$25 to whoever diagnoses my brake problem
09-25-2011, 01:28 PM
#24
"Pusher" (my terminology) is where you force fluid in through the caliper and back to the MC.
bent the line or kinked it?
While running, the pedal will hold, but at the bottom of it's stroke. Once it gets there, does it hold or continue to the floor?
Like discussed earlier, I'm thinking there is a seal issue in the MC. If the pedal strokes way down and then grabs enough to stop the car, that says to me the piston has to go far down the cylinder to seal and build pressure.
Maybe a seal is blown or the cylinder is worn. Once you get down the cylinder, a different combination of seals work or you get past the worn section.
Yes, the LL was installed about 5 years ago so I know everything is routed properly. One thing I did notice was when doing my shock and spring install, I had to move the MC out of the way to get to the shock bolt, and in the process I bent the line going into the proportioning valve. It made a small fluid leak at the flared end into the proportioning valve, but I loosened it, seated it, and tightened it, and haven't had any issues with it since.
It's firm when the car is off, but when I turn it on, it goes straight to the floor. Pumping it does nothing to change pedal height or feel. The brakes will hold enough to stop the car, but the pedal is almost to the floor to do this.
Like discussed earlier, I'm thinking there is a seal issue in the MC. If the pedal strokes way down and then grabs enough to stop the car, that says to me the piston has to go far down the cylinder to seal and build pressure.
Maybe a seal is blown or the cylinder is worn. Once you get down the cylinder, a different combination of seals work or you get past the worn section.
09-25-2011, 01:38 PM
#25
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i dont know if the calipers for this application are interchangeably, but when i went to school, a guy worked on a Fo*d F-250 an he was havin a similar problem, turns out he had the calipers on the wrong sides (they would fit either way with no issues) BUT it put the bleeder nipples in the position and caused air to get trapped above the nipple. he took em off, switched sides and bleed em an all was well.
but like i said, i dont know if this is your problem or even possible on this application, just throwing out an educated suggestion.
oh, and did the line connections have copper washers? my C10 has them, an i've always heard to replace them every time you break the line connection.
but like i said, i dont know if this is your problem or even possible on this application, just throwing out an educated suggestion.
oh, and did the line connections have copper washers? my C10 has them, an i've always heard to replace them every time you break the line connection.
09-25-2011, 04:02 PM
#26
"Pusher" (my terminology) is where you force fluid in through the caliper and back to the MC.
bent the line or kinked it?
While running, the pedal will hold, but at the bottom of it's stroke. Once it gets there, does it hold or continue to the floor?
Like discussed earlier, I'm thinking there is a seal issue in the MC. If the pedal strokes way down and then grabs enough to stop the car, that says to me the piston has to go far down the cylinder to seal and build pressure.
Maybe a seal is blown or the cylinder is worn. Once you get down the cylinder, a different combination of seals work or you get past the worn section.
bent the line or kinked it?
While running, the pedal will hold, but at the bottom of it's stroke. Once it gets there, does it hold or continue to the floor?
Like discussed earlier, I'm thinking there is a seal issue in the MC. If the pedal strokes way down and then grabs enough to stop the car, that says to me the piston has to go far down the cylinder to seal and build pressure.
Maybe a seal is blown or the cylinder is worn. Once you get down the cylinder, a different combination of seals work or you get past the worn section.
The line I bent is bent, not kinked. It affected the angle in which it mated to the proportioning valve, which is why I had to take it off and reseat it.
Once I press the pedal and it goes to the floor, it'll hold there. But it's so damn close to the floor it's hard to tell whether it's at the floor or just very close to it. Either way, it will hold the brakes enough to stop the car.
So you're thinking MC and not leak in the system somewhere? Would a leaky line connection not fit this description? I'm just trying to rule out anything here. I'm going to take a picture of the clear tube when I bleed to show how much air is in the system.
09-25-2011, 04:54 PM
#27
Chasing an air bubble is a bitch. And it's something I thought you might have when I read your description of the line lock and bent line. The fact that it began leaking after it was bent still is a red flag. It was either seated or it wasn't.
But your descrition of the pedal differences while not running (no power assist) and while running makes it sound like a bad seal in MC.
A leaking line would mean as you pump the pedal (build line pressure) the fluid would come out, not draw air in. And you've said there are no leaks.
The air has to be coming from somewhere.
The bad seal in the master cylinder is much like blow-by created by a broken ring. Oil pumps past the rings and gets in the cylinder. In the case of a MC seal, as you stoke the pedal forward, fluid gets past the seal in the void behind the piston, partially filling the cylinder behind the piston. When the pedal comes back, that fluid and now air has to go somewhere. It's a closed system with no vent.
Unfortunately, in cases like this, you are forced to begin changing parts ... taking best guesses. And because I'm not there and only going by what is posted, that's really all any one can do ... make a best guess.
I wish I could say "replace this part and you are done" or "turn this bolt and you problem is solved" ... doesn't work like that in this format.
