Brake Help 2

[1972Blaze]

This is my second post regarding brake issues. Rather than making you read through the entire last thread to follow my progress I thought I would lay it all out here.

I feel I do not have very good stoping power. I apply the brakes and feel almost no response until I am over half way through the brake stroke. The brakes will not lock the wheels up. It seems like I have to put too much pressure on the pedal just to hold the truck in place at a stop sign.

The system was probably all original several months ago. Since then I have replaced the following parts:

Wheel Cylinders
Brake shoes
Brake Calipers
Brake Pads
Master Cylinder
Power Brake Booster
Front Brake Hoses

Also:
Brake Drums turned
Brake discs turned
Flushed entire system

The only thing I have not replaced is the steel lines, rear brake hose and proportioning/combination valve, although I am getting fluid through it to all the wheels. Also, I have replaced these items individually (except the calipers and front hoses which were done at the same time) so I would be able to pinpoint the issue. The only thing that seemed to helped a little bit was the fresh brake booster. I am not sure when this all started, but as I recall it has stopped better in the past.

Am I expecting too much from this system? Any thoughts? I feel like they are properly bled, including the master cylinder. Will the combo valve hold air?

Thanks for any reply.

[weq92f]

If your pedal is not firm, then you could have air in the system and you should pursue getting that out.

If you turned the discs out front, please measure them to ensure they are thick enough to allow your caliper to bite them properly. Somewhere on the disc you'll find stamped a minimum thickness. The performance you describe could indicate a disc that was turned too thin.

While I have no experience dealing with mismatched pedal-to-booster-to-master components/parts, I suspect this could cause a lack of clamping power at the calipers due to not enough piston travel in the master cylinder.

What you are experiencing is definitely not normal. You should be able to lock up the front tires with your foot on the brake pedal. It should take minimal force on the pedal to hold the truck stopped.

Hth

-klb

[jocko]

Stock brake system should provide much more stopping power than you describe. I’ve redine the whole thing like you did, and included lines - but the bleeding took FOREVER. It’s not because you haven’t replaced the lines. It’s just air. And it takes a while to get out when you change all that stuff out like you did. That’s my diagnosis anyway. I just recall having to do much more bleeding than I ever did on just a basic brake job. I bleed old fashioned way, with a helper and a combination wrench.

[randy500]

I recently had the same problem And it was air in the lines, I made an adapter to pressurize the master cylinder, used a regulator at 5psi or so, used a clear tubing at the bleeder valve with a rubber bleeder fitting, I saw the air come out and a strong stream of brake fluid, great pedal now.

You can buy a pressure bleeder for about $90 or so, money well spent.

[LockDoc]

-
On the rear drum brakes, one thing I found on mine is when you put everything back together and adjust the brake shoes you can’t just adjust them out until they start rubbing and quit. You have to adjust them out as far as they will go and you cannot turn the wheel or drum at all. This centers the whole assembly in the drum. (I even tap around the drum as I tighten them to help them center themselves) Then you back them off until the wheel/drum just turns, and stop. If you only adjust them out until they start rubbing and quit, the first time you press on the brake pedal the brake shoe assemblies will center themselves and you will have too much clearance between the shoes and the brake drum. I also put three lug nuts on backwards to hold the drum tight against the axle on the rear when adjusting them.

I know it is a pain in the butt to try and hold the self adjusters off of the adjuster wheel while you back them off, but this is the only way I could get my drum brake shoes adjusted correctly.

Putting the vehicle in reverse and backing up while pumping the brakes will cause the automatic adjusters to activate with each pump of the pedal. The problem is if the shoes are not adjusted out as much as possible to start with, it will take a lot of backing and pumping to get them adjusted all the way out.

LockDoc

[randy500]

Great point locdoc, this is a must and could likely be your problem.

[Pro299]

Just went through all this myself. Assuming you've tried the previous suggestions and everything checks out, have you checked the vacuum to the new booster? Did it come with a new check valve? If so, are you sure the hose is good? Lack of vacuum or a weak booster will cause the symptoms you describe.

[lowbucktrucks]

Dumb question, are your calipers on the right side?? The bleeder should be at the top.

[1972Blaze]

Originally Posted by weq92f

If you turned the discs out front, please measure them to ensure they are thick enough to allow your caliper to bite them properly. Somewhere on the disc you'll find stamped a minimum thickness. The performance you describe could indicate a disc that was turned too thin.

While I have no experience dealing with mismatched pedal-to-booster-to-master components/parts, I suspect this could cause a lack of clamping power at the calipers due to not enough piston travel in the master cylinder.

Hth

-klb

I am good on rotor thickness and all of my pedal to MC hardware is matched up properly, although I am going to double check the pushrod on the booster adjustment.

Originally Posted by randy500

I recently had the same problem And it was air in the lines, I made an adapter to pressurize the master cylinder, used a regulator at 5psi or so, used a clear tubing at the bleeder valve with a rubber bleeder fitting, I saw the air come out and a strong stream of brake fluid, great pedal now.

You can buy a pressure bleeder for about $90 or so, money well spent.

