let's talk 80 series brake bleeding (3 Viewers)

[landcruiser3DP]

I have a broken abs sensor that causes abs to activate very briefly every stop. Just unplug a wheel sensor and drive around to activate abs pump.

i think i need to open up the left rear and check it. i'm getting a bit of a noise from back there and ehe ABS light is on. then today i heart kind of a crunch sound from left rear going over a driveway. and i also got a sort of beeping sound down by the brake pedal when i went to brake it felt like the ABS activated.

i had an issue with it binding when i first assembled it and when i had to pull the caliper and rotor to reseat the caliper.
it felt like it went together fine but i think i need to check that wheel.

 

[landcruiser3DP]

Speed bleeders are BS. The reason is that you need to generate enough pressure to overcome the resistance of the check valve.

Air compresses easily and it takes a large volume to create pressure and the check valve will close before all the air is purged.

Put stock bleeders in and do a traditional bleed.

Then with someone in the cab STANDING on the brake pedal with the engine running. Do another bleed. This will fully compress the air and slow you to purge the ABS system.

thanks man. so traditional bleed with stock bleeders? which i think i can do myself if i keep the jug filled up and make sure the end is always in some brake fluid?
then turn on the truck and get the pedal fully to the floor and crack the bleeders one at a time Rick?

 

[landtank]

Sounds right

The second bleed is meant to compress any air to its fullest so when you open the bleeder it will rush out with the fluid.

This obviously takes 2 people.

 

[jpoole]

I think what LandTank is describing is the brake bleeding technique where one person sits in the drivers seat to pump the pedal and the other person moves from bleeder to bleeder letting the "pumper" know what to do. With this approach that LandTank is recommending the pumper first presses hard on the brake pedal to create high pressure in the system while all of the bleeders are closed, then when the system is pressurized the person under the truck opens a bleeder briefly so that the pressurized fluid can rush out. The person under the truck will then close the bleeder and say "pedal up" or the equivalent so that the person inside the truck only releases the brake pedal and lets it up while the system is closed. I find this approach a little difficult to coordinate and risky for master cylinders that aren't fairly new but I do think it can be helpful in some circumstances.

I almost always bleed brakes as a solo venture which is why I use the modified version of LandTanks process where I have the system under pressure from the pressure bleeding setup and then add short/fast brake pedal pushes which can rush fluid out and hopefully remove any lingering bubbles.

 

[landcruiser3DP]

Speed bleeders are BS. The reason is that you need to generate enough pressure to overcome the resistance of the check valve.

Air compresses easily and it takes a large volume to create pressure and the check valve will close before all the air is purged.

Put stock bleeders in and do a traditional bleed.

Then with someone in the cab STANDING on the brake pedal with the engine running. Do another bleed. This will fully compress the air and slow you to purge the ABS system.

big THANKS to Rick @jpoole @TheBussman and all. i pulled the speed bleeders and i also swapped the calipers left to right because someone elsewhere pointed out i didn't get the memo that the bleeders need to be at the top and i somehow convinced myself these were "handed" and wouldn't go on the wrong side.
i also fixed an issue where i somehow got distracted and didn't drive the inner race on the left rear hub far enough and the hub was sitting out too far. the way to prevent this next time is to know the sensor should be about 1.5mm away from the teeth on the hub when you fit it.
anyway i went back as rick said and i basically cracked the bleeders one at a time, pumped three times and then shoved this slightly curved pallet piece in the jamb and let it sit like this for a minute and a half or something. then closed the bleeder and went onto the next one.
they feel rock solid now and no ABS light.
APPRECIATE you guys.

 

[JoeCova]

Man reading this thread, this is why I just deleted the ABS and LSPV.

