Do you have the original soft brake lines? If so I'd definitely replace those while you're at it. It's possible they're bulging and adding volume to the system. Stainless is not necessary in my opinion. I used OEM.
I'm at my absolute wits end- Fading Brake pedal despite best efforts
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890man
SILVER Star
I just read this entire thread and have to agree with Floridian surfer. You should check your master cylinder. I was bleeding the brakes on an FJ 40 years ago and press the brake pedal too far to damage the seals internally. It could have been because it was improperly adjusted. The piston was pushed too far and went past the retaining bolt you see in the photo. It destroyed the seal and allowed fluid to escape past it creating the pedal you're describing. The screwdriver is pointing to the seal that was ruined. It's easy to disassemble it and check the seal. I have always been cautious about pressing the brake pedal all the way to the floor when I bleed brakes since then.
Looking at the FSM it looks like the MC has to come off to adjust the push rod. Or is there enough to just pull the master back with lines still attached. This is something I have never done/checked also. I bought my truck with a brand new aisin MC installed by PO.
My pedal is descent but if I hold down soft pressure while running at idle it will slowly move down to floor. But still remains stopped. When I really slam on the brakes at speed the pedal seams like its harder than actually making stopping power. I checked the booster a year ago as per fsm with it checking out ok.
My pedal is descent but if I hold down soft pressure while running at idle it will slowly move down to floor. But still remains stopped. When I really slam on the brakes at speed the pedal seams like its harder than actually making stopping power. I checked the booster a year ago as per fsm with it checking out ok.
The oem master cylinder seal and piston kit is cheap, I would recommend looking at that option if you don't want to pay for another complete master. Hopefully you'll have this sorted out soon enough. I rebuilt the master in my truck and with all the SS lines the brake pedal is rock solid. Though my hdj81 is not equipped with ABS from the factory either.
FWIW, I bought an Aisin MC for my cruiser on ebay.
This one: http://www.ebay.com/itm/170717211188
It came in an Advics box, had Advics rubber stamp on the body, and Aisin casting mark in the body. You might save $30 or so over what i spent if you can figure out the Advics part number.
It's perfect. But it wasn't the solution to my problem.
I got my reman booster from Centric, via partstrain, and it appears to be exactly the part i took off, and now i have good brakes again. $200 something with $90 core charge.
But you might have a different problem. In my case, when i was bleeding my brakes after changing out the pads, I probably put a very small tear in the booster diaphragm by pushing the pedal down further than it had been in years. It still held vacuum when the pedal was up.
Sometimes, the same action - whomping on the pedal like an idiot during bleeding - causes a condition where crud that has collected inside the cylinder right past the normal travel range of the piston, gets caught under the seal, and tears the heck out of the seal. I think I've also seen a report that someone found a small ridge in the cylinder, same sort of thing, seal had never been to that ridge until the pedal was down hard during bleeding, damaged the seal.
But none of us have driven your truck.
I'd never bench bled an MC and I was worried that i would eff it up. So i took it to a trusted friend who is the lead tech at a good shop. Right after he drove it into the bay he came out and told me that he was nearly certain it wasn't the MC, and damn near begged me to do the booster instead. 'course, i didn't have a booster, and with his markup the cheapest reman booster i could get That Day was $400+, and the cheapest i could get That Week was still $300+.
I think he even offered to let me take a BMW home while they wait for the part. WHAT WAS I THINKING?!
Replacing the booster wasn't what I'd call "hard" so much as "annoying". I couldn't get the damn thing out until i took the nuts off of the motor mounts and jacked up the engine a centimeter or so. After that it was all down-hill.
This one: http://www.ebay.com/itm/170717211188
It came in an Advics box, had Advics rubber stamp on the body, and Aisin casting mark in the body. You might save $30 or so over what i spent if you can figure out the Advics part number.
It's perfect. But it wasn't the solution to my problem.
I got my reman booster from Centric, via partstrain, and it appears to be exactly the part i took off, and now i have good brakes again. $200 something with $90 core charge.
