MERCEDES-BENZ A0044205783 CYLINDER ASSY, DISC
Product Specifications
Product quality
OEM Equivalent Grade
20 sold
Wholesale price USD
$20.84
Wholesale price CNY
¥141.6
bolt MOQ (Minimal order)
20 pcs
local_shipping Production time
32 days
package_2 Shipping Weight:
5.1 kg
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Application (cross references) 4
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| MERCEDES-BENZ | A0044205783 |
| MERCEDES-BENZ | A0034208783 |
| MERCEDES-BENZ | 0044205783 |
| MERCEDES-BENZ | 0034208783 |
Overview & Operating Principle
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The CYLINDER ASSY, DISC is the hydraulic disc brake caliper assembly that converts brake line hydraulic pressure into the mechanical clamping force that squeezes the brake pads against both faces of the rotating brake disc, generating the friction force that decelerates the vehicle. The assembly consists of a cast iron or aluminium alloy caliper body containing one or more hydraulic cylinders bored to a precise diameter, hydraulic pistons that advance under fluid pressure to push the inner brake pad against the disc face, piston seals that both seal the hydraulic circuit and provide a rollback function that retracts the piston by a calibrated distance when pressure is released to maintain the designed running clearance between pad and disc, dust boots that exclude road contamination from the piston-to-bore interface, and on floating single-piston designs, a carrier bracket with slide pins that allow the caliper body to float laterally so the outer pad is pulled against the disc by the reaction force when the piston pushes the inner pad. On rear calipers incorporating an integrated electric parking brake the assembly additionally includes a DC motor, reduction gear train, and screw-and-nut mechanism that winds the piston against the brake pads independently of the hydraulic circuit to apply and release the parking brake on command from the EPB switch or automatic hold system.
This unit — MERCEDES-BENZ A0044205783 — is manufactured to OEM-equivalent specifications: cylinder bore diameter and surface finish, piston diameter and material, caliper body mounting bolt pattern and anchor bracket geometry, hydraulic inlet port thread size and position, bleed nipple thread, slide pin bore diameter and pin length, and on EPB calipers, motor voltage and gear reduction ratio are matched to the original part. Supplied as a complete assembly ready for installation. Available wholesale from 20.84 USD, MOQ 20 pcs, production lead time 32 days.
Disc brake calipers are replaced when the cylinder bore is scored or pitted beyond the serviceable limit for seal kit repair, when the caliper body casting is cracked from overheating or impact, when the EPB motor or gear train has failed internally, when severe corrosion has seized the slide pins beyond recovery, or when a seal kit overhaul has been attempted and the caliper continues to leak or drag. A caliper that has been overheated — identified by discoloration of the body casting, boiled brake fluid in the circuit, or thermally degraded pad material — should be replaced regardless of apparent bore condition as heat distortion of the bore geometry is not visible without precision measurement.
Symptoms & Diagnostics
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Brake fluid leak at the caliper body — wet staining around the piston face or dust boot that cannot be resolved by seal kit replacement — the bore wall has corrosion pitting that prevents any seal from maintaining hydraulic integrity; the bore can be inspected by removing the piston and examining the bore wall with a light; visible pitting deeper than 0.1 mm requires caliper replacement.
Brake drag at one corner causing the wheel to run hot and the vehicle to pull under braking — a seized piston that does not retract after brake release due to bore corrosion from water ingress through a torn dust boot, or seized slide pins that prevent the caliper from floating off the disc; confirm drag by loosening the bleed nipple — if the drag reduces immediately, the piston is hydraulically seized; if it does not, the slide pins are mechanically seized.
Severely uneven pad wear — one side of the axle consuming pads significantly faster than the other, or the inner pad on one caliper worn to backing plate while the outer pad shows minimal wear — a seized slide pin is holding the caliper body offset from its design position, causing all braking force to be applied by the piston-side pad while the floating side pad makes minimal disc contact.
EPB warning light with fault codes indicating rear caliper motor circuit fault or actuator travel out of range — the EPB motor winding has failed, the motor gear train has stripped, or the actuator has reached its travel limit from a seized screw-and-nut mechanism; diagnose with a manufacturer-specific scan tool that can command individual rear caliper EPB actuation and measure motor current draw.
Cracked or visibly distorted caliper body casting detected on inspection — thermal cracking from sustained brake drag overheating or physical impact damage; any visible crack in a safety-critical hydraulic component requires immediate replacement; a cracked caliper body will fail under brake line pressure without warning.
Soft or spongy brake pedal combined with confirmed fluid loss at the caliper — the piston seal is bypassing hydraulic fluid past the piston into the caliper bore cavity; the pedal firmness is reduced proportionally to the volume of fluid being lost through the bypass path on each pedal application; this fault requires immediate attention as continued driving reduces braking capacity at the affected corner progressively.
Logistics & Customs
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International HS Code
8708.30
EAEU Customs Code (TN VED)
8708 30 910 0
Typical Net Weight
5.1 kg
Country of Manufacture
China
Standard MOQ
20 pcs
Production Lead Time
32 days
Always verify the exact 8-digit or 10-digit subheading with your customs broker for the destination country, as tariff schedules and duty rates vary by jurisdiction.
Installation Tips
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- Open the bleed nipple before retracting the piston when removing the old caliper — pushing the piston back against a closed hydraulic circuit forces contaminated old fluid through the ABS modulator solenoid valves, dislodging valve seat deposits and potentially blocking the modulator; always open the nipple slightly and collect the displaced fluid in a container before compressing the piston; on rear EPB calipers use the vehicle's scan tool EPB service mode to retract the piston electrically rather than using a wind-back tool without first activating the service mode.
