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GMC Brake Questions

Why do GMC brakes become spongy? Why do GMC brakes fail? Are aftermarket GMC brake parts safe? When should GMC brake pads be replaced? GMC vehicle owners often do not know where to find reliable answers to these and other questions on brake systems. The best thing they can do is to get answers from Experts.

Read below where Experts have answered questions regarding GMC brakes and the issues that can arise.

What would cause the brakes on a 2007 GMC Acadia to only work if the pedal is pumped, after all the brake pads were changed?

First, check to ensure all brake pads are correctly seated and not at an angle. Improper seating will prevent the caliper from expanding fully and cause the soft pedal feel. If the pads are okay, the next thing is to do a gravity bleed to ensure that all air has been removed from the brake system. Start at the right rear wheel, then the left rear, the right front and the left front. Remove the master cylinder reservoir cap and open the bleeder at the wheel. Allow the gravity bleed to continue for about 5 minutes, while keeping an eye on the level of fluid in the master cylinder. Top up as needed to prevent the cylinder from going dry. Close the bleeder and repeat the procedure for each wheel. Test the brake pedal. If it is still soft, use vise grips to gently clamp off each brake hose at the wheel. Test the pedal again. If it is now firm, remove the clamps one at a time to see which clamp removal causes the pedal to go soft. . That wheel has either a collapsed hose or a bad caliper. If the pedal is still soft with all the hoses clamped, then either the master cylinder has failed or there is air in the ABS unit which will require the use of a scan tool so that computer bleeding can be done. Open the under hood fuse panel and check the fuse marked STOP/HAZ. If that is okay then the problem is most likely in the brake light switch on the brake pedal which will need to be replaced.

Will the brakes on a 2004 GMC Yukon cause the “Brake Booster” warning light to come on?

If the message that is being seen is “Brake Booster” and not “Service Brake Booster” it indicates a firmware issue in the instrument panel cluster. If the brakes feel and function as normal, then it is unlikely that there is a problem with them. The firmware in the panel will need to be updated. Any shop that can do GM programming will be able to do this and the cost should be in the range of $40 to $50.

What is causing the brake pedal on a 2001 GMC Yukon to feel spongy even after a master cylinder replacement and bleeding that was done exactly per the specs?

If the bleeding was done correctly, then a common cause of this problem on GMC brake systems is the brake calipers. If the side pins are seized, the caliper pistons are given too much play. When this happens the brake master needs to travel further to compress the piston in the caliper. Remove the pins (the outside ones on the picture that can be seen by clicking here), clean them completely and lubricate them with silicone based lube. This should remove the spongy feel. Check to see if the pads are able to slide free in the caliper bracket. Sticking pads can also cause this problem.

What will cause the brake pedal to go to the floor intermittently with a slight vibration on a 2001 Sierra and no warning lights appear?

With the pedal going to the floor and the slight vibration point to the ABS motor momentarily going off is typically when there is a disagreement in the wheel speeds of the two front wheels. The ABS thinks one of the wheels is slipping and cycles the unit. No warning lights will appear under these conditions. Normally when one of the wheel speed sensors signal drops it should result in a stored history code - this is different from a current code and a code scan will reveal which wheel is the problem. Typically the problem arises due to rust developing between the wheel speed sensor and the wheel bearing assembly. GM advises that the area be cleaned and the rust removed to solve the problem. However, it is likely that the condition will occur again in a year or so. Replacing the hub assembly will offer a long term solution as it comes with a new sensor.

Everyone knows that driving with defective brakes is very dangerous. GMC brakes are generally very reliable but when problems arise, they should be attended to immediately. Finding the right GMC brake repair solutions and parts can often be difficult and time consuming. Getting the help and insights of Experts will allow the driver to make the right decisions.
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