Error

Its 2019, and somehow I've decided I need an early Q7 in my life. I'm looking for high mileage owners to chime in a bit here, both 3.6 and 4.2 owners. Cars around 120k miles.

I've done some reading. It seems like the 4.2 has some high mileage work (seals, chain guides) that require the motor out of the car. The Timing chain guide also seems to be a "when" not if issue. I figure this rules out the 4.2 as a reliable high mileage option?

The 3.6 VR6 seems a much better option for a reliable and easier maintenance high mileage car, without any real maintenance issues that cant be performed with the motor IN the vehicle.

If you have a 120K 3.6 or 4.2 Q7, what do I need to know before purchase? The things I have noted to look into first are below, whats missing from your experience now that most of these early vehicles are hitting 100K miles plus?

Sunroof drains / wet spots on floor
Timing Chain noise (4.2)
no 2007 VR6 because of oil pump Bolt issue
Check rear hatch works both up and down
oil leaks (mostly a 4.2 problem)

Thanks!

tigerwillow1

1. My 2008 3.6 has a slow coolant leak where a plastic pipe enters the back of the water pump housing. I'm ignoring that one for now because it's slow and I can easily check the coolant level.
2. A little over 100k miles an ATF leak started at the plastic sleeve surrounding the electric (mechatronic) connector. Fix is not expensive once fluid is drained and pan dropped. At that mileage you should change the ATF anyway. ATF level is not easily checked. Adding ATF is not easy. (Notice the trend: Leaks where plastic parts are involved)
3. Just under 100k miles the valve cover gasket was replaced to stop an oil leak.

With 4.2 you get an Aisin transmission, with 3.6 it's a ZF.

Changing the oil filter in the 3.6 is the worst I've ever encountered. The "only" big problems are there's no opening large enough to lift the cover+filter assembly up to the engine, and a refrigerant hose runs right under the center of the filter cover. It's really pathetic.

xThinG

The 4.2 engine is better, if you are considering to tow then 4.2 engine.

Error

Thanks for the insight.

I had forgotten about VAGs weird obsession with making parts from plastic. As long as I can reach these places, I should be okay to do most seals etc myself.

I have read about oil and filter changes being a pain. I change more than my fair share of Honda B/D series oil filters which are located on the back of the block and run oil down your arm, the block, and drip on the exhaust seemingly no matter what you do, so I'm interested to see how much worse this setup is.

I had planned to put a trans flush and fill on the list of "to do" very shortly after picking it up.Ill leave that one up to a shop. I hadn't thought about the differences in transmissions. Which seems to be the preferred setup or at least the more reliable, the Aisin or the ZF?

tigerwillow1

I can't compare the Aisin and ZF transmissions directly. I can only say that mine works well and the engine also runs well. The same ZF transmission is used on some BMW models and F150s. The Aisin has the same no-dipstick, fill-from-the bottom headache. It's a German thing, with BMW the same and Mercedes more recently having gone that direction. The Ford version of the ZF transmission has a dipstick. Fixing the coolant leak is unfortunately a pain because the plastic pipe is buried under other things. The coolant-cooled alternator, for instance, has to come off. And it's a requirement that the cooling system has to be refilled by pulling a vacuum on it first (probably the same for the 4.2). MPG with the 3.6 is 21 if totally highway miles, drops to around 17-18 for city driving. We have a Honda with a lot of plastic parts, too. No leaks yet, its oil change is about 10% of the work of the 3.6, and the ATF change was reasonably easy.

cuatrokoop

I have a '07 3.6, and had an '07 4.2. I will say, the 4.2/Aisin was a much better combination (better shifting, smarter gear selection, etc). It was not better when visiting the gas pump. Which happened often. I think we were getting slightly less than 12mpg average. My 3.6 gets 15-15.5mpg average, except when I have to run the A/C and I am heavy with my right foot (it is very sluggish if in the wrong gear). Then it gets about 13.5 average (around town). All Audi V8's I've owned or been around leak oil. I still have an early 4.2 in my old Coupe and an older 3.6 32v sitting on a stand, so I'm still in the Audi V8 game. The '07 3.6 is still capable of towing, in fact I just put a brake controller in mine so I can more safely tow the 4-Star horse trailer if needed. Mine only has 89k miles on it, I've put about 30k miles on it in a little more than four years. It is needing some A/C attention (dual/quad system, cools but does not get cold), and it has developed a slight power steering oil leak from a hose crimp, hardly noticable. It looses a little bit of coolant, but it is so slight I just top it up every couple months. It has been a very good vehicle for me in terms of maintenance. The 4.2 was becoming a maintenance *****. I spent several thousand dollars on the suspension alone (air suspension) in the last two years I had it before trading it on the '13 TDI...

Error

Unless I run into a deal I just can’t pass up on a 4.2, it’ll be a 3.6 for me if I can’t find what I want.

a 2007 3.6 premium just popped up near me, and is almost exactly what I want. I haven’t been to check it out yet as the 2007 oil pump bolt issue still scares the hell out of me. But at 185k kms I’m hoping if it was going to go, it would have already.

the more reading I’m doing also makes me wonder about carbon build up in these motors. It sounds like unless the last owner has paper work showing it’s been done, a full tranny flush and carbon service should be first on the to do list.

raj99

@Error what's your budget on the car? Although out of the 2 choices I'd go with the 4.2, hands-down. I'd see what you do to get into a 2012 or newer 3.0T engine and in the long-term you'll be far happier. Since it's a better engine and you'd be getting far more reliability out of it, plus it's a newer gen model.

Error

Raj99

I'm doing this on the cheap. The 4.2 and 3.6 cars around me are priced all around 8-12K CND for 150k-220k KM cars. However, none of them are selling and most have been for sale for a month or more. Most people looking to spend such a small amount are not looking for the hassles that come along with most Luxury high mileage cars. To be honest, for me this is a bit of an experiment into VAG ownership. It could turn out to be a huge mistake, but I can live with a 8-10K mistake.

The Face lifted cars with the newer engines (or the diesels) all sit around 20K plus around me. Just not looking to spend that right now on something out of warranty and used, as Family and house are coming first for the time being.

I'm leaning away from the 4.2 as reliability and ease of repairs are high on the list. From all the reading I've done the 4.2 has some issues like timing chain guides that would require the motor to be out of the vehicle. With this kind of mileage, I expect there will be a lot of examples coming on the market with this exact issue.

raj99

@Error Ok good to know your budget and also since you're in Canada and prices for gas are far from cheap, the 4.2 will certainly impact your running costs. If you really need a quasi-7 passenger vehicle, then the 3.6 is fine. It's similar in many ways to the 3.2 engine found in so many older Audi vehicles. It's reliable and boring, you won't get great mileage, but better than the 4.2. As for the issues you mentioned, yes there can be the potential of timing belt tensioners, but I've had a 4.2 non-FSI for a LONG time and have maintained it pretty darn well and everytime I drive my 4.2 it brings a grin to my face