Mazda 2016 1.6 diesel issues

zippy1978

Hi. This is a long on complex issue. I purchased a 2016 1.6 Mazda Diesel in October 2023, it has a DPF light on when viewing the car but I was assured this was because it had stood idle for several months but I was assured it would be sorted before collection before if I went ahead with the purchase. This should have been my first red flag but not being particularly mechanically minded I did not see it. I purchased the car, note I had driven a diesel car for 4 years prior to this. Within 3 weeks the DPF light had come on, the garage took it back to investigate and returned it withing 7 days with 'everything resolved'. a\t this point we looked at pervious MOT history and saw a failed MOT in Feb 2023 for emissions, another missed red flag. It was not and so started a 2.5 year back and forward with the garage. The car has been back approx 20 times, I know I should have returned the car in the first 6 months but as having a car is essential for me due to having elderly parents with complex medical issues and reliant on me I kept allowing the garage to take it back to 'fix issues'. They always returned the car with no warning lights but they always came back on, either DPF or EML. They did replace a sensor once, and according to them all 4 injectors but they have never provided evidence of anything. Apparently all the other times they just forced the can into regen and gave it me back. In September 2025 things finally came to a head, the car failed an MOT in August due to emissions, the paid to have the DPF cleaned, apparently and 2 days later it passed. 2 days after that the DPF light was on again so I paid for a DPF inspection and a independent local garage. They found that the DPF had completely disintegrated, the system was full of soot and potentially had parts that needed replacing. The garage agreed to change the DPF themselves and complete all recommended works at their cost, as they did acknowledge the car had DPF issues from me getting it. I received the car back mid October 2025. Unfortunately the saga continued. Within a few days the car started to make an awful noise while driving down the motorway, no limp mode, no warning lights, but clearly not good. I managed to make it home and called the garage, on the way there the EML came on. They took it back in and stated a hose had blown off, they reattached and returned the car to me. A few days later the car started to pump out a huge volume of black smoke from the exhaust. I called them again. They took the car back in and said the oil was black, they changed it, and then proceeded to tell me it was my driving style causing the issues. I don't do alot of milage, I made that clear when looking at the car, a couple of trips a week, 10 miles each way, a couple of trips per month, 20 miles each way and then every 4 weeks a 40 mile each way trip, at motorway speed. A few days later the black smoke was back, The car had done just over 1000 miles since the DPF replaced and it had been in the garage for much of this time. I took it for a second inspection with the independent garage, they confirmed that while the DPF had been replaced the system had not been cleaned. They stated in their opinion there was an ongoing mechanical fault with the car and it was not due to my driving style, I finally contact the finance company who started an investigation. I had started to arrange my own certified independent inspection but the finance company said they would pay under a possible failed repair. I was hopeful but 8 weeks later their independent inspection came back ruling it was my low milage that caused the issue, less that 10,000 in 2 years. They made no acknowledgement that the DPF had only recently been replaced, the issue with a hose blowing off or the low mileage before I bought the car and DPF light I had seen. At no point was I contacted to ask what the history of the car was, and as previously stated the garage have zero paperwork. The new inspection stated the DPF was cracked and also highlighted potential engine damage. They also stated the car had a EML on which was not on when I took the car to the garage 2 months earlier.

Does anyone have advice on how to deal with the ombudsman and what I need to highlight?

paul_c123

Step number 1 would be to nip to a computer repair shop and get your keyboard sorted out. I honestly CBA reading that wall of text.

Woodstok2000

The only thing I can see in that block of text is that you' done 10,000 miles over 2 years - that's asking for DPF problems.

Ayr_Rage

"I don't do a lot of mileage, I made that clear when looking at the car, a couple of trips a week, 10 miles each way, a couple of trips per month, 20 miles each way and then every 4 weeks a 40 mile each way trip, at motorway speed"

A classic case of buying the wrong vehicle for the intended use.

Barkin

https://forums.moneysavingexpert.com/discussion/comment/81917618#Comment_81917618

While I agree that the OP's usage pattern doesn't really suit a diesel, on a more general point... it's not the actual mileage driven that can cause DPF etc problems, but the length of the journeys.

j2009

400-500 miles per month with at least one journey of 40 miles each way at speed etc plus several journeys of at least 10miles, that can all be done on one tank of fuel and that usage pattern is fine for a diesel and it should be able to regen once a month.

The car is a lemon I'm afraid, and if what you say is true about the journeys you do it's not you or your usage of the car.

Woodstok2000

https://forums.moneysavingexpert.com/discussion/comment/81917878#Comment_81917878

With that number of short journeys I would be expecting DPF issues, even with one journey a month of decent length. Its just asking for problems.

Goudy

These Mazda diesels haven't been Mazda's finest hour and are prone with lots of issues.

It looks like to start with your car hasn't had the sort of use diesels these days require to maintain it's emissions systems properly and these are particularly prone to that which has caused the initial problems.

Once these issues with the emissions system start, it's an ever increasing issue. Soot and excess unburnt fuel get sucked around to the intake via the EGR valve, clogged that and the inlet up, clogging the inlet valves up more and more.

Next up it's likely it's not been properly diagnosed and the underlying issue fixed to begin with. By the sounds of it there has been repeated attempts to sort the symptoms but the initial problem still exists.

From what I know there are a few issues that actually causes the problem, particularly leaky injector seals, but once the soot and carbon have built up on the valves and intake, it really needs stripping and cleaning.

The exhaust cam shaft needs checking as well, it's prone to wearing once you get into the repeated and failed cycles of DPF regeneration.

Replacing some of the emission sensors can also be an issue. I seem to remember there being an uprated exhaust sensor from Mazda. The original was plastic but I seem to remember the new one is metal and they are particularly prone to throwing major wobblers with aftermarket DPF pressure sensors.

Once the initial problem is solved properly and the symptoms of that issue have been rectified (cleaning up the gunk), the DPF needs a proper clean. Often a "clean" is when a cleaning fluid is poured down the DPF pressure sensor tube but really the filter needs to come off and back flushed.

In all honesty, it needs a proper diesel specialist. Someone who knows how to identify and fix the underlying issue properly and then sort the problems that underlying issue has caused.

Mildly_Miffed

Short version:

Now 10yo Euro6 diesel. Bought 2.5yrs ago. Covers low mileage, <5k/year, but not ENTIRELY short journeys.

40 miles "at motorway speed" gentle cruise once a month is not going to do very much to get the exhaust properly hot, trigger a DPF regen, and allow that regen to complete.

The bigger surprise is that there's no mention of SCR/AdBlue issues… yet? AdBlue crystallises over time when unused, clogging the injector pipework and tank.

I suspect the OP's previous diesel was pre-Euro5, so didn't have a DPF.

Even with regular regeneration, DPFs are a consumable, and ~10yrs is not far off the right timeframe that replacement would be due.

Ectophile

https://forums.moneysavingexpert.com/discussion/comment/81920005#Comment_81920005

Your experience of diesels is obviously totally different to mine.

I have a 2011 Euro 5 Land Rover Freelander 2. I bought it in 2019. I do well under 5000 miles a year. Mostly local journeys. Anything between across town to 30 minutes each way. Then a few times a year I will do something longer, around 200 miles each way.

Never had any problems with the DPF. Never had it replaced. Never had any problems on the MOT emissions test.

Mildly_Miffed

200 mile journey is a very different kettle of fish to 40, when it comes to sufficient time to fully heat the exhaust, start the regen, complete the regen.