Baron/Bonanza Brake Master Cylinder Upgrade/Repair Kit


Category: Baron, Bonanza

Type: Kit

Nobody pays much attention to the piston rod seal in their brake master cylinder until it starts leaking. Even when it does leak it won't cause much more than carpet damage, unless you ignore it. When your brake master cylinder requires repair due to leakage or you want to take a proactive approach, the Marsh Brothers’ Brake Master Cylinder upgrade/repair kit is the solution that will fix it once and for all. Like all Marsh Brothers products, our glands and seals are developed to last for the long haul.

Installation of the Marsh Brothers brake master piston rod seal offers the opportunity to practice preventative maintenance, by eliminating the risks associated with the typical failure modes of traditional O-rings used in the dynamic seal applications.

The Marsh Brothers Aviation Bonanza/Baron brake master cylinder upgrade kit contains all of the hardware to repair/upgrade your Bonanza/Baron brake master cylinder. Additionally, the kit also includes tooling to aid in the re-assembly. The piston rod seal (AeroLas™-Flex) provided is a Marsh Brothers Aviation proprietary lip seal design and is manufactured from a proprietary elastomeric polymer. The Marsh Brothers Aviation Thorseal® replaces both the OEM O-ring and rod wiper. The kit also includes installation instructions, instructions for continuing airworthiness and an authorized release certificate.

Note: The Piston is not included in this kit.

Caution: Thorseal® is made from Marsh Brothers proprietary material known as AeroLas™-Flex. AeroLas™-Flex is not compatible with phosphate ester hydraulic fluid, commercially known as Skydrol. Exposure to phosphate ester hydraulic fluid contamination will damage the seals.

This kit does not fit brake master cylinders manufactured by Gerdes or Paramount.

  • Piston Rod Lip Seal eliminates risk of typical failure modes associated with traditional O-rings used in dynamic applications.
  • The proprietary elastomeric polymer offers improved lower pressure sealing performance and overall cold weather performance.
  • Installation Tooling included - Seal compression ring, thread sleeve, and push tube.
  • Delivery documentation includes copies of all STC certificates and a Transport Canada Form One (authorized release certificate) to keep your logbook up-to-date.
  • Applicable to OEM P/N 96-380034-25 & 96-380034-23 series brake master cylinders manufactured by Commercial Aircraft Corp.
  • NOTE: This kit may fit other OEM brake master cylinder part numbers. Please contact customer service for further details.
  • Approved for installation in Canadian Registered aircraft by Transport Canada Supplemental Type Certificate No. SA21-5 and US Registered aircraft by FAA Supplemental Type Certificate SAO4634NY (FAA)
  • Supplemental Type Certificate
  • FAA Supplemental Type Certificate
  • FAA Approved Models List

    Supplemental Type Certificate

    Bonanza Models 

    Baron Models 

    TCCA: SA21-5

    FAA: SAO4634NY


    35 E55
    A35 E55A
    B35 D55
    C35 D55A
    D35 56TC
    E35 58
    F35 58A
    G35 58P
    35R 58PA

    TCCA: SA21-5

    FAA: SAO4634NY

    35-33 58TC
    35-A33 58TCA
    35-B33 G58
    35-C33 95
    35-C33A 95-55
    36 95-A55
    A36 95-B55
    A36TC 95-B55A
    B36TC 95-B55B
    E33 95-C55
    E33A 95-C55A
    E33C A56TC
    F33 B95
    F33A B95A
    F33C D95A
    G33 E95

    Brake Master Cylinder Kit Picture

    Note 1: The Piston is not included in this kit.

    Note 2: Kit Includes:
    Installation Aids, Seal Compression Ring, Thread Sleeve, and Push Tube.

    Item#  MBA Part # Description Quantity
    OEM Cross Reference
    Part #
    1 AN316-5R NUT ROD END JAM 1 1 AN316-5R
    2 MS16625-1100 INTERNAL RETAINING RING 1 1 MS16625-1100
    3 MBA-03-10000-1 PISTON ROD GLAND SEAL 1 1 A57G401 / AN6227B6
    4 MS28775-117 O-RING (STATIC GLAND) 1 1 AN6227B11
    5-1 MS28775-111 O-RING (PISTON HEAD) 1 - AN6227B9
    5-3 MS28775-113 O-RING (PISTON HEAD) - 1 N/A
    6-1 MS28774-013 BACK-UP RING (PISTON HEAD) 1 - N/A
    6-3 MS28774-113 BACK-UP RING (PISTON HEAD) - 1 N/A
    7 MS24665-132 COTTER PIN 1 1 AN380C2-2
    8 MS16624-1037 EXTERNAL RETAINING RING 1 1 N/A
    9 AN960-616L WASHER, FLAT 1 1 N/A


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