I have bled the system several times, but I keep second guessing if that may be the issue. I guess it is time to invest in a pressure bleeder. Will that get all of the air out of the MC as well?

Originally Posted by LockDoc

-
On the rear drum brakes, one thing I found on mine is when you put everything back together and adjust the brake shoes you can’t just adjust them out until they start rubbing and quit. You have to adjust them out as far as they will go and you cannot turn the wheel or drum at all. This centers the whole assembly in the drum. (I even tap around the drum as I tighten them to help them center themselves) Then you back them off until the wheel/drum just turns, and stop. If you only adjust them out until they start rubbing and quit, the first time you press on the brake pedal the brake shoe assemblies will center themselves and you will have too much clearance between the shoes and the brake drum. I also put three lug nuts on backwards to hold the drum tight against the axle on the rear when adjusting them.

I know it is a pain in the butt to try and hold the self adjusters off of the adjuster wheel while you back them off, but this is the only way I could get my drum brake shoes adjusted correctly.

Putting the vehicle in reverse and backing up while pumping the brakes will cause the automatic adjusters to activate with each pump of the pedal. The problem is if the shoes are not adjusted out as much as possible to start with, it will take a lot of backing and pumping to get them adjusted all the way out.

LockDoc

This will be the first thing I do. This is the first time this has been brought to my attention. I am sure I did not do it right. In fact, I can hear some movement in there that I am sure I should not hear. Thanks for the instruction. I'll let you know if this works.

Originally Posted by Pro299

Just went through all this myself. Assuming you've tried the previous suggestions and everything checks out, have you checked the vacuum to the new booster? Did it come with a new check valve? If so, are you sure the hose is good? Lack of vacuum or a weak booster will cause the symptoms you describe.

I have 17" HG manifold vacuum. The check valve is new and holding vacuum in the booster. I am going to double check the vacuum on the hose to the check valve to see if I am losing any vacuum there.

Originally Posted by lowbucktrucks

Dumb question, are your calipers on the right side?? The bleeder should be at the top.

Calipers are installed right side up.

Thanks for all of the input so far.

[1972Blaze]

I have just finished adjusting the brake shoes. I do not have to apply as much pressure at a stop to hold the truck, but it will still pull away with the brakes fully applied if I accelerate hard and it does not really stop any quicker than it did. Still, I am glad I did it since it clearly needed to be done.

The vacuum at the hose to the booster check valve is 16.5-17" Hg.

I'll check the adjustment of the pushrod in the booster and bleed the brakes with a pressure bleeder next week and report back.

[weq92f]

This is a good thing to do as well once everything is sorted:

https://www.zeckhausen.com/catalog/i...Path=6446_6443

-klb

[El Dorado Jim]

Originally Posted by weq92f

This is a good thing to do as well once everything is sorted:

https://www.zeckhausen.com/catalog/i...Path=6446_6443

-klb

x2, I do this on new brakes.....

[1972Blaze]

I adjusted the push rod on the booster, re bench bled the master cylinder, re bled the rest of the system and still have the same issues. Just about everything has been replaced or serviced.

I ran one check to see if it would create a different result and it did. One of the symptoms I have had is that I can pull out from under the brakes when fully applied if I accelerate enough. However, If I let the truck idle for a short while and fully apply the brakes quickly and try to do this it will hold. When I release the brakes and immediately try again it will not hold.

I am thinking the booster is not giving enough assistance. I double checked the vacuum and am right between 16 and 17" Hg. The booster is a reman from Rock Auto. Any thoughts on this?

[demian5]

I bought a brand new booster/master/combo valve from CPP and the booster check valve was bad. Replaced it and what a difference, however I feel I need a bigger booster as the first stop is solid then feels like manual brakes the next time.

[RichardJ]

Bleeding the MC at this point, simply allows more air to enter the system.
Did you open the metering Valve on the end of the Combination valve when you bled the brakes?
Some metering Valves require the pin to be pushed IN, and held while bleeding. Some require the pin to be pulled OUT, while bleeding.

[Mryan]

Check the pushrod length on the replacement booster, I just replaced from Rock Auto and forgot to adjust the pushrod and had a very firm pedal. If you still have the old one you could check and match to that, otherwise it sounds like to me it may need to be lengthened a bit. Good luck

[1972Blaze]

Originally Posted by Mryan

Check the pushrod length on the replacement booster, I just replaced from Rock Auto and forgot to adjust the pushrod and had a very firm pedal. If you still have the old one you could check and match to that, otherwise it sounds like to me it may need to be lengthened a bit. Good luck

This is one of the steps I had already done. I feel good that the length is okay. Thanks.

[1972Blaze]

Originally Posted by RichardJ

Bleeding the MC at this point, simply allows more air to enter the system.
Did you open the metering Valve on the end of the Combination valve when you bled the brakes?
Some metering Valves require the pin to be pushed IN, and held while bleeding. Some require the pin to be pulled OUT, while bleeding.

