What are the least reliable modern engines?

[white_goodman]

Let's say post-2000, as still readily available but it seems that despite 100+ years of development, there are still quite a few engines out there with poor reliability and major design flaws. Sadly, although Ford/BMW IMHO have made some of the best engines of the last 50 years, some of their recent efforts have some pretty serious design flaws, which is all the more disappointing, as a 1.0 Ecoboost Fiesta or a 320d are fantastic cars that offer class-leading power and efficiency (when they are working). So let's start with:

1) 1.0 Ford Ecoboost engine
2) BMW N47/B47 2 litre diesel engine. The N57/B57 3 litre diesel doesn't seem to suffer quite so badly (not sure why)?
3) Along the same lines as the 3 cylinder Ford Ecoboost engines, the "Puretech" Citroen/Peugeot 3 cylinder petrol "wet belt" engines too (did Honda also have a "wet belt" engine, which share the same issues)?

4) Mazda Skyactiv diesel (and IIRC, Toyota's 4 cylinder diesels aren't that great either)?

5) JLR 4 cylinder Ingenium diesel engine.

And in more limited applications:

5) The 2.3 Ecoboost in the previous gen Focus RS (although this was mainly due to a manufacturing error with fitting the wrong head gasket)?

6) S65/S85 V8/V10 in the E9x M3/E6x M5/M6.

I'm sure that Nissan/Vauxhall/Renault must have made some stinkers over the years too but the above 7/8 engines are the first that come to mind.

From my own experience, I've really only had to give up on one car in 25 years and 20+ cars due to engine issues and that was an R56 MINI Cooper with the 1.6 Prince engine (a Peugeot/BMW collab IIRC). Me and my independent mechanic threw a lot of time and money at that one trying to solve its issues and remain baffled to this day. On only 80,000 miles, that was pretty disappointing. Other than that, I have a failed automatic transmission on a Jeep and some serious electrical issues on a Golf, a crashed Peugeot and that's pretty much it.

A quick word in defence of the venerable Rover K-Series engine. I ran several of these (both 1.4/1.6/1.8 versions) in the early 2000s over several thousand miles and never had a blown head gasket on any of them. I believe that the early K-Series engines were fine but the issues were brought about by lower quality head gaskets and having worked in an MG Rover garage at the time, most of the HGF failures that we saw were in the 1.8s and in applications where the cooling was either compromised (MGF/TF) or where the engine wasn't really up to it for the application ie larger/heavier cars like the Rover 75/MG ZT/mk1 Freelander. In the Rover 200/25/400/45-based cars, we had very few HGF failures.

So what in your opinion (and why) are the least reliable engines of the last 25 years?

[M138]

Porsche 991.1 GT3

[MikeM6]

I'd swap the S85 for the S63. The V10 was actually reliable if well looked after, but most were treated like a normal BMW engine and driven hard from cold. Look after them and 200k has been achieved.

The S63 seems to be more problematic, although that might be down to those that remap and abuse them.

[georgeyboy12345]

The Skyactiv diesel is somewhat unfairly tarnished. Post 2016 versions are very reliable. If you are in the market for a diesel, you can exploit this to your advantage.

[vikingaero]

PSA/MINI N14 engine. You have amazing PH'ers such as .scrw making them work, but they are junk. Lots of MINIs are kept on the road because of their /cutesy image, but look at the decimation in Citroens/DS3s, you very rarely see them.

There's always the apologists "Yeah they just need a bit more maintenance...!"

[georgeyboy12345]

I d add early EA888 (gen 1 & 2) from VW group - so those made before 2012.

The VW group EA111 1.4 turbo & twincharged also pre 2012 had timing chain issues & a host of other things

Also VW group 3.0 V6 TDIs from around the same era

The JLR 3.0 V6 has some issue with it s crank failing IIRC

Edit: the Ford 2.0 Ecoblue (i think it’s called?) diesels - also use a wet belt, to the bane of many a transit driver.

I think the VW 2.0 biTDI was also problematic

Oh and the diesel found in the Lexus IS220d was an unreliable turd

Edited by georgeyboy12345 on Saturday 7th February 14:24

[Ed Boon II]

VW Transporter engine codes - CFCA and CXEB

Both had design flaws and have cost their owners considerable amounts of cash to get fixed/replaced outside of warranty.

[white_goodman]

MikeM6 said:

I'd swap the S85 for the S63. The V10 was actually reliable if well looked after, but most were treated like a normal BMW engine and driven hard from cold. Look after them and 200k has been achieved.

The S63 seems to be more problematic, although that might be down to those that remap and abuse them.

I didn't know that the S63 (4.4 V8 TT in the newer M5s)? were that unreliable. Would that be due to the hot-vee layout (in which case are the RS Audi/AMG Mercedes equivalents just as bad)?

