No boost and strange noise

[Jim Wallace]

I'm hoping someone can give me a few pointers. I have a 2012 E84 25D and recently I've been getting the following intermittent codes:

4862 Air System, Air to EGR Mass Flow, Plausibility

4873 Exhaust-Gas Recirculation Cooling, Plausibility

4530 Charing Pressure Control, Control Deviation

The car drove fine, no loss of power. I removed the EGR and Cooler to check them and there was very little carbon and both clear. Both were replaced around 10k miles ago under the BMW recall. 

The car has now gone into limp mode and is making a weird noise when reved. It's quite at idle but makes a lowish pitched drone or whining noise when the engine is reved. It's not a high pitched whine that I would associate with the bearings in the turbo. I had a fondle of the turbo spindle when I had the intake pipe removed. It spins freely and I cant feel any play in the bearings. The car has only done 55,000 miles and has a full service history with oil changes every 4,000 miles so I'm hoping the turbo hasn't failed already.  

I thought I'd try and check out the control system first. I looked at the parts diagram for the turbo vacuum control and started trying to check things. Connected a vacuum gauge on the supply side and the vacuum appears steady so I don't think there is a leak on the supply side or vacuum tank.  

I removed the vacuum line from the part labelled Vacuum box (15) on the parts diagram and the droning/whining noise stops. I connected a syringe to the Vacuum box and as i draw a vacuum the noise returns. Turned the engine off and used the syringe to draw a vacuum while feeling the actuator arm under the vacuum box and the arms moves/returns freely when a vacuum is applied/released. 

I can't work out what this vacuum box operates. The actuator arm passes down through the exhaust manifold and is connected to the turbo.

 

Can anyone tell me what this does or suggest any next steps to try and diagnose the problem? 

Thanks 

Jim

[Greydog]

Morning JIm

If memory serves your car has twin turbo's a small one for low/mid range and the bigger one below for mid/top end boost. The vacuum drive shifts boost to the larger turbo, so when you felt for any wobble which turbo were you feeling? and which side remember the exhaust side really does take a battering. From your description the Vacuum drive is working but the flap it operates into the large turbo or the turbo it's self needs some investigating

Those are my thoughts

Dave

[Jim Wallace]

Many thanks for your input Dave. My car does have twin turbos. I checked for play on the cold side of the larger/bottom turbo by removing the air intake but I take your point about the hot side taking more of a hammering. I can feel the actuator move at the vacuum box but I can't access or see the point where it connects to the turbo. I don't know if the flap moves freely - maybe the hot side is full of carbon as I tend to do short trips. Time to dig deeper so I've just dropped it off with a local turbo specialists who say they can run diagnostic tests and do a route cause analysis. 

The car has only done 55,000 miles, full service history with oil/filter changes every 4000 to 5000 miles so I'm hoping the turbo hasn't failed already 😟 

Thanks

Jim

[Greydog]

Morning Jim

A Seat owned by a neighbours wife from new but only used for school run duties was completely clogged at lower miles than yours. Predictably the Dealer said new Turbo new EGR and a swathe of other parts £££, a local Diesel specialist stripped, cleaned and rebuilt everything and gave her the advice to give the car a good run at motorway speeds once a month. Years ago my son had issues with his Toyota pickup the dealer mechanic told him an "Italian Tune Up" (engine up to temp and keep revs over 2.5k for half an hour) needs doing every few weeks. As a Tree Surgeon he tended to be trundling around off road at slow speeds and low revs.

With luck it's just the actuator mechanism 

Dave

[Jim Wallace]

Thanks Dave - just noticed your post as Outlook has been filing the notification in Junk Mail. I took it to a local turbo specialist who specialize in diagnosing root cause of turbo faults/failures. They advised that the actuator that switches between the high and low pressure turbos was not holding vacuum. He said he could try replacing it but that wouldn't fix the underlying problem. He pointed out that there was oil in the intercooler pipes and recommended have both turbos refurbished. Apparently, the soot build up in the DPF caused by short trips reduces airflow in the exhaust which increases the pressure on the hot side of the turbo. The seals in the hot/low pressure side are prone to leak if the exhaust pressure increases and the leaking oil is carbonized which further damages the seals. His explanation makes sense to me and I didn't want to pay to have the actuator replaced only to have further problems in the near future. The turbos have been removed and sent for refurb and I'm expecting a bill of around £2,500 ☹️. I asked if the refurbed turbos would fail again if I keep doing short trips and he said not if I ask him to "delete" the DPF. 

[Greydog]

Morning Jim

Just be aware that if an MOT Garage suspect a DPF delete it's an automatic fail plus it's logged so going elsewhere wont work 

Better solution is just give it a good run once a month in my opinion then no risk of MOT fail

Dave

[Jim Wallace]

Morning Dave

I'll bear that in mind. I do the occasional long run but maybe need to do so more regularly. The car didn't smoke and according to my scan tool the DPF have been regenerating. 

When the turbo guy explained that the root cause was the DPF and said he could "cure" it, I asked about the risk of MOT failure. He reckons that the emissions without a DPF are way below the limit and that his particular fix is not detectable. I'm not so sure now. He said something about drilling a hole somewhere but that doesn't sound like it's undetectable to me...