Major brake failure

[pluton]

Can the metal brake lines rust out, develop holes? (I see NY in your sig)
BTW, check those rubber brake hoses. 25 years---if true---is way too old to be in use on the car. They'll be stiff and with a cracked surface if they are that old.

 

[the_welfare_wagon]

Can the metal brake lines rust out, develop holes? (I see NY in your sig)
BTW, check those rubber brake hoses. 25 years---if true---is way too old to be in use on the car. They'll be stiff and with a cracked surface if they are that old.

Yeah I agree they are well overdue for a change. The entire rig is pretty much covered in some sort of factory rust prevention so I doubt a line has a hole. No fluid has been lost either from what I’ve seen


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[3bears]

yes please keep us posted on what you find so we can all learn. I would def replace all the rubber hoses. I have seen when one looked good , it swelled to the inside and that wheel did not want to bleed correctly. I dont think that is your problem right now....but should be on your future to do list....I just replaced mine with stainless.( when doing a brake refresh)...as hey....they were 22 years old

 

[toverturf]

I'm going to take a guess and says it's your ABS pump. I had the same issue where you pretty much had to have the pedal to the floor for the brakes to work. Replaced master cylinder, got steel brake lines, bled it a million times, replaced pretty much all the rear brake hardware, and still nothing. Went to the junkyard and got a ABS pump and issue fixed. Had no ABS codes or anything but something was clearly wrong with it.

 

[Jakeepoo3]

So I’m posting this because I have no idea what to do next. I’m not brake expert and need opinions.

Went down to OBX this weekend and had pretty decent brakes on the way down. (I have the TBU) I had also just adjusted the rear shoes. However on the way down I hit some pretty hard bumps and I noticed my brake pedal started sinking to the floor. It still grabbed but didn’t catch till it was just about on the floor. I figured maybe it was some air that the bump had moved around so I went into ABS to see if that would move it around. The brakes instantly felt way better and were back to mostly normal. They stayed good for the 3 days I was down in OBX then on the way home in WV they went to floor again and kept getting worse. Nothing I did fixed it including ABS. I finally had to stop before someone got hurt and checked the rear brakes. The rear wheel cylinder maybe moved the shoe 1/8th of an inch. The shoes were well adjusted so that is not an issue. I had it towed to an autozone where I swapped the master and bled all 4 brakes twice. The pedal was much better however it only lasted for maybe 15 miles and the same issue started to come back. Any ideas what to do next?

The pedal pretty much sinks all the way to the floor and only has any braking effect at the last inch or so of travel and even then it’s barely enough to stop the car

Things I’ve done:
Changed master(Duralast gold new)
Check brake booster pin(moves instantly)
Master was properly bled
Brake fluid is all new at this point
NO loss of brake fluid at all
Getting a decent amount of fluid at each wheel during the bleed


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Everything sounds in good order. To me the problem may be a simple adjustment. You mentioned the booster push rod moved instantly. That's good but the you need to check for the proper gap between push rod and master cylinder, especially after changing parts. Your soft brakes would mean the rod needs adjusted out. I had the the opposite symptom of dragging brakes, push rod too far out on my Cherokee. Tiny adjustments make big changes so make note of the rods original position and pay close attention to how much you're adjusting. I started by adjusting in small increments until it was dialed in then verified proper gap.

 

[jgue467]

So going down the mountain pass my friend behind me said he smelled my brakes. ...

ya' gotta gear down for engine braking while going down a significant hill or multiple ones, no other way. Even my big boy Tundra will overheat the brakes going down I-70 in either direction west of Denver (Eisenhower/Johnson Tunnel area).

This way you use your brakes less and all is good. BTW, my runner has all original brakes here at 340K and it does I-70 with engine braking like a duck takes to water. Luck.

 

[brillo_76]

Looking like several possibilities:

1] bad or misadjusted master cylinder.

2] abs pump messed up

3] The original rubber flex lines failing causing a check valve like situation

4] wheel cylinder or caliper pistons seizing [ unlikely]

5] bell cranks seized causing rear brake issues

It's definitely a puzzle that's for sure.

Out of curiosity, which tundra calipers did you use? The 199mm or the 231mm?

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[the_welfare_wagon]

ya' gotta gear down for engine braking while going down a significant hill or multiple ones, no other way. Even my big boy Tundra will overheat the brakes going down I-70 in either direction west of Denver (Eisenhower/Johnson Tunnel area).

This way you use your brakes less and all is good. BTW, my runner has all original brakes here at 340K and it does I-70 with engine braking like a duck takes to water. Luck.

I was in 2nd gear going down the hill. With a lot of probably pissed off local drivers behind me haha


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[the_welfare_wagon]

So I haven’t dived too deep yet however this is what I’ve done so far until my friend arrives to help me out:

Pulled ABS fuse- no change
Re bled all 4 again- MAYBE some air in the right rear but I think I cracked the bleeder too much. Other 3 had none whatsoever
Had both rears up in the air to they could freely spin. Wouldn’t stop spinning till pedal was on the floor. The fronts however stopped the second the pedal was applied despite all the travel.


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[Skulking]

So I haven’t dived too deep yet however this is what I’ve done so far until my friend arrives to help me out:

Pulled ABS fuse- no change
Re bled all 4 again- MAYBE some air in the right rear but I think I cracked the bleeder too much. Other 3 had none whatsoever
Had both rears up in the air to they could freely spin. Wouldn’t stop spinning till pedal was on the floor. The fronts however stopped the second the pedal was applied despite all the travel.