[georgeyboy12345]

Ed Boon II said:

VW Transporter engine codes - CFCA and CXEB

Both had design flaws and have cost their owners considerable amounts of cash to get fixed/replaced outside of warranty.

Yes - I think these were the biTDI engines?

[white_goodman]

I guess the "Renesis" rotary engine in the Mazda RX8 also deserves a mention.

[georgeyboy12345]

white_goodman said:

MikeM6 said:

I'd swap the S85 for the S63. The V10 was actually reliable if well looked after, but most were treated like a normal BMW engine and driven hard from cold. Look after them and 200k has been achieved.

The S63 seems to be more problematic, although that might be down to those that remap and abuse them.

I didn't know that the S63 (4.4 V8 TT in the newer M5s)? were that unreliable. Would that be due to the hot-vee layout (in which case are the RS Audi/AMG Mercedes equivalents just as bad)?

There’s nothing inherently unreliable about a hot V layout - the BMW had other issues with rod bearings, turbochargers and oil leaks that were unrelated

[white_goodman]

georgeyboy12345 said:

The Skyactiv diesel is somewhat unfairly tarnished. Post 2016 versions are very reliable. If you are in the market for a diesel, you can exploit this to your advantage.

What did they do post-2016 to address the issues?

[Ed Boon II]

georgeyboy12345 said:

Yes - I think these were the biTDI engines?

But not the later CXEC or the latest DMZA engine, they seem much improved, bloody hope so as DMZA is in my van.

[Heaveho]

Anything wet belt has the ability to give you a stage 5 wallet remap if you aren’t aware enough to drop the sump regularly and clean the oil strainer. st design. Answering a question nobody asked.

[Panamax]

vikingaero said:

There's always the apologists "Yeah they just need a bit more maintenance...!"

That reminds me of the Rover K-series engine (Elise/Discovery etc). "Yeah, you just need the head off to replace the plastic dowels with real ones."

[MikeM6]

georgeyboy12345 said:

white_goodman said:

MikeM6 said:

I'd swap the S85 for the S63. The V10 was actually reliable if well looked after, but most were treated like a normal BMW engine and driven hard from cold. Look after them and 200k has been achieved.

The S63 seems to be more problematic, although that might be down to those that remap and abuse them.

I didn't know that the S63 (4.4 V8 TT in the newer M5s)? were that unreliable. Would that be due to the hot-vee layout (in which case are the RS Audi/AMG Mercedes equivalents just as bad)?

There s nothing inherently unreliable about a hot V layout - the BMW had other issues with rod bearings, turbochargers and oil leaks that were unrelated

Exactly, it was BMW engineering in unreliability haha, or at least not making them strong enough for the abuse owners would give them.

Technically great, but not durable and they sound a bit naff compared to other V8s.

[Escort3500]

Heaveho said:

Anything wet belt has the ability to give you a stage 5 wallet remap if you aren t aware enough to drop the sump regularly and clean the oil strainer. st design. Answering a question nobody asked.

Absolutely. My tame mechanic friend makes real good money from lunched wet-belt Fords, mainly Transits.

[TarquinMX5]

georgeyboy12345 said:

white_goodman said:

MikeM6 said:

I'd swap the S85 for the S63. The V10 was actually reliable if well looked after, but most were treated like a normal BMW engine and driven hard from cold. Look after them and 200k has been achieved.

The S63 seems to be more problematic, although that might be down to those that remap and abuse them.

I didn't know that the S63 (4.4 V8 TT in the newer M5s)? were that unreliable. Would that be due to the hot-vee layout (in which case are the RS Audi/AMG Mercedes equivalents just as bad)?

There s nothing inherently unreliable about a hot V layout - the BMW had other issues with rod bearings, turbochargers and oil leaks that were unrelated

The jury might still be out on that. The problem with a proper hot vee (ie exhaust in the vee as well) is the heat generated and its impact on ancillaries over time and the cooling system on some of these new engines is now quite complex. The later S63 (about the third or fourth technical upgrade) is supposedly much better but they, like many hot vees, are now complex engines - watch a stripdown of one and compare it to an old American V8. You can blame emissions regns., and the race for bhp, for a lot of it.

However, there's no doubt that the application of some basic mechanical sympathy and regular oil changes can make a big difference: an unknown history could be problematic if purchasing a used vehicle. All IMHO.

[A500leroy]

Come on mention the pure tech.

[Tango13]

The Nissan three cylinder variable compression engine isn't known for its durability.

There's a YouTube channel called 'I do cars' where he strips down blown up engines, some are dead due to neglect but some like the ones previously listed are down to poor design.