I need help with the brakes on my 85 TA. The brake pedal goes a little further than it should and the car takes longer to stop. With the wheels off, pressing the brake locks the front but I can still wiggle the drums. The drums do lock solid with parking brake applied. I've bled and bled and bled the brakes because it does feel like there's air in the line somewhere, so there is brand new fluid throughout the whole system. But I'm thinking the problem is with the rear since the drums don't lock tight with pedal pressed like the fronts do.. There are no leaks in the system , most of the lines are new, all 3 rubber hoses are new, the master cylinder is new.. The drums and brake shoes look perfectly fine, I don't see any problem with them. Everything else seems to work correctly, such as the wheel cylinders. Also all the bleeder screws are new. I've seen where you can put a stiffer spring in the combo valve to give more pressure to the rear, but apparently that's only for the aluminum combo valves. Mine is an 85 so I have the cast iron combo valve.. So what can I do? I also have an 86 Firebird with perfect working brakes so I have a reference for how the car should brake and how the pedal should feel.. Any help or ideas of how to solve my problem is greatly appreciated. Thanks.

 

You need to adjust them for a slight drag. If you can't get them to adjust that much, you need new drums...

 

ok thanks.. I did adjust them out as much as I could while still barely being able to get them on and off. perhaps that wasn't enough. the brake shoes have plenty of material left ,, so I could just replace the drums and see if that helps. I don't want to just keep throwing parts at it, gets expensive... I'd like if there were some way to confirm I need new drums before buying them.. again I think I have them adjusted pretty well, but I'm not positive. i'll look into this..

 

i checked and they seem pretty well adjusted. I do feel a drag as i turn the drums by hand. .. i still feel i need more pressure at the rear brakes. The wheel cylinders aren't pushing the brake shoes hard enough. Does anyone know how i can achieve this without having the aluminum combo valve found in the later 3rd gens?

 

Sounds like air in the master cylinder.

It needs to be removed from the car so you can "bench bleed" it.

The MC is at such an angle in these cars, that any air that gets into it, ends up at the top front "corner" of each cyl. Since that region is ABOVE the line outlet, the air can NEVER escape. You can run a gallon of fluid through it pretending to bleed it every single day, and even twice on Sundays just for good measure, and that air will stay there FOREVER no matter how many tanker-car loads of fluid you run past it.

Only solution is to remove it and "bench bleed" it, BEFORE bleeding the lines & wheel parts. Then AND ONLY then, once all the air is out of the MC, will you have a chance of a decent pedal and all that.

 

its a new master cylinder and I did bench bleed it per the instructions before installing.. so i was thinking it was good but I'll look into re-bench bleeding it

 

New wheel cylinders? They do rust and freeze up. Here's a simple test, costs about $5 and no one will ever do it. Remove the lines from the MC, install 2 plugs in the ports and step on the pedal. If it's not rock hard the problem is in the MC.

 

the wheel cylinders aren't new, but they seem to be in working order.. they push the brake shoes out.. just not with very much force.. I need them to push harder.
actually wheel cylinders are pretty cheap,, maybe I should just replace them.
I would consider the master cylinder test you described, but the master is brand new so I can't really see there being a problem with it. as opposed to an old one that has worn out seals.

 

Stuck WCs will cause a hard pedal in addition to that particular wheel having no brakes and/or brakes dragging, not low/soft.

ONLY THINGS that will cause low/soft pedal are failed MC, parts WAY out of adjustment, rubber line about to burst, or air in the system.

 

ok, well my MC is new, all rubber lines are new. shoes are adjusted out to barely touch the drums. so it must be air in the system somewhere..
guess i'll have to try to bleed the system more.. but I feel like i've bled it quite a bit so far.. I'm stumped..

 

update:.. i pinched all 3 brake hoses and pedal got hard as it should be. So I'm thinking this means the MC is good and there's no air in it.. so i guess this means theres air somewhere past the hoses.. either in the calipers or wheel cylinders?

 

Since you decided to pinch your new hoses don't stop now. Remove the pinch from the rear and see how the pedal feels.

 

ok,, so that will tell me if the problem is the front or the rear?

 

Zackly.

Might as well zero in on which one(s) are the actual problem, so you don't waste time fixing something that isn't broken.

 

ok, I'm having problems still... when I tried to zero in on which wheel was the problem, the pedal got hard when I had the right front pinched off.. so I concluded the right front caliper was the culprit... I installed a new right front caliper and bled it but it didn't solve the problem. now I have the new caliper , new master cyl. both new wheel cylinders, which I just put in and bled,. and got plenty of fluid through them.. but pedal still soft. but it does feel pretty hard when I have all 3 hoses pinched off. so i'm really out of ideas.. I need some serious help.. the pedal is soft and the rears don't fully lock up when pressing the brake. ... would it maybe have something to do with the combination valve?

 

i'm pretty sure now it's the combo valve that's giving me problems... I need to rebuild it but i'm having trouble finding info about how to do that.. I removed it from the car, took out the prop valve and metering valve and cleaned them up ,,, but I couldn't get the shuttle thing out of it, I could move it back and forth but don't know how to get it out.. . I reinstalled the valve on the car, hoping that just cleaning the prop and metering valve would be enough , but doesn't seem to have worked. Now I have to remove it again and see if I can find someone to rebuild it.. or figure out how to get the shuttle out. Can anyone help with this?

 

Proportioning valve is a sealed unit and there's no way it causes a soft pedal unless it leaks or has air in it. Too late now but you could easily have checked it with plugging the outputs.

 

that's a good idea.. but i don't have the correct plugs for the combo valve.

