VW Golf MK2 Heater Matrix Recall - Bypass Valve Failure

When I owned my previous MK2 Golf back in 1998 I received a letter from VW inviting me to bring the car in for some recall work to fix a problem with the heater matrix.

Roll the clock forward 16 years and I now have a problem with my current MK2 Golf where the heater is not giving out any hot air. It appears that it is now a common fault on MK2 Golfs that the fix applies for the recall back in the late 1990s is now failing and stopping the heater from warming up!

VW Golf MK2 Heater Matrix Recall - Bypass Valve Failure

The problem that caused the recall notice for VW Golf MK2 cars was that the heater matrix could fail and spill hot water into the car. Amazingly this only became apparent some 10-15 years after the cars were made, probably a testament to how well they were engineered. My car was 13 years old at the time of the recall notice.

The fix from the recall was to fit 2 bypass valves on the pipes that feed the heater matrix so in the event of pressure build up the coolant would divert avoiding the heater matrix. The bypass valves can clog over time which stops any coolant reaching the heater matrix.

The bypass valves are at the rear of the engine bay where the pipes enter the cabin through the bulkhead. One solution is to remove the bypass valves and replace them with sections of 22mm copper pipe which then allows the coolant to pass into the heater matrix and warm the car. If doing this it is also advisable to replace the heater matrix with a Golf Mk3 version which doesn't have the same tendency to burst as the Mk2 version.

Before starting to remove the bypass valves I decided to drain down the coolant from the system. This can be done by removing the bottom radiator hose to allow the coolant to drain out.

Once the valves are replaced I intend to swap the matrix for a Mk3 version too