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521 brakes issue


Arifaeth

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So, on my 69 521, I'm having an issue with the brakes where no matter how much I adjust and bleed the brakes, I still have to pump the brakes 4-5 times to get brake pressure. Brand new brake master, shoes and cylinders. Any ideas?

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You bled the bleeder on the master cylinder first?

 

Slightly loosen off the emergency brake adjustment.

 

Bleed rears next then the fronts.

 

The adjusters are turned in until there is slight rubbing of the shoes on the drum when spinning wheel by hand???

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On 1/10/2022 at 3:46 PM, datzenmike said:

You bled the bleeder on the master cylinder first?

 

Slightly loosen off the emergency brake adjustment.

 

Bleed rears next then the fronts.

 

The adjusters are turned in until there is slight rubbing of the shoes on the drum when spinning wheel by hand???

Yes, I adjusted the brakes till I couldn't turn them by hand, then pumped the brakes a couple times to get pressure, then adjusted them back till I just turn em by hand, and it's just barely rubbing the shoes against the drums. I bled all four wheels. The master cylinder doesn't have a bleed screw. Idk if the emergency brake has an adjustment, I wouldn't know how to adjust it.

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10 hours ago, Stoffregen Motorsports said:

Yes, make sure they are nice and tight, then back them off a bit.

 

Also, check your master cylinder adjustment. If there's too much play between the pedal and master, this could cause the issue you're having.

That's what I did. And the master cylinder is hooked up to where the bar keeps the petal all the way out. So there is no loose play between the pedal and master.

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22 minutes ago, Arifaeth said:

That's what I did. And the master cylinder is hooked up to where the bar keeps the petal all the way out. So there is no loose play between the pedal and master.

 

You need a little play in the pedal so the rod connected to the pedal is loose in the back of the master, just enough so you know it is loose, maybe a 1/16", you do not want tension on that rod except when you're pressing on the pedal, I do not remember what others say about how much play at the pedal itself, an 1/8"???

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1/16" or a few mm is fine. 1/8" is 3mm and is also ok but no more.

 

There should be a bleeder on the top front of the master just forward of the plastic reservoir.

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7 minutes ago, wayno said:

 

You need a little play in the pedal so the rod connected to the pedal is loose in the back of the master, just enough so you know it is loose, maybe a 1/16", you do not want tension on that rod except when you're pressing on the pedal, I do not remember what others say about how much play at the pedal itself, an 1/8"???

What I meant by there's no play, is that when I push the pedal there is no gap in when the rod is being pushed.

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3 minutes ago, datzenmike said:

1/16" or a few mm is fine. 1/8" is 3mm and is also ok but no more.

 

There should be a bleeder on the top front of the master just forward of the plastic reservoir.

That's just where the line comes out of. There's no bleeder on the master, nor have I ever seen a bleeder on a master cylinder 🤷

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My picture looks like a bleeder but it might just be a plug to keep dirt out.

 

Can you borrow a vacuum bleeder? Basically you connect to a wheel cylinder and use suction to draw fluid from the master through the lines.

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Just now, datzenmike said:

My picture looks like a bleeder but it might just be a plug to keep dirt out.

 

Can you borrow a vacuum bleeder? Basically you connect to a wheel cylinder and use suction to draw fluid from the master through the lines.

I don't know someone with one unfortunately

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9 hours ago, Arifaeth said:

That's just where the line comes out of. There's no bleeder on the master, nor have I ever seen a bleeder on a master cylinder 🤷

You could have air trapped in the master still... You could try bench bleeding the master cylinder back into itself...

You can leave it installed, you'll just need someone to push the pedal...

 

Basically disconnect the brake line and attach a short brake line and bend it to put the fluid back in the reservoir....

Have some one press the brake pedal and before they release it put your finger over the end of the line...

When they release the pedal you should see the fluid drop slightly in the reservoir... do that a couple times, in the end hold your finger over the line and see what the pedal is like.... should be nice and solid, then reconnect the brake line and bleed the rest of the system once more like normal....