- Clean the anchor bracket slide pin bores and the caliper mounting face thoroughly before fitting the new caliper — apply a wire brush to the slide pin bores to remove all corrosion deposits and old grease; the new caliper's slide pins must move freely through their full travel without sticking; apply a thin film of the correct caliper slide pin lubricant — copper-free, brake fluid compatible — to the cleaned pin bores and the full length of each slide pin before assembly.
- Confirm the new caliper's hydraulic inlet port thread is compatible with the existing brake line fitting before installation — replacement calipers occasionally have different thread standards from the original depending on the supply source; compare the port thread to the brake line fitting before connecting; forcing an incompatible fitting into a mismatched port cross-threads the hydraulic connection and creates a brake fluid leak under pressure that is extremely difficult to repair without caliper removal.
- Torque the caliper mounting bolts and hydraulic line fitting to OEM specification using a torque wrench — caliper mounting bolts on modern vehicles are often single-use stretch bolts that must be replaced rather than reused; check the OEM specification before refitting old bolts; the hydraulic line fitting must be torqued correctly — undertorquing produces an immediate fluid leak, overtorquing rounds the fitting hex and cracks the line end.
- On rear EPB calipers, perform the EPB service mode piston extension procedure via scan tool before fitting the brake pads — the new caliper's piston must be extended to the correct service position before pads are installed; fitting pads with the piston in the fully retracted factory position prevents correct pad-to-disc clearance and requires a repeat EPB service mode activation after installation; follow the vehicle-specific EPB service procedure precisely.
- Install the new CYLINDER ASSY, DISC (MERCEDES-BENZ A0044205783), connect the brake line, bleed the circuit at the new caliper until no air bubbles are present at the bleed nipple, pump the pedal to seat the pads against the disc, confirm pedal height and firmness meet specification, on EPB rear calipers perform the EPB application and release test via scan tool, inspect for fluid leaks under firm pedal pressure, and complete a brake bed-in procedure before returning the vehicle to service.
Tools: OBD-II scanner with EPB service mode for rear EPB calipers, torque wrench, brake bleed kit, wire brush for slide pin bores, caliper slide pin lubricant, new caliper mounting bolts where stretch-bolt type, brake fluid for topping up reservoir.
Frequently Asked Questions
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Should both calipers on the same axle always be replaced simultaneously when one has failed?
Replacing both calipers on the same axle simultaneously is recommended when the failure is caused by bore corrosion, age-related seal failure, or general high-mileage degradation — conditions that affect both calipers equally. A new caliper paired with a worn or dragging caliper on the opposite side creates a brake force imbalance that causes the vehicle to pull under braking. On vehicles above 150,000 km where one caliper has failed from general wear, inspect the opposite caliper's bore condition and slide pin freedom — if the opposite caliper shows similar degradation, replacing both simultaneously eliminates an identical repair within a short interval. ok.parts supplies calipers individually and in axle pairs at wholesale MOQ from 20.84 USD per unit.
Is EPB system adaptation or coding required after replacing a rear caliper with an integrated electric parking brake?
Yes, an EPB service mode procedure is mandatory after any rear EPB caliper replacement. The EPB control module must perform a caliper calibration sequence that extends the new caliper's piston to establish its current position reference, then retracts it to the rest position — without this sequence the module does not know the piston's travel range and applies incorrect force on the next parking brake application. Additionally, on vehicles with automatic hold and hill start assist that use the EPB calipers, a system reset via scan tool is required to re-enable these functions after the caliper fault code is cleared. Always perform the full EPB service mode procedure and confirm the parking brake holds the vehicle on a gradient before returning it to service.
How does the OEM-equivalent aftermarket unit compare to the genuine OEM part?
OEM-equivalent units in this catalogue replicate the current OEM design geometry and material specification. Quality is verified against OEM cross-reference data. When ordering in bulk, confirm with our team that the specification matches the latest OEM revision for your application.
Is white-label or custom packaging available for wholesale orders?
Yes. ok.parts works directly with the manufacturing facility and can accommodate neutral white-label packaging or fully branded packaging with your company logo, part numbers, and barcode. Minimum order quantities and lead times for custom packaging may differ from standard stock. Contact the team via the inquiry form to discuss your specific requirements.
Frequently Replaced Together
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| Part | Reason for Combined Replacement |
|---|---|
| Brake Pads Axle set, OEM ref. varies | Caliper replacement requires retracting the piston fully and removing the existing pads — this is the mandatory time to inspect pad thickness and replace the pads if they are at or near minimum thickness. Installing a new caliper with worn pads means the piston will advance significantly from new to worn, stressing the new piston seal more than necessary and requiring a repeat piston retraction and pad replacement within a short service interval. |
| Brake Disc OEM ref. varies by axle position | A caliper that has been dragging or leaking will have subjected the brake disc to abnormal thermal and mechanical loading — overheating causing hard spots and thickness variation, or uneven pad transfer from asymmetric clamping. Measure the disc for runout and minimum thickness before refitting; a disc that is outside specification will cause brake judder and uneven wear on the new caliper's pads within a short period and should be replaced simultaneously. |
| Brake Fluid DOT 4 or DOT 5.1 per OEM specification | Caliper replacement requires opening the brake hydraulic circuit and bleeding the new caliper, making this the correct time to renew the brake fluid if it is overdue. Moisture-saturated fluid with reduced wet boiling point promotes corrosion of the new caliper's bore and piston and increases the risk of vapour lock under heavy braking conditions. Always refill with fresh brake fluid of the correct specification when replacing a caliper to protect the new unit and restore full circuit boiling point margin. |