Booster Issue?

[Boaf 32]

This order is wrong for a LHD vehicle. You bleed the longest first (LR), then the next longest (RR), then LF, then RF, since it's closest to the distribution block at the front axle.

You are correct, the distribution hub in the rear is near the RR so the furthest point is drivers side rear, oops.

In the front, the distribution hub is near the drivers side, so Passenger first (right), then driver side (left).

Boaf

 

[Boaf 32]

If you are still having the pedal go to the floor when you step on it(regardless of whether the engine is running or not) and there are NO leaks on the ground--the master is bad, period.
Even if you have air in the system, the pedal will go down until the air is compressed to the max and then it will stop-and yes, it will 'feel' a little mushy, but it WILL get to the point where you cannot compress it any further--how far depends on whether your leg muscles are like mine or like the Hulk's.
(most tractor/trailers run air brakes---)

Thanks, I called Rock Auto and after I have exhausted the final bleeding, may return the defective part.

Boaf

 

[Fast Eddy]

Hmm. Is a drum brake rig different? My soft line comes down on the passenger side in front.

 

[handcannon]

I have an early 71 40. Many years ago I remade all my brake lines, due to rust pits found on one of the lines. The front brake line runs down the firewall on the USA drivers side to the frame, before dropping to the front axle.

I don't know what year, but I did know that at some point the front brake line drop moved to the right side of the firewall.

Don

 

[Boaf 32]

Hmm. Is a drum brake rig different? My soft line comes down on the passenger side in front.

Mine does come down on the driver side. The union joint looks factory.

 

[Boaf 32]

Brake line question:

Can anyone tell me the purpose of the spiraling of the brake tubes as pictured here? My front was replaced and goes straight to the Union coupling with no spiraling.

Thanks

Boaf

 

[BeeJii]

When frame and body mounts flex the spirals in the braketube help tube flex without too much stress in to it.

 

[handcannon]

That coiling gives the brake line a place to extend and compress, just like a coil spring, as the frame flexes. The place you really need the coil is where the line comes down the firewall and transitions to the frame. This is where the movement between body and frame affects the brake lines.

I used off the shelf, pre-made lines when I remade my brake lines. I used these coils also to use up extra length where some of the pre-made lines were slightly too long.

Don

ps- Beejii beat me. He types faster than my hunt and peck style.

 

[Boaf 32]

Thanks Beejii and Handcannon.

 

[Coolerman]

One thing I did not see addressed in your thread is this: Are you SURE you have the brake cylinders in their proper locations? You may not know this, but there are 4 DIFFERENT brake cylinders on your truck, and they each have a specific side (left or right) and location (front or back) and you can get them in the wrong place. The cylinders also have different bore diameters for front to rear. If you (or the PO of your truck in my case) get these mixed up, your brakes will not work correctly. Installing the brake shoes is another area that can be done wrong. There is a certain way to put them on correctly!

I devoted a considerable amount of time rebuilding my brake system and documenting the process. You might find that reading through this information beneficial to your cause. There are 6 pages detailing everything from rebuilding the wheel cylinders to bench bleeding the master cylinder.

Master Cylinder Rebuild this is a link to page one Rebuilding the master cylinder. The other pages are linked at the bottom of that page and every other brake page. There is also a link on every page to the FSM or you can download it from many places. You MUST get the FSM for your truck! Haynes is semi-useful (they do have pretty good schematics) but nothing beats the FSM for this level of work!

 

[Boaf 32]

One thing I did not see addressed in your thread is this: Are you SURE you have the brake cylinders in their proper locations? You may not know this, but there are 4 DIFFERENT brake cylinders on your truck, and they each have a specific side (left or right) and location (front or back) and you can get them in the wrong place. The cylinders also have different bore diameters for front to rear. If you (or the PO of your truck in my case) get these mixed up, your brakes will not work correctly. Installing the brake shoes is another area that can be done wrong. There is a certain way to put them on correctly!

I devoted a considerable amount of time rebuilding my brake system and documenting the process. You might find that reading through this information beneficial to your cause. There are 6 pages detailing everything from rebuilding the wheel cylinders to bench bleeding the master cylinder.

Master Cylinder Rebuild this is a link to page one Rebuilding the master cylinder. The other pages are linked at the bottom of that page and every other brake page. There is also a link on every page to the FSM or you can download it from many places. You MUST get the FSM for your truck! Haynes is semi-useful (they do have pretty good schematics) but nothing beats the FSM for this level of work!

Thanks Cooler, reviewing your write up. I do understand, I I have them right. When I ordered them, I was sure to specify a complete set. The Large Diameter Bore (as I wrote down from RocK Auto), are the Fronts; and the small diameter bore are the backs. Just so I confirm, I could be wrong, it's happened, that is:

Front

• The largest diameter goes in the Drivers Front "Front" and Passenger Front "Front" (Left of Photo) - 1 1/4 Bore
  
• The Smaller diameter goes in the Drivers Front "Rear" and Passenger Front "Rear" (Right of Photo) - 7/8 Bore

Rear

• The 7/8 Bore Goes in Drivers and Passenger Front and Rear

Let me know, I am trying to attach a photo.

