Spongy brakes (1 Viewer)

[NielsC]

I really did not want to open another spongy brakes thread, but after reading so many threads and not finding an answer I am a bit out of options.
My 80 has had the low spongt brake pedal for years, and for some reason I figuered it was just an 80 thing, untill a drove a couple of other 80s that all have a nice and firm brake pedal and have much more stopping power then mine.

Parts replaced are:

Front and rear brake calipers rebuilt + new pads
I've replaced the master cylinder with an aftermarket unit (OEM unavailable here)
Replaced the LSPV since it was totally rusted and could not open the bleeder without snapping it. Since brake lines at LSPV were in the same condition, I've made those out of copper brake line with double flared ends.
All flexi hoses have been replaced with braided steel hoses aswell. (So I cannot clamp of the rubber lines to see if things improve)

I've bled and bled and bled for a lot of times with a pressure bleeder at 25PSI , whilst bleeding with the pressure bleeder I pumped the brake pedal several times with the bleeder open.
I tried all possible sequences bleeding the calipers and LSPV, I've activated the ABS a dozen of times on a stretch of unpaved road, and bled some more.
I still have the same spongy pedal I had before.

2 things I have noticed:
-When I moved the LSPV arm completly up and moved LSPV down on the bracket, and even with the ABS fuse removed, I am unable to lock up the rear wheels when braking hard, even on wet grass!
This make me think there still is air somewhere in the system.

-When pumping the brake pedal with the engine off it gets quite hard, pumping with the engine on makes it spongy, and when pressing hard enough will always sink to the floor slowly, even after pumping it up several times.

The only thing I can think of that is causing me these issues is the ABS actuator.
Is it possible these units are impossible to bleed, or leak internally.
One thing I'm going to try is put the car on 4 jack stands and run it so I can activate the ABS while pressure bleeding it, see if it makes difference.
Other than that I'm thinking of either removing the ABS pump or buy another used one to try it, but might be a waste of money.

Any opinions or help is greatly appreciated!

 

[goingcamping]

Do you have lift or are you at stock height? When I bled my LSPV (also rusty, but could break bleeder free with channel locks, it's on my list) I had to bend the rod down from the axle to completely bleed it. I have 50mm TJM springs, so the LSPV is not sitting "level" compared to stock alignment. I will say, the difference was night/day once I bled it with the rod pushed down, a huge, foamy group of air bubbles came out and the brakes worked like a new car.

This all stemmed from a ruptured line to the LSPV due to rust. I cut it next to the fuel tank, did a double flare and bought a 48" new off-the-shelf line from Vatozone.

Edit: I should also say before I found the ruptured/split line, I replaced the master cylinder with a NAPA one.

 

[NielsC]

I’ve bled with the rod down aswell as up. Made no real difference. But will move it up and down while I bleed it again tomorrow.
Someone suggested to always start with the LSPV as it’s the highest point, so I’ll try that aswell.

 

[goingcamping]

I’ve bled with the rod down aswell as up. Made no real difference. But will move it up and down while I bleed it again tomorrow.
Someone suggested to always start with the LSPV as it’s the highest point, so I’ll try that aswell.

Get someone to help while you crack the bleeder and hold rod down.

 

[NielsC]

Get someone to help while you crack the bleeder and hold rod down.

I’ve unbolted the rod and moved it up and down whilst bleeding

 

[White Stripe]

Things to consider: Did you replace the booster with a new one? Did you bench bleed the master cylinder? Did you bleed the LSPV? Did you measure rear caliper fluid pressure and set the LSPV to the book pressure?

 

[Augustiron]

Do you really need/want the abs?

An ABS and LSVP delete is pretty simple and very effective. No parts to buy (assuming all existing parts are in good shape)

Several threads with good instructions here on Mud.

It removes the.two biggest variables in brake performance and leaves you with the basics, which are very effective on their own.

 

[NielsC]

I have not replaced the booster. I think it’s ok? The pedal pumps up hard with the engine off and sinks down when I start it.

When fitting the master cylinder I put pressure on it with the pressure bleeder then loosened the unions untill no air came out anymore.
The LSPV has not been adjusted yet since I do not have the SST for it.
I’ve tried it in various positions without much difference. It has been bled tough.

I’ve been thinking of temporarly bypassing the ABS with new made copper lines, just to see if it is the culprit.
I’m not sure if I want to remove it for legality reasons (anual technical vehicle inspection) , and because it’s a safety mechanism.
But often I remove the ABS fuse anyway on my offroad trips because I hate it kicking in when braking on a muddy slope.

