Do you perhaps live at a high elevation? Air pockets forming at high elev especially after coming from lower elev can happen,I've seen it and had it happen. Rare? you bet but when grasping at straws grasp them all.
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| Author: | Joshie225 [ Wed May 06, 2009 7:55 pm ] |
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Do you mean to tell us that the caliper bleeders are not at the top of the calipers as installed? |
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| Author: | ppsi [ Thu May 07, 2009 6:14 am ] |
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The bleeders are at the top-that is what has me even more frustrated. The whole thing is put in correctly but will not bleed. I'm on my way out now to do some more bleed attempts but the weather looks real bad and I'll likely get drenched. I'm going to try back bleeding with pressure at the bleeder screws which I am replacing with new ones. If this does not work I bought some speed bleeders for the calipers although I really doubt these will work and finally if this fails I will take off the calipers and move them around trying to free up any air inside them. Wish me luck. Howard |
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| Author: | 6shotvanner [ Thu May 07, 2009 6:47 am ] |
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Do you perhaps live at a high elevation? Air pockets forming at high elev especially after coming from lower elev can happen,I've seen it and had it happen. Rare? you bet but when grasping at straws grasp them all.
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| Author: | 65Dodge100 [ Thu May 07, 2009 6:42 pm ] |
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I’ve never tried it... but it seems like it might be worth a try to push the caliper piston all the way in with the bleeder screw open. Danny |
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| Author: | ppsi [ Fri May 08, 2009 7:01 am ] |
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Quote: I’ve never tried it... but it seems like it might be worth a try to push the caliper piston all the way in with the bleeder screw open.
This is the next idea I had for today. Yesterday I spend 3 hrs with various bleed methods only to end up with fluid all over the place and no improvement. Today I will take off the caliper/remove the pads and make the piston extend out beyond where they are and a little more. If I open the bleed screw while it is oriented att he top and compress the piston I hope to see the air. It can only be the right caliper at this point because if I have the rears hooked up and pinch off the hose for the front left I get a full pedal. I also get a full pedal if I do this AND pinch of the right front hose so there is no doubt about where the air is trapped.Danny I hope this does it because I got the drive shaft back after being shortened for the 8 1/4 I installed and really want to see the car ride down the road. Thanks Howard |
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| Author: | 65Dodge100 [ Fri May 08, 2009 7:21 am ] |
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Quote: It can only be the right caliper at this point because if I have the rears hooked up and pinch off the hose for the front left I get a full pedal.
You may have that backwards. Or maybe you just said it backwards. It could be I’m reading it backwards too. If you clamp one side and it makes the pedal hard, that same side is the one with the problem. Danny |
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| Author: | stonethk [ Fri May 08, 2009 7:41 am ] |
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Reading your previous posts you mention use of a vacuum bleeder. In my experience those things are POS's. While it can be done, doing a solo bleed job sux IMO. The only times I have been happy/successful bleeding hydraulic lines was with a competent helper. Good Luck |
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| Author: | slantfin [ Fri May 08, 2009 8:24 am ] |
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Quote: Today I will take off the caliper/remove the pads and make the piston extend out beyond where they are and a little more.
This sounds like it may be a bad idea. If the piston extends too far, you have to take the caliper apart and reseat the seal, and/or lots of air gets into the caliper. I realized this could happen as my Coronet 500 was headed toward the back of a car that had stopped for a little travel lane-blocking conversation. 
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| Author: | ppsi [ Fri May 08, 2009 5:55 pm ] |
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Quote: If you clamp one side and it makes the pedal hard, that same side is the one with the problem.
