I'm at my absolute wits end- Fading Brake pedal despite best efforts

[Chester]

7 flexible lines, all appear fine, but they'll all be replaced.

 

[NLXTACY]

7 flexible lines, all appear fine, but they'll all be replaced.

Years ago when I did my huge brake overhaul, I had started the project because I was getting spongy brakes. My biggest culprit was the brake fluid had absorbed so much moisture and was black. Second culprit, and ultimate reason for problems, was a front brake hose that bubbled under pressure. I don't mean it created bubbles, I mean the brake hose would actually bulge out. I hadn't seen that since my early Chevy days.

 

[musthave]

UPS just delivered all new brake lines. OEM of course. Also picked up two new rear rotors as mine just need to be replaced. So I am hoping it is a Breakline bubble issue.

 

[IanB]

Have you guys tried blocking off both ports on the MC and pumping the pedal to confirm it's not your issue yet?

 

[atomicshawn]

Having spent many many years under a car and in the 'early' days when there was no such thing as 'forum support' (yes I am that old) and mechanics learnt very early to be as logical as possible when diagnosing any problem, you do get a little frustrated....

Hearing you brother. I think many of us can relate. However, I prefer to use the word "mature"

 

[atomicshawn]

Something else I might add to this discussion is that I'm not personally stoked on the idea of crimping the rubber lines to test unless your planning on replacing them. They are tough, but not necessarily built for that. I'd be a little concerned about threatening the long term integrity of the material. Not a huge deal. If no other option, you do what you have to do, but I would try to avoid it.

This piece doesn't seem like it will apply here. Sounds like you guys are going for the shotgun method. (A nice, fresh braking system is not necessarily a bad idea considering the age of these things.) So a suggestion maybe for those who come after...

 

[math]

R.I.P. @musthave's wits. Seeing as how you and @Chester are better mechanics than we will ever be, it seems like a waste to offer our help, but if you need two extra sets of hands, let us know.

 

[OGBeno]

So I am just not sure why this has become such an ordeal?

The braking systems in these trucks are now basically ancient.

Something I would try:

Remove LSPV and ABS box, reroute lines with spare piping, bleed brakes and see what happens.

If the brakes improve dramatically, then it's either one or the other.

Add LSPV back: Try it this way. If brakes are still good, add ABS back. If brakes are bad, you know your culprit. Vice versa.

Anyway, I'm at a loss at why these brakes are still "spongy" after all of the time, effort and money you have put into this at this point.

The other thing to consider: Maybe the brakes are normal and the user is having issues with accepting it?? (I say this not negatively, but in the sense that maybe the brakes are normally spongy on an 80).

Have you compared to Chester's trucks?? Both his FJ62, his 70?

PS: I don't know what spongy brakes are because I long ago s***canned both the ABS box as well as the LSPV.

I DO NOT IN THE SLIGHTEST ADVOCATE FOR REMOVING THESE SAFETY ITEMS FROM A TOYOTA LAND CRUISER.

 

[NLXTACY]

I've mentioned in other threads about removing the ABS actuator. In California you will be absolutely fxxxed if you modify your brakes and remove safety equipment IF you are in an accident. I'd assume other states are similar.

 

[DARKNESS]

The other thing to consider: Maybe the brakes are normal and the user is having issues with accepting it?? (I say this not negatively, but in the sense that maybe the brakes are normally spongy on an 80)

Could be. The brake pedal on the 80 seems to have a long travel in general. Mine don't really feel firm compared to any other vehicle I've driven, but they stop great. To some extent I think that's just the way the ABS rigs are.

 

[OGBeno]

Could be. The brake pedal on the 80 seems to have a long travel in general. Mine don't really feel firm compared to any other vehicle I've driven, but they stop great. To some extent I think that's just the way the ABS rigs are.

Exactly. Which is why it might be worth comparing to Chester's rigs which are non-ABS.

 

[95ToyCruiser]

My 95 has always had somewhat spongy brakes, despite doing new ss braided lines, calipers, etc, owned it for 6 years and almost 200k...although they always felt safe and adequate...

When I got my 93 I was very pleased with the brakes, they feel great!!! Much less pedal movement and overall stops better than the other one even when the other was bone stock...

I pulled the ABS relays on both and plan to remove as I've never seen a need for it and it makes things much simpler...

Good luck, is there anything that you haven't replaced yet? The booster?

 

[Chester]

I wish it was a problem with relativism, but this truck doesn't have any brakes.
The '62 is a bad comparison, little front disks and drum rear, but it stops even better than it goes, in spite of the mileage on most of the components.

 

[OGBeno]

I was going to say, by FJ60 stops incredibly next to my 80 that has been de-ABS'ed and de-LSPV'ed.

 

[Chester]

R.I.P. @musthave's wits. Seeing as how you and @Chester are better mechanics than we will ever be, it seems like a waste to offer our help, but if you need two extra sets of hands, let us know.

Neither one of us are mechanics, I've been a bag boy all my life and musthave is some kind of computer dude. Not much room, but if you've got those little tiny hands or vise grip fingers, come on down.

 

[Chester]

Exactly. Which is why it might be worth comparing to Chester's rigs which are non-ABS.

80 is stock, stops very well, no sponge, no fade, and the ABS is still fine.
62 has too many miles, but it stops real well, and has probably eaten up 10 rotor sets over the years.
70 has the best brakes of all, but once they heat up, whiplash when they bite.

On musthaves truck, it's been sponge all the way through. No improvement yet.

 

[OGBeno]

Tim has three items remaining at this point:

LSPV, ABS actuator (STOOOPID EXPENSIVE), and the booster.

 

[Azca]

I am reading all of this and understand the frustration. I did the same thing for MONTHS chasing the sponge demon. Spent way too much time on it only to find out it was the brake booster push rod. I don't have the sports car level of feel but I am more than happy with them.

Here I don't see that it has been checked but, for something so easy to do, I would rule that out before removing any safety equipment or spending any more money. Worst case scenario, you over tighten it and have to back it off a few turns. Just sayin

 

[Chester]

I am reading all of this and understand the frustration. I did the same thing for MONTHS chasing the sponge demon. Spent way too much time on it only to find out it was the brake booster push rod. I don't have the sports car level of feel but I am more than happy with them.

Here I don't see that it has been checked but, for something so easy to do, I would rule that out before removing any safety equipment or spending any more money. Worst case scenario, you over tighten it and have to back it off a few turns. Just sayin

it's been checked, but via pressure gauge and travel contact, which is not the FSM method. The new master is coming off tomorrow, we'll mic it up, but I'm near certain it's not an issue. I haven't wanted to clamp off soft lines either, so we now have caps and plugs to isolate and test portions of the system, but didn't get to using them yet.

Tim has three items remaining at this point:

LSPV, ABS actuator (STOOOPID EXPENSIVE), and the booster.

LSPV replaced it today. pretty simple, but I can see where it might be a pain not worth enduring, I'm keeping the old one to use for a manual differential manifold, and a test jig.
ABS modified the jig we built yesterday, but there's only so much a 3 valve modulator can do, and I'm pretty sure it's doing it the way it's supposed to.
BOOSTER. is there any way the booster could cause these symptoms?

 

[DSRTRDR]

I do not agree with the description of the 80s brakes as "normally spongy" - neither do I agree with the claim that they have a particularly long pedal travel - actually, I prefer to have some travel in the pedal so I can modulate the brakes better when wheeling

the brakes on "antiquated" vehicles like the 80 and the LX work better that those wire-controlled POS things on the "modern" rental cars I often drive