 

[clx16]

How did you actuate the abs pump to get the air out?

Post in thread 'Is there a way to trigger ABS actuator to combat spongy breakes?' Is there a way to trigger ABS actuator to combat spongy breakes? - https://forum.ih8mud.com/threads/is-there-a-way-to-trigger-abs-actuator-to-combat-spongy-breakes.309314/post-12937094

 

[NielsC]

I tried the procedure in there but I think it will make a short circuit.
I’m going to put it on jack stands and get the wheels spinning, then apply the brakes while I’m bleeding each bleeder, see if it improves any.

 

[clx16]

You can alter alternatively manually activate abs by hitting the brakes while two tires are on loose gravel...repeat for each side a couple of times and bleed again.

 

[NielsC]

You can alter alternatively manually activate abs by hitting the brakes while two tires are on loose gravel...repeat for each side a couple of times and bleed again.

Did that already a dozen times

 

[BILT4ME]

when pressing hard enough will always sink to the floor slowly,

The above part of the whole equation tells me you have a bad master cylinder, even though you just installed a new aftermarket one.

Going all the way to the floor is either a leak to the outside or an internal leak allowing it to continue to move to the floor.

If you're exaggerating the going to the floor, then it's still air in the lines. During bleeding did you let the MC get low enough to expose the holes in the bottom?

Sometimes aggressive two man bleeding is better than one man with a pressure bleeder.

Also, the order in which you do this is important.
For a LHD truck:
RR
LR
LSPV
RF
LF
LSPV

 

[clx16]

I put in a new master cylinder a couple of months back. Bench bled it before installing and that then pressure bled the truck a few times. That peddle did nothing once installed and many many pumps. Eventually it started going to the floor slowly. I live in a place there I can drive in a loop and so I did 3 loops but half way through the 3rd loop those bad boys started working. I don't know what it was but it eventually worked through. I am thinking the seals in the master were dry or something and I probably should have ordered another one and replaced it.

 

[NielsC]

A faulty new master could be, but it would be unlikely I think.
It must be either air, or a seal in the master or the ABS pump leaking internally.
I’ve agressivly pumped it while the pressure bleeder was doing it’s think, bleeder open only slightly for some resistance.
I can do one more time on the oldschool 2 man method, but I think I’m safe to say there is no more air inside.
I just ran another bottle fluid trough it while the 4 wheels were spinning on jack stands and brake so the ABS activated with the bleeder open, in the correct bleeding sequence.
I’ve tried different sequences with no luck.

 

[flintknapper]

Has to be frustrating. I've read so many stories just like this over the years.

I am currently in the process of removing the ABS and LSPV on mine. Not recommending it to others, but I'm darn sure doing it.

 

[robnicko]

'

I have not replaced the booster. I think it’s ok? The pedal pumps up hard with the engine off and sinks down when I start it.

The above sounds like the booster is possibly at fault, i had this happen on a Mazda i previously owned.
Endless bleeding and pedal would go hard (engine off) however once started the pedal would go almost to the floor and brakes hardly worked
Replaced the booster and problem solved.

 

[NielsC]

'



The above sounds like the booster is possibly at fault, i had this happen on a Mazda i previously owned.
Endless bleeding and pedal would go hard (engine off) however once started the pedal would go almost to the floor and brakes hardly worked
Replaced the booster and problem solved.

Would this not be against the common sense? Not saying it didn’t fix your problem, but what would the logic explanation be for the booster being the problem?

 

[NielsC]

Did some more testing today, I found that when I press the brake pedal, the brake fluid level rises up, when releasing, it drops again.
is this normal behaviour due to a compensating port from cylinder to reservoir, our does it automatically mean leaking seals? Anyone could check this on his ABS equiped 80?

 

[flintknapper]

Would this not be against the common sense? Not saying it didn’t fix your problem, but what would the logic explanation be for the booster being the problem?

Sticky or failing Poppet Valve in the booster. But typically a failed booster only results in a 'hard' pedal since you don't have the vacuum assist to help apply pressure to the Master Cylinder.

Spongy Pedal in our Land Cruisers will nearly always be a worn out Master Cylinder and/or air trapped somewhere in the system.

Old rubber soft lines can contribute to this as well. Since its a brake 'System'....all of the components need to be in proper working order. A single item might be at fault or a number of them. That's what makes brake troubleshooting so much fun.