A few months ago a customer bought their Skoda Octavia to our workshop with a heater problem, it wasn’t getting as hot as it once did. We ran a diagnosis of the heater system, starting with a check of the electrical components using our V.A.G ODIS computer. This didn’t show up any faults with the sensors or actuators associated with the heater. Next, we checked the cooling system of the vehicle to ensure it was providing enough heat to warm the inside of the vehicle. As soon is we removed the cap from the coolant bottle we could see a problem, something had contaminated the coolant. There were dark-coloured deposits stuck to the sides bottle and it was suspected that this substance had spread further into the pipes and throughout the cooling system. Researching this issue further our fears were confirmed in the way of a TPI. It would seem that to aid the longevity of the aluminum components within the cooling system a silica bag was added to the expansion bottle, the problem is this bag would split, causing the silica inside to stick to the inside of the hoses and block the heater matrix.

In this case, we removed the blocked matrix, flushed the system thoroughly before fitting a new matrix and new expansion bottle (new bottles come without a silica bag fitted). The problem was fixed and the vehicle was now getting nice and hot inside once again. It would seem the silica bag
is fitted to many models of Audi, Volkswagen, Skoda & Seat from around 2014-2018 and the fact replacement bottles are supplied without the silica bag fitted it appears it was an unnecessary addition, to begin with. Since discovering this problem we check for the presence of silica bags when carrying out routine servicing and if necessary we replace the bottle before the bag splits leading to a costly repair. We would advise anyone who owns a V.A.G vehicle made around 2014-2018 to check theirs!