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Carl Heydon
Experienced User
Username: car

Post Number: 33
Registered: 2-2004
Posted on Sunday, 30 September, 2012 - 19:47:   Edit PostDelete PostView Post/Check IP

I'm looking for a Mk VI brake servo in almost any condition. B148MD has an intermittant severe brake judder, usually after a full day driving with the brakes operating beautifully. The linings are new, cylinders rebuilt, all rods checked and adjusted. I suspect some distortion in the servo.
Anything considered.
Thanks
Carl
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NORMAN GEESON
Unregistered guest
Posted From: 86.25.209.251
Posted on Saturday, 27 October, 2012 - 22:59:   Edit PostDelete PostView Post/Check IP

Carl

I have only just seen your post. Have you checked to see if the washer, part no GB 5083, parts book section J9, item 19, has been replaced with corrugated washer R5037 ?

Most Bentley MkVI located overseas do not have this modified washer fitted.

It is important with your particular chassis to be 100% certain of bleeding the front brakes, and if needed remove the drums and clamp the cylinders inwards, before bleeding. Also note that there are no correct instructions in the manuals on how to assemble these front brakes correctly. Refer to www.kda132.com under 'Brakes' for step by step photographs of the correct assembling of the front brakes.

Hope this might help.

(Message approved by david_gore)
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Carl Heydon
Experienced User
Username: car

Post Number: 34
Registered: 2-2004
Posted on Sunday, 28 October, 2012 - 19:49:   Edit PostDelete PostView Post/Check IP

Hi Norman,
I haven't determined if the washer has been replaced. But all the Mk VI brakes I look at are checked against your information. I am enormously grateful to you for the wealth of information you share with us. Thank you, thank you, thank you.
I cleaned the lining several years ago when I replaced the oil seal. The owner was in the habit of spraying it with degreaser before each outing. The servo cover is split radially and dented on the edge. This being the probable cause of the reaction. I drove the car yesterday for about fifty miles on a cool 24c day and I could predict when the reaction would occur by the temp gauge. I had intended to arrange a system to spray water on the servo while driving but time got away.
The effect is severe with the brakes being completely inoperative with violent feedback at the pedal. But if the handbrake is half applied, to the point where one can just feel it on a gentle slope, then they operate almost normally
We believe we have eliminated all other faults and have bought a reconditioned servo to eliminate any uncertainty.
I shall report back.
Carl
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Martin Cutler
Prolific User
Username: martin_cutler

Post Number: 190
Registered: 7-2007
Posted on Tuesday, 04 December, 2012 - 20:10:   Edit PostDelete PostView Post/Check IP

Hi Carl,

Did you try re-lining the servo, sounds like it is either glazed or oil soaked. The face that the lining bites into could need machining? B256MD had the same violent shudder a while back, but it was not heat related. It was worse when the brakes where cold. Problem was oil on the lining in the servo. Changed out the lining, new seal in the gearbox, and all is right with the world.

cheers

Marty
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Carl Heydon
Experienced User
Username: car

Post Number: 35
Registered: 2-2004
Posted on Wednesday, 05 December, 2012 - 07:02:   Edit PostDelete PostView Post/Check IP

Thanks Marty,
The brakes were perfect cold. We could never induce the reaction in winter (however hard we tried).
Seal replaced, lining checked and cleaned with 'brakleen'. At least five summers the issue reappeared.
Complete reco servo at surprisingly reasonable cost (love the exchange rate) from FS and all is wonderful. I believe the cover was the problem but wanted to be sure.
Now I can use the old bits to tweak B14BH.
Carl