The copper seal where the line meets the caliper is a good thought. But it would be leaking fluid when the system builds pressure
But your descrition of the pedal differences while not running (no power assist) and while running makes it sound like a bad seal in MC.
A leaking line would mean as you pump the pedal (build line pressure) the fluid would come out, not draw air in. And you've said there are no leaks.
The air has to be coming from somewhere.
The bad seal in the master cylinder is much like blow-by created by a broken ring. Oil pumps past the rings and gets in the cylinder. In the case of a MC seal, as you stoke the pedal forward, fluid gets past the seal in the void behind the piston, partially filling the cylinder behind the piston. When the pedal comes back, that fluid and now air has to go somewhere. It's a closed system with no vent.
Unfortunately, in cases like this, you are forced to begin changing parts ... taking best guesses. And because I'm not there and only going by what is posted, that's really all any one can do ... make a best guess.
I wish I could say "replace this part and you are done" or "turn this bolt and you problem is solved" ... doesn't work like that in this format.
The copper seal where the line meets the caliper is a good thought. But it would be leaking fluid when the system builds pressure
Last edited by mitchntx; 09-25-2011 at 05:00 PM.
09-25-2011, 07:04 PM
#28
Chasing an air bubble is a bitch. And it's something I thought you might have when I read your description of the line lock and bent line. The fact that it began leaking after it was bent still is a red flag. It was either seated or it wasn't.
But your descrition of the pedal differences while not running (no power assist) and while running makes it sound like a bad seal in MC.
A leaking line would mean as you pump the pedal (build line pressure) the fluid would come out, not draw air in. And you've said there are no leaks.
The air has to be coming from somewhere.
The bad seal in the master cylinder is much like blow-by created by a broken ring. Oil pumps past the rings and gets in the cylinder. In the case of a MC seal, as you stoke the pedal forward, fluid gets past the seal in the void behind the piston, partially filling the cylinder behind the piston. When the pedal comes back, that fluid and now air has to go somewhere. It's a closed system with no vent.
Unfortunately, in cases like this, you are forced to begin changing parts ... taking best guesses. And because I'm not there and only going by what is posted, that's really all any one can do ... make a best guess.
I wish I could say "replace this part and you are done" or "turn this bolt and you problem is solved" ... doesn't work like that in this format.
The copper seal where the line meets the caliper is a good thought. But it would be leaking fluid when the system builds pressure
But your descrition of the pedal differences while not running (no power assist) and while running makes it sound like a bad seal in MC.
A leaking line would mean as you pump the pedal (build line pressure) the fluid would come out, not draw air in. And you've said there are no leaks.
The air has to be coming from somewhere.
The bad seal in the master cylinder is much like blow-by created by a broken ring. Oil pumps past the rings and gets in the cylinder. In the case of a MC seal, as you stoke the pedal forward, fluid gets past the seal in the void behind the piston, partially filling the cylinder behind the piston. When the pedal comes back, that fluid and now air has to go somewhere. It's a closed system with no vent.
Unfortunately, in cases like this, you are forced to begin changing parts ... taking best guesses. And because I'm not there and only going by what is posted, that's really all any one can do ... make a best guess.
I wish I could say "replace this part and you are done" or "turn this bolt and you problem is solved" ... doesn't work like that in this format.
The copper seal where the line meets the caliper is a good thought. But it would be leaking fluid when the system builds pressure
Your MC piston explanation makes sense and kind of seems like what's going on here. I actually just bled the entire system again: MC and all 4 calipers, using gravity bleeding, then the power bleeder. I can say the pedal actually feels slightly better, I'd describe it more as spongy now than no pedal at all.
All banjo fittings are tight with new copper washers on both sides. No leaks there.
I think I'll get a new pre-bent line from SJM and grab a used MC off here to see if either fixes the situation.
10-08-2011, 04:28 PM
#29
Update.
I replaced the MC, but the issue is still there. So that rules the MC out.
So the only 2 things I can think of now is there is a leak somewhere that I can't see, or there's an issue with one of the new calipers. Would a bad caliper cause an issue like this?
I replaced the MC, but the issue is still there. So that rules the MC out.
So the only 2 things I can think of now is there is a leak somewhere that I can't see, or there's an issue with one of the new calipers. Would a bad caliper cause an issue like this?
10-08-2011, 04:57 PM
#30
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i dont know if the calipers for this application are interchangeably, but when i went to school, a guy worked on a Fo*d F-250 an he was havin a similar problem, turns out he had the calipers on the wrong sides (they would fit either way with no issues) BUT it put the bleeder nipples in the position and caused air to get trapped above the nipple. he took em off, switched sides and bleed em an all was well.
but like i said, i dont know if this is your problem or even possible on this application, just throwing out an educated suggestion.
oh, and did the line connections have copper washers? my C10 has them, an i've always heard to replace them every time you break the line connection.
but like i said, i dont know if this is your problem or even possible on this application, just throwing out an educated suggestion.
oh, and did the line connections have copper washers? my C10 has them, an i've always heard to replace them every time you break the line connection.
