Audi A6 / C6 - 2007 Avant - 2.0 TDI - BRE Engine - Turbo failure?

[rjsdavis]

Hello to all

I've got a problem with my car. It's presently smoking (a bit, and enough so that it should have failed it's MOT), but in the last few days has developed an additional problem in that it appears to go into "limp home" mode when attempting to reach and cruise at motorway speed (circa 70mph) when the engine is not fully upto working temperature.

About five weeks ago, I had the dreaded oil pressure warning light come on. I had thought that I had been lucky, in that it occurred within a couple of minutes of leaving my house, so I gently drove her back and back to my home, parking up - never starting her again. My local specialists thought it was likely that the hex drive on the pump had rounded off and we were hopeful that this was all that was going to be required. It was. New shaft in. Car seemed to driving perfectly again.

It was MOT'd a couple of days later, and it should have failed. I've experienced the smoke ever since, and have been pouring in injector cleaner and emissions reducer to help reduce the smoking. It hasn't really worked, and might (I guess?) have ended up exacerbating the situation?

Anywho... I've been thinking about this, and the only logical conclusion that I can come up with, is that the very short drive home with the oil pressure problem has managed to damage the turbo, which would explain the smoking, and also the power failure/limp mode issue whilst the engine is working upto temperature?

I live relatively near a dual carriageway, and what I'm finding is that when I leave my village, get straight onto the dual carriageway, the engine temp is only about half-way to the 1/4 mark on the gauge. It goes into limp mode where it will struggle to crawl along at 50mph, so I come off the next junction, pull up, stop, fully reset the car and start off again. The engine has had time to get to working temp by the time I get off at the next junction, so that after the car reset, it then drives perfectly for the rest of the day (albeit with some smoking!).

I just wanted to check my logic before I track down a new turbo, have it fitted and go to the expense of it all... my local specialists also thought it was the turbo, but I just wanted to be belt and braces about it!

Many thanks for any replies...

[Crasher]

Turbo failure after hex shaft failure is just about 100% certain.

[smiffypr]

I will start by saying that I know nothing about this particular engine, but I have lots of questions.
1) the failed oil pump drive, was that still causing the oil pump to turn or was it a complete failure, i.e. zero oil pressure?
2) if it goes into limp-home mode, there must be fault codes, have you read those out?
3) If you drove home very gently after the oil pressure warning came up, surely the turbo would not be working hard, or getting hot, why would you expect that to be damaged and not your engine bearings?

[rjsdavis]

Thanks for the reply Smiffy

I will start by saying that I know nothing about this particular engine, but I have lots of questions.
1) the failed oil pump drive, was that still causing the oil pump to turn or was it a complete failure, i.e. zero oil pressure?

I don't actually know. Best guess is that it was a complete failure. I've attached a couple of pics of the hex driveshaft that failed and was replaced. It's not in a good state!

2) if it goes into limp-home mode, there must be fault codes, have you read those out?

No - there are none. I have VCDS. This was the first thing I looked for. I'm guessing that if I took the time and took some turbo pressure readings that whilst the engine is not up to temperature that there is too much variation between the pressure that the turbo is actually creating, and what is expected by the ECU, which is causing the limp mode (best guess, but logical to me), and that perhaps when the engine has reached working temperature, any damage to any of the seals inside the turbo close up as it heats up, making it largely work again? Again - best guess from my non-expert thinking!

3) If you drove home very gently after the oil pressure warning came up, surely the turbo would not be working hard, or getting hot, why would you expect that to be damaged and not your engine bearings?

This is what I also thought and hoped. When it occurred [oil pressure failure], I immediately took the shortest possible route back to home (3-4 mins) avoiding a short steep hill specifically to try and avoid putting any avoidable stress on the engine at all. Journey was 3-4 mins at 20 mph.

I don't "expect" the turbo to be damaged, but I am aware that if the turbo had been starved of oil, even for only a short space of time, the chances of damage are high. They tell me that it's quite typical for an oil pressure failure to occur at motorway type speeds, and if this happens, turbo destruction is pretty much instant.

