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Thread: Brake Servo/Booster information/specifications

  1. #1
    Member Shug's Avatar
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    Post Brake Servo/Booster information/specifications

    Hello,

    I've been enjoying getting out and enjoying the XJ6 Coupe in the sunny weather but I'm growing a little disappointed with the stopping power, a recent incident lead to stamping on the brakes which lead to the rears locking but not the fronts. So I'm now looking to understand the braking system a little better especially the brake servo. I have a reasonable understanding of how it functions but trawling the internet doesn't give a lot of specific details about the servo.

    My brakes are 4 piston Girling's to the front with vented discs standard solids at the rear and are in good condition eg new/refurbished, master cylinder refurbished, EBC Green Stuff pads and Goodridge over-braided hoses. Caliper pistons are all moving freely.

    Some info found so far about the brake servo/booster, but I need to get some confirmation:-

    1. Girling Type 100?
    2. Dual Diaphragm?
    3. the servo may have been used on subsequent Jaguars including the XJ series 3 and XJS models.

    Has anyone got any details? or serviced a servo/booster and has some photo's they would like to share? Or can anyone recommend somewhere in the UK to get the servo refurbished.

    Is there a way to test the servo is functioning to full potential especially if it is a dual-diaphragm? (could one diaphragm be functioning correctly and the other not?)

    Are the later model servos better than the 1977?

    Any information is welcome.

    Thanks
    Jaguar XJ6C 1977 4.2 (HIF44 carbs) UK RHD ZF4HP22

  2. #2
    Junior Member
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    Had a wooden brake pedal.
    Servo wouldn't hold a vacuum.
    Replaced with CAC1226/7 from David Manners - £155.00 last year.
    My bulk head needed tidying under pedal box mount and a new gasket to sit on - used some old lino, as I wanted to get it finished.
    Also bought vacuum hose as fitting were different between servos.
    This is what I replaced.

    Click image for larger version. 

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    Regards
    John

  3. #3
    Senior Member rchiv's Avatar
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    Did all that sawdust come out of the Servo no wonder you had a wooden pedal haha.

    Roger
    HEY I THOUGHT I HAD RETIRED, Ex Auto Electrician
    2006 X Type 2.2d SE Manual Estate. Zurcon Blue Champagne/Mocca, F/R Parking sensors, ,Auto Lights, Auto Wipers, Headlight Washers, Sat Nav 2012 update, 17 in Wheels, 112K Mods:- Electric Autofold Mirrors on Locking , HID Dip Beams
    Simple Autofold Mirrors on Locking,http://www.jaguarforum.com/showthrea...irrors+locking
    UPDATE YOUR SIGNATURE http://www.jaguarforum.com/showthread.php?t=91945

  4. #4
    Senior Member rchiv's Avatar
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    The Servo does not operate front and rear brakes. It assists only the pedal pressure. The master cylinder is a split system applying pressure to the brakes and normally operates O/S/R, N/S/F and N/S/R and O/S/F so for the rears to lock up together under emergency braking could be the weight being transferred to the front making the rear lift. Front suspension could be weak.

    Roger
    HEY I THOUGHT I HAD RETIRED, Ex Auto Electrician
    2006 X Type 2.2d SE Manual Estate. Zurcon Blue Champagne/Mocca, F/R Parking sensors, ,Auto Lights, Auto Wipers, Headlight Washers, Sat Nav 2012 update, 17 in Wheels, 112K Mods:- Electric Autofold Mirrors on Locking , HID Dip Beams
    Simple Autofold Mirrors on Locking,http://www.jaguarforum.com/showthrea...irrors+locking
    UPDATE YOUR SIGNATURE http://www.jaguarforum.com/showthread.php?t=91945

  5. #5
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    Like it!
    Could equally have been from between my ears.

  6. Likes rchiv liked this post
  7. #6
    Member Shug's Avatar
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    Thanks for the replies and the good humored banter.

    J Green - have you been out in the car since the swap of the servo - did it make a difference, how does it feel now.

    rchiv - Interesting about the weight transfer, it does make a lot of sense, at least for some of my concerns. Riding motorcycles it is easy to get the same affect, hence why they typically have monster brakes on the front with fairly small on the back.

    Thanks
    Jaguar XJ6C 1977 4.2 (HIF44 carbs) UK RHD ZF4HP22

  8. #7
    Senior Member rchiv's Avatar
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    On motorcycles the front brake is the main brake and the rear is just for stability. Else you would be locking the rear wheel all the time.

    Roger
    HEY I THOUGHT I HAD RETIRED, Ex Auto Electrician
    2006 X Type 2.2d SE Manual Estate. Zurcon Blue Champagne/Mocca, F/R Parking sensors, ,Auto Lights, Auto Wipers, Headlight Washers, Sat Nav 2012 update, 17 in Wheels, 112K Mods:- Electric Autofold Mirrors on Locking , HID Dip Beams
    Simple Autofold Mirrors on Locking,http://www.jaguarforum.com/showthrea...irrors+locking
    UPDATE YOUR SIGNATURE http://www.jaguarforum.com/showthread.php?t=91945

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