Troubleshooting

What's the Correct Order?

Dear Roy,
After repairing a leaking right rear brake line on a 1992 Buick LeSabre Custom (VIN 1G4HP53L8NH543523) with a 3800 engine and a 4T60E transmission, I bled the master cylinder because it was empty. Then I bled all four wheels. 

Now I'm getting air from the right front, and when road testing, I can tell the front brakes are barely operating at all. When the car is on the lift, the left front stops but not the right. The caliper seems to move OK, so I bled them in order according to Mitchell: right rear (RR), left rear (LR), right front (RF), left front (LF). 

Is this correct, or should it be RR, LF, LR, RF? Any help would be greatly appreciated.

Thank you,
Bill Reichert, Service Op. Manager
Knoll's Mobil Sheridan, Tonawanda, NY

Dear Mr. Reichert,
The factory-recommended bleeding sequence for this vehicle is RR, LR, RF and LF. 

From your description, it appears that we have a loss of pressure to the right front wheel. This loss of pressure could originate anywhere from the hydraulic control assembly to the RF caliper. 

Loosen the line at the hydraulic control that goes to the right front. Have someone hit the brakes and check pressure. If pressure is good here, I suspect that you have a defective hose or caliper seal on the right front of this vehicle. 

If pressure is lacking at the control assembly, try this little trick before replacing the assembly: With the key on and engine off, locate the ABS control module. Take a grounded test lamp and tap on the brown/white wire while someone holds the brake pedal down. Repeat this process with the black/pink wire. 

In many cases, this will free up valves that may become stuck from foreign material entering the system.STUMPED?Let Roy take a crack at your problem. Our "Troubleshooting" column is for automotive service professionals. If you have a particularly perplexing problem in your bay, Contributing Editor Roy Ripple may be able to help. We need to know the vehicle year, make, model, engine, transmission, accessories and VIN. Include your name, address and phone number so we can contact you. To send an electronic message to Roy,click here.