890870 Brake Master Cylinder for Clark / Tug CT30 / CT40 / CT50 Baggage Tractors

Your Clark or Tug baggage tractor's brakes are failing — pedal going to the floor, spongy feel, fluid leaking from the master cylinder, or you've lost braking entirely. On a baggage tractor operating on an active airport ramp, around aircraft, fuel trucks, belt loaders, and ground crew, brakes are safety-critical. The tug dealer wants $189.98 for a replacement master cylinder. That's nearly $200 for a standard cast iron brake component.

We sell the direct replacement for $149.00 — saving you over $40 vs the competition. This is the same specification master cylinder: 1-1/8" bore, cast iron body, manual brake configuration with the correct deep piston pocket for the pushrod, and standard inverted flare port threads (1/2"-20 and 9/16"-18). It bolts directly into the firewall mounting location and connects to the existing brake lines with no modifications. Replaces Clark/Tug part numbers 890870 and 2226085.

⚠️ Important: Manual Brakes Only — Deep Piston Pocket Required

Clark and Tug baggage tractors use manual (non-power assisted) drum brakes — there is no vacuum booster. This master cylinder is specifically designed for manual brake systems with a deep piston pocket that properly engages the brake pedal pushrod. Do NOT substitute a power-brake master cylinder — power brake versions have a shallow piston pocket and the pushrod will not seat correctly, resulting in a pedal that falls through or has no braking force.

Manual Brake (This Part): Deep hole in the primary piston — the pushrod seats fully into the piston bore. Correct for CT30, CTA40, CT50, MA.
Power Brake (WRONG Part): Shallow hole in the piston — designed for a booster pushrod. The manual brake pushrod will bottom out or fall through. NOT compatible.

The Problem

Baggage tractors operate in one of the most demanding brake environments in ground support: constant stop-and-go on smooth concrete and asphalt, towing heavy baggage carts in all weather, operating in rain, snow, de-icing fluid, and jet exhaust. The master cylinder is subjected to thousands of brake applications per shift. When it fails, the tug is grounded:

Internal seal failure — pedal slowly sinks to the floor under sustained pressure
External leaks — brake fluid dripping from the cylinder body, pushrod boot, or line fittings
Spongy pedal — air entering through worn piston seals
Complete brake loss — catastrophic internal bypass of both circuits
Contaminated fluid — moisture ingress causing corrosion inside the bore

A grounded baggage tractor backed up during a bank of flights costs the airline thousands in delays. This is an urgent, safety-critical replacement item with zero tolerance for downtime.

The Solution

This is the same specification brake master cylinder used in Clark and Tug baggage tractors. Cast iron body for durability, 1-1/8" bore for the correct brake line pressure, dual bowl (tandem) design for independent front/rear circuit separation, and the correct deep piston pocket for manual brake pushrod engagement. Remove the old master cylinder, bench bleed the new one, bolt it on, connect the lines, bleed the system, and the tug is back on the ramp.

How to Verify This Is the Correct Part

Before ordering, verify the casting number on your existing master cylinder:

Casting Number 29910 — This is the correct part
Casting Number 2225647 — Also correct (same cylinder, different production run)

The casting number is typically raised lettering on the side of the master cylinder body. If your existing master cylinder shows either of these numbers, this is the direct replacement.

Specifications

Clark/Tug OEM Part Number: 890870 (also replaces 2226085)
Type: Brake Master Cylinder — Manual (Non-Power)
Bore Size: 1-1/8" (1.125")
Design: Dual Bowl (Tandem) — Separate Front/Rear Circuits
Piston: Deep Pocket — Manual Brake Pushrod Configuration
Port Threads: 1/2"-20 and 9/16"-18 (Standard Inverted Flare)
Casting Numbers: 29910 / 2225647
Material: Cast Iron
Brake System: Drum/Drum
Includes: Master cylinder with reservoir and cap
Condition: Brand New

Compatible Equipment

The 890870 brake master cylinder fits Clark and Tug ground support equipment with manual drum brake systems:

Tug CT30
Tug CTA40
Tug CT50
Tug MA Series
Clark Baggage Tractors (models using the 890870 / 2226085 master cylinder)

⚠️ Verify Clark/Tug part number 890870 or casting number 29910 / 2225647 on your existing master cylinder before ordering. Contact us with your equipment model and serial number if you're unsure.

Installation Notes

Bench bleed the new master cylinder BEFORE installation — this is critical. Clamp in a vise, install bench bleed fittings, fill with fresh DOT 3 brake fluid, and slowly stroke the piston until no air bubbles appear in the reservoir
Disconnect the battery before working on the brake system
Place rags under the existing master cylinder — brake fluid damages paint and plastic
Disconnect the brake lines from the master cylinder ports — use a flare nut wrench to avoid rounding the fittings
Cap or plug the open brake lines to prevent fluid loss and contamination
Remove the mounting nuts/bolts securing the master cylinder to the firewall
Remove the old master cylinder — note the pushrod alignment
Install the new (bench bled) master cylinder onto the mounting studs
Verify the pushrod seats properly in the deep piston pocket
Install and torque the mounting fasteners
Connect the brake lines to the correct ports — front circuit to front port, rear to rear
Fill the reservoir with fresh DOT 3 brake fluid
Bleed the entire brake system — start at the wheel furthest from the master cylinder
Check all connections for leaks
Pump the brake pedal — it should feel firm and hold steady pressure
Test brakes at low speed on a clear area before returning to ramp operations

Symptoms of a Failing Brake Master Cylinder

Brake pedal slowly sinks to the floor when holding steady pressure
Spongy or soft brake pedal feel
Pedal goes all the way to the floor with little or no braking
Brake fluid leaking from the cylinder body, pushrod boot, or fittings
Low brake fluid level in the reservoir with no visible external leak (internal bypass)
Having to pump the pedal multiple times to build pressure
Brakes pull to one side (one circuit failing)
Contaminated brake fluid — dark, cloudy, or milky appearance

Frequently Asked Questions

How do I know if I have manual or power brakes?
Clark and Tug CT30/CTA40/CT50 baggage tractors use manual brakes — there is no vacuum booster. Look at the firewall behind the brake pedal. If the pushrod from the brake pedal connects directly to the back of the master cylinder with no large round canister (booster) in between, you have manual brakes. This is the standard configuration for these tugs.

What is the "deep piston pocket" and why does it matter?
Manual brake master cylinders have a deeper hole in the primary piston to accept the longer pushrod stroke from the brake pedal (since there is no booster multiplying the force). A power brake master cylinder has a shallow pocket because the booster provides the additional force. Using a power brake master cylinder on a manual brake system will result in improper pushrod engagement — the pedal will feel wrong and braking will be compromised.

Do I need to bleed the brakes after replacement?
Yes — always. Bench bleed the new master cylinder first, then bleed the entire brake system at all four wheel cylinders after installation. Any air trapped in the system will cause a spongy pedal and reduced braking performance.

What type of brake fluid should I use?
DOT 3 brake fluid. Do NOT use DOT 5 (silicone) unless the entire system was designed for it. DOT 3 and DOT 5 are not compatible — mixing them will destroy every rubber seal in the brake system.

How do I verify the casting number?
Look at the side of your existing master cylinder body. The casting number (29910 or 2225647) is typically raised lettering cast into the iron. It may be partially covered by dirt or paint — clean the surface to read it. If you see either number, this is the correct replacement.

Clark / Tug

Equipment Models

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Clark / Tug Parts (1)

890870 Clark Tug Brake Master Cylinder - 1-1/8" Bore - Manual Drum Brakes - CT30 CT40 CT50 MA Series - Replaces 2226085