91 FJ80 brake issues (1 Viewer)

[wildsidelife]

So I've been having issues with my brakes on my FJ80 for a little bit now. It has about 220k on it and I do wheel it pretty hard. FYI, I love working on my car, but I am very new to all of it and am by no means a mechanic, I just enjoy building, romping, breaking, and repeating.

It all started when my booster went out. I bought a new one and installed it back in May 2024. I'll admit, I sort of eye-balled the push rod on the booster to mate with the MC. I later learned how important that tolerance is and paid the price by coming back from a trip and seeing that excessive use with improper rod placement had caused a leaky MC. Since then, I've learned the importance of a FSM, so I now have that as well. I replaced the MC (and the shock below it because the brake fluid ate up the seals and caused that to break as well) and bled the system. Everything seemed to work that night and I was stoked. Until the next day, I go to drive and the first push of the brake pedal doesn't do much and I have to slam my foot to the floor to stop, and even that takes a while to stop the vehicle. There is a lack of stopping power, but it doesn't feel like a lack of vacuum. I got fed up and took it to a mechanic to diagnose. They said with it being a new MC and the lines being bled, it sounds like I need a new booster. There's a chance that the MC has leaked and ruined my not-so-old booster, but I am also getting advice that a spongy pedal is usually the hydraulic system. Has anybody gone down this route? I looked at the FSM but the diagnosis is a bit all over the place. I'd like to replace what's needed and not my whole brake system if possible. Is it possible to have spongy brakes due to the booster, or is it strictly hydraulic at that point? Maybe I didn't bleed the lines enough?

I appreciate any and all advice!

 

[ColoradoBoy]

Brakes are pretty important- if you are wheeling hard, I would be all in on a full system rebuild (I just did mine recently.) and would be worth rebuilding the whole system to keep you and others safe out on the road or trails. Rebuilding the calipers in front and the drums in back will do nothing but help on a truck of this age- and not too expensive for parts. New brake hoses are recommended. Set up your booster and MC per the FSM and bleed the system correctly, and you'll be confident in your brakes again. Lots of threads on this topic...
Cheers!

 

[Trail Teq]

Before going and replacing anything, I would do a full bleed including the master cylinder.

1. Remove MC, and bench bleed it with one of the kits that feed the outlet ports back into the reservoir. Reinstall in car when finished making sure not to push the piston in or pump the brake pedal until all lines are done up on the MC.

2. Bleed brakes as per FSM, preferably with 2 people. Passenger rear, driver rear, passenger front, driver front, LSPV last. Bleed with a clear tube on the nipple into a small container of brake fluid, tube submerged.

Have a helper in the car pump the brake pedal 2-3 times until firm, then have them hold it down as hard as they can. Under the car, you crack the bleed nipple for no longer than 1 second, and immediately retighten it. When you crack the nipple, the pedal will sink to the floor, it's critical that your helper holds it down and doesn't let it raise whatsoever or else you will suck air back in. Repeat this process until no air comes of the bleeder, then repeat it a few more times for peace of mind.

If that fails to remedy it, you can do a DIY test on the booster by feeding a shoe lace into it as a sort of "dipstick" to see if its filled with fluid.

 

[wildsidelife]

Before going and replacing anything, I would do a full bleed including the master cylinder.

1. Remove MC, and bench bleed it with one of the kits that feed the outlet ports back into the reservoir. Reinstall in car when finished making sure not to push the piston in or pump the brake pedal until all lines are done up on the MC.

2. Bleed brakes as per FSM, preferably with 2 people. Passenger rear, driver rear, passenger front, driver front, LSPV last. Bleed with a clear tube on the nipple into a small container of brake fluid, tube submerged.

Have a helper in the car pump the brake pedal 2-3 times until firm, then have them hold it down as hard as they can. Under the car, you crack the bleed nipple for no longer than 1 second, and immediately retighten it. When you crack the nipple, the pedal will sink to the floor, it's critical that your helper holds it down and doesn't let it raise whatsoever or else you will suck air back in. Repeat this process until no air comes of the bleeder, then repeat it a few more times for peace of mind.

If that fails to remedy it, you can do a DIY test on the booster by feeding a shoe lace into it as a sort of "dipstick" to see if its filled with fluid.

