09/02/2026
2 Inch Master Cylinder for Bosch Hydro-Max® Brake System, Remote Reservoir w/ Differential Pressure Switch (2.00" / 50.80 mm)
By the Sweeting Performance Team
When you're running four-wheel disc brakes on a heavy commercial chassis, a 2.00" bore master cylinder is necessary to push enough fluid volume for those larger multi-piston calipers. But on many specialized builds, tight overhead clearance or frame-mounting makes an attached reservoir impossible to reach or fit.
This version solves the packaging problem with a remote-reservoir adapter while adding an integrated differential pressure switch. That switch wires directly into your vehicle's dash warning system to alert you immediately if either the primary or secondary brake circuit experiences a pressure loss.
Sweeting Performance Part Number: HMMC200RRDS
Product Link: https://www.powerbrakeservice.net/hymacywirere.html
Specifications:
* Bore Diameter: 2.00" (50.80 mm)
* Fluid Compatibility: DOT 3 Brake Fluid
* Reservoir: Remote
* Differential Pressure Switch: Yes
* Primary Line Port: 9/16"-18 Inverted Flare
* Secondary Line Port: 1/2"-20 Inverted Flare
* Material: Iron, Steel, Aluminum, Rubber
What the Differential Pressure Switch Does
Inside dual-circuit master cylinders, the primary and secondary braking sections operate independently. If a brake line fails, a hose bursts, or a caliper seal leaks, hydraulic pressure drops on that side. The differential pressure switch senses the pressure imbalance between the two circuits and immediately trips the brake warning light on your dash—giving drivers an early alert that they are now only braking with their front or only braking with their rear brakes.
Why Use a Remote Reservoir?
It comes down to two practical shop issues: clearance and maintenance access.
1. Zero Overhead Clearance: Cab-over trucks, frame-mounted boosters beneath floorboards, and 90-degree reverse-linkage pedal boxes rarely have enough vertical room for a top-mounted reservoir.
2. Easy Maintenance Access: Checking brake fluid shouldn't require pulling floor plates or crawling under the truck. With a remote setup, the master cylinder stays tucked away on the frame, while the reservoir mounts high on the firewall or bulkhead for quick, clean checks and top-offs.
How the Remote Adapter Connects
* Adapter Plate: A low-profile adapter plate mounts to the top of the master cylinder body.
* Remote Reservoir: A dual-chamber reservoir mounts vertically in an accessible spot (usually the firewall).
* Supply Hoses: Two hoses connect the reservoir outlets to the adapter plate inlets to keep both circuits gravity-fed.
A Quick Reminder on Fluids
The Hydro-Max® booster and the master cylinder bolt together, but their fluid circuits are separate:
* Hydro-Max® Booster: Uses power steering fluid (or manufacturer recommend transmission fluid) from your engine's power steering pump.
* Master Cylinder & Reservoir Supply Lines: Uses standard DOT 3 brake fluid.
Never use petroleum-based fluids in the master cylinder or reservoir supply lines, as petroleum will cause the rubber to swell and fail rapidly.
Dealing with "Obsolete" Dealer Part Numbers
Because 2.00" remote master cylinders with pressure switches are used on everything from delivery vans and step vans to school buses, motorhomes, mining machinery, and airport ground support equipment (GSE), there are dozens of OEM part numbers for what is fundamentally the same core Bosch cylinder.
When dealers update their catalogs, older numbers often get flagged as "Obsolete" or "No Longer Available." The good news is that the core Bosch Hydro-Max® master cylinder is still actively put together and available through Sweeting Performance.
Common Applications:
* Frame-mounted Hydro-Max® brake setups with brake warning light circuits
* Mining and Heavy Industrial Equipment
* Cab-over trucks, step vans, and delivery vehicles
* Motorhomes and RV chassis
* Commercial buses and shuttle chassis
* Airport Ground Support Equipment (GSE) and tow tractors
* Medium-duty vehicles using 9/16"-18 primary and 1/2"-20 secondary hard lines with limited overhead space
Need Help Identifying Your Setup?
Power Brake Service and Sweeting Performance have been re-engineering, rebuilding, and supplying commercial hydraulic brake systems since 1950. Across three generations, we've handled pretty much every Hydro-Max® setup out there.
If you aren't sure if you need this 2.00" remote-reservoir unit with the differential pressure switch:
1. Check your VIN, vehicle details, and look for raised casting numbers on the cylinder body as genuine Bosch units will have the bore size cast onto the side.
2. Check the thread sizes on your hard lines (9/16"-18 and 1/2"-20) and confirm if your harness plugs into a pressure switch between the ports.
3. Send photos of your master cylinder, mounting location, and hose routing to our tech team.
Ordering & Tech Support
* Product Link: https://www.powerbrakeservice.net/hymacywirere.html
* Phone: (714) 330-5286
* Tech Email: [email protected]
* Website: www.powerbrakeservice.net