What is it with Swedish brands and installing engines the wrong way around? The Saab 99 famously had a longitudinal engine turned back-to-front in a front-wheel-drive application, and Volvo played around with transverse inline-sixes. While Saab eventually switched to a transverse layout and Volvo eventually went with just four-cylinder engines, Volvo’s last experiment was extra-wonky. Let me explain.
Inline-sixes are smooth, wonderfully-balanced engines that deserve much praise. They’re also incredibly long. That isn’t much of an issue in a longitudinal application like in front-engined rear-wheel-drive vehicles, but Volvo hasn’t built a car on a longitudinal platform since 1998. As such, this new inline-six would have to fit sideways between the strut towers, a total packaging pain in the ass.
To Volvo’s credit, the SI6 engine is remarkably compact for an inline-six, measuring one millimeter shorter than the inline-five that preceded it. However, it was still an incredibly tight squeeze in the engine bays of various Volvo product, which meant that the accessories needed to be flipped around. Yep, Volvo ran parts like the alternator, power steering pump, and air conditioning compressor off the transaxle side of the SI6 engine, a method that shouldn’t really work because there’s no crank pulley on that side of the engine. So how did Volvo pull it off?
Well, Volvo used gears. I take it we’re all familiar with gears, right? One of the key simple machines, these toothed wheels are made to multiply and transmit force when used together, which is exactly what Volvo did to create the READ, short for Rear Engine Accessory Drive, a clever little gearbox on the side of the SI6 engine.
How does it work? Well, drive to accessory and upper engine timing components is the responsibility of two different gears on two concentric shafts that spin at different speeds. This arrangement also takes the load of the accessories off of the top end timing system. If you’re getting flashbacks to the Dodge Viper’s cam-in-cam shenanigans, yes, but also no. Each of these gears is driven by a dual-patterned gear on a shared intermediate shaft. Drive to the intermediate shaft gear is provided by a gear on the crankshaft. Oh, and that gear on the crankshaft also drives the oil pump. YouTube user Smilyeez gives a great look at the READ system in the video above.
The result of all this geared wizardry is that accessory drive is moved up and out of the way of the transaxle, preventing any packaging interference. The downsides? Well, other than the fact that the alternator sits beneath the intake manifold, Volvo didn’t quite get the READ perfect.
As with anything that spins at high speeds, all the READ parts ride on bearings to reduce friction. Unfortunately, every part on a car is a wear item on a long enough timeline, and READ bearings don’t last forever. While a 2007 and newer six-cylinder Volvo emitting a whining noise could just have a bad pulley, that unusual noise has the potential to be far more serious.
In the words of our friends at FCP Euro, the bearing in the main READ gear “commonly goes bad, creating a growling noise from the front of the engine near the alternator pulley. Failure to address this noise can result in gear drive wear and failure.”
I don’t know about you, but failure of a part that prevents your valves and pistons from joining in holy matrimony sounds bad to me. Oh, and because READ parts live within the bowels of the engine, don’t expect repair to be cheap. We’re usually talking deep into four-figure territory. On the plus side, sudden, catastrophic failure is virtually unheard-of, so owners of these engines will at least have some warning that expensive repairs are imminent. Oh, and this engine was also the most reliable powertrain U.S.-based Land Rover owners got in the LR2, so you know, upsides.
Taking a step back for a second, it’s wild as hell that Volvo’s SI6 uses a weird combination of gear-drive and chain-drive to keep the camshafts in step with the crankshaft, but the READ assembly is also an elegantly simple solution to a problem that wouldn’t exist without a little bit of insanity. Keep in mind, Volvo’s previous-generation inline-six didn’t use a crazy READ unit, and that thing fit in early XC90s just fine. Sure, the GM 4T65-E transmission attached to it offered the durability of a Faberge egg, but you know, such was the technology of the time. Regardless, the READ unit is a neat footnote in the history of automotive engineering, and exactly the sort of thing you’d expect from a company that later decided to twincharge most of its model lineup.
(Photo credits: Volvo, YouTube/Smilyeez)
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I’m quite familiar with the READ system, seeing as mine failed on my 2010 V70. Fortunately I was able to find a competent independent Volvo specialist to take care of it, a lot o shops try to condemn the whole engine when these start making noise. Plenty of trouble free miles since. Excellent car.
The 3.2 and 3.0T are awesome engines.
Why not reverse it do it right first tie
Idiots
No room for the transmission otherwise.