I didn't think I needed the FSM for bleeding, but I guess I do... This was actually my first time bleeding brakes being on the "bleeding" not "pumping" side, so this may very well be the problem. I missed that the other end of the tube needs to be submerged. I also definitely bled for over a second each time I cracked it, which is making me think air may have crept back into the lines. I will rebleed tomorrow and let you know. Thanks again for the support and cheers from Colorado

 

[wildsidelife]

Brakes are pretty important- if you are wheeling hard, I would be all in on a full system rebuild (I just did mine recently.) and would be worth rebuilding the whole system to keep you and others safe out on the road or trails. Rebuilding the calipers in front and the drums in back will do nothing but help on a truck of this age- and not too expensive for parts. New brake hoses are recommended. Set up your booster and MC per the FSM and bleed the system correctly, and you'll be confident in your brakes again. Lots of threads on this topic...
Cheers!

Rebuilding/replacing everything is definitely on the list (although I'm basically halfway through the list already). I will be knocking calipers and drums out afterward, but would like to solve this problem first for peace of mind and because I would like to avoid replacing parts that are in good working condition if I don't have to quite yet. As stated earlier, I think my fault was in the bleeding portion of the process, but I will report back with what I find. I appreciate the feedback!

 

[Trail Teq]

I didn't think I needed the FSM for bleeding, but I guess I do... This was actually my first time bleeding brakes being on the "bleeding" not "pumping" side, so this may very well be the problem. I missed that the other end of the tube needs to be submerged. I also definitely bled for over a second each time I cracked it, which is making me think air may have crept back into the lines. I will rebleed tomorrow and let you know. Thanks again for the support and cheers from Colorado

It's tricky the first time you do it but once you figure it out, it's not as hard as it sounds. If you follow my steps you should end up with a good result. I can't stress enough the need for the master cylinder to be bled and free of air though, as well as how important it is for the person on the pedal to not let the pedal raise at all whilst that bleeder is open!

Having the bleeder open longer than a second isn't the end of the world, as long as that pedal never raises. The longer you have it open though, the more can go wrong. If it's open and the pedal lifts, it will suck air back in, so having it open and closed in <1 second just helps minimise that risk. Any air that wants to come out will come out in a second anyway, you will see it shoot bubbles out of the clear tube.

 

[jonheld]

Couple of thoughts.
Everything below is useless if the calipers/cylinders/pads/shoes/rotors/drums/4 soft lines haven't been addressed in 30 years.
The drum brake rears have an adjuster that keeps the shoes properly adjusted by using the handbrake. Again, the internals need to have periodic maintenance, just like every other system on the vehicle.

Hard pedal with reduced braking force is a clear sign of a faulty booster/check valve.
Soft pedal with reduced braking force is a fluid leak or air in the system.

As previously stated, the replacement master needs to be bled before attaching any brake lines.
I remove the bleeder valves and coat the threads with a bit of grease. This prevents air from leaking past the threads while bleeding.
I use the old school method of clear tubing into a clear glass jar with a touch of brake fluid at the bottom. This ensures that when releasing the pedal only fluid can get drawn back into the system.
With a new master, you can pump to the floor as the internal seals have a new, clean surface to ride on.
With a used master, I put a piece of 2x4 under the brake pedal to prevent it from going down too far.

Follow the FSM procedure for the bleeding sequence.

 

[ColoradoBoy]

As stated earlier, I think my fault was in the bleeding portion of the process, but I will report back with what I find. I appreciate the feedback!

I hear you on the bleeding process. I purchased the Motive Power brake bleeding kit; it made bleeding the system a breeze.
Motive Power

 

[wildsidelife]

I do indeed think the issue is from inadequate bleeding of the system, but I decided to just pull the trigger and fork up the extra cash for rebuilding the front and rear as well. I figured if I plan on doing it eventually I may as well do it now. As @ColoradoBoy stated, brakes are not exactly something you want to skimp on, plus it was much cheaper than I thought it would be. Rather than bleed it now and bleed it again a couple of months later, I'll knock it all out at once. Waiting on parts now. I'll report back with any odd issues that continue, or just to celebrate fresh, working brakes. Again, I appreciate everyone's input and guidance on bleeding. That will help me the next time around. The LC community has been a massive help so far. Cheers!

