Water Ingress

water ingress

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.

Air Chamber pushrod web

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). If necessary use a 6mm drill bit to clear the hole. If, on clearing the hole, a lot of water drains out then we would recommend replacing the air chamber.

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.

Prevent Water Ingress Fig 3 web

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.

Prevent Water Ingress Fig 2 web

End Caps

end caps

Calipers not sliding?

Open guide sleeves are a compromised design feature. They let water in; causing sliding issues and rust jacking, which leads to unnecessary workshop maintenance and service costs.

That is why we invented our patented fully sealed short guide sleeve system. All MEI calipers for Knorr-Bremse applications now have 100% closed guide sleeves.

However, badly fitted end caps are still our No. 2 field service issue.

Sometimes it is obvious to spot badly fitted end caps:

end cap badly fitted Endcap dent 2

But not always. Below we see what happens when the end cap is inserted correctly (left) and incorrectly (right).

endcap crash

If the end cap is then levelled up (see image on the right), the end cap can appear to be fitted correctly but can still allow water to enter. endcap level leak

Remember:

Always take care when fitting end caps.
Where possible use our service tools.
Follow the instructions and videos that can be found on our website - details are below.

The easiest and safest way to fit end caps is to use MEI's End Cap Tool Kit - 5K0020 - and our End Cap Pack - 5R0505.

To fit the Long Guide Sleeve you will require: Tools M21 &M22, a copper head hammer and the 14mm cap

To fit the Short Guide Sleeve you will require: Tools M21 & M23, a copper head hammer and the 24mm cap

Long Guide Sleeve

Fitting the protective cap(s) can only be done after the caliper has been fully bolted to the carrier. The guide sleeve boot(s) must be in a compressed condition or the caliper’s freedom of movement will be limited.

Locate the 14mm protective cap for the long guide sleeve into the caliper bore - the protective cap and bore must be clean and free from lubrication. Press the protective cap into the bore ensuring it is seated squarely until the cap protrudes 0 to 2 mm from the cast boss.

end cap long

For Video Instructions please see below -

Short Guide Sleeve

Locate the 24mm protective cap for the short guide sleeve (where applicable) into the caliper bore - the protective cap and bore must be clean and free from lubrication. Press the protective cap into the bore ensuring it is seated squarely until the cap protrudes 15 to 16mm from the cast boss.

end cap short