The real problem with DAF truck air processing units

Over the last two years we have seen a considerable increase in warranty claims in respect of Air Processing Units or Air Drying Units fitted to DAF trucks in the UK. Most of these claims appear to be in regards to the larger DAFs, namely the CF85 and XF95; however, any DAF truck equipped with these air processing units appears to be eligible for a claim. Most of the warranty claims brought to us have been denied due to serious contamination i.e. air compressor oil deposits which is the main cause of failure in these units. In an attempt to combat this problem, the vehicle manufacturer has recommended that the air dryer unit be relocated along with other modifications, depending on the vehicle model, to accommodate a larger air dryer filter. The old filter part number is 1391510 and should be replaced with 1681575. This filter not only reduces moisture entering the air system, it also filters out any oil vapor, reducing contamination. In my opinion, this is impractical, costly to the vehicle owner, and does not address the real problem, which ultimately lies with the air compressor.

There will always be some oil vapor, however excess oil will still pass through, especially when operators do not change filters regularly enough. When a DAF truck requires a replacement air processing unit, the main dealer or parts supplier must request that the old unit be returned and inspected for excessive contamination; however, this might be considered acceptable if the unit has been in service for several years. and that any carbon buildup had been slowly progressive. The air dryer muffler is usually a good indicator if there is excess oil going into the air system; a light matte-looking dust layer is considered normal, while thick, shiny deposits are considered abnormal. It is also worth noting that whenever we supplied the air dryer and air compressor together, no subsequent problems were experienced. Other operators have accepted that their DAFs have quirks, this being one, and that if air dryer filters are changed regularly, problems rarely occur.

All parts suppliers are required to notify Customers of the potential problems of failing to ensure that the Air Compressor is in satisfactory condition and that all supply lines to the Air Dryer are clean and unobstructed. This also covers the Supplier in the event of a future warranty claim. Unfortunately, the cost of replacing the air compressor and air dryer is such that many operators will choose to ignore the cause (air compressor) and replace the problem (air dryer) and while a temporary solution is achieved, it is just a matter of of time. before the replaced unit is causing problems and the warranty process begins.

Therefore the questions are:

Is it a poorly designed drive in the first place?

Does the Operator carry out the necessary checks and regular maintenance?

Are the air tanks drained regularly?

Are vehicle manufacturers and air brake manufacturers singing from the same sheet music or is there a difference of opinion?