Diesel engines
The diesel engines can reach 300 000 km or even 400 000 km without major issues. But sadly, not always! Because they can have some very interesting problems which can occur much earlier:
Oil consumption
First thing first, all the diesel engines have the same bad oil scraper ring design like some of the already mentioned petrol engines. This means, that oil consumption can be an issue in all the diesel engines. However I have to add that it’s still not common. Well, except maybe the most powerful 2.0l TDI (CUNA engine code) which is for some reason more prone to oil consumption. There are numerous cases of excessive oil consumption in these engines rarely even at around 100 000 km, but more often at or after 200 000 km. The oil consumption can be at 1L / 10 000 – 12 000 km, but in the worst case even 1L / 1 000 km.
But again, I’m not saying that all of these engines do have issues with this – they are just simply more vulnerable to clogged oil scraper rings causing oil consumption.
To minimize oil scraper rings clogging you should change the engine oil preferably after MAX 10 000 km / 6 200 mi and use the car mainly for long distance driving!
Cooling system
All of these engines have a more complex cooling system with additional electric coolant pumps + there is the main switchable water pump.
Even bleeding this system is not that easy, since you need a vacuum pump and also a computer to bleed it properly. Without these tools you are gonna have air bubbles in the system in a fully warmed up engine which is not ideal to say at least.
Why it’s better to bleed the system properly? If you bleed the system with vacuum and with computer – according to the manufacturers recommendation, then you are not gonna have air bubbles in the system. If you are NOT GONNA bleed it this way then after warming up the engine – you can still have air bubbles in some parts of the coolant path – this is pretty bad, since this will create local hot spots – in this case if you are unlucky then you can end up with a leaking head gasket or cracked cylinder head.
But the 2 main possible issues of this cooling system are related to the coolant itself and to the main water pump.
1.Water pump
The main water pump is a switchable water pump, so there is a cover on it which can slide up or down and this way the water pump can be turned off or on. The problem is, that the cover can get stuck in closed position! In this case it’s not gonna help to circulate the coolant and the engine is gonna overheat. If the engine had been overheated a lot (and damaged), then first its gonna have issues with starting – long cranking. Later the engine will loose compression, which means that you will have to repair or replace the engine. So before buying it’s definitely worth to pay attention to engine start: if the engine has issues with starting then walk away!
the engine has to start immediately without delay
The water pump was updated, so mostly the early before facelift cars are more prone to this issue. However be ready that the pump can fail on newer cars too!
2.Coolant
Before buying it’s very important to also check the coolant. It has to be clean and it need to have a pink-ish or violet color. If the coolant is darker, brown or orange and if it has strange deposits and particles in it – then you got an issue with coolant degradation! Long story short: VW used not the best coolant from the factory, and because of this it can go bad prematurely or it gets burnt in other words. The degraded coolant deposits clog up the heater core and also parts of the coolant system – which can even cause usually slight issues with overheating + it can also help to start the internal corrosion of the engine-which is pretty bad!
ALL IN ALL: if the coolant looks bad then run away from the car and after buying you should replace the coolant to the newest G12 EVO which doesn’t have problems with degradation !
Timing belt tensioner fail – engine K.O.
All of these diesel engines are equipped with a timing belt. The belt itself can withstand a lot but on some of these engines the belt tensioner can fail prematurely even before 150 000 km. If the belt tensioner fails then the belt gets damaged and jumps which will destroy the engine. So definitely check for strange hissing, chirping or squeaking noises from the timing belt pulley after cold start. These noises are caused by the failing tensioner pulley, however the water pump can make these noises as well since it can fail prematurely too – rarely even before 100 000 km, but more cases of premature failure or leak at around 150 000 km.
tensioner squeaking noise video
tensioner squeaking noise video 2
Classic diesel engine issues
-Be ready that the injectors can be faulty after 200 000 km, even though I have to add that they are more reliable than in the predecessor
-The high pressure fuel pump can fail in high mileage cars, even though I have to add that it’s more reliable than in the predecessor
-Older or high mileage cars equipped with the adblue emission system can have some issues with it. So it’s better to be ready for issues with:
- adblue NOx sensor
- adblue injector
- adblue tank heating
- incorrect adblue fluid level warning massages
- slight adblue leaks
-Certain 2.0 TDI engines are equipped with a variable valve timing valve. This valve can be clogged which will cause long start/long cranking. Some owners fixed the issue by removing and cleaning the valve, but you can buy a new updated valve and fix the issue without trying.
The weakest 1.6 TDI with 66 kw is NOT WORTH IT since it’s not powerful and it’s often mated only to a 5 speed manual gearbox which is not suitable for highway driving.
The oil pump is fckin noisy
ALL the diesel engines can make a knocking / clattering noise from the lower part of the engine – from the oil pump area. video of the noise
The oil pump is combined with the vacuum pump and it can make this clattering rattling noise which can be mostly heard when the engine is cold. It seems that this funny noise is not affecting anything and even owners who replaced the oil pump (because of this noise) got the noise back after some time.
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