 

[NeverFinis]

big THANKS to Rick @jpoole @TheBussman and all. i pulled the speed bleeders and i also swapped the calipers left to right because someone elsewhere pointed out i didn't get the memo that the bleeders need to be at the top and i somehow convinced myself these were "handed" and wouldn't go on the wrong side.
i also fixed an issue where i somehow got distracted and didn't drive the inner race on the left rear hub far enough and the hub was sitting out too far. the way to prevent this next time is to know the sensor should be about 1.5mm away from the teeth on the hub when you fit it.
anyway i went back as rick said and i basically cracked the bleeders one at a time, pumped three times and then shoved this slightly curved pallet piece in the jamb and let it sit like this for a minute and a half or something. then closed the bleeder and went onto the next one.
they feel rock solid now and no ABS light.
APPRECIATE you guys.

View attachment 3717197

Good to know. I pulled my speedbleeders after @landtank comment and I agree that they make bleeding much more difficulty. You need fast and free flow to move the air out of the lines.

I am having issues bleeding myself and I came to the conclusion that I had loose front wheel bearings. I redid my front wheel bearings right before the truck was taken off the road years ago. After taking the front hubs apart, it looks like the passenger front wheel bearing wasn't tight. I am not sure how I messed that up but I did.

I am doing a complete knuckle rebuild now.

 

[ZetheGSD]

Good to know. I pulled my speedbleeders after @landtank comment and I agree that they make bleeding much more difficulty. You need fast and free flow to move the air out of the lines.

I am having issues bleeding myself and I came to the conclusion that I had loose front wheel bearings. I redid my front wheel bearings right before the truck was taken off the road years ago. After taking the front hubs apart, it looks like the passenger front wheel bearing wasn't tight. I am not sure how I messed that up but I did.

I am doing a complete knuckle rebuild now.

I’d bet quite a few 80 owners have this issue and think their brakes or master cylinder are bad. I’ll even admit I was struggling with a soft pedal issue from my passenger front wheel bear being slightly loose. I couldn’t get play from the tire, but after another year of driving I finally got some play and it fixed my pedal travel issue.

 

[landtank]

I’ll mention this. I had a situation when off-roading that after an aggressive hill I’d have no brake pedal. Another pump and it was back.

Turned out to be 2 issues with the truck.

First the slide pins on the rear calipers were a little sticky. Not wearing out pads sticky, just a little sticky.

Second. The rear wheel bears were loose. So during the climb where the truck was rocking side to side abruptly the shifting rotors were bumping against the rotor pads and because the slides were sticky the calipers would open up so the first application of the brakes did nothing but close the calipers, the second push increased line pressure and brakes returned.

That was a severe instance but this could happen at a lesser degree and be perceived as a soft pedal.

 

[RobE30]

Great thread and suggestions!

 

[tech_dog]

I'm about to replace my FZJ80s MC & booster, the seven soft lines, and all four calipers. I plan on doing the MC first, bench bleeding and then pressure bleeding, and making sure it's working well before I mess with the rest of the system. I'm staying stock, keeping ABS and the LSPV.

I keep reading I should bleed the longest brake line first, but I'm struggling to figure out why I'd do that. I know I'll introduce SOME air when I install the new MC, and I'm very much inclined to send those bubbles out the shortest, easiest to bleed line, with no LSPV or other possible air traps.

I'm considering doing the front left first after the MC install, and then going back and doing longest to shortest. Am I missing something? I have that feeling I get right before I do something stupid.

Assuming the MC goes well, I'll do the front soft lines next, bleed again, then do the back soft lines, and bleed again, all with a pressure bleeder.

Thanks,

T.

 

[stevenmichael]

I also use a pressure bleeder and run it around 20 psi.

