Brakes binding..

Ok, so this is a common problem in the threads it seems... Series 3, 2.25 petrol.

Replaced the drums, cylinders, shoes, pull off springs (correctly fitted)...slackened off the adjusters more than the "2 clicks" and all wheels spin freely. The master cylinder has a servo and was replaced a few years ago. It has two pipes exiting the cylinder and there is a safety front/back splitter valve bolted to the chassis.

After around 20 minutes of driving the brakes lock on. They free up if the vehicle is left standing for a while.

I often see "master cylinder free play adjustment" suggested as the cause...but it doesn't have any way of adjusting free play, certainly not on mine anyway..The non return valve has been replaced on the servo and the "test vacuum light" on the dash illuminates when checked. The pedal also sinks a little (foot on pedal) when the engine is started...

Which brakes lock on?
Fronts, Backs or all?
I don't know the answer.

J

I would also say pushrod free play
Does the servo look like this? You might need to remove in order to get to the pushrod. Not something I've done

kermit_rr said:

I would also say pushrod free play
Does the servo look like this? You might need to remove in order to get to the pushrod. Not something I've done
View attachment 300109

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Sorry...did you read my post? There isn't any adjustment.

marjon said:

Which brakes lock on?
Fronts, Backs or all?
I don't know the answer.

J

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All of them to my knowledge...but all of them spin freely with no rubbing at all when "cold" as I said in the post? I have slackened them off to beyond the usual 2 clicks..

davidpurton said:

Sorry...did you read my post? There isn't any adjustment.

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Plus, as stated, it's a twin pipe master..

If no adjustment, then it is most likely a po hack job, so for a fix remove master and grind some off the end of the push rod until you have some freeplay.
To test the idea before grinding, you could fit a washer or two between master and servo on the mounting studs.

davidpurton said:

Sorry...did you read my post? There isn't any adjustment.

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davidpurton said:

The master cylinder has a servo and was replaced a few years ago. It has two pipes exiting the cylinder and there is a safety front/back splitter valve bolted to the chassis.

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Ok calling @dag019
Did we not go through this on your rebuild and you left out the valve cos it was a 2 pipe master.

Why you have a front back splitter if its 2 pipe i am not sure need to look in my manuals to refresh.
But normally 2 pipe is already split front/back isnt it?

J

lynall said:

If no adjustment, then it is most likely a po hack job, so for a fix remove master and grind some off the end of the push rod until you have some freeplay.
To test the idea before grinding, you could fit a washer or two between master and servo on the mounting studs.

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It's one of these...doesn't tell you much I guess!. I've had her 23 years and this was replaced I guess about 5

marjon said:

Ok calling @dag019
Did we not go through this on your rebuild and you left out the valve cos it was a 2 pipe master.

Why you have a front back splitter if its 2 pipe i am not sure need to look in my manuals to refresh.
But normally 2 pipe is already split front/back isnt it?

J

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Don't think so, just joined today? It's always been there!! Infact, think I replaced it few years ago. Its just a ball valve that detects the pressure drop in one of the circuits and shuts it off...last reply got truncated with pop up ads

davidpurton said:

Don't think so, just joined today? It's always been there!! Infact, think I replaced it few years ago. Its just a ball valve that detects the pressure drop in one of the circuits and shuts it off...last reply got truncated with pop up ads

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No I was asking somebody else to join the discussion (note the @davidpurton is how it works ).

J

Going to space the mc as a first cheap attempt. Makes sense...can only be binding on when the fluid can't return fully? If that works, might trim the length of the plunger to suit. Thanks !!

marjon said:

Ok calling @dag019
Did we not go through this on your rebuild and you left out the valve cos it was a 2 pipe master.

Why you have a front back splitter if its 2 pipe i am not sure need to look in my manuals to refresh.
But normally 2 pipe is already split front/back isnt it?

J

Click to expand...

We did indeed have this discussion as part of my rebuild here is the thread: LINK. I have a 110 so is a little different to OP and I converted my Salisbury rear axle to discs using the "diesel Jim" conversion: LINK. But with the use of a later master cylinder on my 110 rebuild I did not need the bias valve and it was eliminated completely. However, I believe that even with rear discs a 90 still used the bias valve although why I am not sure.

davidpurton said:

Going to space the mc as a first cheap attempt. Makes sense...can only be binding on when the fluid can't return fully? If that works, might trim the length of the plunger to suit. Thanks !!

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I have had a couple of mcs seize up on my series due to lack of use, certainly get me thinking as we slowed down with no input from me!
Hope it works, cheap/free fixes are always the best.

The safety front/back splitter is probably a pdwa. Does it have wires?





Your master cylinder, if standard is either a pre or post rationalisation MC. Does it have a odd shaped fluid tank, almost as if to align with the angle of the wing?



All have adjustment, though it's not obvious if the latter.

For all four to lock, it's got to be the MC, bar a previous owner bodge/non standard parts.

Please post up some photos, this will assist.

Is there adjustment on pedal height

Wildefalcon said:

The safety front/back splitter is probably a pdwa. Does it have wires?

View attachment 300141

View attachment 300142

Your master cylinder, if standard is either a pre or post rationalisation MC. Does it have a odd shaped fluid tank, almost as if to align with the angle of the wing?

View attachment 300140

All have adjustment, though it's not obvious if the latter.

For all four to lock, it's got to be the MC, bar a previous owner bodge/non standard parts.

Please post up some photos, this will assist.

Click to expand...

Think mine same as yours and don’t think there is adjustment on brake MC like there is in clutch MC