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I am almost reluctant to post on this subject.  But I have read all the previous posts on brakes and brake bleeding and am running out of ideas.

6997 had been sitting for 30 years before the rebuild.

I have fully rebuilt all of the brakes on 6997 . All the calipers are rebuilt , standard, with new seals and pads ex Halls , all installed no leaks. All new Goodrich flexible braided lines . All bleeders have been assembled with gas tight seal tape.

The master has had a Halls seal rebuild kit put into it and it was rebuilt including re-sleeving by a local brake shop who has credibility. Mind you I think it held a few challenges for them.

All the ancillaries items are are new. The pressure differential and pressure regulator assemblies are out of the box Wilkinson sourced. The old ones were paperweights.

I bench bled the master on the bench and then via releasing the tube couplings once it was in the car - and noted allot more flow pulsing from the rear outlet for the front brakes than the front outlet for the rear brakes but ploughed ahead anyway.

I had one try to bleed the system and finally realized the internal  plunger must not have been adjusted inside the master when the shop  rebuilt it. Dumb.  I disassembled the master and adjusted the plunger point forward almost 1/2 inch to give it around 0.30 thou clearance but was almost out of adjustment on the piston plunger thread at the end . I re-bench bled the master and reinstalled the master cylinder again noting only low flow from the front port.

I have now run what appears to be the forum standard  gallon of brake fluid through the system and bled from the shortest to the longest runs multiple times, using both traditional pumping and vacuum bleeding techniques. I am getting no residual bubbles at all  from  any of the  bleed points but allot more flow from the front bleeders during traditional pumping. There is flow from the back bleeders but at about half the front volume.  No Bubbles at any point.

The pedal feel still feels spongy at the top - not the rock hard solid feel I would have expected. There is a hard pedal close to the floor .

My questions - am I missing something on the rear brakes or the master cylinder bleeding or adjustments . Is it possible there still residual air in the master rear brake front piston  after liters of BF through the rear brakes?

Any other points of adjustment that I may have missed ?  Any common mistakes on the master rebuild that may have occurred?

completed rebuild

Any other suggestions on what to check next or other actions that might help would be very gratefully received.


Images (1)
  • Completed Master rebuild
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FWIW, I've been told to generally bleed from longest to shortest, and that has worked successfully for me on Panteras.  Technically my current JFZ system does revert back to a spongy pedal a few minutes later, but those JFZ systems are notoriously that way--I need to re-research the best way to get those to a hard pedal, as I recall that involves something like rotating the calipers, wood blocks and such while bleeding.

Make sure you don't have any residual assembly grease from the caliper rebuild gunking up the bleeders. That was my problem, I thought all air was out, but the pedal was soft. I used a pressure bleeder and whilst under pressure, took out each bleeder, gave the caliper a quick clean with a Q-tip where the bleeder screws in, and then put it back in, and changed bleeders for new ones in some cases when there was greeae inside. Messy, but solved my problems. Watch the reservoir if you use a simple pressure system, so you don't run it out of fluid...

Cheers, Tim.

After sitting for 30 years I expect a few solidly plugged areas. I have had to DRILL out some bleeders and ports to remove solidified varnish. Check visually and with wire probes for clear areas. I've also had to do this to the cam bearing oil feeds on older engines, especially those with oil feed restrictors.This in spite of boiling blocks out in very hot solvent washers. Age hardened varnish is very tough stuff!

With the movable shuttle valve and the movable non-adjustable stock proportioning valve, I doubt if a rock-hard brake pedal is possible even if perfectly bled. Thats one reason why I deleted both in my Pantera back in the last century. Others gut those parts for a more stable platform with the stock look. You will almost always feel moving parts inside any hydraulic system. Manual adjust proportioning valves have no spring-controlled movable parts, and all the shuttle valve does is turn on a red dash light if one caliper somehow develops a leak.. Which a perceptive driver will see in low fluid level during "preflight" look-overs anyway.

I put completely new front and rear calipers on. It took just over 1 quart of Dot 5 fluid to get the purple out of the bleeders.

I'm not entirely certain that you can get a rock hard pedal with rubber hoses?

In my experience you need to go to -3 braided teflon hoses to achieve that. Is that what the Goodrich hoses are? Teflon?

If you are going to this extent to analise the system, I think that you need to put a pressure gauge in line, possibly on T fittings to see what the master is putting out and then what the calipers are receiving.

