Bleed brakes. The final solution ?

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Yes it will pump and hold on about the second or third press down

I have hard lines so no soft ones... but it leads mto some new was to block off one side

This is my experience only. I'm not an expert and don't play one on TV. It seems you've tried everything suggested with little improvement so I'm just throwing this out there. I'm not trying to discount anything previously said or suggested but...


78 models have a dual circuit system. Discs in front and drums in the rear.

Once the front circuit locks up the pedal will not travel any further. It doesn't matter how loosely adjusted the rears are. If the rears are adjusted overly tight I guess it could affect pedal travel and cause the front to fail to grab. The proportioning valve should have been engineered to prevent this so no worries there I would think.

It's possible that your issue - i.e. pumping the slack pedal eventually gets it firm and holds - is in the front circuit and, more specifically, the calipers. You need to inspect and bleed those before proceeding to the rears. Most of your stopping power is in the front circuit. It's dominant over the rear drums.

Either that or you have two kakked masters in a row. Anything is possible. If your original was OEM get a rebuild kit and a hone and rebuild it.

I've had my 78 for more than 20 years. The braking system was fersizzle when I got it and I rebuilt the whole thing with only the factory manual. I purchased some new hard lines and made a few. I used OEM soft lines. You have four total. One from the frame to each axle and one to each knuckle. I used a Crap Croozers of Taiwan master and it has held up until now so I may be eating my words when the new OEM master (47201-60050) goes on in the next few months. HTH
 
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This is my experience only. I'm not an expert and don't play one on TV. It seems you've tried everything suggested with little improvement so I'm just throwing this out there. I'm not trying to discount anything previously said or suggested but...


78 models have a dual circuit system. Discs in front and drums in the rear.

Once the front circuit locks up the pedal will not travel any further. It doesn't matter how loosely adjusted the rears are. If the rears are adjusted overly tight I guess it could affect pedal travel and cause the front to fail to grab. The proportioning valve should have been engineered to prevent this so no worries there I would think.

It's possible that your issue - i.e. pumping the slack pedal eventually gets it firm and holds - is in the front circuit and, more specifically, the calipers. You need to inspect and bleed those before proceeding to the rears. Most of your stopping power is in the front circuit. It's dominant over the rear drums.

Either that or you have two kakked masters in a row. Anything is possible. If your original was OEM get a rebuild kit and a hone and rebuild it.

I've had my 78 for more than 20 years. The braking system was fersizzle when I got it and I rebuilt the whole thing with only the factory manual. I purchased some new hard lines and made a few. I used OEM soft lines. You have four total. One from the frame to each axle and one to each knuckle. I used a Crap Croozers of Taiwan master and it has held up until now so I may be eating my words when the new OEM master (47201-60050) goes on in the next few months. HTH
Well absolutely worth trying!!

here is the patient. Just itching to be driven

0A560915-F7D0-425C-B784-DDF8A312D5D6.jpeg
 
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I'm late to this thread but I noticed in your set up to recirculate the fluid on the first page that the brake fluid looks blue. You're not using DOT 5 are you? I ask because I've used DOT 5 in my Harley's for years and it's blue. It works great in a bike which has much shorter lines and smaller volumes than cars but DOT 5 is more compressible than DOT 3 or 4 and thus isn't acceptable in an automotive system. No direct experience myself with DOT 5 in a car or truck, just what I've read.

Just a thought....good luck

Pete
 
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Already lots of good advice on this thread from folks that know what they are doing. I'm a hobbyist, not a pro, so I will only try to add what I have learned doing this on my 79 rear drums (which should be identical to your 78's). It's important to get BOTH wheel cylinders adjusted tight on each drum. It's easy to fool yourself into thinking that a drum is properly adjusted when, in fact, only one of the two cylinders behind it is properly adjusted. In this situation, one of the two shoes is dragging nicely, but the other cylinder and shoe on that drum is still too loose. If this is happening, it will cause the symptoms of a soft pedal and 2 pumps to firm it up. I'll try to describe what I have done in order to get them adjusted properly:

1. I pick one side of the axle to start and complete this procedure before moving to the other side. Before I install the drum I will expand the wheel cylinders out as much as possible by hand, and still be able to barely slide the drum on. This minimizes the amount of adjustment you need to do on your back with the adjustment tool.

2. With the drum installed, using the adjustment tool through the backing plate, expand a SINGLE wheel cylinder until it alone locks up the drum from turning. Then back it off 2-3 clicks, no more (Start with 2. If it's still locked, go to 3). You should then be able to spin the drum with considerable dragging of that shoe.

3. Then, expand the opposing cylinder on that same drum, until it locks up the drum again. Then back it off 2-3 clicks, no more (again, start with 2. If it's still locked, go to 3). Your drum will feel tight with considerable drag, but if you mount your rim and tire on it for more leverage, you should be able to spin it 360.

4. Repeat steps 1-3 of this procedure on the other side of the axle. After you do this on both sides, go for a short drive and check for heat. You WILL smell a little bit of warm brake lining for the first 5 miles or so, but it should not be "burning". If it's too hot, then you can back off both cylinders by one click (no more), and repeat the check for overheating. This technique has worked for me, and should also provide you with a firm pedal.

Credit for everything I have learned on this topic goes to Mark A @65swb45 , and Coolerman @Coolerman . Thanks for their wisdom and mentorship.
 
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Already lots of good advice on this thread from folks that know what they are doing. I'm a hobbyist, not a pro, so I will only try to add what I have learned doing this on my 79 rear drums (which should be identical to your 78's). It's important to get BOTH wheel cylinders adjusted tight on each drum. It's easy to fool yourself into thinking that a drum is properly adjusted when, in fact, only one of the two cylinders behind it is properly adjusted. In this situation, one of the two shoes is dragging nicely, but the other cylinder and shoe on that drum is still too loose. If this is happening, it will cause the symptoms of a soft pedal and 2 pumps to firm it up. I'll try to describe what I have done in order to get them adjusted properly:

1. I pick one side of the axle to start and complete this procedure before moving to the other side. Before I install the drum I will expand the wheel cylinders out as much as possible by hand, and still be able to barely slide the drum on. This minimizes the amount of adjustment you need to do on your back with the adjustment tool.

2. With the drum installed, using the adjustment tool through the backing plate, expand a SINGLE wheel cylinder until it alone locks up the drum from turning. Then back it off 2-3 clicks, no more (Start with 2. If it's still locked, go to 3). You should then be able to spin the drum with considerable dragging of that shoe.

3. Then, expand the opposing cylinder on that same drum, until it locks up the drum again. Then back it off 2-3 clicks, no more (again, start with 2. If it's still locked, go to 3). Your drum will feel tight with considerable drag, but if you mount your rim and tire on it for more leverage, you should be able to spin it 360.

4. Repeat steps 1-3 of this procedure on the other side of the axle. After you do this on both sides, go for a short drive and check for heat. You WILL smell a little bit of warm brake lining for the first 5 miles or so, but it should not be "burning". If it's too hot, then you can back off both cylinders by one click (no more), and repeat the check for overheating. This technique has worked for me, and should also provide you with a firm pedal.

Credit for everything I have learned on this topic goes to Mark A @65swb45 , and Coolerman @Coolerman . Thanks for their wisdom and mentorship.
This is a good trick... I get to work on my problems tomorrow night!
 

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