Another Brake Issue

[Neu]

Heyo,

so i have soft brakes and I've been troubleshooting it.

My symptoms are pretty simple: 1. the e-brake barely works at all. 2. The initial press of the brake pedal is soft. it goes down about 80% and works okay. A quick second pump will get it to engage at about 20% and the brakes work great. 3. If I pull the e-brake and use the brakes then the pedal engages quickly.

I've replaced rear shoes and did a full rebuild of the back(springs, adjustors, shoes etc) with exception of the cylinders(nobody in town had them in stock, they're on order now). I also replaced the master cylinder(needed replaced, it was pretty corroded). The entire system has been flushed a few times to get the dirty DOT out. I've also adjusted the e-brake cable pretty much as far as I can which made no difference. I'm also pretty sure there is no air in the system, as I've bled a lot of fluid through and I bench bled the new cylinder pretty well.

So next up I'll be replacing the wheel cylinders to see if that fixes it. I inspected them when I rebuilt the rear brakes and they seemed alright, but I know that can be deceiving. If the wheel cylinders dont fix it then I'll start looking at the front brakes I guess.

The e-brake thing, I'd assume, is a pretty obvious tell for what's happening. If the e-brake isn't engaging then im likely not getting a lot of brakes in the rear anyway. The rear shoes measured correctly and the drums didnt seem especially worn.

If anyone has a strong idea of specifically what this would be that would be rad. Thanks a bunch.

[rer233]

Stupid question- but did you adjust the rear shoes? Also, are the new shoes the correct ones?

[Neu]

I did adjust them and the shoes are the correct width/diameter.

I'll take another look but shouldn't they auto adjust anyway?

[rer233]

I never trust the "auto adjust" feature. I adjust 'em out 'till there's a slight drag against the drum. Think it'll fix your problem...

[dlb]

I adjust 'em out 'till there's a slight drag against the drum.

+1. If pulling up on the hand brake doesn't do much and the cable is adjusted as far as it will go, either the shoes are not close enough to the drums (like Rich mentioned, they should make a slight scraping sound when you rotate the drum) or the park brake cables themselves are frozen.

[Neu]

I adjust 'em out 'till there's a slight drag against the drum.

+1. If pulling up on the hand brake doesn't do much and the cable is adjusted as far as it will go, either the shoes are not close enough to the drums (like Rich mentioned, they should make a slight scraping sound when you rotate the drum) or the park brake cables themselves are frozen.

Will do again. The brake cable is p much fully adjusted short, so i'm not sure what else I can do.

The cylinders are on order so I'll do all this at the same time.

[xirdneh]

Not sure if this can be done on a tercel cause i never tried it
A friend installed calipers on wrong sides of his truck so bleeder screw was too low and air bubble inside would not go out during bleeding.

[xirdneh]

Also not bench bleeding master cylinder properly will mess it up
When bench bleeding its important not to push the piston too far in
It can damage the seal, so i've heard

[Petros]

it is difficult and time consuming to get all of the air out of a system that has been opened all up. it takes much more pumping and cycling the master/bleeder valve than you might think. Espcially when you have an impatient "helper" who does not want to help (that would be my wife, even though I tell her it is the safest way to make sure the brakes will work proprely, she bregrudingly but dutifilly pumps the pedal until all the air is out, give your helper something to entertain themselves with). The signs of air in the system is mushy pedal that will pump up firm, but when released, goes back to mushy again.

simple test: pump up the brake pressure with 3 or 4 pumps, and hold it down hard for 30+ seconds. if it does not move down, the wheel cycinders and calipers are fine, no leaking. the cause is either air still in the system, or the rear brakes need more manual adjustment so the shoes have less clearance inside the drum. You must adjust the rear brakes, the auto adjuster will not do it, that is to just compensate for the small amount of wear on the shoes as you drive it.