 

Still need help.. parking brake works great.. easily locks up rear drums. When pressing the pedal.. front brakes lock up fine but not rear.. with brake pedal pressed i can still slide drums off. I need the drums to lock up with the pedal as well as they do when parking brake is pulled. Shoes are adjusted out. Brakes have been bled extensively.. no air bubbles. Getting plenty of fluid through the system. Lots of new parts. I can't find any problems but i can't get rears to lock up with brake pedal. Anyone?

 

Try adjusting them out some more. Adjust until you can't get the drums at all on anymore then just barely back em off from there.

 

I'll do that.. but I'm wondering.. since the shoes grab good with the parking brake.. why don't they grab with the brake pedal?

 

:shrug:

Does that matter?

 

I agree with trying to adjust the shoes out further. With the drum on and wheel installed, use the little window on the backing plate to get to the adjuster wheel. Adjust the shoes out until you feel a slight drag when rotating the wheel.

 

I just tried that.. adjusted them out some more using the little window. with the wheels on. there's a little drag but I can rotate them just slightly.. then I push the brake pedal in pretty hard and jam a rod on it up against the seat to the brake pedal stays pushed in.. then check the wheels and I can still move them the same amount with the pedal pressed in.... I don't get why there's no braking force in the rear.. the pedal doesn't activate the rear brakes at all. this is why it takes way too long to stop the car.. I have to push harder and harder when i'm trying to stop to get it to stop cause I only have front brakes. this is driving me crazy.. the shoes are fine, the drums are fine, the wheel cylinders are new, there's plenty of fluid going through when I bleed. why don't they work??

 

Possibly because they need adjusted up.

Take off the drums. Adjust the shoes out as far as you can and still get the drums back on. Keep doing that until you absolutely cannot get the drums back on anymore.

If the drums have ANY DEGREE WHATSOEVER of a lip around the edge, as in if they're not brand new, grind that COMPLETELY off, first. Obviously a lip will prevent the drum from going back on over the shoes, unless the shoes are so far de-adjusted that they clear the lip, which then, there'll be a GINORMOUS gap between the shoes and the active part of the drum surface.

 

You messed with the proportioning valve and clamped lines and bled sections. You might have off centered the valve. Is the brake light on in the dash?

 

the shuttle thing is centered.. i used the tool that threads in place of the switch when bleeding..

 

ok, just adjusted my shoes out even more... til I could just barely turn the wheel by hand... shoes definitely touching the drums. went for a 3 or 4 mile drive. . got back and drums were billowing smoke.. definitely cooked the shoes.
also, the pedal wasn't great before I drove it (with shoes adjusted all the way out). and when I started the engine, the vacuum made pedal sink so much further. . while I was driving it would stop but i'd have to push the pedal kinda far before it would get hard and really grab. so I still have the problem with shoes adjusted out so far that they are burning up inside the drums.. so the shoes being in too far was definitely NOT the problem.
I'm really getting frustrated with this. What do I do?

 

$5 worth of plugs, isolate your problem.

 

Once the shoes "burn up" like that, what we all used to call "bedding in" before that term got co-opted by the different behavior of disc brakes, they're properly adjusted. Basically, all the loose or uneven or excess material around their circumference that was just hanging out in space somewhere being useless, is now gone. Nothing wrong with that. Totally normal.

In a properly built "modern" (I use the word loosely... let's say, from the last 60 years) drum system starts working, then using the brakes when in reverse, adjusts them up. If they're loose, aka in need of adjustment, then when the shoes torque in the reverse direction, they **** that "adjuster" mechanism, which if it moves far enough to engage the next tooth on that little starwheel, turns the starwheel enough to adjust the shoes out one more quantum. They should ALWAYS be kept just at the point where they almost drag by this mechanism, one click at a time.

Now that the shoes are "bedded in", try backing up vigorously, and stomping on the brakes, several times in a row. No need to kill anything over it; a more vigorous backing up than, say, leaving a parking place at Kroger, might be needed, butt you don't have to do a full J-turn or any such; butt, maybe 5 mph in reverse should do the trick. You might even be able to hear the little click of the adjuster mechanism working, if the rest of the car isn't too loud. You can do this with either the parking brake (there's no such thing as "e-brake" or "emergency brake", only "parking brake", because that's ALL it's designed to do, is hold the car still when parked, NOT provide some kind of hypothetical mechanical "emergency backup" when the hydraulics fail) or the regular hydraulic system.

 

100%

 

I don't think the brake shoe adjustment is the problem because i had them adjusted out so far they were burning and the pedal still wasn't firm. I'm looking for other ideas of what could be causing the soft pedal and the rear drums not grabbing.

 

I would tend to agree here. I have always adjusted the shoes out until I felt some drag when rotating the wheel and left it at that. The brakes then worked right away on the first test drive. I think your issue is in the hydraulic system. Maybe try bench bleeding the master cylinder again?

 

OK.

OK also.

Since you're not interested in logic and reality, go for it. Whatever "other ideas" you can find, enjoy. Seems to be the general zeitgeist: "other ideas" are more important than established facts. What a shame. I never thought it would come to this.

Too bad you're not willing to listen to experience and long-term familiarity. Some folks just have to learn the hard way.

​​​​​​​Have a nice day!!

 

i did listen to everyone on here.. and took the advice. And proved it to be wrong.

 

YES!! thank you.. I pulled the master off again to re-bench bleed it.. put it all back together, re-bled all 4 corners.. now my back brakes work!! Seems like that was the issue. Brakes work much better now.

 

Excellent! Glad it finally worked out.

 

Now the question is...did you learn anything?