HELP Brake pedal goes to floor slowly

[2fpower]

Is master number three from the same source as the others? I’d assume the re-mans are batch produced and could have the same defect (or new guy).

First was used OEM. second and third will be same Cardone --- which I have put on two other cars with no issues. Recall that when I plugged both sides of master, it has no drift -- so I just can't imagine the master is the issue.

 

[thatcabledude]

@thatcabledude "I switched to using my home brew pump up garden sprayer with Motive Toyota MC cap"



Guess it is time for me to build one of these..... can you point me in a direction?

You can buy a “Kit”, but you can throw one together in no time for almost nothing.

Something like this:





I believe this is the exact part number of the cap I have was thinking it was made by Motive. There are several out there that fit Toyota:

VW, Mercedes, BMW, Volvo, Volkswagen, Audi, Ford, Dodge and other Tools for Specialty Applications

Tools

asttool.com

 

[ppc]

The difference when you plug the lines is that the piston and seals move very little. When the master is connected to the caliper the piston and seals travel a longer stroke. It is then possible the defect in the master within the longer stroke area like a pit in the cylinder wall that lets the fluid bypass the seals. I would be disassembling the masters checking each of the bores. Honing them with new seals from a rebuild kit might solve your problem.

 

[Tedward]

My money, yours actually, has been on the Master Cylinder all along.

Even a known working one can be made bad

by bleeding the brakes, as I do, the old fashioned way if the seals are just about worn out.

New master or rebuilt is only that. Doesn't guarantee it's any good. Working on vehicles and forklifts I've gone through multiple new master cylinders right out of the box until one worked properly.

 

[2fpower]

Well, bought the pressure bleeder kit and had same day amazon delivery, so was at my door when i got home. For all processes tonight I bled with the pressure bleeder. those keeping track that is 2 more quarts of fluid tonight, so we are almost at 2 gallons of fluid.

1. Bled out the brakes with pressure bleeder. NO CHANGE.

2. plugged the right (pass) front line so only had left driver side operating. seemed better.

3. unplugged the right (pass) side and made a new hard line for T at master to the pass side soft line. bled them out, NO Change. Then plugged the driver (left) side at the T and it seemed better. Seems like that the brakes work fine the less system is hooked up. The more volume needed, the worse the system is.

4. so swapped out the master with one I got from the junkyard off a T100. also made a new hard line from the master to the T - no change. That is the 3rd master now.

5. scratched my head.... what the heck.....

6. plugged the connection at the front axle after the soft line from the driver side to the axle. seemed better again.

7. swapped out the driver side caliper for a brand new one. no change.

I have not swapped the pass caliper yet. Thinking about putting another new soft line on the driver front too.

 

[dogfishlake]

I pretty much speed read this but did you activate the abs, like a bunch of times? Hit some gravel road and haul butt and stand on the brakes and make that sucker buzz. Do it a bunch of times. Then try to rebleed. It still may be spongy but I suspect the brakes will come around. I had the exact issue on both 80 series on the same day trying to flush them with new fluid. The abs purge did the trick.

 

[2fpower]

I pretty much speed read this but did you activate the abs, like a bunch of times? Hit some gravel road and haul butt and stand on the brakes and make that sucker buzz. Do it a bunch of times. Then try to rebleed. It still may be spongy but I suspect the brakes will come around. I had the exact issue on both 80 series on the same day trying to flush them with new fluid. The abs purge did the trick.

ABS is deleted. We are working with a very stupid simple system that is kicking my ass. I need to get the project out of my garage so I can cut up my other 80 (The Foo) and fit 40" tires under it for next month's trail ride.

If anyone has an Idea. I am all ears!

 

[satchel]

And this isn't only happening while driving, it also happens just idling correct? I had a wheel bearing on a truck that was way out and the wobble of the wheel would push my pads in more than normal, making it take soft travel to firm the wheel back up each time, but that shouldn't be a problem sitting still.

The braking would suck, but do you notice the same degradation in braking if you unplug your booster? I had an issue where my booster was causing me to feel like I had a ton of soft travel, then like a binary switch, it would kick in a crazy amount of boost pressure. I went through everything as this was part of an upgrade to 4runner brakes, 3 different bores of MC for differing pedal firmness, but it all turned out to be a really poorly operating booster. Changed that out and pedal feel went back to perfect.

Just shooting in the dark here, but wasn't seeing that you had changed that part out yet so thought it might be something to try.

 

[2fpower]

Just shooting in the dark here, but wasn't seeing that you had changed that part out yet so thought it might be something to try.

I appreciate your thoughts as I am shooting in the dark and open to anything. I was just telling a friend I have quit trying to be logical and just try anything now.

I am on the 3rd booster now. Note: I did not adjust the pushrod on the booster.... so I am thinking about putting a stack of washers between the master and booster to see if that changes anything.

FYI.... 3rd master too.

will be 3rd calipers for all corners tonight.

I do have a complete parts car that I am thinking about pulling that booster /master combo and swapping in. I have no logical reason why I should do this.....