The thing is, I very strongly suspect that the turbo is damaged, not failed, which is why it does still drive and seems to explain the symptoms I'm experiencing. After the guys repaired the oil pressure hex drive, they did test drive the car and signed it off and handed it back to me as good to go. They were looking for turbo (or other associated) damage before handing the car back to me - as I say, at normal working temperature she runs fine (apart some excess smoke at idle) and accelerates/drives well/as she should.

IMG_20231019_1243099.jpg IMG_20231019_1243373.jpg

[rjsdavis]

Turbo failure after hex shaft failure is just about 100% certain.

FML!

(but thanks x)

[MFGF]

Hello to all

I've got a problem with my car. It's presently smoking (a bit, and enough so that it should have failed it's MOT), but in the last few days has developed an additional problem in that it appears to go into "limp home" mode when attempting to reach and cruise at motorway speed (circa 70mph) when the engine is not fully upto working temperature.

About five weeks ago, I had the dreaded oil pressure warning light come on. I had thought that I had been lucky, in that it occurred within a couple of minutes of leaving my house, so I gently drove her back and back to my home, parking up - never starting her again. My local specialists thought it was likely that the hex drive on the pump had rounded off and we were hopeful that this was all that was going to be required. It was. New shaft in. Car seemed to driving perfectly again.

It was MOT'd a couple of days later, and it should have failed. I've experienced the smoke ever since, and have been pouring in injector cleaner and emissions reducer to help reduce the smoking. It hasn't really worked, and might (I guess?) have ended up exacerbating the situation?

Anywho... I've been thinking about this, and the only logical conclusion that I can come up with, is that the very short drive home with the oil pressure problem has managed to damage the turbo, which would explain the smoking, and also the power failure/limp mode issue whilst the engine is working upto temperature?

I live relatively near a dual carriageway, and what I'm finding is that when I leave my village, get straight onto the dual carriageway, the engine temp is only about half-way to the 1/4 mark on the gauge. It goes into limp mode where it will struggle to crawl along at 50mph, so I come off the next junction, pull up, stop, fully reset the car and start off again. The engine has had time to get to working temp by the time I get off at the next junction, so that after the car reset, it then drives perfectly for the rest of the day (albeit with some smoking!).

I just wanted to check my logic before I track down a new turbo, have it fitted and go to the expense of it all... my local specialists also thought it was the turbo, but I just wanted to be belt and braces about it!

Many thanks for any replies...

Are there any codes stored, and does the EML light come on when the car goes into "limp mode", or is it just lots of smoke and loss of power with no other symptoms?

The reason I ask is that my old A6 with BRE engine had a similar issue - no EML and no codes. It turned out to be a broken EGR valve. Something to check, maybe, before you spend lots on a new turbo?

Cheers!

MF.

[rjsdavis]

Are there any codes stored, and does the EML light come on when the car goes into "limp mode", or is it just lots of smoke and loss of power with no other symptoms?

Hi MF

Thanks for the reply.

No, there are no codes stored at all. No lights on the dash at all, particularly not the EML.... just the loss of power, with no smoke. The smoking only occurs when the car is idling or maneuvering at low speed, or from pullaway from sitting stationary at some lights for example.

[MFGF]

The issues I had which seemed to be common faults (in my experience with the car) were the broken EGR valve and a split intercooler. Maybe look into these and rule them out before an expensive turbo replacement?

Good luck!

MF.

[rjsdavis]

The issues I had which seemed to be common faults (in my experience with the car) were the broken EGR valve and a split intercooler. Maybe look into these and rule them out before an expensive turbo replacement?

Good luck!

MF.

Thanks MF

The EGR and Throttle Body were replaced with brand new gen parts about 3-4 years ago as they were both clogged up with years of diesel crud. Intercooler looks good, with no leaks and no visible damage.

I think it's inescapable that it's the turbo...