SAVE 10% SITEWIDE Click to Apply
Brands Vehicles
Lowest Prices
Free Returns
Online Since 2009

ACDelco 18M66 Brake Master Cylinder

ACDelco 18M66 Brake Master Cylinder Image 1
ACDelco 18M66 Brake Master Cylinder Image 2
ACDelco 18M66 Brake Master Cylinder Image 3
ACDelco 18M66 Brake Master Cylinder Image 4
ACDelco 18M66 Brake Master Cylinder Image 5
ACDelco 18M66 Brake Master Cylinder Image 6
ACDelco 18M66 Brake Master Cylinder Image 7
ACDelco 18M66 Brake Master Cylinder Image 8
ACDelco 18M66 Brake Master Cylinder

ACDelco
Brand:ACDelco
Part Number: 18M66
UPC: 00036666695533
Weight: 9.77 lbs
Condition:New



On Sale:

$56.24

Availability:
12 in Stock
Warehouse: US-4
Quantity:

Product Information

Description:

MASTER CYL (SLP)

ACDelco Professional Brake Master Cylinders use both aluminum and iron castings, making them a high quality replacement for many vehicles on the road today. These master cylinders contain both Ethylene Propylene (EPDM) and Styrene Butadiene (SBR) rubber components to provide superior resistance to heat, corrosion, and leakage. ACDelco Professional Brake Master Cylinders are ready to bench bleed and install right out of the box - no assembly required. These premium aftermarket replacement brake master cylinders are manufactured to meet your expectations for fit, form, and function. ⚠ WARNING: Cancer and Reproductive Harm - https://www.P65Warnings.ca.gov

Features and Benefits:

  • Cast iron and aluminum specifications; no extra stress on the brake boosting mounting
  • Geometrical tolerance ensures that the body and plastic reservoir match for a proper fit
  • Meets the brake performance requirements of SAE J1153 and J1154 testing, providing reliability and quality
  • Piston assembly and return spring help to prevent brake drag, which can cause premature brake pad wear
  • Pressure tested to ensure safe and confident braking

Specifications:

Bleeder Hoses Included:
Yes
Bore Size:
1.125 in.
Brake Booster Included:
No
Height (in):
4.8 in
Length (in):
9.4 in
Master Cylinder Bore Diameter:
1.125 in.
Master Cylinder Bore Diameter:
28.575 mm
Master Cylinder Cap Included:
Yes
Master Cylinder Material:
Iron
Mounting Bracket Included:
No
Mounting Hole Diameter:
0.423 in.
Mounting Hole Quantity:
2
Port Quantity:
2
Primary Outlet Thread Diameter:
0.5625 in.
Primary Outlet Thread Diameter:
14.287 mm
Programming Required:
No
Push Rod Included:
No
Reservoir Included:
Yes
Secondary Outlet Thread Diameter:
0.5 in.
Secondary Outlet Thread Diameter:
12.7 mm
Weight (lb):
9.77 lb
Width (in):
5.8 in

Features and Benefits:

  • – Calipers and wheel cylinders should be checked every brake inspection and serviced or replaced as required.
  • – Check brake fluid level at every oil change. Replace fluid according to owner's manual recommendations.
  • – Check the thickness of your brake pads.
  • – Inspect the brake lines for rust, punctures, or visible leaks (You may be able to do this, but consult a qualified technician if necessary).
  • – Inspection of brake lining and pads for wear or contamination by brake fluid or grease.
  • – Inspection of the brake hoses for brittleness or cracking.
  • – Inspection of wheel bearings and grease seals.
  • – Parking brake adjustments (as needed).
  • The following inspections and maintenance procedures can help prevent potential brake problems:
  • The following should be conducted by a qualified technician:

Specifications:

Country of Origin:
US

Select a vehicle to narrow ACDelco 18M66 Brake Master Cylinder fitment info!

Last Updated: 03/09/2024

Years Vehicle Per Vehicle Fit NotesFitment Notes
Cadillac Calais

8.2L V8 Gas OHV
1
 
Professional
 

Cadillac Calais



8.2L V8 Gas OHV Professional

1 Per Vehicle
Cadillac DeVille

8.2L V8 Gas OHV
1
 
Professional
2 Doors
 

Cadillac DeVille



8.2L V8 Gas OHV Professional
2 Doors

1 Per Vehicle
Cadillac DeVille

8.2L V8 Gas OHV
1
 
Professional
4 Doors
 

Cadillac DeVille



8.2L V8 Gas OHV Professional
4 Doors

1 Per Vehicle
Cadillac Fleetwood

8.2L V8 Gas OHV
1
 
Professional
Except Commercial Chassis
 

Cadillac Fleetwood



8.2L V8 Gas OHV Professional
Except Commercial Chassis

1 Per Vehicle
Chevrolet C10 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
 

Chevrolet C10 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional

1 Per Vehicle
Chevrolet C10 Suburban

5.0L V8 Gas OHV
1
 
Professional
 

Chevrolet C10 Suburban



5.0L V8 Gas OHV Professional

1 Per Vehicle
Chevrolet C10 Suburban

5.7L V8 Diesel OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
Power Brakes
 