But you might have a different problem. In my case, when i was bleeding my brakes after changing out the pads, I probably put a very small tear in the booster diaphragm by pushing the pedal down further than it had been in years. It still held vacuum when the pedal was up.
Sometimes, the same action - whomping on the pedal like an idiot during bleeding - causes a condition where crud that has collected inside the cylinder right past the normal travel range of the piston, gets caught under the seal, and tears the heck out of the seal. I think I've also seen a report that someone found a small ridge in the cylinder, same sort of thing, seal had never been to that ridge until the pedal was down hard during bleeding, damaged the seal.
But none of us have driven your truck.
I'd never bench bled an MC and I was worried that i would eff it up. So i took it to a trusted friend who is the lead tech at a good shop. Right after he drove it into the bay he came out and told me that he was nearly certain it wasn't the MC, and damn near begged me to do the booster instead. 'course, i didn't have a booster, and with his markup the cheapest reman booster i could get That Day was $400+, and the cheapest i could get That Week was still $300+.
I think he even offered to let me take a BMW home while they wait for the part. WHAT WAS I THINKING?!
Replacing the booster wasn't what I'd call "hard" so much as "annoying". I couldn't get the damn thing out until i took the nuts off of the motor mounts and jacked up the engine a centimeter or so. After that it was all down-hill.
He's been through this every which way. He's been buying brake fluid by the gallon lately. On the next pass through, new LSPV will go on, and we'll be causing the ABS module to engage.
Questions,
Is it possible soft lines can expand under pressure, but not be visible? They look fine, no cracks, don't appear to swell visibly under pressure and no leaks.
Does fluid flow towards the Master Cylinder when the ABS is actuated? I know it flows back and forth towards the calipers, and there's a reservoir in the top of the module, so I'm thinking it might flow the other way too.
Questions,
Is it possible soft lines can expand under pressure, but not be visible? They look fine, no cracks, don't appear to swell visibly under pressure and no leaks.
Does fluid flow towards the Master Cylinder when the ABS is actuated? I know it flows back and forth towards the calipers, and there's a reservoir in the top of the module, so I'm thinking it might flow the other way too.
- Thread starter
- #128
Hard to believe that a rebuilt MC and a brand new OEM MC would both be bad, so I'm thinking that the MC is good.
Ordered all new brake lines today, along with LSPV and boot for same. Another $500 later, let's see where that gets me.
Based on FSM, signs of a bad booster don't include anything that I am experiencing. I don't have hard pedal, brake drag.
Pedal piston rod - I've not adjusted it, so, what would be a reason that I need to adjust it now? I'm trying to locate the SST for it though, just in case.
Does fluid flow towards the Master Cylinder when the ABS is actuated? I know it flows back and forth towards the calipers, and there's a reservoir in the top of the module, so I'm thinking it might flow the other way too.
Ordered all new brake lines today, along with LSPV and boot for same. Another $500 later, let's see where that gets me.
Based on FSM, signs of a bad booster don't include anything that I am experiencing. I don't have hard pedal, brake drag.
Pedal piston rod - I've not adjusted it, so, what would be a reason that I need to adjust it now? I'm trying to locate the SST for it though, just in case.
Does fluid flow towards the Master Cylinder when the ABS is actuated? I know it flows back and forth towards the calipers, and there's a reservoir in the top of the module, so I'm thinking it might flow the other way too.
Because your brakes don't work.
- Thread starter
- #130
I suppose at this point, that's reason enough
Wonder if it's worth it to try to adjust without the SST.
I don't think you need one. It's just a couple nuts.
Booster Push Rod Adjustment.
BRAKE PEDAL ADJUSTMENT
If you need more, get an FSM and follow it.
Things need to be done in an order and you seem to be bouncing around like a fart in a mitten and just throwing money at it.
BRAKE PEDAL ADJUSTMENT
If you need more, get an FSM and follow it.
Things need to be done in an order and you seem to be bouncing around like a fart in a mitten and just throwing money at it.
Azca
If there is a harder way - I will find it...
