School me on the v8

[G Men 08]

I am looking in to picking up a 2005 allroad with the 4.2 chain driven engine. Just over 100,000 miles on it, and comes with a no start issue. Research and talking with the owner leads me to believe it is starter, coolant temp sensor, or crank positioning sensor. The purchase price reflects the issue which is why I am considering it.

This car will need to last me 10 years or so, so obviously maintenance issues will arise. As many of you, I am no stranger to maintaining my cars (owned audis for nearly 10 years now) and I typically do all of my own work. Doing timing belts and the associated components is no big deal, but this timing chain makes me a bit apprehensive to say the least! From what I've read the V8 in the allroad, A6, and A8 are fairly problem free in comparison to the higher performance S4 and S5 with the carbon issues etc.

Is it unreasonable to hope for 175,000 miles out of the chain drive without major issues/replacement? (provided quality, on-time oil changes with quality filters)

[LINDW4LL]

The allroad V8 is shared with the B6/B7 S4 and is plagued by timing chain issues and oil consumption due to cylinder scoring. Timing chain being the big concern.

When timing chain issues arise, You can usually get away with a basic service for about $1,600 in parts from JHM (they have updated guides to prevent the issue from returning in the future). Cost is not horrible if you can do it yourself, but the engine will need to come out.

[G Men 08]

What causes the cylinder scoring?

How bad are the transmissions in these, is it *just* the torque converter (that's what I've always assumed) or does the transmission grenade?

[moyenecorniche]

I have 164,000 miles on my S4.. The motor was replaced at 11,000 miles but that was another issue irrelevant to timing components, just to be clear.

(1) It is a motor which demands steadfast attention to servicing... AND when minor parts fail or about to, replacing them now is critical.
(2) That being said, if you are wrenching your own Audi's for 10 years, then you know what to expect...
(3) Because of the small engine bay and size of the V8, plan on doubling the time to access components. ( unless you are 3ft high with hands the size of a 5 year old lol )

As for the scoring, it's an aluminum block, cannot be resleeved like the RS4 4.2 which is a different block. ( lots of threads here on the 4.2, read up. )
I have to say the motor ( my S4 ) is reliable but finicky as in maintenance required. ( Yes I have to emphasize this point )
One issue with the 4.2 is the immense heat dispensed in the bay so plastic and rubber components do not have long lives.
Oil consumption issues are often due to PCV valve not functioning, the rattle at start is also conducive to the 3 oil valve below the valley pan remaining open instead of closing at motor shutoff..

As for the transmissions, I have never had an issue with the 6 sod manual or my previous Tip. But these are not race cars and if its been launched ( 1/4 ) repeatedly then expect to look into the entire drivetrain for problems ( if there are ) key word here is IF the car was not loved.

If this Allroad passes important health checks then I would suggest replacing all the gaskets up top... Valley pan, heads ... and thoroughly checking out all the plumbing...
Look under at the oil pan, it is prone to corrosion and developing leaks.. ( I just replaced mine ) and BTW the oil pan bolts are not reusable ( but are cheap from the dealer ) and the torque setting is in inch pounds... Not foot ... You will shear the heads off if using the latter..

I would check the tensioner for the auxiliary belt, if somewhat frozen, do replace... Although when my belt snapped, I drove from Holyoke Mass to Westerly R.I. without any alternator..
Didn't use any electronic equipment other than what the motor needed... Needless to say I would not try that stunt again.

You may also want to refresh all fluids in the differentials.

Good Luck with it ...

[rollerton]

From what I've read the V8 in the allroad, A6, and A8 are fairly problem free in comparison to the higher performance S4 and S5 with the carbon issues etc.

What they said ^^. That V8 is NOT the V8 that comes in the A8, A6.
It DOES have the V8 that comes in the S4 that you mentioned above. So..if it's cheap, you could do just fine. But, it's a HUGE hit if the chain guides/ tensioners start acting up.
For me it would depend on price and maintenance history of the car. I'd be tempted to have a spare 2.7 laying around just in case...

[G Men 08]

Thank you for the thorough response Moyen. Very informative.

As for the 2.7 swap, I did have that thought out of curiosity. Any idea how bad the swap would be?

[G Men 08]

I can get the car for $3k. Unsure of the maintenance history.

[mithril]

What causes the cylinder scoring?

How bad are the transmissions in these, is it *just* the torque converter (that's what I've always assumed) or does the transmission grenade?

Assuming the V8 Allroads use the same ZH 5HP24a as the A6/S6 the torque converter is almost never the issue, TC failure is a 2.7T and 4.2T issue. In Audi's the 5HP24a fails for 1 of 2 reasons, either real seal fails over time allowing loss of ATF pressure or Clutch Basket A breaks from repeated pressure spikes hitting the clutch packs for forward gears 1 to 4. The main symptom for the first issue is a loss of reverse, reverse requires the highest ATF pressure so it's the first gear you loose when pressure drops. The other is usually noticed when gear shifts get extremely clunky, like shake the entire car clunky, and the fault is caused by sticking valves in the valve body causing uneven ATF pressure.

In both cases the fix is to remove the transmission and rebuild it. You could try the 6MT swap as well, but I don;t know if anyone's done that in the 4.2AR. Rebuild and swap both cost about the same.

[mr_dave]

Assuming the V8 Allroads use the same ZH 5HP24a as the A6/S6...

I believe all Allroads use the 5hp19, v6 and v8.