Bleed The ABS Module
Let's Get Technical
For Everyone
Updated:
It's quite possible that bleeding the brakes normally will not remove air stuck inside the ABS module, so what you need to do to purge air from the ABS module is to make the pump work it out for you. The activation of the ABS pump will force trapped air down into the brake lines, where it can be bled out.
There are two main ways to actuate the ABS pump. The first is the manual way, which requires loose ground and plenty of it, and the second is the automatic way, which requires a diagnostic tool capable of actuating (not all of them can).
The Manual Way
Assuming that you have bled your brakes and they can be somewhat relied upon (please check before proceeding), the manual method requires you to take the van to a place with a fair amount of loose ground (gravel, mud, etc.). You will need to gather some speed and then slam on the brakes, and I do mean hard. This will cause the ABS to kick in. That's when you will hear and feel a strong vibration in the brake pedal and all the teabags will fall off the shelf.
If there is air in the ABS unit, you will probably notice that the brake pedal has gone right to the floor during this exercise. Pump it a few times to get the pressure back and repeat. When you've done this five or six times, you will need to go and bleed the brakes again.
This entire process, including brake bleeding, may need to be repeated several times in order to fully purge the air from the ABS unit. Each time you do it, you should notice that your brake pedal is firmer and travels less. Once your brakes feel normal, you can stop humming the A-Team theme tune.
The Automatic Way
If you are able to get your hands on a diagnostic computer that can actuate the ABS pump, you will find this option very simple. Just plug the computer into the OBD2 socket under the steering wheel and follow the on-screen instructions. You may find this process easier with an assistant, but it can be done alone.
The ABS pump will actuate for a period of a minute or more and you will probably find all your worries resolved after the process. If not, you can always run it again.
Once the ABS module is free of air, just remember to top up the brake fluid and that's another job in the bag.