MP4.2+6.0

Just 4.0T's since it is the T = turbo set up. 4.2 was the very end run of a well regarded normally aspirated motor that had 25 years of running improvements with 3+ generations of them. For 4.2, watch the coolant ingress into wiring harness issue for D4's IIRC. Search on prior threads where it was discussed and run into by some. At very high miles, the 4.2's have the mechanical intake flap system I suspect has a finite lifespan. Affects whole intake parts wise and hard to find used as they age, with yards that either want to sell full motor or where others also need the same part and buy up what is around. Dealt with it on my 2000 A6 4.2 at about 12 years old. But, still 3-5 years away probably from even the earlier cases for D4.

Also watch the possible faulty windshield seal near inside center mirror on any early D4. Obvious if it pees water, awkwardly in rain or a car wash, or opportunistically if you hose test it with towel at the ready. That one merits a recall, but I bet Audi is trying to bury it.

KnappAttack

4.2 does not have turbos and are not pushed by the tunes, so no worries about the 4.2 NA engines.

Tunes in a turbo 4.0 running that hard on the throttle for that length of time is never going to be foolproof. "Stuff" happens fast under big boost. One little bit of deto will take pistons out, either holing them or taking out ring lands or even breaking the rings and valves too, when it happens it will waste the turbo impellers as you have carnage running thru the turbos.

Even with the best detonation protections in place it happens. I've seen the best Motec ignitions and injection stuff in the world not save an engine from a bit of overboost or poor fuel. There is a reason the factory only pushes them so far. If you add HP, you have to be prepared to pay the price. There is an obvious reason the factory will not warranty a "tuned" ECU vehicle. Its easy to crank up the boost and power, its also easy to blow them up when put into the hands of the uneducated public that knows nothing about boost, intake temps, octane and fuel quality and all its other workings on the subject.

codydemmel4

I appreciate the replies a lot!

How would you you spot the coolant issue before it’s too late? The AC not working as well or is that a different issue?

codydemmel4

MP4.2+6.0

Coolant issue on 4.2 leads to flaky electrical stuff and wiped out ECU worst case IIRC. Search archives if needed. By chance see this couple year old thread for example that resurrected again today: https://www.audiworld.com/forums/a8-...acing-2888829/

Most common A/C issue is probably that refrigerant needs to be replenished; best by professionals. Need it on my D3 by 7-8 years, and was back to perfect with that.

codydemmel4

Yeah I brought up that old thread today hoping some other people will chime in. Flaky electrical stuff and wiped out ECU sounds really bad to me but I also do not know much. I assume that wouldnt be covered by Audi for a 7 year old car that has 50k miles and I will be the 3rd owner.

They are going to be fixing the AC today they said

MP4.2+6.0

Nuanced, but as the cars age, the final last ditch warranty is the emissions one. But it only goes out a longer period on the California "CARB" state compliant ones. Basically California and the west coast states, and Northeast down to about MD. Search web if you aren't sure about your state or the significance of CARB. The longer CARB warranty for those states covers various newer emissions items. Not sure on ECU without looking at the warranty book.

Needless to say, Audi says as little as possible about the emissions warranties even pre Dieselgate. I doubt many ever try to make a claim that way unless a state emissions station gives someone the exact "how to" roadmap.

Kingscote Boxing Gym

both turbos were badly damaged. one side the propeller had fallen down the down the down pipe the other one was just rattling about like a straw in a coke can if that makes sense. no bits got into the engine. 2 new turbos all in 100% fixed at a cost of £5500. unit 20 audi specialist UK England would highly recommend for any repair.
https://www.unit20.com