I'm at my absolute wits end- Fading Brake pedal despite best efforts

[murf]

I see you say no brake hose bulging while the brakes are under pressure...but

what about the 3 other brake hoses to the axles besides the ones at the calipers?

Just some thoughts. Good luck, hope you find it soon.

I had this issue and after replacing all 7 of my brake lines with stainless and a power brake flush, it was restored to normal.

 

[Pin_Head]

It is hard to get the air out of the FZJ80 system. It is easy to do ineffective bleeding. You need to develop the maximum hydraulic pressure to compress all the bubbles before you crack the bleeder and shut the bleeder off before the fluid stops flowing to avoid sucking air back.

 

[1FZj80]

I think he means the main ABS control unit that is on the driver's side fender under the hood.

yes, the whole abs unit. there are internal valves that control fluid flow/pressure when the abs is doing its thing. I don't know for sure, but believe these may leak and effect pedal feel during braking.

 

[1FZj80]

It is hard to get the air out of the FZJ80 system. It is easy to do ineffective bleeding. You need to develop the maximum hydraulic pressure to compress all the bubbles before you crack the bleeder and shut the bleeder off before the fluid stops flowing to avoid sucking air back.

there is more to it than that. before removing the abs, I could bleed and get a hard pedal, but after a few days of driving the sponginess came back. it is easy to bleed and get a hard pedal, the trick is to keep it that way

 

[musthave]

I see you say no brake hose bulging while the brakes are under pressure...but

what about the 3 other brake hoses to the axles besides the ones at the calipers?

Just some thoughts. Good luck, hope you find it soon.

I had this issue and after replacing all 7 of my brake lines with stainless and a power brake flush, it was restored to normal.

I haven't checked the hoses, other than those at the caliper. Good thought.

 

[Pin_Head]

I could bleed and get a hard pedal, but after a few days of driving the sponginess came back. it is easy to bleed and get a hard pedal, the trick is to keep it that way

If it gets air back in it, then it must be leaking somewhere. That is a different situation.

 

[musthave]

For certain, there is no fluid leaking at all anywhere. That's one of the few things I can be sure of.

 

[DSRTRDR]

Close, I'll give you a hint. I needed a new direction and distraction.
View attachment 999704

as far as brake bleeding: the two-person method has always worked well for us

and the LSPV needs to be bled between every caliper

 

[jkilcullen]

Did you just disassemble the ABS unit on the fenderwell? Did you replace the LSPV, OEM?

I rerouted all lines to eliminate abs and lspv

 

[musthave]

I rerouted all lines to eliminate abs and lspv

That's tempting. Moreso the LSPV than the ABS as it's a DD with the kids. Any issue with eliminating the LSPV entirely? Or is the one from NAPA worth installing?

 

[DSRTRDR]

why ?

 

[musthave]

as far as brake bleeding: the two-person method has always worked well for us and the LSPV needs to be bled between every caliper

Whenever we bleed the LSPV, we don't get any air though. We are using two-person method now, but from what most are saying, there is still air somewhere. We don't get any at LSPV or any caliper.

 

[jkilcullen]

Dont know anything about the napa lspv. Ive removed it from numerous rigs thus effectively making bias 50/50 front and rear which is not ideal for some applications. And as far as removing abs its not something I recommend anyone doing but I personally knew all the risks/rewards and am happy with my decision.

 

[Timpanogos Slim]

most helpful tip i got from a professional tech was to use the hoses and bottle from a vacuum bleeder system and use some wire or twine or whatever to suspend the bottle above the caliper.

air isn't going to suck back into the system if it's not at the bleeder.

whether or not you believe in the check valve speed bleeders, the thread sealant sold by the same outfit makes a hell of a lot of sense, too.

 

[jkilcullen]

there is likely an air pocket either in the abs module or lspv circuit somewhere near front of truck. you can jack rear of truck way up in the air to try to force air pocket to rear while bleeding rear and lspv. you can also attempt to burp fluid at abs module by cracking each line while pressure is applied. also, bleed with truck running in case you werent already.

 

[musthave]

there is likely an air pocket either in the abs module or lspv circuit somewhere near front of truck. you can jack rear of truck way up in the air to try to force air pocket to rear while bleeding rear and lspv. you can also attempt to burp fluid at abs module by cracking each line while pressure is applied. also, bleed with truck running in case you werent already.

Ok, that's one way to try to do it. We've been bleeding with LC off, does that make a difference?

 

[musthave]

I have bled a zillion vehicles and some have been very stubborn. For the very stubborn ones I have developed a easy method that works well for me. First question though-do you have an air compressor? Second you need a vacuum bleeder like the one from harbor freight for like 30 bucks that you hook the air too. If you have those things, then hook it up. As you crack each bleeder with it hooked up, leave the bleeder open and pulling fluid and then get in the vehicle and pump the pedal for like 20 seconds. Do this for each wheel. This has always worked. If you don't have this style bleeder you can't do it. They are worth the money as you can use them for various things. With this method you don't even have to bench bleed the master if you don't want too if its new.

Have an air compressor, and a good vacuum bleeder. Mine doesn't hook into air compressor though. MC is new, we bench bled it even though it shouldn't be necessary. We've cracked the bleeder and left it hooked up with vacuum and bled for 15 minutes + on each cylinder, absolutely no air bubbles appearing. Then closed the bleeder and moved to the next. But it seems like we still have air, or there is an issue at ABS or LSPV.

I keep saying, if fluid isn't coming out (leaking) then air can't be getting in.

Is it possible that there is still air in the ABS assembly? A few have said to bleed that, but I've not tried that yet.

 

[Pin_Head]

If you installed your calipers with the bleeder valves upside down (by swapping them L to R) you will play hell trying to bleed them.

 

[scrowley]

When my brakes worked poorly and I did EVERYTHING new (not all OEM) the last thing I did that helped a lot was: In the snow I got ABS to kick a few times then did it while sliding right into my garage. Then bled. I did get air out. AND this was after it was on a VAC for approx. 10 min. per caliper at my buddy's shop (and after I put like a gallon through the system!!

AND two yrs later.... My brakes still don't feel great. Also my ABS is INOP right now with no effect to braking.

 

[musthave]

If you installed your calipers with the bleeder valves upside down (by swapping them L to R) you will play hell trying to bleed them.

They are rightside up on the correct side. I wish this were it