What to replace while changing the timing belts of VW group V6 engines and 4 cylinder engines of Vauxhall/Opel
Workshops that keep costs down for their customers have an advantage over their competitors. The immediate reflex is: "Change only those components that really need replacement". But for certain applications it is better to change one more component while you are at the job so you can prevent your customer from running into higher repair cost afterwards.
This is especially the case for some Volkswagen group V6 engines and some 4 cylinder engines of Vauxhall/Opel. A timing belt replacement on these engines can easily take up 3 hours of labour time. While this labour-intensive job is being performed it makes sense to also consider a thermostat replacement.
Audi A6 (C5) 2.4 - V6 (AML)
Some applications from the VW group and from Vauxhall/Opel have their thermostat located right behind the timing belt drive system. This means that the entire timing belt system needs to be removed before the thermostat can be accessed and replaced. Consequently a new set of drive system parts needs to be purchased and installed as those can never be re-used.
Examples of VW group applications where the thermostat sits behind the belt drive system include Audi A4 2.4 Petrol, Audi A4 Cabrio 2.4 Petrol and 2.5 Diesel, Audi A6 2.4 & 2.8 Petrol and 2.5 Diesel, Audi A8 2.8 Petrol. Vauxhall/Opel models with such a configuration are the Vauxhall/Opel Astra 1.6 & 1.4 Petrol and the Vauxhall/Opel Corsa 1.2 & 1.4 Petrol.
Why is replacement of the timing belt not enough?
By now, we all know that replacing just the timing belt is not good workshop practice. We cannot expect the metal components such as tensioners and idlers to run until the next timing belt service interval. In addition, worn tensioners or idlers can cause a newly installed timing belt to fail prematurely.
What about the water pump?
In these applications the water pump is also driven by the timing belt. If the water pump fails, coolant will leak and contaminate the belt and tensioner. Coolant contamination will eventually lead to premature timing belt failure. Therefore, Gates recommends replacing the timing belt driven water pump while servicing the timing belt drive.
Why should you replace the thermostat as well?
From a labour point of view it makes sense to also replace the thermostat in some Volkswagen group V6 and some Vauxhall/Opel engines at the time of the timing belt service. The thermostat which is located behind the drive system in these specific applications is likely to fail between the first and second service interval of the timing belt drive. Do not run the risk of having to do the labour-intensive job again and replace the thermostat during the first timing belt service interval.
From a cost point of view replacing the thermostat during the timing belt service interval makes even more sense. The additional cost of the thermostat is relatively small compared to having to replace the timing belt drive and the water pump a second time in case you have a failing thermostat in between timing belt service intervals. In addition, buying a total kit solution including the timing belt drive components, the water pump and also the thermostat is more economical than ordering all the parts separately. You can also be certain that all components perfectly match the application and all fall under the same warranty.
Thermostats are the watchdog of the engine’s cooling system, as they constantly monitor the temperature of the coolant and accurately regulate the coolant flow through the radiator to obtain and maintain the optimum engine operating temperatures. The consequences of a failing thermostat in “open position” may be less catastrophic than those of a “locked failure” but both scenarios are nevertheless undesirable since they increase fuel consumption and reduce cabin temperature.
Therefore, it is advisable to include the replacement of the thermostat in the timing drive overhaul for Volkswagen group V6 engines and some Vauxhall/Opel applications. It’s only a small effort but workshops can benefit hugely by avoiding costly comebacks and increasing their service towards their customers.