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With the rear in the air, what happens if you spin the wheels and then pull the parking brake? If you have the same behavior with the parking brake I'd check shoe adjustment. If the parking brake stops the rears, then there is a problem with getting pressure to the rear brakes.

 

[the_welfare_wagon]

So after a few more bleeds and troubleshooting I finally gave in and adjusted the rear brakes even more. The one side was already dragging so I adjusted it a bit more and then adjusted the other side to what felt like roughly similar and there you go. Completely fixed. No idea why the master swap fixed it. Hardest problems always turn out to be the simplest solutions I guess. I’m going to replace both wheel cylinders and redo the brakes in the back just to be safe even though they adjusted ok.

I don’t understand why that fixed it because both rear brakes were dragging already but I’ll take what I can get


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[Bad Luck]

So after a few more bleeds and troubleshooting I finally gave in and adjusted the rear brakes even more. The one side was already dragging so I adjusted it a bit more and then adjusted the other side to what felt like roughly similar and there you go. Completely fixed. No idea why the master swap fixed it. Hardest problems always turn out to be the simplest solutions I guess. I’m going to replace both wheel cylinders and redo the brakes in the back just to be safe even though they adjusted ok.

I don’t understand why that fixed it because both rear brakes were dragging already but I’ll take what I can get


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When you rebuild your rear brakes I found it helpful to use the parking brake a couple times once I thought I had the shoes adjusted correctly just to make sure the shoes were evenly centered and not off to one side causing premature drag on one side and a large gap on the other. While I'm thinking of it, you have 1 inch wheel cylinders since you have a Limited. I ordered the 15/16 inch ones originally when I rebuilt my old runner's rear brakes.

 

[brillo_76]

Great news OP. Bleeding and rear adjustment got it fixed.

 

[the_welfare_wagon]

Great news OP. Bleeding and rear adjustment got it fixed.

Still not sure how the rear brakes could have done all that. One drum took a hammer and pry bar to come off. The other side wasn’t as tight but was still dragging. I don’t see how that could have possibly been an issue. My girlfriends father is a Mercedes master tech of 25 years. He took one look at the back and he even said they were adjusted properly so I’m left scratching my head at this one. But alls well that ends well I guess


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[PlutosT4r]

Hard to tell, a lot of extra details in the OP, but I think you may have had brake fatigue from limited rear braking. You learned this by now, but the drums are hard to get off no matter how little they're adjusted.

If it happens again in a few hundred miles, could be an adjustment issue --> frozen bell crank, parking brake malfunction, siezed or broken cable pivot. Maybe some other broken stuff in there. I haven't heard anyone reporting a stuck piston on drum brakes, but who knows, that could happen. You said yours only moved 1/8 of an inch, but we need context.

 

[3bears]

So after a few more bleeds and troubleshooting I finally gave in and adjusted the rear brakes even more. The one side was already dragging so I adjusted it a bit more and then adjusted the other side to what felt like roughly similar and there you go. Completely fixed. No idea why the master swap fixed it. Hardest problems always turn out to be the simplest solutions I guess. I’m going to replace both wheel cylinders and redo the brakes in the back just to be safe even though they adjusted ok.

I don’t understand why that fixed it because both rear brakes were dragging already but I’ll take what I can get


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well glad you got it,
if your gonna replace wheel cylinders, get the bigger ones...dont know if it makes much difference... Supposedly there was a 15/16 bore and a 1 inch bore. When I did mine I made sure to order the 1 inch bore

 

[the_welfare_wagon]

What I’m still trying to understand is why didn’t the front brakes take up the slack from the rear? I don’t really have much knowledge on braking systems but I don’t get how one shoe slightly out of adjustment could cause the front 2 calipers both of which have new pads and rotors to basically produce no braking power. I understand that they were fatigued but the tundra front brakes should be more than enough to stop the car by themselves IMO. Am I wrong in assuming this?


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[jgue467]

No or little rear brakes overheats the front ones, any brakes that are too hot by design loose lots of braking ability, that is why your big ol' tundra fronts are not of much value alone.

 

[brillo_76]

What I’m still trying to understand is why didn’t the front brakes take up the slack from the rear? I don’t really have much knowledge on braking systems but I don’t get how one shoe slightly out of adjustment could cause the front 2 calipers both of which have new pads and rotors to basically produce no braking power. I understand that they were fatigued but the tundra front brakes should be more than enough to stop the car by themselves IMO. Am I wrong in assuming this?


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Maybe I missed it. Which size of tundra calipers did you go with? I think you had a combination of things going on.

1] air in the brake lines somewhere

2] the rear breaks don't take much movement to effect pedal travel. So one adjusted good and the other bad would effect the pedal height.


3] The tundra calipers come in 2 sizes. The wide 199mm size and the larger 231 mm size. The 199 mm is the same diameter rotor as stock. Just accepts a lot wider rotor and stock rims fit.

The 231 mm caliper is larger and the stock rims don't fit. Lots of members have reported soft brake pedal after doing this upgrade because the there is a difference in the caliper itself besides being wider.

4] it's best to get your emergency brake cable and bell cranks in good working order as you can use your emergency brake cable to keep your rear brake shoes well adjusted.

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