Boaf

 

[Boaf 32]

Coolerman, One more thing.

There was talk about Proportioning Valves in the MC. I called SOR and they said for the 1972 with Drums they did not have Proportioning Valves. I see from your Thread, and some earlier discussion here, that there are Residual Valves that are located under the Brake Line attachments.

When I installed the new Master Cylinder, I did not open up those holes to confirm the Residual Valves were in there, I just assumed. Something tells me that they are missing, here's why:
When press the brakes with the drums removed, the Wheel cylinders do not engage until the brake pedal is half traveled. Your thoughts?

Spoke with A1 Cordone to determine if the Residual Valves are included in the MC, he said the OEM removed them and indicated that the rear brake shoes just need to be adjusted tight! Argh???

Boaf

 

[honk]

This is too weird and getting so deep into almost inconsequent individual details will not be likely to be productive for a solution in the end.

I mean that if you still have no pedal after all of this has been correctly done then the problem has to be a simple thing that's been overlooked because of inexperience.

Boaf, have you examined every union and brake line throughout the truck for leaks? Is there fluid coming out anywhere. Pay close attention to the driver side firewall and anywhere under your truck, including inside the frame rails where you can see or feel. Use a strong light and clean rags for looking and wiping.

You've bled the heck out of this system. That fluid doesn't evaporate, you're not drinking it (I'll generously assume), so it has to be going somewhere.

 

[Boaf 32]

This is too weird and getting so deep into almost inconsequent individual details will not be likely to be productive for a solution in the end.

I mean that if you still have no pedal after all of this has been correctly done then the problem has to be a simple thing that's been overlooked because of inexperience.

Boaf, have you examined every union and brake line throughout the truck for leaks? Is there fluid coming out anywhere. Pay close attention to the driver side firewall and anywhere under your truck, including inside the frame rails where you can see or feel. Use a strong light and clean rags for looking and wiping.

You've bled the heck out of this system. That fluid doesn't evaporate, you're not drinking it (I'll generously assume), so it has to be going somewhere.

I agree with the weirdness thing. It is to the point of absurdity. I may just bow away and have another look at it. I just don't like being beaten by something I've done for 30 years. I have other projects on the truck to complete and may eventually go back to the brakes. I want to close this thread after a few more confirmations as you indicated. Thanks for all your help.

Boaf

 

[Boaf 32]

Gents,

One more thread question. My local yocal mechanic who's been around for 35+ years asked me if I was using synthetic Brake fluid in my 72 LC and I told him no. Went back and saw my Dot 3 was a Prestone Dot 3 Synthetic. Is that really a potential reason why it won't stop???

Thanks!

Boaf

 

[shawnfj40]

All brake fluid is synthetic. It always has been.

 

[BeeJii]

All brake fluid (Dot 3 Dot 4 and Dot 5.1) is ok to mix exept DOT 5 witch is silicone based fluid and it is not supposed to mix with any other fluid in any situation.

 

[srgould41]

I just replaced my master with the final sized one (1 1/8"). It was a long odyssey to put together a matched system. The last two masters seemed perfectly bench bled, but I still had a spongy pedal and could pump the pedal up. Signs of air for sure. I swore the masters were bled and that something else had to be the cause. With this last master I spent 30 minutes with it at my work bench and came up with a method that ended up getting every bit of air out (worked for the iron GM master, might not on others). When I swapped it for the other master I didn't even get air into the lines. Hard firm pedal. I have been working on cars for 40 years and thought I knew when a master was bled properly.

Just wanted to mention this since I had been so sure the master was not the cause. Even a few micro sized air bubbles can cause havoc.

I agree with the weirdness thing. It is to the point of absurdity. I may just bow away and have another look at it. I just don't like being beaten by something I've done for 30 years. I have other projects on the truck to complete and may eventually go back to the brakes. I want to close this thread after a few more confirmations as you indicated. Thanks for all your help.

Boaf

 

[Weber Sarge]

One trick to bench bleeding a master cylinder is to hold it in the vise at a slight angle - with the intake hole in the reservoir at the high end . It helps to force the air to move to the intake port in the bottom , otherwise some of them somehow just hold the air pocket in place..and it shouldn't do so ...
We fought for 4 days years ago on an International pickup - angling the master slightly finally got the last air bubbles out .
Sarge

 

[srgould41]

That is similar to what I did. I angled it so the plunger end was slightly higher. I then used very short movements on the piston. 1/4" max. This kept burping air bubbles out the intake port in the reservoir and none in the clear tubes I used to route fluid from the outlets to the reservoir. It too at least half an hour, but worked perfectly.

One trick to bench bleeding a master cylinder is to hold it in the vise at a slight angle - with the intake hole in the reservoir at the high end . It helps to force the air to move to the intake port in the bottom , otherwise some of them somehow just hold the air pocket in place..and it shouldn't do so ...
We fought for 4 days years ago on an International pickup - angling the master slightly finally got the last air bubbles out .
Sarge