Last edited by panteradoug

Thanks so much for all of the informed and detailed comments.

For the record - the caliper positions are checked as  correct. The lower and upper bleed points on the front were done. The goodrich lines are 3- braided high pressure. The calipers were detailed cleaned before reassembly and there is no residual gum anywhere in the system. The bleeders are free flowing.

I wanted to keep all the brake system parts stock to keep the car close to original so replaced both the in line brake valve and shuttle with the original parts.

Feedback from others I have now received  are the same as Bosswenches comments - that it is likely with the movable shuttle valve and the movable  stock proportioning valve, a rock-hard brake pedal is unlikely.

A tentative shakedown drive has been suggested , then a final re-beed following the action of the booster and the system in general. I will get this done and give some feedback after that.

Thank you to everyone.

Decades ago (when I still had OEM calipers), I recall being frustrated by a mushy brake pedal. I decided to try bleeding the front calipers off of the car. I removed the caliper mounting bolts, put a 3/4" piece of plywood between the pads and moved the calipers around into different positions while tapping them with a mallet and bleeding. To my amazement, I got air bubbles...and a hard pedal.

Might be worth a try. 

Doug's suggestion about rubber hoses is a good thought. Under the pressures used in max braking, rubber hoses swell. I use AN braided-stainless which helps, and going to dash-3 in place of the commonly used dash-4 size helps more. That's old-tech from the Korean war, though. Nowadays, serious go-fasters use lighter weight braided-kevlar hoses, still in dash-3 size. And (personal preference)- I discard any 'residual pressure valves' found in some aftermarket and even performance production master cylinders. Owners install them in (usually front) brake lines for slightly quicker response and also slightly more pad-drag & wear..

Personally I've expeienced more controversy with people claiming the brakes are soft/hard, etc.

Street cars in my views should have a softness to them. They are not race brakes.

If you need to go further, research just about any Ford service manual of any car of any year that is using power brakes.

You are going to find a picture of a brake pedal having the effort on the pedal measured with a dial gauge.

That's how that is measured. Not weather you were barefoot, had Nike's on or your bed room slippers.

Production cars are made for average everyday people, not Nicky Lauda's demands.

You are getting nowhere unless you read pressures directly from the master and the calipers. You need hard numbers to compare to.

Last edited by panteradoug

Percy, I can't tell about your hoses from here. Braided-stainless-reinforced plastic lines pretty much all look alike. But inside are the real differences: The original lines had/have translucent whitish poly-tetra-fluoro-ethylene (teflon) hose and use the braid as reinforcement & protectant against weathering and external-object damage. Others use poly-sulfone plastic (not translucent) that are higher temp rated than teflon. The fittings were/are 6061-T-6 aluminum with 410-stainless steel hose attachment parts, as sold under the Aeroquip brand. They are aircraft flight-certified and test loaded to over 3000 psi burst pressure for dash-3 and -4  sizes. They work fine for brakes & clutch hydraulics and are monstrous-overkill for automotive fuel, cooling or vacuum systems. The 37-degree cone fittings do not seal well against AC freons. The slick teflon lines flow 4- 5% more fluids at any given pressure than other plastics.

There are visually identical hoses available in which NONE of the listed plastics or metals are used. On our Sept '72 car, there was a stock braided-metal hose used as part of the fuel or smog system. It was visible from the engine compartment and ran across the rear firewall above the engine screen to- I think- the charcoal canister. Since our canister and the hose have been gone for decades, I can't really remember. Inside the braid was a cheap rubber hose crimp-fastened to fittings and the braid was dull tin-plated mild steel. It leaked. I've found others that use brass inner hose fitting parts. They seem OK but cannot mix-&-match.with stainless Aeroquip stuff. I stay away from those. YMMV-

Bleeder valves seal by the tappered seat, not by the threads. You can use some anti-seeze on the threads but keep extras and expect that if they have been locked up and unbled for years that you may strip them out.

For some still unexplicable reason, often the hex is not a full 3/8" and more like 11/32".

I just replace the valves when I do a major bleeding which is a good thing since you should flush out the old fluids periodically anyway.

Watch the color of it. It changes color as it absorbs moisture which is natural just from the atmospheric humidity.

Caution is advisable on ANY pure stainless steel threaded parts. "Stainless" has a nasty habit of stripping the threads for no reason at all. You need to use anti-seeze on them but that doesn't always eliminate the issue.

