Is there a major fault with the DPF-equipped Mazda 6 diesel engine?
The Mazda 6 diesel engine, from its first incarnation to the current model, has a new form of diesel engine with a diesel particulate filter. According to Mazda this can cause a warning light to come on from time to time, but driving for 10 minutes at more than 40mph is supposed to clear the problem. However, our car has suffered a catastrophic engine failure due to this and is a write-off due to the cost of repair. It was bought secondhand but has a full Mazda main dealer service history with most services undertaken before they were due.
The internet forums are awash with people with the same problem and it affects new and old cars. It can also cause the engine to rev dangerously out of control, which happened to my wife on the motorway, or stall completely whilst driving along, which has happened many times. Mazda advise that the car needs a long run and should not be used on short journeys around town. It is a motorway car. Expert consensus is that the engine is not fit for purpose, but Mazda of course do not want to admit this.
The internet forums are awash with people with the same problem and it affects new and old cars. It can also cause the engine to rev dangerously out of control, which happened to my wife on the motorway, or stall completely whilst driving along, which has happened many times. Mazda advise that the car needs a long run and should not be used on short journeys around town. It is a motorway car. Expert consensus is that the engine is not fit for purpose, but Mazda of course do not want to admit this.
Asked on 27 July 2010 by Simon Dunn
Answered by
Honest John
This is well known and is covered in car-by-car breakdown on this site. On 2.0-litre Mazda 6 diesels with DPFs the DPF uses extra fuel injected into the combustion chambers to create the hear to regenerate. But if the filter is too blocked the fuel does not ignite and dribbles down the bores into the sump. Mazda 5 2.0 diesel owners are advised to check their sump levels regularly (it's in the handbook) because if the level rises too high from fuel oil, then the compression ignition engine can run uncontrollably on its sump oil and can only be stopped by force stalling it against the brakes or by cutting off its air supply.
The problem is also common on the first Subaru Legacy diesels, the FIAT 500 diesel and Vauxhall Corsa vans fitted with the 1.25 FIAT diesel engine and a DPF. The Mazda 6 2.2 diesel uses direct injection of fuel into to the DPF itself with an ignitor to avoid this problem, as do later Subaru diesels.
The problem is also common on the first Subaru Legacy diesels, the FIAT 500 diesel and Vauxhall Corsa vans fitted with the 1.25 FIAT diesel engine and a DPF. The Mazda 6 2.2 diesel uses direct injection of fuel into to the DPF itself with an ignitor to avoid this problem, as do later Subaru diesels.
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