Brake Help (1 Viewer)

[YangFJ40]

I have been having a tough time with my brakes for the last 4 months and cannot figure it out. I have a brand new master cylinder from orielly but thought it was that and exchanged it for another one. But the problem still persists. The problem is that the brakes no matter what always have air in them I've bled them continuously with no solution and have tried many different methods. When driving around to test I have to pump once then I have great pressure and brakes work as they should. When brakes are hit I can hear the rear drum brakes hit which I assume is normal? No leaks anywhere and wheel cylinders were recently rebuild. Any suggestions on what to look for this is driving me nuts. 1978 FJ40

 

[Cmatt1605]

take a look at the rubber flex line from the frame to the axle. Have someone sit inside and press the brake pedal down and feel/watch the rubber line to see if it swells. You may have to replace it if there are small cracks or if it swells. That could be what is letting the air in. Also you could try to use a brake bleeder from phoenix systems and add fluid from the bottom up, causing any trapped air to be forced up through the master and out of the system.

 

[honk]

Adjust your rear brake shoes.

Follow exactly the adjusting procedure that is contained in your Factory Service Manual (FSM).

You've bled enough.

 

[YangFJ40]

Replaced the rubber axle hose and rebled but still no cigar have yet to adjust brakes because I know there is still air in the lines somehow. I did go out and buy a vacuum pump for the brakes but it is a suction type and still no avail. I still can't find any leaks did a triple check today. Brake fluid is coming out clean with very little particles. The driver side rear isn't shooting out as hard as the others though

 

[DougAustinTx]

Do you have the proper residual pressure valve in the drum brake port to maintain slight pressure on the brake shoes? If they retract too far between uses, you'll have to pump twice to get them back in contact with the drum. This isn't usually a problem, but you might have gotten a master cylinder with a bad residual valve. I quit trying to use O'Reilly brake masters on my '79. I didn't have the problem you are having. I couldn't get enough braking force on the O'Reilly's. I went to a new Aisin and the problem went away.

 

[YangFJ40]

Do you have the proper residual pressure valve in the drum brake port to maintain slight pressure on the brake shoes? If they retract too far between uses, you'll have to pump twice to get them back in contact with the drum. This isn't usually a problem, but you might have gotten a master cylinder with a bad residual valve. I quit trying to use O'Reilly brake masters on my '79. I didn't have the problem you are having. I couldn't get enough braking force on the O'Reilly's. I went to a new Aisin and the problem went away.

Hmm not 100% sure what you mean I have the original residual valve in it. The one that sits on the brake booster below the master. Is that what your talking about? Should I order a new one after all it is old? Tomorrow I will be popping off the tires and try adjusting shoes I'll keep you guys updated. According to my manual I should adjust shoes to where they rub my drums and back off 3-5 clicks correct? Would it have to do anything with pedal height not to sure where I should adjust that to or if I even need to it worked previously with my old master before it started leaking. The disc brakes seem to be doing okay still not positive because of the spongy pedal. Brakes are not my thing.

 

[YangFJ40]

Hmm not 100% sure what you mean I have the original residual valve in it. The one that sits on the brake booster below the master. Is that what your talking about? Should I order a new one after all it is old? Tomorrow I will be popping off the tires and try adjusting shoes I'll keep you guys updated. According to my manual I should adjust shoes to where they rub my drums and back off 3-5 clicks correct? Would it have to do anything with pedal height not to sure where I should adjust that to or if I even need to it worked previously with my old master before it started leaking. The disc brakes seem to be doing okay still not positive because of the spongy pedal. Brakes are not my thing.

Scratch that I got the residual pressure valve and proportioning valve mixed up. O'Reilly gives no specs on the pressure valve supplied. I have my original master laying around still I'll play around and throw that pressure valve into the new MC see if it does anything different

 

[honk]

According to my manual I should adjust shoes to where they rub my drums and back off 3-5 clicks correct?

That's not what the FSM instructs. The shoes are adjusted until the wheel cannot be turned. Then the brakes are applied in attempt to make the shoes tighter, if possible. Once both are tight then the shoes are retracted until the wheels can be just turned, tightly. The retraction can be 4-5 notches (not clicks)

There are FOUR rear adjusters, two per wheel each adjusting just one brake shoe. All are used in a rear brake adjustment since adjusting one shoe while leaving the other loose will result in a spongy feeling low brake even with the perception that the adjustment is tight, finished, because of the one tight shoe.

IMO this is the trap a lot of owners fall into - using one adjuster as is common to most American drum brakes and is the adjusting practice we all got used to at some time leaves these Toyota rear drum brakes poorly adjusted.

 

[snaggletto]

Did you bleed the master before installing? You make up a small brake line for each circuit of the master and curve it up and back down, submerged, into the oil cups for each circuit. Do a google search for bench bleed master cylinder. A picture makes this very clear. After this is done, then hook your real lines up and bleed at the calipers as you have done. I have a mityvac device and it works up to a point but could never get all the air. Had to have my kid push and hold the pedal while I turned the bleed nipples to get it done right.

 

[JAFO2014]

You rebuild the wheel cylinders or someone else? Trust their work?
Adjusting drum brakes is important so the shoes don't need to travel so far before becoming tight against the drum. Yes you adjust the brake shoes so as when you spin the wheel you hear a slight rub. I don't think you should hear much drum brake shoe movement. They may be way loose.
I use a self bleed device ($10 from NAPA) and can bleed by myself. You always start bleeding from the wheel fartherest from the master cylinder, then work around to the next closer and so on. If you have a self bleeder it will let out air and not let it in (check valve). Bleed until nice clean fluid comes out at each bleeder, Flush the system while you bleed. Brake fluid absorbs water, so the darker the fluid the more water it contains. You want clear liquid in your system.
If you have someone to help, then they pump the pedal and hold. You crack the bleeder. Pedal to the floor...hold...close bleeder. Repeat.

 

[YangFJ40]

I have bench bled and have bled the way I'm supposed to. The weird thing is why it still has air in the system. I will re do everything once again today and see what happens

 

[Weber Sarge]

I have on a couple of rare occasions seen wheel cylinders suck air back into them from having very worn out springs to retract the shoes - just a quick thought..
Sarge