Chevrolet C10 Suburban



5.7L V8 Diesel OHV Professional
Reservoir Cap Is Round In Front and Back
Power Brakes

1 Per Vehicle
Chevrolet C10 Suburban

5.0L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
Power Brakes
 

Chevrolet C10 Suburban



5.0L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back
Power Brakes

1 Per Vehicle
Chevrolet C10 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
Power Brakes
 

Chevrolet C10 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back
Power Brakes

1 Per Vehicle
Chevrolet C20

4.8L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet C20



4.8L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet C20

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet C20



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet C20

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet C20



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet C20

4.8L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet C20



4.8L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet C20 Suburban

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet C20 Suburban



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet C20 Suburban

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet C20 Suburban



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K10 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV
1
 
Professional
 

Chevrolet K10 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV Professional

1 Per Vehicle
Chevrolet K10 Suburban

5.0L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
 

Chevrolet K10 Suburban



5.0L V8 Gas OHV,
6.6L V8 Gas OHV Professional

1 Per Vehicle
Chevrolet K10 Suburban

5.0L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
 

Chevrolet K10 Suburban



5.0L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back

1 Per Vehicle
Chevrolet K10 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
 

Chevrolet K10 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back

1 Per Vehicle
Chevrolet K20

4.1L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20



4.1L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K20

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K20

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K20

7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20



7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K20

4.1L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20



4.1L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K20 Suburban

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20 Suburban



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet K20 Suburban

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

Chevrolet K20 Suburban



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
Chevrolet P20

4.8L L6 Gas OHV,
5.7L V8 Gas OHV
1
 
Professional
w/ 11 Rear Brakes
 

Chevrolet P20



4.8L L6 Gas OHV,
5.7L V8 Gas OHV Professional
w/ 11 Rear Brakes

1 Per Vehicle
Chevrolet P20

7.4L V8 Gas OHV
1
 
Professional
w/ 11 Rear Brakes
 

Chevrolet P20



7.4L V8 Gas OHV Professional
w/ 11 Rear Brakes

1 Per Vehicle
Chevrolet P20

7.4L V8 Gas OHV
1
 
Professional
w/ 11 Rear Brakes
 

Chevrolet P20



7.4L V8 Gas OHV Professional
w/ 11 Rear Brakes

1 Per Vehicle
GMC C15 Suburban

5.7L V8 Diesel OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
Power Brakes
 

GMC C15 Suburban



5.7L V8 Diesel OHV Professional
Reservoir Cap Is Round In Front and Back
Power Brakes

1 Per Vehicle
GMC C15 Suburban

5.0L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
Power Brakes
 

GMC C15 Suburban



5.0L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back
Power Brakes

1 Per Vehicle
GMC C15 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
Power Brakes
 

GMC C15 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back
Power Brakes

1 Per Vehicle
GMC C1500 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
 

GMC C1500 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional

1 Per Vehicle
GMC C1500 Suburban

5.0L V8 Gas OHV
1
 
Professional
 

GMC C1500 Suburban



5.0L V8 Gas OHV Professional

1 Per Vehicle
GMC C25

4.1L L6 Gas OHV,
5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C25



4.1L L6 Gas OHV,
5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C25

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C25



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C25 Suburban

6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C25 Suburban



6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C25 Suburban

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C25 Suburban



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C25 Suburban

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C25 Suburban



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C2500

4.8L L6 Gas OHV,
5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C2500



4.8L L6 Gas OHV,
5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C2500

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C2500



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C2500

6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C2500



6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C2500 Suburban

5.7L V8 Diesel OHV,
6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C2500 Suburban



5.7L V8 Diesel OHV,
6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC C2500 Suburban

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC C2500 Suburban



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K15 Suburban

5.0L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
 

GMC K15 Suburban



5.0L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back

1 Per Vehicle
GMC K15 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
Reservoir Cap Is Round In Front and Back
 

GMC K15 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
Reservoir Cap Is Round In Front and Back

1 Per Vehicle
GMC K1500 Suburban

4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
 

GMC K1500 Suburban



4.1L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional

1 Per Vehicle
GMC K1500 Suburban

5.0L V8 Gas OHV
1
 
Professional
 

GMC K1500 Suburban



5.0L V8 Gas OHV Professional

1 Per Vehicle
GMC K25

4.1L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25



4.1L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K25

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K25

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV,
7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K25

4.1L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25



4.1L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K25 Suburban

5.0L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25 Suburban



5.0L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K25 Suburban

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25 Suburban



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K25 Suburban

7.4L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K25 Suburban



7.4L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K2500

4.1L L6 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K2500



4.1L L6 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K2500

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K2500



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC K2500 Suburban

4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC K2500 Suburban



4.8L L6 Gas OHV,
5.7L V8 Gas OHV,
6.6L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC P25

4.8L L6 Gas OHV,
5.7L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC P25



4.8L L6 Gas OHV,
5.7L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle
GMC P2500

4.8L L6 Gas OHV,
5.7L V8 Gas OHV
1
 
Professional
with 11 IN Brakes
 

GMC P2500



4.8L L6 Gas OHV,
5.7L V8 Gas OHV Professional
with 11 IN Brakes

1 Per Vehicle