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With the front raised and brakes and MC bleed yet again, I did noticed the front calipers are both missing the guide pin bushings and rubber boots... The drivers side never seemed to release so I took it apart and there was rust inside the piston chamber. I decided to just replace the two front calipers due to the internal rust (Only $23 each). They are due in today and I will see what happens after the new calipers are put on.

Dont think it will.change anything with pedal going to the floor though.

Still trying to wrap my head around how boosted brakes makes it go to the floor when the pedal is rock hard with ending off.

Let me clarify going to the floor. It has some resistance so it's not like a bleeder left wide open, but the pedal does go all the way down till it hits a stop.
 

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There is a lot more force applied to the MC when the brake booster is assisting in braking.

You need to get all 4 wheels off the ground.

Also, our cars use a "Dual Diagonal" brake system.
The MC applies hydraulic pressure to the L/F and R/R, R/F and L/R.
The bleeding sequence is R/R, L/F, L/R, R/F.
 

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There is a lot more force applied to the MC when the brake booster is assisting in braking.

You need to get all 4 wheels off the ground.

Also, our cars use a "Dual Diagonal" brake system.
The MC applies hydraulic pressure to the L/F and R/R, R/F and L/R.
The bleeding sequence is R/R, L/F, L/R, R/F.
There is a lot more force applied to the MC when the brake booster is assisting in braking.

You need to get all 4 wheels off the ground.

Also, our cars use a "Dual Diagonal" brake system.
The MC applies hydraulic pressure to the L/F and R/R, R/F and L/R.
The bleeding sequence is R/R, L/F, L/R, R/F.
Some have recommended taking vice grips and pinching off a rubber brake line one at time to see if that helps. I assume if I do that and suddenly gain good brake pedal with engine running, then that pinched off caliper/line is bad. If I do that and no change, then I am back to bad MC, bad PV, or air still in the system even after over a gallon of brake fluid flushed through the system.

Makes me mad as this is such a basic system, but kicking my tail. Oh the joys of a car that has sat for so long. Oh well, I will get it sorted out eventually, but wish it were sooner as I still have not driven this car more than 50' and would like to see what else is fubar such as shocks/struts/squeaky sway bar bushings etc.

Oh, and then still need to troubleshoot the high idle. I thought I had found a culprit, the vacuum line to the HVAC controller had come loose and was open down near the battery. I hooked it back up, but still high idle. Once brakes are sorted out, I will pull the car out and spray around with a can of carb and choke cleaner to see if I can track down the vacuum leak. I believe it has a leak as the boost gauge only reads about 10-11" at idle (1250 rpms)

Thanks for your help!
 

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Pinching the rubber brake hose (hoses) will help you determine if the issue is with the MC or a Caliper, however, keep in mind that when using vice grips to pinch the rubber hose you may damage the hose internally causing a blockage, yes, folks have been doing this for years (including myself), I am just making you aware that it has happened and may happen again.

I would recommend you remove the brake lines from the MC and seal the two ports and see if the pedal drops.
Also, after sitting for 9 years the brake fluid may also have been contaminated, contaminates such as petroleum based products will cause the seals to swell.

Again, this is all moot if you do not get all 4 wheels off the ground, apply the brake and see if all 4 wheels lock.
 

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Pinching the rubber brake hose (hoses) will help you determine if the issue is with the MC or a Caliper, however, keep in mind that when using vice grips to pinch the rubber hose you may damage the hose internally causing a blockage, yes, folks have been doing this for years (including myself), I am just making you aware that it has happened and may happen again.

I would recommend you remove the brake lines from the MC and seal the two ports and see if the pedal drops.
Also, after sitting for 9 years the brake fluid may also have been contaminated, contaminates such as petroleum based products will cause the seals to swell.

Again, this is all moot if you do not get all 4 wheels off the ground, apply the brake and see if all 4 wheels lock.

Just replaced the front calipers, bled the entire system again, and with the car in the air put it in gear and got the tires spinning then hit the brakes. Everything seemed to work so I took it off the jacks and for a quick spin. For slow stops the brakes seemed to work fine, but bad CV joint are keeping me from taking it out and doing a 45 mph hard stop to see what happens.

Thanks all for the help!
 

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If the front calipers were at fault, pinching off those rubber hoses would have isolated the problem.
Well I appreciate your input, but I guess your going to stay irritated. When you troubleshoot a system with no results, eventually you must change parts, especially on a car that Sat 9 years.
And yes I am fully aware new does not always mean good. Still does not answer why a hard pedal with engine off and soft pedal engine on. A faulty MC does not only fail with engine on. A bypassing MC would do it all the time and not just when boosted.

Or would you care to tell us all how that can be?
All I can do is theorize on it since I am not there to see it happening. With vacuum assist, much more hydraulic pressure can be applied. With that being the case, any leak that isn't noticeable with manual brakes will be more evident with the assist.

Suppose the square cut O-ring around the caliper piston is leaking for whatever reason. Perhaps there is pitting in the caliper bore, and with the extra power assist, it is deforming that O-ring just enough to leak there. But there are no external leaks? There's a lot of room between the dust boot seal and the piston seal, and it doesn't take much leakage to let the pedal go to the floor like that. I would take a stab at the idea of if the car was continued to be driven like that, eventually fluid leaks at the caliper would have become evident as the cavity filled up.

The same principle could apply with a master cylinder. All the booster does is turn you into He-man or a 350 pound gorilla. Take apart a few remanufactured calipers.... yeah, there is sometimes pitting still in the bore. All the rebuilders do is run a light hone through them, if at all, install new seals, slap a coat of paint on it, and ship it.

I have replaced a lot of rusty brake lines in my day. More than once, I replaced the rusted-through stuff, bleed it, stand my 165 pound princess force on the pedal and hold to try to feel for leaks. Instead of trying it with vacuum assist in the garage, the inner ding dong comes out and waits for me to nail the vacuum assist version on the test drive where I proceed to rupture another brake line that was also rusty.

That is the best I can do from behind the computer keyboard. More force, more stress, more problems.
 

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Phantom,

Thanks for the replies and I get what you are saying about pinching off the brake lines, and I did that with no change (one at a time. Wish I had four vice grips so I can pinch all four and see if there is any difference). I am not saying the calipers fixed it, just that the piston bores were very rusty (and not leaking). I have exercised the brakes SEVERAL times probably on the order of a couple hundred and none of the calipers were/are leaking. The only real problem I found was with the proportioning valve not working since a valve seal was fubar (When I bought the car the RR was not getting any fluid to the caliper. Took the line off the PV and caliper and blew air back through it and fluid shot out verifying no blockage). I cleaned up the PV valve seal land and put it all back together and it seems better. I took the car for a quick drive and the car seems to stop fine, but I need to get other items fixed so I can take it out and do panic stops to make sure all is well. I just wonder if that seal on the PV valve came off again?

However while working on a squeaky serpentine belt, I have noticed a large puddle of brake fluid under the area near the PV. I ended up buying a CSX PV and will just replace the leaking valve. Hopefully that PV is the source of my frustrations. At the very least my only brake leak I can see. No fluid from the MC or lines from the MC. Only other thing it could be was the PV and its a booger to pull.

I did replaced all the rubber brake lines, but decided to go SS and have the FWD SS lines on order (nearly a month now and was told back ordered). Hopefully they come in while I am busy doing work stuff so when I get a free weekend I can spend it on the PV and SS brake lines. Then the panic stops.
 
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