I'm at my absolute wits end- Fading Brake pedal despite best efforts (1 Viewer)

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I noted you said bleeding and getting a good pedal is easy....it is only a couple of days later that there is a problem right? If that is the case then you ARE bleeding all the air out and getting a good pedal, so air is slowly working it's way back in, the result a long pedal. And yes you can get air in and NOT fluid out if for example you have a porous pipe somewhere. Also of note, have you checked the wheel bearings all round?

regards

Dave

And the wheel bearing check?

regards

Dave

Or anything else that's preventing proper square alignment with the calipers/brackets/etc-causing excess travel tor the pads to be pushed back too far and have the excess travel be used up pushing them back into place on the rotor-same symptoms as shoes not adjusted or stuck caliper slides on single piston vehicles. Look for excess movement of the pistons at one or more wheels.
 
I noted you said bleeding and getting a good pedal is easy....it is only a couple of days later that there is a problem right? If that is the case then you ARE bleeding all the air out and getting a good pedal, so air is slowly working it's way back in, the result a long pedal. And yes you can get air in and NOT fluid out if for example you have a porous pipe somewhere. Also of note, have you checked the wheel bearings all round?

regards

Dave

Dave - With the first MC I installed it took a couple of days for the air to come back. This one, it's like it's instant. All axles, birfs, bearings, OEM replaced within the last 8 months.
 
No. I'm throwing the MT (Mierda de el Toro) flag on this one.
Now bleed the brakes again and you should be done.

I'm going to hit the grass and gravel on my way home, stop and see Chester and bleed the ABS. Hope that has me done, but I've got a Phoenix system on the way just to be sure.
 
Or anything else that's preventing proper square alignment with the calipers/brackets/etc-causing excess travel tor the pads to be pushed back too far and have the excess travel be used up pushing them back into place on the rotor-same symptoms as shoes not adjusted or stuck caliper slides on single piston vehicles. Look for excess movement of the pistons at one or more wheels.
Calipers are brand new OEM installed yesterday, all alignment is in check with the calipers, brackets as far as I can tell. New shoes too, and there isn't much distance at all between the new shoes and the rotor. How do you adjust the shoes though? I didn't adjust them.
 
Try moving your LSPV down significantly. My brakes sucked until I did that. They felt really spongy. I bled everything, activated the abs by jumping some wires while bleeding, and replaced the calipers and lines. Moving the lspv finally made them feel solid. At one point I did have a slight leak at a connection as well. Definitely make sure there are no leaks too.
 
Try moving your LSPV down significantly. My brakes sucked until I did that. They felt really spongy. I bled everything, activated the abs by jumping some wires while bleeding, and replaced the calipers and lines. Moving the lspv finally made them feel solid. At one point I did have a slight leak at a connection as well. Definitely make sure there are no leaks too.

You physically relocated the LSPV? How, and where to? Do you recall what wires you jumped on the ABS to activate it?

I think I'm leak free as I am absolutely not losing any fluid.
 
I appreciate the repairs 8 months ago but, you must check the wheel bearings, 'pad knock off' is a common problem.

The LSPV can be disconnected had held/tied in the 'maximum pressure' setting, i.e. the sensor will flow fluid without restricting it. Another idea I did not see mentioned (AFAIK) is clamping of certain areas of the braking system for example, the flexible line to the rear brakes, use a proper brake pipe clamp and close off that hose, you can now bleed the remaining fronts. Check what happens now, only once did I see a similar problem that you are having i.e. bleed and loose pedal pressure later and it was on an elderly BMW. When the brake pistons on the rear discs retracted they took a little air with them, took a day or two to make it unsafe to drive, clamped off the rear and drove it around for a week with no loss in pressure, we followed it up from there.

Just a warning here, if you clamp off the rear of course your braking effort is reduced and your fronts will cope but, if you try it on one wheel on the front, you find even the most gentle touch of the brake pedal will snatch the steering wheel out of your hand. You need to clamp as near to the crimp on the flex without damaging it, this will help you discount that particular hose from ballooning.

Be careful out there!

regards

Dave
 
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I appreciate the repairs 8 months ago but, you must check the wheel bearings, 'pad knock off' is a common problem.

The LSPV can be disconnected had held/tied in the 'maximum pressure' setting, i.e. the sensor will flow fluid without restricting it. Another idea I did not see mentioned (AFAIK) is clamping of certain areas of the braking system for example, the flexible line to the rear brakes, use a proper brake pipe clamp and close off that hose, you can now bleed the remaining fronts. Check what happens now, only once did I see a similar problem that you are having i.e. bleed and loose pedal pressure later and it was on an elderly BMW. When the brake pistons on the rear discs retracted they took a little air with them, took a day or two to make it unsafe to drive, clamped off the rear and drove it around for a week with no loss in pressure, we followed it up from there.