Neither can they take the torque load often required in the original engineering specs. I've had them pop out of the casting. Stainless to an aluminum casting in particular is just not a good idea at all.

I've had aluminum -3 ends SPLIT from just the normal brake pressure generated by the master.

There are SOME ordinary AN fittings not made in -3 sizes. Take a different route.

You are better off using the cad plated steel hose ends and fittings and never use aluminum fittings on brake lines. They just don't have the tensile strength of steel.

You can create reliability issues by trying to be too fancy because you want to add bling.

In panic stops master cylinders can produce instant pressures of 900 to 1000 psi loads in the lines. With the wrong materials you can absolutely strip the threads and pull the fittings out. That probably isn't a good thing.

Remember that "braided metallic" lines and fittings were initially adapted by racers from aircraft applications but aircraft has regular document service intervals that will often require complete replacement of hoses and fittings periodically.

AC lines generally use SAE 45° fittings but good luck on getting even those to completely seal in your refrigerant. That's why you need to recharge your system  periodically and often annually.

All materials have a porosity to them. In the case of A/C lines, some materials are better then others.

It's like raw magnesium castings that leak air when they are cold because the porosity at a molecular level when cold becomes larger then the "air" molecules and escapes through them. You have to coat magnesium wheels to prevent that.

A/C lines are that way but have less porosity so they leak right through the material but at a much slower rate. If you get two years without having to recharge your Pantera's system, you did good.

Those are long hoses and give more surface are for microscopic leaks.

Last edited by panteradoug

Goodridge was the first company to produce braided stainless steel brake lines for automotive use and established them as the standard in motorsport around the world. Each line they sell is tested to 3000 psi.  Their brake line kits are the best money can buy.  I promise you these are not your problem.  The Pantera line kit is an identical fitted set to to stock in terms of fittings, down the the washers and banjos. They will outlast most other components of the car once installed properly.

FWIW, I use several turns of teflon tape around bleeder screw threads- not as a sealant exactly but to keep air from being sucked back in during bleeding when you release the brake pedal after each stroke. Might not happen with pressure or vac bleeders but it does when you're doing it by yourself. As several have said, the actual fluid sealing is on the tip of the bleeder needle, not on the threads. Take the tape off after you're done bleeding if it bothers you.

Thanks so much for all of the detailed information and advice. This is the first time I have used gastight teflon around the bleeders and I think it did improve the prevention of air being sucked back into the bleeder. I would do it again like this. I would also go the extra yard to manipulate the front calipers to extract the last of the air.

I have re-inspected the Goodrich braided lines and steel fittings and they are very very solid. No issue there  re metallic differences.

Dougs comments on gas porosity in metals and hoses are very interesting . At the risk of going off topic I offer a  personal observation on this.

A good example of gas porosity is in  heavy wall high pressure pressure vessels working in  hydrogen rich environments. These in operation can develop blisters on the inside surface where hydrogen seeps through the steel ( one molecule at a time ) and binds up at a point of laminar inclusion in the plate. This results in a high pressure  hydrogen bubble inside the steel that, if untreated, will split the pressure wall. Treatment was simple and nerve wracking   - use a mag drill to puncture the blister.

Unfortunately the high pressure hydrogen would come out the hole when it reached the blister and spontaneously ignite - very tough on the front of the mag drill and on the operators nerves !! ( always seemed to be holding your breath  ....!!)

This was the most graphic example of osmosis of gas through metal that I have seen. A little off topic for this post but interesting none the less.


It is surprising to most until they get into the engineering.

Another example that comes to mind and not to be off color. That is not my intent.

Standard latex condoms are only 32% effective against the HIV virus. What exactly is only 32%? Beats me. I need explanation of that term.

What I read was that the HIV virus is small enough to pass through the porosity of the latex. How small is that? I don't know. Ask the engineer but still very concerning scientific fact.

The first I came into contact with this subject was with magnesium wheels. American was making them in the '60s uncoated. Just as cast and machined.

Racers were having issues with the tires the next day as they were going flat. No leaks could be found.

At some point it was found that it was the porosity of the magnesium itself would vary according to temperature.

Maybe some of you Aerospace engineers are aware of this from the beginning but I have to learn by the empirical method. So far it hasn't been fatal and I suppose as long as you hear the bullet go past, you live...for now?

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