I am going to try and get the abs engaged today

 

[1973Guppie]

With all the rerouting of lines, you may want to post up a pic of how you hooked it up.

I can post pics but basically I cut out the bottom line (sensing line) from the lspv, removed the lspv and used the front fender 2 way fitting bracket that sits on the frame in place of where the lspv is. I also removed the T 3 way connector and bracket under the MC and the lines. One of these lines goes to the rear port on the MC and one to the #2 port in jcardona's thread. I reused one of the these lines to connect #2 straight to the rear of MC, or #3 in the pic.

 

[1973Guppie]

I deleted the ABS because I was having a similar issue. Once I did that, the brakes became amazing(at least as amazing as they can be for such a large truck).

I am considering it at this point. If I can't get the abs to actuate to get the air out I really have no choice. What is the reasonable lifespan for these abs units? Are there internal components that degrade over time? Just wondering if these wear out similar to a master cylinder or other component.

 

[2fpower]

I deleted mine a few weeks ago, so I can mail you a replacement ABS unit -- you pay postage -- if we determine that is the issue.

I am confused on your plumbing. The front of the MC is for the rear brake circuit. So that line goes from there to the ABS unit as it originally did?? Then the old line out of the abs, that went toward the front of the rig, then goes all the way back connects to your rear brakes?

The pipe out of the rear of the MC is for front brakes, you deleted the T, so it basically goes straight to the ABS unit now?

 

[Heckraiser]

Keep bleeding, homey. I think I had to bleed 4 times? Each time, I was getting clean bubble-free juice in the mountain dew bottle, but I just kept bleeding and it got a little better each time. I'd also try what someone suggested, activating the ABS on gravel a few times and then bleed.

 

[1973Guppie]

I deleted mine a few weeks ago, so I can mail you a replacement ABS unit -- you pay postage -- if we determine that is the issue.

I am confused on your plumbing. The front of the MC is for the rear brake circuit. So that line goes from there to the ABS unit as it originally did?? Then the old line out of the abs, that went toward the front of the rig, then goes all the way back connects to your rear brakes?

The pipe out of the rear of the MC is for front brakes, you deleted the T, so it basically goes straight to the ABS unit now?

yes exactly, maybe I did this wrong? I basically removed all of it, lspv, 2 way bracket on frame, 3 way T. I noticed when it was original it went to #2 so I just recconected it to this. Does anyone have a diagram of the ports on the abs unit and where they should go? I will post some pics