If the pedal does slowly move down as you press on it, there is a leak in the system, most common by far is the rear wheel cylinders. Pull back the boots on the wheel cylider, if there is any wet brake fluid, you must replace that one wheel cylinder. they recommend to do them in pairs, but it is not really necessary, if one is still good, no leaks, cracked rubber, and it is dry under the boot, it will hold just a good as a replacement. (they will tell you stupid logic, like the "extra" pressure from the new wheel cylinder will cause the other old one to "blow out"....err NO, the pressure is the same on both sides, it is called hydraulics, if it does not leak it will hold the pressure). However, new wheel cylinders do not cost much, and you can replace them both if you want.

do not buy remanufactured wheel cylinders or master cylinders (or calipers), most are junk. they will suck in air and even if pumping and bleeding the fluid for a long time, you will still get bubbles in the new fluid. New ones do not cost much more, and are far more reliable.

good luck

[marlinh]

Before you try adjusting the rear brakes, you need to back off the emergency brakes at the handle. If it is too tight, the brake levers will be partially applied at the wheels and your brakes will feel spongy. This is because the shoes aren't in full contact at the wheel cylinders. You also must make sure the cables aren't hanging up. With the drums off, apply the e brake and watch the movement of the levers and ensure they go back to neutral (against the shoe) when released. The e brake levers need to be as close to the corresponding shoe as possible. That will be your starting point. Then, adjust the star wheel to bring the brakes into contact with the drum. Apply the brakes a few times with the pedal to make sure the shoes are centered. Continue adjusting the brakes until they make contact with the shoes. If there is a rust ridge on the edge of the brake drum you will have troubles removing the drum after the brakes are adjusted. I usually grind it off with a dremel so the drum can slide on and off easily. That is a job I do at least twice a year, like tire changeover time so the drums always come off for inspection. I live in a road salt area so this is a problem if not addressed. It is much easier to see what you are doing by adjusting the brakes with the drum off than using the hole in the backing plate.

I hope that helps.

[SirFoxx]

I'm having a kinda similar issue. When the car is off, the pedal is hard and it doesnt move. However, once the car is running, the pedal goes straight to the floor, causing the car to snap your neck. If you turn the car off and expend the vacuum pressure in the booster the pedal becomes rock hard again.

I have literally replaced everything with either new or known working parts, only for the problem to persists. I am probably going to take it to a shop as I have no clue what the issue could be

[Petros]

I'm having a kinda similar issue. When the car is off, the pedal is hard and it doesnt move. However, once the car is running, the pedal goes straight to the floor, causing the car to snap your neck. If you turn the car off and expend the vacuum pressure in the booster the pedal becomes rock hard again.

I have literally replaced everything with either new or known working parts, only for the problem to persists. I am probably going to take it to a shop as I have no clue what the issue could be

I have seen this before, I do not remember the cause. might be a bad master cylinder, that is leaky, or a bad brake booster perhaps. one or the other, I think perhaps a bad master. do not assume that because you have a new one installed that it is good. too often, unfortunately, it might be junk right out of the box.

go to the brake section of the service manual and run through the brake system checks, it does not take long, but will give you an organized way to test each part of the system.

[SirFoxx]

I'm having a kinda similar issue. When the car is off, the pedal is hard and it doesnt move. However, once the car is running, the pedal goes straight to the floor, causing the car to snap your neck. If you turn the car off and expend the vacuum pressure in the booster the pedal becomes rock hard again.

I have literally replaced everything with either new or known working parts, only for the problem to persists. I am probably going to take it to a shop as I have no clue what the issue could be

I have seen this before, I do not remember the cause. might be a bad master cylinder, that is leaky, or a bad brake booster perhaps. one or the other, I think perhaps a bad master. do not assume that because you have a new one installed that it is good. too often, unfortunately, it might be junk right out of the box.

go to the brake section of the service manual and run through the brake system checks, it does not take long, but will give you an organized way to test each part of the system.

I will check, though I have replaced the master with used but known good ones a few times. Same with the p-valve and booster. I am leaning towards either bad rear wheel cylinders or a bad booster.

[Neu]

I ordered two wheel cylinders and I'm gonna replace them. That was on my list of parts to replace anyway so I'm just gonna do them.

The pedal does lose pressure after 10 or so seconds of being pressed, so there is a leak somewhere. I haven't had the drums off since I was last in there so I'm not quite sure where the leak would be. I have a bad history with leaky wheel cylinders in these cars so that's why I'm just gonna replace them. They're pretty quick/easy.

I'll also re-adjust the shoes while I'm in there. I'm not sure if I actually did that when I rebuilt the rear brakes. I think I did but ..ya know.

I bench bled the crap out of the master cylinder so I dont think there's any air in that. When I bled the system afterwards I used a clear tube so I could visually check how much air was in the system. I *doubt* there is air in the system but we've all thought that.

This might be relevant. Even after replacing the master cylinder my pedal feels basically the same. The first pump goes down like 80% with little resistance, second pump builds pressure quickly and has plenty of pressure/stopping power. If I let off the pedal for a few seconds it goes back down to 80% the next time i press it.