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Discussion Starter #1
Hi All,

For some time my 110 has had "spongy" brakes, I can press hard but they don't seem to brake very effectively. I took it to a local rover shop and they verified that the brakes had been bled properly, and noted that they still felt soft; but at the time they weren't so bad that I was overly concerned. However, it seems they've ogtten progressively worse over time - now the stopping time is very long and I'm concerned.

Any thoughts on where to look to diagnose this problem? I can see the vaccum hose is plugged into the brake booster; and it appears to have vaccuum. I swapped in fresh fluid and re-bled the brakes until the fluid came out clear. I have speed bleeders on all 4 wheels, so I don't think that I got air in the lines. Fluid is topped off (brake fluid.)

I read a bit about sometimes the brake boosters being undersized - and replacing with one that is larger can help, but I'd prefer to try and track this one down before I go about replacing parts and whatnot.
 

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You have drum brakes that are not self adjusting. You must periodically get under the truck and adjust them per the manual for them to work well.
 

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Discussion Starter #3
You have drum brakes that are not self adjusting. You must periodically get under the truck and adjust them per the manual for them to work well.
So more detail here - I had the rear drums adjusted by a reputable rover shop locally, and they still ended up spongy. Eventually, I just gave up and switched the rear to a single pot disc setup - eliminating the need to adjust the drums altogether. That being said - still spongy (probably more so than before actually.) Bleeding the brakes worked great - lots of fluid coming out with each pump (engine off); I'm wondering if the brake booster might be the cuplrit here?
 

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Probably the master.
 

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A failed booster would not make the brakes spongy, it makes the brakes rock hard.
Do you feel any vibration when you touch the brakes ? If you do a couple quick pumps does the pedal firm up?
 

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A failed booster would not make the brakes spongy, it makes the brakes rock hard.
Do you feel any vibration when you touch the brakes ? If you do a couple quick pumps does the pedal firm up?
I’m very interested in this topic. If I do a continuous pump my brakes don’t start to really grab till a third of the way down. If I tap a couple times it firms right up. Is this normal? Rear drums disc front.
 

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if you have rear drum brakes, it is possible the slave cylinders are or sometime in its life have been replaced by those of small capacity thus, upon application of your brakes it takes a few pumps for the piston to extend the shoe to touch drum, it is worsened if shoes are not well adjusted.
the fix, locate/install the proper size OE slave/wheel cylinders.
 

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if you have rear drum brakes, it is possible the slave cylinders are or sometime in its life have been replaced by those of small capacity thus, upon application of your brakes it takes a few pumps for the piston to extend the shoe to touch drum, it is worsened if shoes are not well adjusted.
the fix, locate/install the proper size OE slave/wheel cylinders.
Thanks, I’m going to monkey with my shoe adjustment and see if that doesn’t help some. Seems to be a bit of an art.
OP has discs now so that’s not his issue.
 

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How does the fluid look at the master? Nice and clean or a bunch of schmoo in there with the fluid?

What you describe was a predecessor to a complete master cylinder failure for me.

I wouldn't mess with resizing the master or anything like that. Your issue is more fundamental - are the drums adjusted as noted above, and is fluid being pushed properly by the master. In my case, the seals around the piston in the MC were degrading. Much debate was had at the time and I was using high-quality DOT5.1 which is SUPPOSED to be backward compatible DOT4. But after replacing my master (for the 2nd time) with some NAPA DOT4 it (knock on wood) had no issues.
 

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Discussion Starter #10
A failed booster would not make the brakes spongy, it makes the brakes rock hard.
Do you feel any vibration when you touch the brakes ? If you do a couple quick pumps does the pedal firm up?
No vibration when I hit the brakes. If I pump it a bunch it does firm up some...
 

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I’m very interested in this topic. If I do a continuous pump my brakes don’t start to really grab till a third of the way down. If I tap a couple times it firms right up. Is this normal? Rear drums disc front.
usual causes of a soft pedal with dsc brakes are
dead master cyl
a fluid leak
warped rotors - the warp pushes pads away fro rotor so it takes a pump or to to get them back in contact and clamping
loose wheel bearings -allow rotor to move a bit -same result as above
loose caliper bolts- same result
air in system- reputable shop or not
 

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Discussion Starter #12
I will try to re-bleed the system this evening - to see if things improve. If the rotors are warped should I be able to tell that with a level against them? I would assume so? I can try to pull both front wheels off and see if they are warped.

If the bearings are loose, would I be able to wiggle the rotor a bit with the wheels off? Or would it be too difficult to do that by hand?

I know the caliper bolts are tight and the pads are good. I don't see fluid leaks anywhere...

Would a good next step (after the above) to be to swap out the master cylinder?

thanks!
 

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if your master cylinder has internal leak yes, your brakes will feel spongy. of course any internal leak means fluid is bypassing the seals and this fluid will eventually seep to the outside and show it self trailing down the vacuum booster.
 

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It can leak at one of the internal pistons without ever leaking to the outside. There are seals behind the pressure pistons. If the secondary piston seal goes, you get all the braking from the primary.
 

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It can leak at one of the internal pistons without ever leaking to the outside. There are seals behind the pressure pistons. If the secondary piston seal goes, you get all the braking from the primary.
In my case, the internal seals failed. You could see fluid shifting about when looking at the reservoir.
 

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Here is a picture of the internals from the workshop manual to see what I mean. There are four seals. If one of the high pressure ones goes, it just leaks back to the reservoir and you only get half the braking and it is spongy.
 

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Here is a picture of the internals from the workshop manual to see what I mean. There are four seals. If one of the high pressure ones goes, it just leaks back to the reservoir and you only get half the braking and it is spongy.
I'll put money on this as the OP's issue
 

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Discussion Starter #18
So I swapped in a new master cylinder - I pressure bled it until fluid ran out of all the lines (from the furthest to the closest). However, when I pump the pedal I don't get any pressure.

I'm wondering if I got the piston properly aligned to the input in the master cylinder - if I missed it, I was figuring the pedal would be hard - and not soft; but perhaps that is not the case? If not, I'll try to bleed some more and see if perhaps I screwed something up and left fluid in the lines somewhere. The total fluid required to bleed was a little under a quart - should it be more than that?

thanks!
 

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Did you bench bleed the master first?
 
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