You are right-I had the clamped off hose stated wrong.Danny Again today I spent 6 hours on this incredible brake system. Not paying attention and having the MC go dry didn't help my efficiency. I did try the pump deal I bought and indeed it is a total POS I had brake fluid everywhere under the hood and on the floor after trying to push fluid through. I used the Speedbleeders and they work great-they come with a sealnt around the threads which is one of the main issues I think. Regardless of this I still could not get the pedal right and no matter what I tried, from regular bleeding with a jar, to using the pump, to taking both calipers off and manipulating them to try and get the most perfectly positioned bleed screw I still came up with a low & soft pedal. I can only think there is some internal seal that is making the fluid leak past (but not out) the piston. These are a single pistong caliper and use the lame spring metal slides/holders. I ordered a set of calipers today and will put them on Monday. At least I was able to get the drive shaft in and take the car for a ride which was some satisfaction. The 8 1/4 has a bit taller gearing and seems like it goes down the road better with a real BBP. Plus I added a leaf to the sorry @ss springs and the car sits and rides nicer. I understand that pushing the piston beyond the point where it should max out is a bad idea and I didn't do this. I don't have a cut away picture of these calipers but in looking at some others in the FSM I have for a 1970 Challenger there is a single piston caliper cross section and it looks as if it is possible that is an inner seal is damaged it could allow fluid to go past it and still not leak out of the caliper. I am grasping but the car did sit for 2 years and perhaps these calipers are no good now due to either seal damage from me moving the piston during the pads being changed or are just rusty on the inside to the point that the seals would get Fubar by having a ring of rust travel past them. All I can say for certain is a clamp on the right side hose provides a very high & hard pedal and when I take that hose, both of which are new, off the pedal goes back to being low and spongy. Thanks for all the helpful posts. I can't believe this stupid lame brake job is turning into such a problem. Howard |
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| Author: | tophat [ Sun May 10, 2009 8:44 am ] |
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I seem to remember that corvettes of the 70's had a "square cut" seal in the caliper, these when worn would allow the caliper to suck air in past the seal when the pedal was released, with no visible fluid leak. IIRC the square cut seals were used to try to help the piston retract an extra few thousands upon release. Sounds like it could be similar to your problem. Hope the new calipers fix it. TopHat |
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| Author: | SlantSixDan [ Sun May 10, 2009 8:59 am ] |
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All disc brakes use a square-section O-ring to retract the piston a few thousandths when you take your foot off the brake pedal. I don't know that I've ever seen one develop a one-way leak (air in, no fluid out) but I suppose it's possible. It seems more likely to occur with old calipers than with new ones. |
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| Author: | tophat [ Sun May 10, 2009 6:20 pm ] |
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Most caliper seals are slightly rectangular, almost but not quite square. My understanding of caliper engineering is that the less square (more rectangular) the seal is, the less it pulls the piston back when released, but less likely to suck in air. The more exactly square it is the more it will pull the piston back, but the more likely it is to suck air. Granted, we are talking about thousands of an inch, but it does make a difference, not that there is anything you can really do about it but change to another caliper design. I do know it was a problem on corvettes and I'm sure it was on the rears of mid to late 70's cars. With the flood of chinese parts and pieces, it is hard to know you (or the "rebuilder" even) is getting parts that are exactly the right size for the application. TopHat |
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| Author: | ppsi [ Mon May 11, 2009 6:53 am ] |
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Hopefully today I will see if the calipers are to blame. I don't mind replacing them all that much because they are 6+ years old and sat without being used for 2 years. My problem is I've run out of things tp point to other than the combination valve and I hate just throwing parts at a problem-makes me feel like my Dodge service department. |
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| Author: | 65Dodge100 [ Mon May 11, 2009 8:39 am ] |
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It’s not very hard to rebuild your calipers if you want to try it. It is usually impossible without an air compressor to remove the piston. I wouldn't try it if you don't have one. Danny |
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| Author: | ppsi [ Mon May 11, 2009 5:02 pm ] |
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I replaced the calipers today. I have rebuilt many in the past and have used compressed air to remove the piston. I am glad I replaced them because I opened up one and it had a rust ring on the piston due to condensation or water in the fluid. I still can't get a good pedal though and it is really making me crazy. The only thing I can think of doing is using a helper to pump the brakes and hold the pedal while I release the fluid. All along I have been using speedbleeders and a jar of fluid but I bet I've bled them 20 times and it is absolutely the front that is holding air. I've never had to resort to a helper since learning the one man system 30+ years ago but I have nothing else I can think of. I am hoping the pressure on the pedal makes the air move out??? |
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