Troubleshooting brake problem... (1 Viewer)

[treerootCO]

I had, past tense, no brakes and I wanted to make the snow run this Saturday. We bled everything with a vacuum pump, then old school with someone inside on the pedal. If I hit the pedal after waiting a few, engine on or off, it would go to the floor. If I pumped it up and held it, the pedal would slowly go to the floor.

I figured it was the master so I bought another. No Aisin at NAPA, Toyota, or Carquest... Went with new NAPA because the dealer said he couldn't get one. I just finished the install and bled everything again. I made sure to bench bleed the master.

Pedal is much happier now. I can stand on it and maintain pressure. Problem is I still can't crowd the brakes in an emergency. It takes two or three pumps to stop the 40.

After a few hours adjusting the rear pads...I POR15ed the drums to the axle and the adjuster would not budge...I tightened everything so I can spin the tire one revolution before it stops.

Back on the street to terrorize the neighborhood at 11:30 at night. I can actually stop again...the pedal is much higher, one pump to pitch the car forward enough to unload the ass end and lock the rears.

I still can't crowd the brakes on the first stomp. 12/78 production, huge booster. I did the FSM tests on the booster and I think everything is good there.

Brake lines are all stainless up front. The only rubber hose is brand spanking new. No leaks anywhere. Pads front and rear are new. Is this just the way it is or did I miss something?

 

[Pin_Head]

Wow, I read all that and I'm still not sure what the problem is.


If you still have to pump the pedal to get good firm brakes, the drums are not adjusted tight enough. It might not be the only problem, but fix this one first. You need to tighten each adjuster until the wheel won't move and then back off a couple of clicks until you can spin it but you still hear the drag. If the pedal is spongy, it still needs bleeding or the shoes aren't arced properly. Get manly with them and quit pussy footing around.

 

[Poser]

Weight transfer to the front will typically not allow the front to lock up with larger tires...


Is that what you mean by 'crowd' ?


Fast in reverse, will the front lock up then?




At the bar....

Let me know.


Hope all is well.



You going to TX in Mar?



-Steve

 

[bustanutley]

if you put some cream on it would it feel better?

 

[Poser]

Brake shoes need to be centered in order to adjust properly...


I typically adjust them, then drive it forward and in reverse, stopping in both directions.. and then re-adjust the brakes...I make them drag a bit...like what pin_head said...

 

[treerootCO]

If I had to stop in an emergency and didn't have time to pump the brakes, the pedal would go to the floor and I would not stop. That is the problem.

I drove it in reverse and the brakes chirp the front tires. The rears are adjusted so there is a slight drag.

 

[1FE pig]

After u pump it up will it bleed away, or is it solid. If it is solid, it is adjestment.If it drops fluid related.

 

[1FE pig]

Sometimes you can raise pedal by adj,rod in the booster.You pull the master off and use vice grips and 8mm. But if you make it to long the front left calper will hang. --last resort-- most time it 's in brake shoe adj. Rob

 

[Jukelemon]

Tree:

Not following the ajuster being frozen and tire one revolution thing. You adjust the drums with the cylinder i.e. unless you had an aerosol can of POR, you would not be touching the adjuster. Did you adjust ALL 4 cylinders? Take out then adjust again? I am not sure what you mean exactly by drag but I have always adjusted my wheel cylinders to complete stop, as in no tire rotation by hand. Back off 3 clicks and do the other cylinder, same side in the same way. You will hear the drum on the shoes. With this method, they will stop very well.

Also, did you ever check the drum cylinders, shoes or any other component in the drums? You could have a leak in one of the cylinders that is creating a pressure issue but not a total failure. You might have had either both a bad MC and bad drum parts or maybe just bad drum parts. If I were you, I would take the time to yank off those drums and replace the entire system-especially if you are going to keep it. It really is not that bad of a process (although people with disagree) to set up your drums for optimum performace.

 

[treerootCO]

On my '78, there are two cylinders per wheel. Only one cylinder is adjustable. I thought it was stuck like the other until I took it apart and confirmed that only the rears can unscrew.

Last year, I went through the rear axle and painted it all pretty like. POR15 was the paint I used at the time. Since then, the paint dried and the drums were stuck to the axle. That really had nothing to do with the brake problem, just a nice surprise last night. I didn't paint any of the brake parts but I did have to remove the wheel cylinder in order to get the adjuster to turn.

I adjusted both sides until I couldn't rotate the tire and then backed it off until I could only spin the tire one revolution before it stopped spinning. From what I was told, that is sufficient drag for a drum brake setup.

 

[Jukelemon]

Each drum has two adjuster holes for each cylinder-one for left and one for right shoe. They are covered by a rubber plug that needs to be pulled out. Am told by others that OFTEN this plug is gone from the PO not replacing after a brake adjustment/job. But nevertheless, there are two and both cylinders/per wheel have to be adjusted. There is a good tech article onthis I believe by Jeff Zepp.

As well, and if I understand you, only being able to turn your wheel one rotation is too much drag. My wheels spin freely with a hint (read sound) of shoe drag on the drum. My brakes are VERY good with 0 pedal issues.

I am still not following you on the drums being stuck to the axle. My drums, when I rebuilt my drum setup, were so damn stuck on the vehicle, that I had to , literally, bang on them with a sledge. Now, the biggest reason was that my adjusters were frozen and would not release.

If you cannot adjust all cyls. (for whatever reason), then you have to take those drums off and replace cylinders. If not, there is no point in even trying to do a brake set up.

 

[60wag]

Any chance the booster pushrod is too short? That would use up some of the pedal stroke wo/ creating any hydraulic pressure.

 

[Pin_Head]

If the pedal rises when you pump the brakes, they need to be adjusted.

No if ands or buts; there is no other explanation.


Through 7/80 there are two cylinders per wheel and both need adjusting. Sounds like you just adjusted 1. If the adjuster is stuck, you can pop the adjuster out, put it in your bench vise and wrestle with it to get the screw to move.

 

[treerootCO]

I was going to measure the pushrod but the FSM showed some SST for the measurement. I was cold and tired and decided not to mess with it.

Both front cylinders in the rear are new. Zinc coating on the adjuster and no surface rust on the cynlinders. They are not adjustable. I took them out and cleaned everything. I even put them in a vise and tried to unscrew them just in case I was missing something.

Has anyone ever come across this. Maybe they are crappy knockoffs or something. Is it possible that in '78 only the rear cylinder needs to be adjusted?

 

[toddslater]

Did your new MC have a residual pressure valve for the rears ?

 

[Pin_Head]

If you have 1 cylinder per wheel, they don't need adjusting because they are self adjusting. If you have two cylinders per wheel, they both need adjusting.

Take a careful look at the cylinders and you can see that all of them have threaded adjusters. They do tend to get really stuck and you just have to get manly with them. Heating helps.

 

[Jukelemon]

Man, I do not know except that the configuration, according to parts, states that all four cylinders in the rear are adjustable. They do have specific locations as well.

See here:

http://store1.yimg.com/I/coolfj40_1827_344507250

I ordered this set and it matched up exactly to my stock 76 set up.

 

[1FE pig]

If the cylinders are fixed to backing plate you need 2 adj.Or one shoe will never stay in adj because it has no adjustment . Brakes in a 60 rear has one cylinder and adj in the center, not on the cylinder, like a chev.I bet it is the wrong cylinder if it has no adj on it.

 

[treerootCO]

I'll take it out again tonight....

The valve for the rears is connected just under the master and I didn't replace it.

 

[1FE pig]

Residual valve is used to keep fluid from draining back .You should have a pro valve on that one.