Just a warning here, if you clamp off the rear of course your braking effort is reduced and your fronts will cope but, if you try it on one wheel on the front, you find even the most gentle touch of the brake pedal will snatch the steering wheel out of your hand. You need to clamp as near to the crimp on the flex without damaging it, this will help you discount that particular hose from ballooning.

Be careful out there!

regards

Dave

I'll have to look at trying to work around the LSPV perhaps. I'm not particularly fond of going to 50/50 brakes on the 80 though. I could always spring for a new LSPV if I determine the problem is there. Question becomes, in this instance, how do you isolate a defective LSPV? Just remove it and test?
 
No, I just adjusted the LSPV down. It's on a slotted bracket and is designed to be moved. Loosen the two nuts, pull it down, and tighten them up again. Pretty simple. Mark where you started with a sharpie so you can easily go back if you want to. It's a pretty quick and simple thing to do if it's not insanely rusted. I noticed an immediate difference. Worth a shot.
 
No, I just adjusted the LSPV down. It's on a slotted bracket and is designed to be moved. Loosen the two nuts, pull it down, and tighten them up again. Pretty simple. Mark where you started with a sharpie so you can easily go back if you want to. It's a pretty quick and simple thing to do if it's not insanely rusted. I noticed an immediate difference. Worth a shot.

Ahhh, got it! I'll drop it to the bottom and see if I get better results. Probably have to hit mine with some PB Blaster I'm guessing.
 
You could also disconnect the lever from the axle and tie it up with something. Basically the same thing.
 
I didn't read the full thread, so I apologize if this has already been mentioned or evaluated.

About 8 years ago, I had brain fart moment, and accidentally poured motor oil in the brake fluid reservoir. I was multitasking; changing the engine oil and bleeding my brakes because I thought I was a badass multi-tasker. Unfortunately, I was reminded again that my brain can only process events in series. This was for a 350Z, but bear with me, as I'll get to the point shortly. I soon discovered a problem with braking. Apparently, the engine oil caused the seals in the master brake cylinder to swell and block the flow of brake fluid. The brake calipers wouldn't release the rotor, so I was stuck at an intersection about 5 miles from home. The pedal was also rock solid. I had the master cylinder replaced because the mineral based oil had caused the seals to swell up; thereby restricting proper flow to the brakes. The problem was solved...for 1 year...

Suddenly, the problem cropped up again; solid pedal and severely diminished braking, but ABS light was on this time. After a good deal of bleeding and testing of the system, I sent in the ABS module for repair. That didn't work. Then, I replaced the ABS actuator assembly, and THAT's what caused the problem. Apparently, the engine oil finally caused the seals inside the actuator to swell thereby constricting proper flow of brake fluid to the calipers. I could hardly get any braking, but my pedal was rock solid!

Luckily, sourcing an integrated ABS actuator/brake hub (where all the hard lines connect) only cost me $150. I tore into the ABS actuator, and confirmed that one of the two ABS pistons was immovable; swollen seal. The description of your problems seem to be similar to the problem I had. I'm not necessarily saying you dumped engine oil in the brake system, but the seals inside the ABS actuator/hub may be swollen.
 
I had my shop remove the lsvp and put in a manual valve..I'm not running 50/50. I've upgraded to all new calipers pads/discs/ss lines for the whole truck. While i wouldn't want to be cut off; the brakes are decent. I will need to drive another truck to see how well mine work vs theirs. I'd recommend removing the lsvp but keep the abs. If anything it'll be easier to bleed :)
 
So, today I hit the grass and gravel several times, going from about 40 and slamming on the brakes with both feet and all my weight.

ABS kicked in perfectly and stopped quickly. After several times of doing this I went to my brothers.

Bled front right, brake oil looked like really rusty morning pi$$. Best description I can give, you get the visual. Very little air, very little.

Bled left front, a little more air, much cleaner fluid.

Opened top front port of ABS, and used a bleeding type process. Tiny amount of air.

Opened rear port of ABS, used bleeding type process. A good amount of foam like fluid.

Very slight improvement in braking. Awaiting Phoenix reverse bleed , but going to hit the abs again in the morning.

Any idea how to activate ABS while parked would be helpful.
 
We did, the first five or six times. Still have air.
 
I'm not. Would love to speed up the process, but I'm still patient.

Still would like to know how to activate the ABS while parked.
 
The Phoenix system makes the most sense so far. Bleed in reverse, get air out better. I'll be trying that on Wednesday. Meantime, I'm going to use the ABS functionality several more times and see if I continue to get more disgusting colored fluid instead of clean brake fluid.
 

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