 

[satchel]

Ok, wasn't sure you had done that yet. Not sure how accurate you get with measuring the booster rod, but usually what I do is put it pretty far out where I know it will hit when putting on a MC, then put the MC on and see how much of a gap there is. Then I just keep turning it little by little until the gap is gone and I can finally butt the MC up to it firmly. Also assuming you have connected the pedal back up firmly to the booster.

This one is a head scratcher for sure.

Have you verified you have the lines hooked up to the correct port on the MC? Like 0 percent this is causing an issue but hey, idk...

 

[2fpower]

Have you verified you have the lines hooked up to the correct port on the MC? Like 0 percent this is causing an issue but hey, idk...

That is interesting. With the ABS gone, it is totally different hard line routing. I originally traced the lines with ABS and thought that the front port of the master went to the rear of the car. That is how I originally hooked it up. I double checked this and that appears to not be correct. The front goes to the front and the rear port to the rear brakes. That is how we have it now. I should note that there was no change in this issue either way.

 

[dogfishlake]

That is interesting. With the ABS gone, it is totally different hard line routing. I originally traced the lines with ABS and thought that the front port of the master went to the rear of the car. That is how I originally hooked it up. I double checked this and that appears to not be correct. The front goes to the front and the rear port to the rear brakes. That is how we have it now. I should note that there was no change in this issue either way.

I'm thinking that is backwards. Not sure. Great notice @satchel

 

[dogfishlake]

The larger reservoir on the MC will pretty much always feed the front brakes

 

[2fpower]

The larger reservoir on the MC will pretty much always feed the front brakes

All masters I have only have one reervoir. plastic is split about evenly.

Anyone have an early non-abs 80 series rig to confirm or deny? Found several threads for fj62's that says front -front , rear-rear.

fj62 master cylinder port order

forum.ih8mud.com

I tried looking at parts diagram, but inconclusive......

looking at the ABS delete threads it does look like rear to front and front to rear.

 

[dogfishlake]

I hope this works out for you. So frustrating getting sidelined with these things. I would like to delete my ABS and LSPV and expect a lot from it.

 

[satchel]

Don't want to spread false information here but had a thought from something I remembered when I did my lspv delete on my 62. I haven't done that yet on my 80.

Anyway, I thought I recalled after doing the delete, that the two circuits were somehow connected afterwards, meaning if I lost my rear brakes I lost my front as well, cause they were tied together afterwards. Think it had to do with the return that went from the original lspv back to the front? It's been forever since I did it so I could be dreaming, but I do remember having that thought and now it makes me want to go back and double check cause that sounds pretty scary, but my truck was stolen somewhere in there and I lost track of that progress.

So, while I'm sure this isn't the case for you, thought I would throw it out there that maybe doing the lspv delete tied both front and rear circuits together for you and therefor, blocking off one or the other port on the master is still actuating all 4 and not helping to troubleshoot which circuit is bad????? Idk man, really grabbing at straws here.

 

[2fpower]

Anyway, I thought I recalled after doing the delete, that the two circuits were somehow connected afterwards, meaning if I lost my rear brakes I lost my front as well, cause they were tied together afterwards. It's been forever since I did it, but I do remember having that thought and now it makes me want to go back and double check cause that sounds pretty scary, but my truck was stolen somewhere in there and I lost track of that progress.

So, while I'm sure this isn't the case for you, thought I would throw it out there that maybe doing the lspv delete tied both front and rear circuits together for you and therefor, blocking off one or the other port on the master is still actuating all 4 and not helping to troubleshoot which circuit is bad????? Idk man, really grabbing at straws here.

No, that is not accurate. The reservoir has two portions or some masters have two cups. Each feeds one of the two circuits of the master, and the lines then coming out of the master go to the front or rear circuit. One goes to a T then to L and R front, the other circuit uses one of the old LSPV lines to the rear T then goes L and R.

here are some diagrams. notice the first three show the primary circuit is in the rear. Based on this, I will swap this back around......

 

[satchel]

That is correct, the master has two circuits. What I mean is, I have a recollection that somehow the routing of the lines going to the lspv and the fittings I used, ended up in tying the lines together when I did it. There was a third brake line that went to the lspv so that when fluid wasn't cycling through it, it cycled back to the front, and removing the lspv made it so that basically either circuit of the master would cycle all of them. I know in stock form they are completely separate, just remember when doing the delete I felt like somehow they were tied together. Anyway, likely not your problem but something I recalled after looking at the routing on mine post delete.

Edited for slightly more clarity...

 

[2fpower]

Yes, one line going back/forth to LSPV is abandoned when you delete ABS/LSPV.

 

[satchel]

Was just trying to refresh my own memory of what I did. So like previously mentioned, on my 62 anyway, it had a line going as a supply line to the rear brakes and when it got to the lspv, and fluid not being pushed to the brakes were recirculated back up to a tee in the front that joined up with the front brakes. I believe I actually just deleted that recirc line and capped that portion of the tee and am good, but do remember at first glance about how the rear circuit was recirculating back up to the front circuit for the portion of the fluid that wasn't passing through the lspv.

Just saw you replied, figured it wasn't an issue but like I said, grabbing at straws...