I dealt with the same thing, push rod solved everything. You don't have to take it appart but you can play with it.... See this post.
https://forum.ih8mud.com/threads/the-cure-for-spongy-brakes.816019/#post-9335569
https://forum.ih8mud.com/threads/the-cure-for-spongy-brakes.816019/#post-9335569
Do you have an FSM? If you need to borrow one, let me know. Mine is for a 94 I think.
"Spongy brakes feel like you have a sponge on the pedal". Pin_Head
That was the condition that needed to be corrected in the beginning.
That's the condition now.
That was the condition that needed to be corrected in the beginning.
That's the condition now.
Thanks, we're using a '96 manual.
there are FSMs for download here: https://forum.ih8mud.com/threads/40-50-60-and-80-series-fsm-for-a-hell-of-a-price.610994/
Agreed, follow the FSM. Do the tests and check the distances.
Doubt that's it, could happen I guess.
Park the truck with good brakes, get back in and the pedal goes to the floor.
I'm wondering about how all this got started. When did the symptoms appear? Did it just happen one day, or slowly over time? Any correlation with another repair or service work?
You've got to be seriously frustrated at this point. I wouldn't want to suggest anything that would waste any more of your time or money. But I keep thinking there has got to be a way of testing components through process of elimination. Like disconnecting the lines right at the the MC, bleeding and plugging the ports, thus eliminating the rest of the system. If the pedal stays firm, move down the line to the ABS unit outputs, and so on... Finding/creating something to plug the ports might prove difficult, and bleeding would be a pain. And messy. But if you could do it, no more guessing you know?
Believe me dude I am in awe of the vast knowledge and experience I've observed over the years on this site. Very humbling. Makes me feel like I don't know jack ****. But for what it's worth, I was a tech at a mits dealership for 20 years. Mits and Toyota brake/clutch systems are very similar. Use a lot of the same suppliers. Everything you describe reminds me of symptoms I've experienced in association with bad MCs. But I know you've gone there... I will say my experience has been that often times, when replacing a MC with OEM part (typically Aisin), the rod needs adjusting.
I also remember replacing a MC on a Honda for a friend. Instructions said to bench bleed. I ignored them and installed it dry and bled on the car. Afterword brakes had the same symptoms you describe; slam hard and pedal stayed firm, press it slow and it went to the floor. No amount of bleeding helped. Took the MC back off, bench bled, reinstalled. No change. Got a new MC, bench bled, installed. Problem solved. Maybe bad part from the beginning, or maybe we damaged the plungers bleeding it dry? Or maybe some other variable we affected unawares. Who knows.
Probably not helping much here. Just feeling your pain and racking my brain. We'll all be celebrating when you get it figured out.
You've got to be seriously frustrated at this point. I wouldn't want to suggest anything that would waste any more of your time or money. But I keep thinking there has got to be a way of testing components through process of elimination. Like disconnecting the lines right at the the MC, bleeding and plugging the ports, thus eliminating the rest of the system. If the pedal stays firm, move down the line to the ABS unit outputs, and so on... Finding/creating something to plug the ports might prove difficult, and bleeding would be a pain. And messy. But if you could do it, no more guessing you know?
Believe me dude I am in awe of the vast knowledge and experience I've observed over the years on this site. Very humbling. Makes me feel like I don't know jack ****. But for what it's worth, I was a tech at a mits dealership for 20 years. Mits and Toyota brake/clutch systems are very similar. Use a lot of the same suppliers. Everything you describe reminds me of symptoms I've experienced in association with bad MCs. But I know you've gone there... I will say my experience has been that often times, when replacing a MC with OEM part (typically Aisin), the rod needs adjusting.
I also remember replacing a MC on a Honda for a friend. Instructions said to bench bleed. I ignored them and installed it dry and bled on the car. Afterword brakes had the same symptoms you describe; slam hard and pedal stayed firm, press it slow and it went to the floor. No amount of bleeding helped. Took the MC back off, bench bled, reinstalled. No change. Got a new MC, bench bled, installed. Problem solved. Maybe bad part from the beginning, or maybe we damaged the plungers bleeding it dry? Or maybe some other variable we affected unawares. Who knows.
Probably not helping much here. Just feeling your pain and racking my brain. We'll all be celebrating when you get it figured out.
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