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3 hours ago, Crashtd420 said:

You could have air trapped in the master still... You could try bench bleeding the master cylinder back into itself...

You can leave it installed, you'll just need someone to push the pedal...

 

Basically disconnect the brake line and attach a short brake line and bend it to put the fluid back in the reservoir....

Have some one press the brake pedal and before they release it put your finger over the end of the line...

When they release the pedal you should see the fluid drop slightly in the reservoir... do that a couple times, in the end hold your finger over the line and see what the pedal is like.... should be nice and solid, then reconnect the brake line and bleed the rest of the system once more like normal....

The issue is, I have to pump the brakes and can watch the fluid level drop like half way, and then come back after it sits

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Did you put the shoes in the correct way? It sounds like something is binding, so you think the adjusters on each wheel are adjusted correctly because it's dragging, when in reality, there's too much room in there and the slave cylinders need to come out too far to get pressure on the shoes.

 

I would adjust everything too tight, really step on the brakes hard to get everything centered, and then back the adjusters off so the wheels don't drag too hard.

Edited by mainer311
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56 minutes ago, mainer311 said:

Did you put the shoes in the correct way? It sounds like something is binding, so you think the adjusters on each wheel are adjusted correctly because it's dragging, when in reality, there's too much room in there and the slave cylinders need to come out too far to get pressure on the shoes.

 

I would adjust everything too tight, really step on the brakes hard to get everything centered, and then back the adjusters off so the wheels don't drag too hard.

I put the shoes in the way the repair manual told me too, but I'll try that next. I thought I did the whole adjust to much, step on em hard, but it can't hurt to do it twice

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OK, I see a possible issue, you need to disconnect the emergency brake cable from the center pull near the cross member, it should have a cotter key or clip, once you disconnect it then adjust the rear brake drums again, then you will have to re-adjust the emergency brake cable to re-connect it.

This cable can be a pain, sometimes one has a hard time putting the drum on when installing new brake pads, the issue is the shoe is held away from the brake cylinder when it should be resting on it because of the tension from the cable.

 

I cannot say for sure this is the issue, but it sort of sounds like it could be the issue if everything else has been dealt with.

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I seen that you touched on that subject by saying "Slightly loosen off the emergency brake adjustment.", but it is easy to just pass right by that without explaining the reason why it can be an issue, I say remove the cable from the center pull, adjust the brake drums and then re-connect the cable, it is surprising how much one has to change the adjustment nut, slightly loosen is not even close sometimes, so this was the reason for my post.

If the guy had put disc brakes up front I would have suggested the calipers were on the wrong sides/upside down as I did this once myself and had the same exact issue, I had to pump the brakes 4 or 5 times to get decent resistance.

 

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I would pull the parking brake then see how far or how many pumps it takes to brakes to harden up more on the top.  really the brakes should act better if the parking brake is pulled. Loosening the cable will be oppisite wont it? means you have to tighten(expand) the adjuster even more where the drum barely fits on

 

As for the claim of bench bleed the master to itsself.??? whats the differece if I just keep refilling it. once the fluid leaves out the bottom of the master who cares.  the air in the lines will, get pushed out along the way till it come out steady with no airbubbles.

You got to hook it back up to the brake line anyways and still have to bleed that air out that might get back in there when screwing the nipple back on.

I never have bench bleed a master brake or clutch.

 

only time I had proplem was i had to put my finger over the hole inside when fluid to get it to suck then it worked.

 

 

just my thoughts

 

 

only other thing i can think of is the aftermarket Brake masters I always have to cut the threaded rod as its too long. it usually engages the pedal arm to soon pressing on the master as its mounted to the firewall. .  not releasing its the common part. dont know if it can affect the  mutiple pumps to get the brakes going right

 

tighten up the adjusters then drive and then do it again

Edited by banzai510(hainz)
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