 

[Marco Lau]

most likely air in the brake lines. There is a procedure on bleeding air from the lines and a speed bleeder valves will do wonders,

 

[wildsidelife]

So I changed the front calipers and bled the system (correctly this time) and we are back in business! She stops pretty aggressively now (for an 80) when slamming the brakes, so I feel much safer now. However, when I press the pedal lightly, it seems to be slightly sinking. I think when I incorrectly bled the first time around and had my "pumper" push the pedal to the floor, I fear I may have caused damage to my new master cylinder and have internal bypassing. Not a difficult fix, just sad that the cylinder is brand new and may need replacing.

I'd also like to do the rear drums. The rear was inspected recently by a shop and they told me I don't need to change them but I'd like to make sure everything is adjusted correctly. Are there any recommended kits or any specialty tools I'll need? There are a couple of SSTs called out in the FSM, are these necessary?

Thanks again all!

 

[jonheld]

So I changed the front calipers and bled the system (correctly this time) and we are back in business! She stops pretty aggressively now (for an 80) when slamming the brakes, so I feel much safer now. However, when I press the pedal lightly, it seems to be slightly sinking. I think when I incorrectly bled the first time around and had my "pumper" push the pedal to the floor, I fear I may have caused damage to my new master cylinder and have internal bypassing. Not a difficult fix, just sad that the cylinder is brand new and may need replacing.

I'd also like to do the rear drums. The rear was inspected recently by a shop and they told me I don't need to change them but I'd like to make sure everything is adjusted correctly. Are there any recommended kits or any specialty tools I'll need? There are a couple of SSTs called out in the FSM, are these necessary?

Thanks again all!

If the master is new, then the seals are likely fine as there would be no corrosion internally to damage the seals.
Trust no shop. Your truck is older than the child working on it. Unless they are a Land Cruiser specialty shop, they are not going to be familiar with drum brakes, auto shoe adjusters, etc
No special tools required for the rear. Follow the FSM and remember that each side is a mirror image of the other. All parts are still available.
If they haven't been serviced in 30+ years, I would have all parts on hand before starting.

 

[wildsidelife]

If the master is new, then the seals are likely fine as there would be no corrosion internally to damage the seals.
Trust no shop. Your truck is older than the child working on it. Unless they are a Land Cruiser specialty shop, they are not going to be familiar with drum brakes, auto shoe adjusters, etc
No special tools required for the rear. Follow the FSM and remember that each side is a mirror image of the other. All parts are still available.
If they haven't been serviced in 30+ years, I would have all parts on hand before starting.

You're right, they have been very wrong in the past so probably not a good idea to take their advice. I'll gladly change everything just for peace of mind. Could the slight pedal drop be related to the rear drums?

 

[jonheld]

You're right, they have been very wrong in the past so probably not a good idea to take their advice. I'll gladly change everything just for peace of mind. Could the slight pedal drop be related to the rear drums?

Could be a vacuum leak amongst other things.
You should reach out to one of the 5 local Colorado Land Cruiser clubs and stop messing around with mechanics that don't know.

 

[wildsidelife]

 

[Marco Lau]

Did you replace brake lines in the front?

 

[wildsidelife]

Did you replace brake lines in the front?

I changed out the chassis-axle soft lines for extended ones to account for the lift. Haven't touched any hardlines.

 

[jonheld]

I changed out the chassis-axle soft lines for extended ones to account for the lift. Haven't touched any hardlines.

As previously stated, there are 4 soft brake lines on your truck.
1 for each axle drop from the frame, and 1 for each front caliper.
They should all be changed at the same time if you don't know the history.
90947-02612 Left soft line
90947-02613 Right soft line
90401-10015 Banjo bolt (1 for each caliper)
90430-10074 Copper washer (2 for each caliper)

 

[wildsidelife]

Just wanted to update you all. I rebuilt the drums. Found two leaky brake cylinders in the process. Still had a strange pedal feel when finished. I had a shop power bleed in case that was my issue and it turns out it was. It seems I'll be in the market for a power bleeder. Didn't realize how difficult it was to get all of the air outta these things! Either way, my issues have been solved. I appreciate everyone's input and hope this thread helps anyone else having troubles and are also underestimating the power of pesky air bubbles. Cheers