4.2TDi sudden death

MikkiJayne · #1 23rd November 2018, 07:31 PM

I'm not sure we are talking about the same thing here.

This is the G40 sensor removed with the trigger ring on the end of the cam. The pic is from a 1.8T, but its the same concept as the V8.

It should be simple to see the trigger ring turning, but your description of looking down a hole suggests its a completely different arrangement to this?

I'm inclined to agree it doesn't sound (literally) like a mechanical issue - if the cams on one side were stationary the engine likely wouldn't even turn over. There's no wiggle room in a diesel engine.

erubus · #2 23rd November 2018, 11:16 PM

We're not talking about the same thing.... Well, we sort of are. The G40 on the 4.2tdi looks much the same as a crank sensor. There is a hole in the bottom rear of the left bank rocker cover that the sensor fits into. Although fairly accessible for an A8, it's still really awkward to get to and all the action is happening 3/4" down a hole that you can't see down.

Putting the endoscope down makes me fairly certain that the left bank camshafts aren't turning.

MikkiJayne · #3 24th November 2018, 08:12 AM

Ah that makes more sense now. Interesting that its a hall effect sensor in that configuration. Usually those are inductive pickups, but the wiring diagram is definitely a hall sensor.

How hard is it to get the cam cover off?

erubus · #4 24th November 2018, 08:50 AM

Getting the cam cover off will be a pain as all the injectors will have to come off first. This isn't a huge Hasse but I won't be able to turn the engine over with the cover off without getting all new seals etc. It's not something I want to be doing unless I'm 100% sure the head needs to come off. I think I'll be better taking the manifold off and eyeballing the valves first to confirm 100% then I can decide whether to fork out for a new engine/head or whether to break the car and try and make some money back.

ivanhoe · #5 24th November 2018, 09:11 AM

Sorry to hear of your problems. Is the vcds mileage correct at 365000km, 226000miles?

erubus · #6 24th November 2018, 04:37 PM

No, the mileage, like the date and time, isn't correct. That's not to say it's not a high mileage car but it was a one owner car that had been religiously services at an Audi dealer. There were receipts for absolutely everything. The only job not done by Audi was the gearbox oil and filter changes every 40k. If it wasn't for that and the price, which reflected the (90% motorway) miles, plus all the extras and generally excellent condition, I wouldn't have bought it.

I've been offered a 20 year old Toyota Corolla for sweetie money until I decide what will happen with the A8. It's going to be a change. My last three cars have been 8's and I've only had Audi's for the last ten years or so except for the landys.

erubus · #7 1st December 2018, 02:36 PM

Little update. I put the endoscope down the little plugged holes on top of the cam sprocket housings. On the n/s bank, you can see everything spinning away clear as day. O/s has no movement at all so definitely got a snapped chain and presumably a wrecked head.

How much do you guys think I'd make selling the car as is, 2008 excellent condition in general, gearbox oil changed at 60k intervals.

Probably make more breaking it but I don't have the time and fixing it is unlikely given the cost of parts and time involved.

Gill