Thanks for the input. Used a tool like the one pictured (it seated all the way so I assume the pressure differential valve was in place), but I did not do anything with the metering valve. It does not seem to want to move either direction and I do not know enough to know if it is out of position or not. The combination valve is the original Kelsey Hayes part for a 72 truck. It looks like the one in the diagram shown. Any explanation on the proper procedure for bleeding as it regards this combo valve would be great. Thanks.

[Wrenchbender Ret]

I had a 70 stepper like that at one time. The pedal was good but it just didn't have the stopping power. I put a different brand of shoes on the rear. Try to find ones with FF on the edge of the linings. That made a big improvement. I changed the front pads to ceramic linings & that made it into a good driver. (it had 71 disc brakes on the front.)
George

[Duner97]

1972Blaze, what ever came of your brake problem? Your scenario sounds exactly like what I am dealing with now.
Posted via Mobile Device

[LockDoc]

Originally Posted by Duner97

1972Blaze, what ever came of your brake problem? Your scenario sounds exactly like what I am dealing with now.
Posted via Mobile Device

It's been about a month since he has been on the board. Hopefully he will be back on soon.

LockDoc

[1972Blaze]

Originally Posted by Duner97

1972Blaze, what ever came of your brake problem? Your scenario sounds exactly like what I am dealing with now.
Posted via Mobile Device

I finally got it fixed. I literally replaced everything except steel lines, bought special tools I never would have used before to get the correct pushrod length on the booster and correct shoe adjustment. I even ended up replacing the booster and master cylinder a second time and bought a combo set up. I re-bled the brakes numerous times. I even put in a new proportioning/combination valve. Finally I thought about the comment on ceramic pads and I did some research on pad material. I never would have believed that the difference between organic and semi-metallic would be so great. I did not pay attention to the pads I took off, but at first I went back with organic material. Bad idea. Once I put semi-metallic everything changed. I thought about going to ceramic, but I understand that they are hard on the discs. I never changed my rear shoes to semi-metallic, but I will next time for sure. I may even go with ceramic pads next time since I drive the truck relatively little and the brake dust makes my white wheels look bad very quickly.

[Duner97]

Very good! I finally figured out my problem as well. The switch on my proportioning valve has never been hooked up to the dummy light in the dash, but I checked it, and it indicated a fault, but I couldn’t correct it, so I removed the switch and used a pick to get the plunger in the valve centered again. I gravity bled and got a lot more air at that point. All of the sudden the clouds parted and my pedal was hard, problem solved.
Posted via Mobile Device

[Happy_dan]

Originally Posted by 1972Blaze

Thanks for the input. Used a tool like the one pictured (it seated all the way so I assume the pressure differential valve was in place), but I did not do anything with the metering valve. It does not seem to want to move either direction and I do not know enough to know if it is out of position or not. The combination valve is the original Kelsey Hayes part for a 72 truck. It looks like the one in the diagram shown. Any explanation on the proper procedure for bleeding as it regards this combo valve would be great. Thanks.

I assume this is with power brakes and front disc brakes?
I have drums and no power. I am still having an issue with my brakes.

I replaced both front rubber lines and emptied the master and cleaned it all out.
I flushed all the front out really well but not the rears.

Sometimes when I am sitting with my foot on the brake pedal, it will suddenly drop. I would think if it was just air, it would be a problem all the time.

I am going to flush out the rear and replace the rear rubber line and bleed everything thoroughly once again but I am not confident that will resolve my issue. Could it be the master or the add on rear brake controller?

My next step is that rear rubber line and flushing.
Then I think I will eliminate the brake controller.

But I am wondering if it might be the master.

Thoughts?

[demian5]

On older vehicles getting everything new, they appear to appreciate the following:

1. Bench bleed master is a must.
2. Install master into vehicle (put rags down under where it goes to minimize the damage to the engine compartment finish).
3. Fill master as full as you can, leave cap loose so it doesn't seal.
4. Open all bleeders.
5. Go have dinner.
6. Come back and wonder where fluid is. Wait longer.
7. Tap on calipers and wheel cylinders with wrench. Fluid finally flows from fronts.
8. Close each bleeder once decent amount of fluid comes out from gravity (usually works on calipers, not so well on drums).
9. Top off master. Install lid tight.
10. Bleed Rear Brakes
11. Pump brakes 10 times.
12. Hold pedal firm.
13. Open bleeder on rear wheel furthest from master. AND contrary to popular belief, the wheel furthest from the master is the driver rear.
14. Pedal drops to floor.
15. Tighten bleeder.
16. Don't forget to top off fluid.
17. Repeat by alternating rear wheels until all air is gone and fluid flows and drips off differential all over the place.
18. Move to the front wheels.
19. Open bleeder on passenger front, push pedal slowly to the floor and hold, close bleeder, release pedal.
20. Repeat for each side and alternate until all air is gone and fluid flows.
21. Give up on a clean driveway.
22. Don't forget to top off fluid.
23. Do the rears again a couple more times till the pedal gets solid.
24. Don't forget to top off fluid.
25. Oops, didn't adjust parking brake.
26. Test drive (noting brake fluid all over driveway when backing out).