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Rear Brakes InOp - what am I missing ?


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Hello All,

 

Working on the garage find '74tii again.  Last weekend I got the front calipers replaced with Cardone rebuilts and successfully bleed the brakes (at least the fronts) and road tested.  Before replacing the front calipers, I attempted to bleed the system - the front barely bleed and the rears not at all.  After replacing the calipers the fronts bleed fine and the rears still didn't bleed at all.  I used a Motive pressure bleeder, and pushed at least a quart of fluid through for good measure.  On the road test the pedal was a little soft, or just different from my '73tii, but I certainly was able to stop and also lock the brakes (at least the fronts) on demand.

 

So now I'm working the rears.  It appears, if my knowledge about brakes is correct, that the lines have been replaced in the past with stainless braided lines (see photo).  I'm wondering what the next steps are.  Perhaps an important note, the hubs do NOT turn freely, it takes quite and effort to spin either side, sort of like the brakes are partially on.  

 

One question is - what is the lower line in the photos - the one that attaches to be bottom of the brakes?  Could that be my culprit?  Any advice of course if welcome, and encouraged.  

 

Thanks,

 

David

 

 

 

So, the rears

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Any society that would give up a little liberty to gain a little security will deserve neither and lose both.

Benjamin Franklin

73 tii (Verona, survivor, owned since '92)

66 DS21 (most technologically advanced car of the 20th Century)

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Hi,

 

Two thoughts - check the adjusters and check the handbrake.

 

The adjusters allow you to move the shoes radially in and out.  Yours may be dragging, based on your description.  The cable you mention that goes to the bottom of the shoes is the handbrake cable.  If it's too tight, it will also cause binding.  You adjust those at the handbrake lever (pretty straightforward).

 

Hope that helps.

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4 minutes ago, Healey3000 said:

Hi,

 

Two thoughts - check the adjusters and check the handbrake.

 

The adjusters allow you to move the shoes radially in and out.  Yours may be dragging, based on your description.  The cable you mention that goes to the bottom of the shoes is the handbrake cable.  If it's too tight, it will also cause binding.  You adjust those at the handbrake lever (pretty straightforward).

 

Hope that helps.

 

Healey,

 

Thanks.  Yes, adjusting the handbrake is on the punch list for this weekend.  From what I've read on here, its pretty bone simple (I also have the Haynes and factory manuals).  

 

Still wondering about the non-bleeding though... 

 

I'm assuming you have a BN(J)7/8 from your ID, nice cars (I worked at an antique British sales and restoration place in College).  Nice cars, though I like the simplicity and lay flat windscreen.  

 

  

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.

Benjamin Franklin

73 tii (Verona, survivor, owned since '92)

66 DS21 (most technologically advanced car of the 20th Century)

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Hi,

 

Non-bleeding most likely implies there's a blockage someplace.  If both sides are behaving the same way, it is probably in the common section.  Start from one end and see if you can find the block.

 

What happens if you completely remove the bleeders?  If still no flow, move up to the flex line to hard line junction and check for flow.  It could just be that the fluid was never changed and corrosion has taken a toll on the steel lines.

 

You are correct, it's a BJ8.

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Perhaps rust in the bleeder holes or something clogghing it. Ive changed my rear shoes, wheel cylinder and rehab the rear bearings this past weekend. Although the old wheel cylinders function ok, one side bleeder screw broke off when i tried to remove it. The internal wheel cylinder had some rust when disassembled. 08b0d562cd94ffcf03c2b7a53f0fe658.jpg

Sent from my SAMSUNG-SM-G900A using Tapatalk

2002cool2

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thanks for the "moving back to front" suggestion.  Yes, I've fully removed the bleeder and still no flow, so its gotta be something in the lines...(?)

 

 

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.

Benjamin Franklin

73 tii (Verona, survivor, owned since '92)

66 DS21 (most technologically advanced car of the 20th Century)

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The usual places for things to plug, given how your wheel cylinders look,

start with right at the bleeder port itself inside the cylinder (fills with rust),

then the soft lines (not your problem, since you seem to have braided- steel jacketed teflon)

then the fittings at the wheel cylinders,

then the tee,

followed by the fittings and ports at the master.

Very seldom do the hard lines get plugged.  They do occasionally get crimped closed,

which you discover by physical inspection.  More frequently, they rust through from either the inside or the outside.

 

If you like a good mess, put the drums back on, loosen a rear bleeder and put a tube and bottle on it,

then step on the brakes.  That will usually clear most blockages AS LONG AS your master's supplying pressure to the

second (back and front combined) circuit.

It often gets messy because fluid will ooze (or squirt) out of the threads of the bleeders.

And if you want to avoid having to bleed the heck out of the back circuit after this, have a longish stick

of the right length stand

to wedge the pedal down with  so you can close the bleeder before the pedal comes back up.  That'll

keep much air from getting back in via the rear bleeders.

 

In your position, I would change the rear cylinders just based on appearance before going much farther.

In that process, you'll discover where the blockage is.

 

Lotsa words, hope it helps

 

t

 

"I learn best through painful, expensive experience, so I feel like I've gotten my money's worth." MattL

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7 hours ago, TobyB said:

Lotsa words, hope it helps

 

Thanks for the words, they most likely all will be needed.

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.

Benjamin Franklin

73 tii (Verona, survivor, owned since '92)

66 DS21 (most technologically advanced car of the 20th Century)

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I would just replace the rear wheel cylinders first.  They are relatively cheap.  $12-13 from Rockauto, and even Bavauto has some for $10 each.  They are the most likely source of the problem. 

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My tii had good brakes but I found a bad RR wheel cylinder that leaked fluid all over the shoes so I replaced everything on both sides (parts sourced from Blunttech). The most important thing is to make sure the two shoe adjuster bolts can move before you install new parts.  Mine were almost frozen to the backing plates. 

Jim Gerock

 

Riviera 69 2002 built 5/30/69 "Oscar"

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8 hours ago, jgerock said:

The most important thing is to make sure the two shoe adjuster bolts can move before you install new parts.  Mine were almost frozen to the backing plates.

 

Thanks,  I was able to move both adjustment bolts on both side.  

 

New rear wheel brake cylinders will be here in a couple of days.  

 

 

Any society that would give up a little liberty to gain a little security will deserve neither and lose both.

Benjamin Franklin

73 tii (Verona, survivor, owned since '92)

66 DS21 (most technologically advanced car of the 20th Century)

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Try loosening the connection to the front of either rear flex line, and then press the brake pedal.  If you get fluid leaking, that's good.  Then tighten that connection and loosen the connection to the rear of that flex line, and again depress the brake pedal.  No fluid leakage= plugged flex line.  That is exactly how I discovered that both my rear flex lines were 100% occluded.  The steel lines were fine.  I replaced the flex lines and pressure bled the system, and now have excellent rear brake action. 

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