Plenty of engines have accessories driven off the wrong side of the engine. Many GM Ecotecs have the power steering pump driven directly from the transmission side of one camshaft.
Also, every two stroke Detroit has a similar gear drive for driving accessories off the back of the engine.
Similar to the first thing I thought of, the Quad 4.
A vacuum booster pump as well on some of the Ecotec’s.
Try to guess how much fun it is when either of those accessories fail and seize up causing the camshaft to twist itself into a pretzel?
161,000 miles on my 2012 S60 T6 and so far no READ issues, but I’m sure they’ll come eventually. Worth it though for the rest of the engine. With the Polestar tune especially these engines just pull from low RPM like a freight train. Very underrated engines overall IMO; truly a shame that they only lasted a decade or so.
Agree – the engine in my wife’s XC60 T6-R Polestar is sublime.
Oh oh I was wondering what the noise was on the xc60 the other day
In the LR2 with the SI6, the A/C compressor sat on top of the transmission! Did the Volvo version do it like that? The SI6 has a bizarre crankcase ventilation system too if I recall it correctly. I was a tech training instructor for Land Rover circa 2011-2014, but that was a long time ago and I didn’t deal with the SI6 very much.
Are you saying that the SI6/Aisin ATX is a more reliable combo in the LR2 than the Ecoboost 2.0L/Aisin?
I had a 2010 V70 R Design with that engine. Loved the car but was burning a quart of oil every 500-1000 mi or so when I traded it in with around 100k miles.
As an owner of a 2015 XC70 with a 3.0L I -6 ( with a Polestar tune) I am not sure how I should feel. Is there doom in my future?
No SB Doom is not in your future, I had a READ service done on my XC70, replaced the AC compressor, timing chain guides, alternator, and any other part my independent shop could get at while doing the service. As I remember it was around $2500. I’m now coming up on 160,000 mi., and the motor is as smooth as silk. Mines an 08 with the 3.2, I take it yours is a T6. Later engines had an improved, READ design. I love this car BTW.
Thank you for the response! I was suffering from a bit of anxiety and I feel a bit better now!
And yes, mine is the 3.0L T-6
I wouldn’t worry about it much, to be honest. Even on the odd chance READ issues do crop up, in my experience, they won’t happen without nigh-on moon miles (think 150,000 miles) or serious neglect. Plus, as John Crouch said, later cars have revised components, as Volvo liked to make rolling revisions (see: 3.2L piston rings).
Think of it this way: It might result in a bit of cost eventually, but what else is there that does everything an XC70 T6 does? Even a new E-Class All Terrain doesn’t hold a candle to those older Volvos. Keep that thing on the road and enjoy it as long as possible. It’s truly one of the greatest daily drivers of the 21st century.
Thomas, you have nailed it, for me, is one of the greatest daily drivers I’ve ever experienced! ( with the Polestar tune) Talk about a “sleeper” the I -6 with the Polestar tune is just whack!
Lol did you just say 150k miles is sky high
My take is this is a far more reliable design that won’t fail catastrophically with no warning like a timing belt can, and will likely last 2-3 times as long, but when it comes time to do maintenance, it’ll be 3-5 times as expensive…
edit, I take part of that back, it still drives a timing chain, so 2 times as reliable as a timing belt, but 4-6 times as expensive…
Current timing belts have replacement intervals comparable to timing chains. My ’15 VW TDI’s interval was 130k miles, and when I replaced it, the belt looked like new.
As far as the ‘far more reliable’ timing chains go, there are plenty of known issues with prone-to-failure chain guides & tensioners on lots of engines, so I’m not sure they’re more reliable on average. The only timing mechanism I’d call bulletproof reliable is the good ole’ gears, and nobody does those anymore (seems like Volvo could’ve tried it here instead of the very short chain).
IMHO I’d rather do 2 timing belts instead of 1 timing chain replacement, the belts are so easy to do in comparison, especially for a DYI in your garage.
Haha, Polestar-tuned XC70s unite! Mine is a 2012 former dealer-demo car currently at 160k with zero (noticeable) signs of READ failure. It goes to my indie a couple times a year to get checked over so I trust they’d let me know if anything sounds or seems amiss. It absolutely pulls like a train and is so unsuspecting otherwise and can haul cargo like nobody’s business. It’s such a great only car as it really is a jack of all trades.
It Truly is a sleeper with the Polestar tune! I just love it!