![]() ![]() The modulator is held by two banjo bolts at the master cylinder’s two upper outlet ports, and two transfer tubes at the two lower outlet ports. The front brakes are controlled separately, but the rear brakes share a common ABS circuit.Īttached to the master cylinder is the hydraulic modulator and motor pack assembly. It has four wheel-speed sensors, but is a three-channel system. The Delco VI system is a nonintegral ABS system with a conventional master brake cylinder and power booster. Introduced in 1991 as an option on Saturn, Buick Skylark, Oldsmobile Cutlass Calais and Pontiac Grand Am models, the Delco ABS-VI anti-lock brake system has been used on a wide range of General Motors front-wheel-drive vehicles, including Chevrolet Lumina and APV, Chevrolet Beretta, Corsica and Cavalier, Pontiac Grand Prix, Sunbird, Oldsmobile Cutlass Supreme and Buick Regal. To better understand what may be required, let’s look at some bleeding procedures for some common General Motors ABS systems. Others do not and require the use of a scan tool to cycle the ABS solenoids while you bleed the system. Some ABS modulators have special bleed screws to help you vent the trapped air when bleeding the system. The modulator may have eight to 10, or more, ABS/traction control solenoid valves, plus various check valves and dead-end ports. The most common bleeding procedure is to bleed the brake furthest from the master cylinder first, then bleed the other brake that shares the same hydraulic circuit (which may be the other rear brake on a rear-wheel drive car or truck, or the opposite front brake on a front-wheel drive car or minivan).Īfter these have been bled, you then bleed the other brake circuit starting with the furthest brake from the master cylinder.Īlways refer to the vehicle manufacturer’s recommended bleeding sequence as this may vary from one application to another depending on how the system is configured.īut what if you replaced the master cylinder, a brake line or valve ahead of the ABS modulator? Or, what if you had to replace the modulator or high pressure accumulator? Now you have a more difficult job ahead of you.Īir can be very difficult to remove from an ABS modulator assembly because of all the nooks and crannies inside the unit. It doesn’t make any difference which method you use as long as all the lines and components are flushed with enough fluid to remove any trapped air bubbles or air pockets. If the only components you replaced were downstream of the modulator (calipers, wheel cylinders, brake hoses or lines), chances are normal bleeding procedures will clear the lines of any unwanted air.īrakes can be bled manually, with a power bleeder, injector tool or vacuum bleeder. Air is compressible, so when the brakes are applied any air bubbles in the system must first be compressed before the hydraulic fluid will transmit pressure to apply the brakes.Īs a rule, the brake circuits on most vehicles with anti-lock brakes can be bled in the usual manner - provided no air has gotten into the ABS modulator assembly. ![]() Air trapped in the lines, calipers or wheel cylinders will make the pedal feel soft and spongy. You can check out all of Classic Performance Products brake system parts and tools right here.Bleeding the brakes after brake components have been replaced is a step you don’t want to skip if you want a firm brake pedal. If you don’t happen to have the syringe you can still use a screwdriver to actuate the piston in the master cylinder to move fluid during the bleeding process. You start the process by filling the master cylinder up with plenty of fluid and then injecting each port. Using the syringe lets you circulate fluid into the chambers much easier and fill the ports up inside the master cylinder. The CPP bleeder tool kit makes the entire master cylinder bleeding process even easier with its tubes, port plugs, tube holders, and syringe. Having the master cylinder level might not seem like a big deal, but it gives you the opportunity to make sure there are no additional bubbles trapped inside. Bench bleeding provides total access to the master cylinder, plus it allows you to make sure the master cylinder is level during the bleeding process. Classic Performance Products put together this neat video that shows how to do it, plus it demonstrates how to use its bleeder tool kit.ĭepending on your vehicle space can be pretty tight where your master cylinder is located and that can make the bleeding process a challenge. ![]() There are a plethora of tools on the market, along with countless tricks out there to make the job easier, and one that some might not know about is bench bleeding a master cylinder. Getting a braking system ready after an upgrade or maintenance isn’t a glamorous process - in fact, it’s downright monotonous and time-consuming.
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