1969 Jaguar 420 Brakes seizing

Jaguar 420 Problem
The Problem
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Terry Lloyd
Fixes: 2
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Brakes seizing
Nov 19, 2013 (6 years ago)
Brakes gradually start to seize on after driving a short distance. I have fitted new front and rear discs and pads and refurbished all calipers with new pistons. Problem persisted. I then fitted master cylinder kit. Following this I had difficulty getting brake fluid to pump to rear brakes (cleaned sludge from both brake fluid resevoirs to resolve)
Problem still there.
The only component I have not touched is the Servo. Could this cause this fault or do I need to fit a new master cylinder or is there something else causing the problem. (near to tearing out the few hairs I have left) Grateful for any help.

Car details
Car: Jaguar 420
Model Year: 1969
Category: Steering, Suspension, Brakes, Wheels & Tyres

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Parts mentioned in this problem
Replies and solutions
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bustedknuckles
Fixes: 1,458
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Nov 19, 2013 (6 years ago)
When the fault occur,s you could loosen off your bolt,s that secure your master cylinder and see if that unlock,s the system ,that way it will tell you if it,s the master cylinder that,s causing the issue.
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whittingehame
Fixes: 12,290
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Nov 19, 2013 (6 years ago)
Sounds like master cyl.If only fronts , check flex hoses .They can collapse inside restricting fluid flowing back and holding pistons on.
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Terry Lloyd
Fixes: 2
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Nov 20, 2013 (6 years ago)
Thank you, your advise is much appreciated.
Do you mean loosen the bolts that secure the master cylinder to the brake pedal assy?.
Also I failed to mention that the brakes did release around 30 mins after switching off the engine. From this do you think I can discount the servo as the cause or do you think this is still a possibility.
I will also change the flexible brake hoses.
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whittingehame
Fixes: 12,290
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Nov 20, 2013 (6 years ago)
I think " busted knuckles " theory is if you loosen the master cyl bolts it will give more clearance between pedal push rod and master cyl and possibly release pressure .Might work ,but if internal fault on cyl. like seals ???? In my opinion I would favour master cyl over servo .
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Terry Lloyd
Fixes: 2
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Nov 22, 2013 (6 years ago)
I released the master cylinder and inserted washers of approx eighth of an inch to create a gap. The pedal biting point lowered accordingly.
I thought this might be the answer but alas after driving around one mile the brakes started to bind and got progressively worse.Is there a way that I can isolate the servo to eliminate this before confirming I need to order a new master cylinder.
If you don't mind your continued advise it would be greatly appreciated.
Terry
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whittingehame
Fixes: 12,290
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Nov 27, 2013 (6 years ago)
You could pull of and blank the servo vacuum hose . .But it would mean no brake assistance and very hard to push brake pedal .
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