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

[1973Guppie]

I agree with you on keeping the ABS. In panic braking situations it matters. Experience really does not matter. I was in big bear with the family and almost hit a dog that shot right out into the road. Missed him by a hair and the ABS system did it's job nicely, stopping me in time but not allowing the brakes to lock up.

For me as well I am carrying 2 kids and a wife. On long trips my wife will drive the cruiser and I feel that having the ABS working is important.

 

[Qball]

Here is the thread with pictures:

https://forum.ih8mud.com/threads/lspv-nightmare-solved-kustom-mount-w-pics.277890/

I used a piece of aluminum from Home Depot because it's easy to drill/modify.


The idea is to make an extension bracket as length as your lift.

 

[Qball]

Searched & found this as well....


https://forum.ih8mud.com/threads/lspv-adjustment-with-pictures.165499/

you can't adjust the lspv enough for even a 2 inch lift......believe me I tried.

 

[medtro]

Got a pic by chance??

If you want to get a bit more scientific - Replacing Brake Lines, Adj LSPV and Bleeding Brakes.

 

[IanB]

I agree with you on keeping the ABS. In panic braking situations it matters. Experience really does not matter. I was in big bear with the family and almost hit a dog that shot right out into the road. Missed him by a hair and the ABS system did it's job nicely, stopping me in time but not allowing the brakes to lock up.

For me as well I am carrying 2 kids and a wife. On long trips my wife will drive the cruiser and I feel that having the ABS working is important.

Not to get technical, but ABS actually increases the distance required to stop, it's function is to allow you to continue to steer while in a panic braking situation. The pulsing keeps the front tires from locking up so you can still get steering input to the ground, but you'd stop faster in a straight line with the tires locked up.

 

[Pippylongsausage]

Not to get technical, but ABS actually increases the distance required to stop, it's function is to allow you to continue to steer while in a panic braking situation. The pulsing keeps the front tires from locking up so you can still get steering input to the ground, but you'd stop faster in a straight line with the tires locked up.

Sorry, but I think you are mistaken about that. Keeping the wheels from locking up actually shortens the distance because you maintain static friction against the road instead of kinetic friction which has a much lower friction force.

 

[IanB]

Sorry, but I think you are mistaken about that. Keeping the wheels from locking up actually shortens the distance because you maintain static friction against the road instead of kinetic friction which has a much lower friction force.

From the Transport Canada website:

"Is the stopping distance shorter with ABS?
No! From early commercials, it may have looked like you could stop on a dime. That instantaneous stop is not realistic. When braking on dry or wet roads your stopping distance will be about the same as with conventional brakes.
You should allow for a longer stopping distance with ABS than for conventional brakes when driving on gravel, slush, and snow. This is because the rotating tire will stay on top of this low traction road surface covering, and effectively "float" on this boundary layer.
A non ABS braked vehicle can lock its tires and create a snow plow effect in front of the tires which helps slow the vehicle. These locked tires can often find more traction below this boundary layer."

https://www.tc.gc.ca/eng/motorvehiclesafety/tp-tp13082-abs2_e-215.htm

 

[Pippylongsausage]

Huh, well I guess that settles that

 

[1973Guppie]

Sorry, but I think you are mistaken about that. Keeping the wheels from locking up actually shortens the distance because you maintain static friction against the road instead of kinetic friction which has a much lower friction force.

I tend to agree with you but there are really too many variables in play. The quoted dmv link talks more about in snow or wet conditions. It really depends on conditions. With my wife driving and kids in the car I lean towards keeping the ABS if it is working correctly. Of course, if it were to cost a ton to fix it I would consider a delete. So far I have had no problems with my ABS.

 

[IanB]

I tend to agree with you but there are really too many variables in play. The quoted dmv link talks more about in snow or wet conditions. It really depends on conditions. With my wife driving and kids in the car I lean towards keeping the ABS if it is working correctly. Of course, if it were to cost a ton to fix it I would consider a delete. So far I have had no problems with my ABS.

I should clarify, I am talking specifically about winter conditions, we deal with that 6 months out of the year here. ABS is a valuable safety feature on a vehicle, but you shouldn't get a false sense of confidence about the stopping distance with ABS.

This is off topic though, on topic, I picked up my Motive Power Bleeder last night, still waiting for my new master cylinder to show up so I can swap it and make sure it fixes my issues.

 

[musthave]

I received the Phoenix reverse bleeder. Reverse bled at all 4 calipers and the LSPV. Then did a normal bleed just to be certain.

Result - No difference, and that really suck$

The more I'm at this, the more I feel like it can't be air in the system, except for the symptoms sound like it is. Not ready to delete the ABS yet, in fact I have a replacement on the way. BUT, I'm told that they really don't go bad. Not ready to delete LSPV and instead am going to buy one tomorrow and have it shipped overnight.

Situation a little different, what do you think?

Note - If I step on the brakes quickly ie. going 45 and step on the brakes abruptly and hard, it stops pretty quick, but it is bottomed out with no more pedal left and little brake effect left.

However, if I am behind someone, and approaching a red light, I step on the brake slower and it just fades right to the floor with minimal stopping power. So, I end up trying to pump twice quick and try to stop.

Does this point to something different than air somewhere?

 

[blkprj80]

That sounds like a classic bad brake master cylinder since you say you aren't losing fluid.

There are only two pressure lines leaving the M/C, front and back. Can the ABS dump excess fluid from the front system to the back somehow? Seems like you could see that with how the fluid moves around inside the reservoir. Wrap the lid/float in a ziploc bag and watch what the fluid does. Slowly depress the pedal like you would approaching a red light.

 

[Pin_Head]

It points to excess compressible volume: Either air, balooning lines or excess dead volume in the calipers or elsewhere in the system. If your pedal starts out close to the floor, it could also be exacerbated by low pedal height.

 

[musthave]

It points to excess compressible volume: Either air, balooning lines or excess dead volume in the calipers or elsewhere in the system. If your pedal starts out close to the floor, it could also be exacerbated by low pedal height.

If I determine that this is all because of a exacerbated low pedal height, I'll .... and then and then

 

[Pin_Head]

If you replaced the master, you want to be sure that the booster rod is properly adjusted. Otherwise, it may take a lot of pedal travel before the master starts to develop pressure.

 

[DARKNESS]

There's a whole section in the FSM on how to check pedal height, freeplay, etc... Probably should go through it and do all the tests.

 

[HDJDub]

I still think for piece of mind it wouldn't help changing all your brake lines to new SS lines. I do tend to agree it sounds like the new master is bad. I had the same issue with an RX-7 years ago. I replaced the master and almost everything else only to end up replacing the master again to finally solve my soft/spongy pedal.

 

[70Cruza]

If you want to get a bit more scientific - Replacing Brake Lines, Adj LSPV and Bleeding Brakes.

Thank you much for that. I will be ordering the part from summit tomorrow & doing mine over the weekend.

x2 on the correct MC rod adjustment. I dealt with that on my 70 FJ40 with discs up front. After it was adjusted properly brakes were perfect.

 

[floridan surfer]

I agree with the others-it really does sound like a bad master cylinder.

I've heard that if you depress the pedal too far during a bleeding process, it can push the piston inside the master cylinder past the sealing surface, which could damage the seals internally. I don't know much about this; maybe someone can expand on it.

 

[DARKNESS]

He has a new OEM master cylinder. It seems unlikely that it failed immediately. Not being properly adjusted seems more likely.