Hmm any petrol at this budget which will do 40mpg is going to be pretty horrible to live with - the mention of a 1.6 Astra backs that up! Remember an auto box will sap a reasonable amount of that too, especially on gutless small petrols.
OP seems quite comfortable with the associated risks of modern diesels, which is normally half the battle in posts like this.
I also think that they're not as much of a huge risk as they used to be - the risks are still present but a few years ago this sort of money would only buy one of the early first generation common rail diesels like the mk3 mondeo. Things have moved on several generations since then. I had an aforementioned mk3 mondeo quite a few years ago and had to replace the DMF/clutch and it was getting a bit smokey on cold starts when I got rid of it. More recently I ran a Saab like the one linked above which had a lot more mileage than the mondeo and it was faultless for the 30k+ miles I had it. Obviously this is anecdotal but it does seem that the technology is improving and having a few quid aside is completely sensible.
I think OP is on completely the right track although I think do think a merc is a bad idea. A Volvo would be a good shout too. Anyway, the diesely issues and what to look for
1 - injectors. Make sure you can start it from cold after it's been sat overnight if possible. A plume of smoke (white/grey fuel smoke) means an injector has dribbled into the cylinder. You'll often get rough running or EML when booting it when they're closer to death.
2 - DMF. Yes petrols have DMFs, we don't need that argument again. In diesels the low down torque is more punishing and the DMF failing isn't uncommon whereas on petrols it's rare. A rattly idle is normally the first sign, but you might get a noisy clutch release bearing (not relevant here) or difficulty starting as the swarf gets into the starter.
4 - turbo. Really not that common apart from at higher mileages. I've heard about a higher proportion of VAG 2.0 TDIs with turbos failing than others, but that might be because everyone and their dog has one. The VAG ones sound like a police siren quite often, but check for blue smoke. If you can pull a pipe off the turbo and reach the shaft then check it for play
5 - DPF/EGR. Not much you can do to check these beyond looking at the history and usage - lots of short journeys is the worst thing for these but DMF removal and EGR blanking are relatively cheap normally and can be a simple fix of preventative measure
OP seems quite comfortable with the associated risks of modern diesels, which is normally half the battle in posts like this.
I also think that they're not as much of a huge risk as they used to be - the risks are still present but a few years ago this sort of money would only buy one of the early first generation common rail diesels like the mk3 mondeo. Things have moved on several generations since then. I had an aforementioned mk3 mondeo quite a few years ago and had to replace the DMF/clutch and it was getting a bit smokey on cold starts when I got rid of it. More recently I ran a Saab like the one linked above which had a lot more mileage than the mondeo and it was faultless for the 30k+ miles I had it. Obviously this is anecdotal but it does seem that the technology is improving and having a few quid aside is completely sensible.
I think OP is on completely the right track although I think do think a merc is a bad idea. A Volvo would be a good shout too. Anyway, the diesely issues and what to look for
1 - injectors. Make sure you can start it from cold after it's been sat overnight if possible. A plume of smoke (white/grey fuel smoke) means an injector has dribbled into the cylinder. You'll often get rough running or EML when booting it when they're closer to death.
2 - DMF. Yes petrols have DMFs, we don't need that argument again. In diesels the low down torque is more punishing and the DMF failing isn't uncommon whereas on petrols it's rare. A rattly idle is normally the first sign, but you might get a noisy clutch release bearing (not relevant here) or difficulty starting as the swarf gets into the starter.
4 - turbo. Really not that common apart from at higher mileages. I've heard about a higher proportion of VAG 2.0 TDIs with turbos failing than others, but that might be because everyone and their dog has one. The VAG ones sound like a police siren quite often, but check for blue smoke. If you can pull a pipe off the turbo and reach the shaft then check it for play
5 - DPF/EGR. Not much you can do to check these beyond looking at the history and usage - lots of short journeys is the worst thing for these but DMF removal and EGR blanking are relatively cheap normally and can be a simple fix of preventative measure
