Turbo failure

[bob6600]

Wasn't sure whether to post this in other marks as it is regarding a BMW (sorry) but it's a general question regarding turbo failure.

Friend of mine recently bought a '09 520 diesel BMW and his car broke down yesterday. AA came out and confirmed the turbo has blown and there is no oil in the car which I'm assuming having seen this before that it sucked the oil out. Car was bought to a halt almost immediately but there is now the question of engine damage. The AA has said what I was thinking, that the engine is probably knackered.

The garage where it was purchased from have replied this morning stating that the turbo had failed but it is only 'a small job' and car will be fixed. Now my friend knows nothing about cars and wouldn't know if it was fixed correctly or not and is worried if he has the car back he will be left with a damaged or unusable car needing further repairs. I have agreed to drive it once it's 'fixed' listening out for knocks from the engine but question is will it be very obvious if it has any top end or bottom end damage? Will he have a very rough running engine?

I can get access to BMW diagnostics but not sure if it will show much? Any help appreciated.

 

[a111r]

If it doesn't knock and sounds OK, you could measure the oil pressure (at idle when hot)?

 

[Bellow]

How does the compressor wheel look? Bits broken from it that have possibly gone through the engine? In which case I'd not trust the pistons or valves not to be damaged - or injectors. Depending on the exact circumstances of the failure, even with a wrecked compressor wheel, if the engine shut down quickly enough, it may have avoided dining on itself. Debris damage to valves or seats (or propping valves open - checkable from above) would I expect, lead to starting difficulties.

No oil? Every bearing in the engine wiped out? Is there enough oil left to analyse (even visual inspection) for bearing metal debris (probably very very fine particles)?
No oil? Where did it go? Through the exhaust contaminating every bit of emissions kit?

Lack of boost (due to turbo failure) shouldn't have stopped the engine. Either (I'm guessing) it seized or maybe BMW software has a low oil pressure threshold below which the engine is shut down. In the latter case, things may not be so very bad.

 

[a111r]

Turbo seals going usually results in diesel runaway, so it is good that that didn't happen.
But yes, the mains, big ends and camshaft will be damaged with 'no oil' to float on.

 

[Bellow]

Turbo seals going usually results in diesel runaway, so it is good that that didn't happen.

Good point. And if the oil from the turbo didn't go into the engine then it must have gone out via the exhaust in which case I'd expect plumes of smoke not mentioned at all.
Which raises the possibility that the engine was run low on oil which then caused the turbo to fail. In which case, this...

But yes, the mains, big ends and camshaft will be damaged with 'no oil' to float on.

....is a given. Ouch!

 

[a111r]

I think any amount of boost present means oil always goes out via the compressor bearing, rather than the turbine bearing?

Bob, worth asking the garage to remove the inter cooler if the compressor wheel looks damaged. They maybe swarf and oil within... that lot goes through the valves and cat with the new turbo operational.

 

[Bellow]

I think any amount of boost present means oil always goes out via the compressor bearing, rather than the turbine bearing?

Tricky one. Pressure is high on both sides. No run away and no (reported) smoke from exhaust.
What is normal failure mode for diesel turbo - seizure or bearing disintegration and unrestrained turbine and compressor wheels?

Bob, worth asking the garage to remove the inter cooler if the compressor wheel looks damaged. They maybe swarf and oil within... that lot goes through the valves and cat with the new turbo operational.

Plus 1.
Any damage to compressor wheel (and/or housing) requires chasing down the debris upstream from the turbo.

 

[Rory]

I think turbocharger failure is pretty common on that engine.

 

[Bellow]

I think turbocharger failure is pretty common on that engine.

Do the turbos just seize or fling their innards at the engine?

 

[bob6600]

Thanks gents for the replies. Unfortunately, I won't get to inspect it as the garage is having it fixed and I will only get to see it when the owner gets it back. The owner knows nothing about cars so doesn't want the wool to be pulled over his eyes. I will try and find out if there were plumes of smoke when the turbo went.

 

[Rory]

Do the turbos just seize or fling their innards at the engine?

I only know from stuff I've read, and it happened to a colleague's 520d - I think usually the bearings go. People say the oil should be changed far more frequently and I recall something about servicing the crankcase oil breather. Also changing the turbo oil supply pipe when the turbo is changed.

I had one go on a car years ago and nothing dramatic happened, it just felt like the car was being strangled.

 

[a111r]

Do the turbos just seize or fling their innards at the engine?

I blame both extended drain intervals and poor routine maintenance. Turbo twin brass bearings have a very small surface area, thus are easily eroded.
When too much radial play develops through such wear, the excessive play finally results in the compressor wheel hitting the A/R housing.

If the engine has lost / consumed it's oil by other mechanical faults and runs too low, the insufficient oil supply will seize the turbo's shaft within the bearings.

I'd also ask the garage for proof of what they fitted. A £150 Chinese unit would suit them...