Mild hybrid braking noise - normal or fault?

[neilgorin]

The only cars that do the engine off freewheeling are fitted with the 7 speed DCT gearbox. This is limited to late v60 2wd cars, non UK spec S60s and 2wd Xc40 after some time in 2022. The rest don't do it. Some 8 speed cars do a version where the gear disengages but the engine remains on.

Back to back driving a v60 B4 with the feature and a v90 B4 without gave me 44mpg and 36mpg respectively over the same route which includes a 2 mile downhill 70mph dual carriageway, which is more than you'd expect to save just on the smaller car being marginally lighter.

[SSM]

Thanks for this, it’s the first time anyone has tried to describe what is happening.
Looked at software version and we have 3.0.3 installed and the system states we are up to date but, when I look at the release notes I see there is is a newer version, 3.1.5 I think it is.
Can’t seem to download that one as software updates only happen automatically.
Thanks again.

[cbarrow]

Not liking the idea of engine off freewheeling - I was thinking of getting a late model V60 but that has put me off.
Are the late model V90s or V60 AWDs equally blighted or are they on the 8-speed box?

[neilgorin]

They are on the 8 speed so don't power off.

What issue do you have with the engine being off out of interest? You can restart it at will by just tapping the throttle. Same system is in the latest BMW and Audi mild hybrids, both of which switch off when coasting.

The power steering, brake servo, air con etc are all driven from the 48v battery on these cars rather than the engine.

My biggest issue with the 7 speed isn't the engine off when coasting but the terrible throttle response when approaching roundabouts when the engine goes off and then on again which needs very careful use of the pedal to avoid it being totally dead momentarily when entering fast moving traffic - something that 8 speed S60 and v90 that I have driven also do with their Mhev setup even though they don't coast.

Fact is that an old style auto with no hybridisation or stop start is a far nicer drive - a fact I'm reminded of every time I rent a car in the US where they're less inclined to install these features.

[cbarrow]

Thanks for the info. I didn't realise the 8-speeds are also a bit weird on throttle application after coast too.. Maybe that rules out a Volvo to replace my current Volvo? Would need to try it.

Much as you said. The engine having to fire up each time I go for throttle 'on' and also I can't see how so many forced engine-off/ons can be good for any engine, and I would be buying a second hand one with a view to keep it 10 years (for economics). Even more to go wrong.
Even on my old S60 I turn off the stop start. If I am going to get stuck at lights etc. I turn the engine off manually. I want a car that is a pleasure to drive, not one that is irritating on behalf of a few extra mpg. I use "lift and coast" a lot to save fuel so for me the engine is going to be on/off/on all the flippin' time I suspect

[neilgorin]

On the 7 speed it would be off, on the 8 speed it would be on.

The only time I notice an issue is approaching roundabouts where you have to make a quick decision whether to move into traffic or wait for the next gap. If I remember I tap the throttle just before I reach the junction, but it shouldn't be necessary.

It is what it is however I doubt I'd buy another. Not least the noise this thread was initially discussing has come back twice this week after not doing it for several months, I certainly won't keep the car past the end of the warranty unless I can extend it for sensible money - I've never worried before with Volvo cars.

[cbarrow]

That's a real shame to hear (about your car) and I hope you can get it resolved okay.
I worry too nowadays about Volvo longevity, (having owned various models for the past 30+ years). I know that many modern cars suffer similar problems (owing to complexity and need to get emissions down, mpg up, and servicing intervals lengthened).

I might take a punt on a pre-MHEV V60 at some point, since I think they don't suffer and hoping a little more reliable. But they are getting old now (2020 vintage) so likely into the realms of other gremlins.... especially as I need to keep it to at least 10-years old to make it economically viable.

Or sadly, for the first time in over 35 years, have to get something non-Volvo....