Personally, I wouldn't do glow plug / injector removal if it wasn't necessary to replace a faulty component. In a petrol car, removing / replacing the spark plugs could lead to stripped threads in the cylinder head (especially with current long service intervals between plug changes), which would be costly to remedy.
I believe the big issue with out-of-warranty ownership of a modern diesel with DPF etc is the longevity of the various pressure and temperature sensors that control DPF regeneration and emissions.
From experience with my previous Volvo V60, if one of these sensors should fail, it can take even a main dealer several attempts to properly diagnose the problem. I had a DPF pressure sensor fail, and it took three trips to the dealer and several days of workshop diangostic time for them to fix the fault.
I had an in-depth chat with the dealer service manager about this, and he told me (subsequently verified on a Volvo forum) that in the Volvo diagnostic system, there is no specific fault code for the DPF sensors. The fault code logged in the ECU relates to the EGR valve.
So the dealer replaced the entire EGR valve and pipework, only for the fault to pop up again. In the end, they had to resort to swapping sensors from a fault-free car one at a time, to identify which component was faulty.
Of course, my car was still under warranty, and I had a courtesy car, so it wasn't really a big problem for me. But if the car was out of warranty, I would have ended paying for several days of workshop time and replacement parts that were not needed before the problem was actually found and fixed.
So it concerns me that even a main dealer, with the proper factory diagnostic computer and software, cannot easily locate a fault. I've no idea if this issue is limited to Volvo, or if the lack of accurate fault codes applies to other marques too.
But based on that experience, I would only own an 3+ year old DPF-equipped diesel on condition of having a warranty that specifically covers the costs of replacing faulty DPF sensors.
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