Water Ingress is the No. 1 cause of all ADB warranty claims - and the number 1 cause of ADB warranty rejections.
Even with well established ADB servicing practices, water ingress to the caliper remains an issue for many end-users and most of these cases are due to water ingress through the air chamber.
To understand this fully we recommend that you watch the video below and then read the rest of this article. You can also download an A4 leaflet on water ingress by clicking
here.
As water ingress to the caliper often occurs through the air chamber it makes sense to inspect and check your air chamber when replacing a caliper or carrying out regular service checks.
There are two areas to check: the flange seal on the air chamber (1) and the bungs on the air chamber (2).
1. The most important thing to check is the flange seal visible on the air chamber mounting face. The protruding seal should be at least 3mm proud of the air chamber body and without any damage or nicks. If this seal is damaged, or ineffective, the brake will quickly become permanently damaged through corrosion.
To repeat: the pushrod has to be fully sealed against air chamber so that water is kept out of the brake.
After checking the flange seal, carefully inspect the visible part of the pushrod. If water or rust staining is present on the pushrod, it is a clear sign that the pushrod seal/boot has split or is not seating correctly.
The inside of the boot and the pushrod should look like the image below.
2. As the air chamber has to be open to the atmosphere it is likely that water will be present in the air chamber. Having said this, there are steps you should take to ensure that the amount of dirt and water within the air chamber is kept to a minimum. This is because water in the air chamber can rust the spring, causing damage to the internal boot. If this occurs, water will transfer freely from air chamber to caliper, leading to caliper failure.
Always place bungs in the top breather holes of the air chamber (1) and unblock the lowest breather hole to allow the water to drain out (2). It is the failure to carry out (2) that allows water and corrosion to build within the air chamber (3).
Once you have checked the bungs, examine the pushrod and the inner part of the seal for any damage or evidence of water entry through the boot. It is difficult to see fully inside the boot, but a torch will help. Remember, if the pushrod shows signs of corrosion (after wiping away any grease), boot damage is the likely cause.
Please see below for an example of corrosion within the air chamber, leading to a tear in the boot.
So, what happens if the air chamber seal is damaged or ineffective? The following photographs show the resulting corrosion after brakes have been fitted with an air chamber with a damaged seal.
This brake had a reported fault after less than two weeks service – water entered through the air chamber seal, which created an electrical fault, highlighting the issue as a ‘worn-out pad’ signal in the cab.
More normal is for water to enter the brake and be undiscovered for weeks or months, until brake efficiency reduces, which is then picked up on rolling road inspection or test. This brake is completely beyond repair and had been fitted with an air chamber with a damaged seal.
