In an attempt to buy myself a year or so before I do the disk brake conversion I recently decided to do shoes and fluid on my exsisting drums. The logic was that for safteys (and budgets) sake I'll just spruce them up a bit.

Well, 2 wheel cylinders and a huge amount of adjustment and hassel later I find that although they work pretty well and feel pretty solid I have this one issue:

When driving on the highway for extended periods and reach for the brake at say a tool booth I SOMETIMES push all the way to the floor, then the next pump has them right there. This NEVER happens in around town or secondary road driving situations. It only happens once on the highway, and then they are good for another hour or so.

Is this a classic case of air in the lines? I've bled them and flushed them twice already.
Todd

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72 Scamp 225 /6, auto, radio delete, alum super six, cold air duct, pertronix ignitor II and flame thrower, 3.23 rear, 2.25" free flow exhaust

The biggest problem with the brakes on older cars is the tiny master cylinder IMO. when you bleed the brakes make sure you refill the reservoir after each wheel. 3-4 pushes can drain the master cylinder and create a bubble in the lines.

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I am 110% with you Brothers and sisters!!!

I just got done doing a bunch of work to my 72. Included was 73+ SPC Front discs (10.75" or 11" if you perfer), 3.21 geared 8.25 in the back with 10" drums. LCAs with factory Anti-Sway tabs, HD Sway Bar, .990 Torsion bars, new hard lines, and a Manual Disc Brake Master Cylinder... Care to guess what's giving me trouble?

I have the exact same problem It's almost guarnteed to be the MC or serious air bubbles in a bad place. In my case its the crappy MC from the 75 4 door that we canniblized for parts, but Yea... Bleed and feed, bleed and feed.

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When in doubt, empty the magazine.
'72 Dart Swinger /6 - My Yard Dart!
'01 Ranger P/U 4x4 X-cab
We buy and sell MOPARTS & Ford Parts!!!
http://www.usironauto.com

72Swing, sounds like you did basically the same thing I did with the suspension(I have a rear sway bar, front factory bar, .99 torsion bars, 8 1/4 axle with 2.71 gearing and sure-grip, 11 inch front disc, B body spindles, 10 inch rear drums). Were you as happy as I was with the improvement over the stock suspension?

Oh yeah, I have the same problem with my MC, drive for too long or hit a hard bump and my pedal gets squishy, two press downs and it's hard again.

Shivadart

Hi Everyone,

I love the brakes and suspension work I have already done (and yes, the difference is INCREDIBLE), but I am never "finished".

I can't wait until all the rest of the suspension mods are done. I'm going to get a set of FFI Tubular Upper Control arms, welded up K member, and a Feedback capable power steering box so I can actually feel the road. The rear suspension still needs some work, but the business end first I guess

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When in doubt, empty the magazine.
'72 Dart Swinger /6 - My Yard Dart!
'01 Ranger P/U 4x4 X-cab
We buy and sell MOPARTS & Ford Parts!!!
http://www.usironauto.com

This problem sounds like a bad master cylinder with an inturnal leak.
One way to test this is to press on the peddle really slowly and lightly to see if you can get it to "drift" down to the floor, if so, replace the MC.
DD

Thanks for the replies. The very first thing I did when I bought this car 18 months ago was replace the master cyl because it was bleeding down to the floor badly. After that it was solid, never a problem (just worn shoes). So I suppose it could be the Master with a leak again but I'll try yet another 'bleed and feed' before I go replacing parts.

Curious what you guys are paying for 9" wheel cylinders, I paid over $50 each from NAPA, I was expecting about $15 each.
Todd

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72 Scamp 225 /6, auto, radio delete, alum super six, cold air duct, pertronix ignitor II and flame thrower, 3.23 rear, 2.25" free flow exhaust

here a wheel cylinder for 9" brakes is $32. for 10" brakes $13. master cylinder $34. I(or my wallet) can feel your pain.

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Fixing a 35 year old 9" brake system can be a futile effort. In my experience, once you fix one part, another fails. Even if you replace all the cylinders, you will have a failure. Primialy because the brake lines have rust inside them. This rust will cause the cylinders to fail. To fix that you will need to replace the steel brake lines. When you get done with all of that, you still have a marginal 9" brake system.

Much better to upgrade to 11" disks, 10" drums on the back. This is time and money well spent.

Suspension upgrades are something that'll suprise you with how happy you are with them. I would rather have a 100 horse, 3000 lbs car that can stop and handle extremely well than a 400 horse, 3000 lbs car with 9 inch brakes and stock, squishy suspension. We may drive old cars, but for relatively cheap the stock torsion bar setup can be upgraded to handle as well or better than most modern cars(maybe a bit rougher since the torsion bars stick the bumps right under your seat, but still not harsh).

-Shivadart

"When you get done with all of that, you still have a marginal 9" brake system."

Unfortunatly, rusted metal lines are just as problematic for 9" brakes as they are for anything else. If your brake fluid is dark and rusty (it should be clear), then the metal lines all should be inspected or replaced if you upgrade or not.

Buy a cheap tubing bender, a flaring tool, and 2 standard size line wrenches (about $40 total and will last forever) and learn how to plumb new lines. It sucks, because it's about 1 full day worth of work, and anything too old or marginal will break and need replaced during the process. When you are done, you won't have to worry about rust or popped brake lines for many years. It's worth the trouble if you are serious about keeping the car around, and is another good step twards preparing to upgrade to disk brakes.

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1980 Aspen 225 super six

When redoing the brake lines it is better to by the tubing lengths than to make your own. The reason is the flare on the end. The tool you can easily get is a flare tool, you want a double inverted flare. It is a stronger system and is less prone to failure.

Yes, a double flare is the tool to get (is there anything else?) I forgot to mention a pipe cutter (because I already owned one years before I started doing brakes.) You might be nearing $100 worth of tools if you're buying brand name stuff.

Buying lines to length is nice, but not always easy and practical (too many trips to the parts store) I've also done work on lots of foreign cars, and the standard fittings that come on the new lines must be cut off and replaced with the old metric fittings that match the car. I doubt it's an issue with a mopar, but I've come to expect the need to flare a few lines even in the best of situations. Sometimes you just want an exact length and cutting and re-flaring the fitting on is a nice option to have. Buying 1 long line and cutting to fit is cheaper than 2 short lines and a union, less likely to leak, and looks better. (if anyone is looking that hard)

The skill and tools often will pay for itself the first time a friend or neighbor needs some brake lines repaired. I make them get a quote first , they are always willing to pay HALF the price and I still make a double overtime wage on my effort. Well, most of the time.

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1980 Aspen 225 super six

Any 35 year old brake system will have rust inside the lines. Brake fluid absorbs water. Brake lines are made out of steel. Water and steel makes rust. It dosen't matter what color the brake fluid is, there is rust within the lines. When this flakes off, it ruins the seals on the cylinders. This is why you have continual failures with the cylinders.

The longest pre-cut straight brake line you can get from the parts store is 8'. The distance from the front distribution block and the rear junction is about 12'. There is no way to use pre-cut, parts store, brake lines without a coupler. A coupler is only a couple of bucks.