10-08-2011, 05:39 PM
#31
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my bad. i missed this post lol. i'd put the old lines back on an see what happens. if that dont work, throw the old calipers back on. that will at least narrow down the field.
10-08-2011, 10:34 PM
#33
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my old roommate had a very similar issue with his tahoe a few years ago. turned out he had to bleed the brakes in a particular order. not sure what the order was, or if that's even relevant to the issue you're having.
10-09-2011, 09:57 AM
#34
Months ago I replaced my calipers with another used F-body set and my brake lines with some Russell Stainless lines. I replaced the calipers because I was getting rid of my Pro Stars and didn't want the shaved ones anymore. My brakes had always performed flawlessly and I had a good pedal feel.
If you start the car with the vacum line feeding the booster plugged, does it make any difference in the pedal feel?
Are you 100% sure you have the lines at the MC feeding the correct ends? the port furthest from the booster feeds the rear brakes.
Is the level in the MC reservoir going down? If not, then you have no leaks.
10-09-2011, 11:36 AM
#36
I forget after reading through the thread but have you tried swapping the brake lines back on instead of the stainless?
When I bleed brakes I just let them gravity bleed. I keep the MC full and open all of the lines until only fluid comes out, them shut them off farthest to closest.
10-09-2011, 11:39 AM
#37
No other changes? No cam, no intake?
If you start the car with the vacum line feeding the booster plugged, does it make any difference in the pedal feel?
Are you 100% sure you have the lines at the MC feeding the correct ends? the port furthest from the booster feeds the rear brakes.
Is the level in the MC reservoir going down? If not, then you have no leaks.
If you start the car with the vacum line feeding the booster plugged, does it make any difference in the pedal feel?
Are you 100% sure you have the lines at the MC feeding the correct ends? the port furthest from the booster feeds the rear brakes.
Is the level in the MC reservoir going down? If not, then you have no leaks.
I'm 100% sure the lines are hooked up correctly. The front MC line goes to the proportioning valve. I haven't changed this.
The level in the MC isn't going down at all and all the fittings and connections are bone dry.
I'm starting to think it's a bad caliper. Like I said earlier, I think I'm going to cap off one brake line at a time to see if the pedal gets better. If it does, then I'll know which caliper is bad. Does anyone know what size cap I could use on the hard line going to each caliper?
10-09-2011, 11:41 AM
#38
Thats what I was going to suggest.
I forget after reading through the thread but have you tried swapping the brake lines back on instead of the stainless?
When I bleed brakes I just let them gravity bleed. I keep the MC full and open all of the lines until only fluid comes out, them shut them off farthest to closest.
I forget after reading through the thread but have you tried swapping the brake lines back on instead of the stainless?
When I bleed brakes I just let them gravity bleed. I keep the MC full and open all of the lines until only fluid comes out, them shut them off farthest to closest.
I've tried bleeding furthest from the MC in, and closest out. Either way, no change.
10-09-2011, 12:35 PM
#39
run a bolt and flat washer and new crush seal through the banjo fitting and seal it off on the back side with another crush seal, flat washer and nut.
That should seal it off.
You driven it like this, right? Is there an odd pattern on the rotor like the pad is only partially engaging the rotor and flexing the caliper?
I'm not going all the way back through this thread ...
Have you checked the guide pins? Do they move in and out and spin easily?
I'm about out of ideas ...
10-09-2011, 01:11 PM
#40
Take the flex line loose at the caliper.
run a bolt and flat washer and new crush seal through the banjo fitting and seal it off on the back side with another crush seal, flat washer and nut.
That should seal it off.
You driven it like this, right? Is there an odd pattern on the rotor like the pad is only partially engaging the rotor and flexing the caliper?
I'm not going all the way back through this thread ...
Have you checked the guide pins? Do they move in and out and spin easily?
I'm about out of ideas ...
run a bolt and flat washer and new crush seal through the banjo fitting and seal it off on the back side with another crush seal, flat washer and nut.
That should seal it off.
You driven it like this, right? Is there an odd pattern on the rotor like the pad is only partially engaging the rotor and flexing the caliper?
I'm not going all the way back through this thread ...
Have you checked the guide pins? Do they move in and out and spin easily?
I'm about out of ideas ...
Yes, I have driven it like this. It's funny you mention the odd rotor pattern. It appears only about half the width of the pad is engaging the RR rotor. I removed the caliper and realized that one of the "ears" that sticks out of the front of the pad was coming in contact with the caliper when I closed the caliper. I had to shave about .1" off to get the caliper to slide over the pad without contacting that "ear".
Just to make it clear, I'm talking about the metal part of the pad pointing to the top of the picture here. When I closed the caliper over the pad, they would make contact and I had to force it back to get the caliper bolt it. So I shaved this part off and it closes fine now with no force. I'm not sure if this would cause the uneven wear, but I figured it was the reason.
I took the guide pins out and regreased them and they all appear fine. None were seized or anything.