A few additional steps that I take:

• As each individual circuit is open and letting fluid out I give the brake pedal short, fast pushes to possibly flush out trapped air bubbles with the rush of fluid.
  • Deep strokes into new territory can damage the MC seals as mentioned above.
• I activate the ABS pump in the bleeding/flush process to help remove air/old fluid from the pump (see photo below).
  • I'll typically have this wired and ready to go and then activate the pump for just a few seconds when I've gotten up to pump the brake pedal a few times and check the pressure bleeder air pressure gauge which I do for all 5 bleeder ports.
  • Credit for the image below goes to @cartercd from this thread: 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/
• After flushing all 5 bleeders I then will crack/loosen slightly the lines on the ABS pump. I do this since it may help eliminate air / old fluid in one/more of the lines/circuits. This is also a good way to run the last of the fluid out of the bleeder and get the fluid level in the reservoir down to the level where you want it since you can be standing/watching the levels closely.
  • Brake fluid is hygroscopic / bonds to water easily so, once you've done your fluid flush, gotten the MC reservoir level right and buttoned things back up you need to rinse the area around the ABS pump/MC well to remove any residual brake fluid. Brake fluid can melt paint so I typically pre-wet the area and then do the final step where I bleed the ABS lines quickly so that the brake fluid is on paint for a very limited amount of time.

View attachment 3705852

I just want to be clear about a few thing as far as the wiring goes . From the post above that shows a photo on a printed paper that there is a x for the center green pin . For a 97 year is this pin not connected ? If all the green connections are connect at the same time does that mean that all the pumps are going to be pumping at the same time ? Is it better to just run one green connection at a time ? If so which green connection runs what wheel ? What are you using to connect the wires to the pins ? After the 10 seconds how long do you need to wait till you can run it another 10 seconds ? Thanks . Is this where the ground goes for the 97 year in the attached photo I changed around ?

 

[Malleus]

Which "green connections" are you asking about?

There is only one ABS pump, but it does have several valve spools in it: one each for the front wheels and one for the rear. The pump is lubricated by brake fluid, which isn't a great coolant. That's why it is recommended to cycle the pump for a few seconds only. This allows the metal to cool and prevents the valve spools from sticking in their bores. A few seconds (10-15) are all that's necessary to cool them; the heat dissapates pretty quickly. This is far less than the time it'll take to move from one wheel to the next to bleed the caliper, so you should be OK.

This is how the ABS pump operates anyway; it cycles on and off several times every second, so the designers saw no reason to provide any cooling capacity. Serious shortsightedness, most likely resulting from accounting department pressures.

You need to read the post by @cartercd that was referenced. It has all the information you need in it.

 

[stevenmichael]

Is there a video out there that shows the abs coming on and wired up and the fluid being bleed out ?

 

[stevenmichael]

Which "green connections" are you asking about?

There is only one ABS pump, but it does have several valve spools in it: one each for the front wheels and one for the rear. The pump is lubricated by brake fluid, which isn't a great coolant. That's why it is recommended to cycle the pump for a few seconds only. This allows the metal to cool and prevents the valve spools from sticking in their bores. A few seconds (10-15) are all that's necessary to cool them; the heat dissapates pretty quickly. This is far less than the time it'll take to move from one wheel to the next to bleed the caliper, so you should be OK.

This is how the ABS pump operates anyway; it cycles on and off several times every second, so the designers saw no reason to provide any cooling capacity. Serious shortsightedness, most likely resulting from accounting department pressures.

You need to read the post by @cartercd that was referenced. It has all the information you need in it.

In the photo the green drawing lines that are going to the pins . Sorry I didn't word that very well .

 

[Malleus]

Understood. You should connect them one at a time. A small alligator clip on a test lead will do the job. Make sure it has a condom; you don't want to fire two solenoids at once. Not the end of the world, but not good practice, either.

 

[jpoole]

You should connect them one at a time

That's good to know. To date I've been grounding all 4 green wires and then adding power to the two red wires for a few seconds at a time for each bleeder port on the truck. Until I know which wires do what I will move to grounding each of the green pins for a few seconds, one at a time, with each open bleeder port.

Any guesses or suggestions for determining which wire corresponds to which wheel/circuit? As I understand it the front wheels are independently controlled by the abs system and the two back wheels are controlled together so I don't know how that would translate to the 4 green wires.

 

[Malleus]

The original post that @cartercd put all the information in has that too. It's also in the EWD. I don't have it at hand, at the moment, but I'll post it later, unless someone else gets to it before me.