tigerdurham

I have a Legacy 2L Diesel 2010, and it's started having issues with the oil level increasing. The first time, the DPF warning light was flashing, and the fault reported was over dilution of the oil. The engine is sounding much rougher, with a regular tapping audible. I have monitored the oil level since it's been back from the garage, and it's increased again. I have it booked into a Subaru garage for diagnostic testing, but wondering if you guys have any ideas.... - is this something that is a known issue? I also want to prepare myself if it's looking like a big bill!

modrich

iTrader: (2)

This is a common problem related to DPFs and thy're actually meant to do that unbelievably! Whenever there is a failed DPF regen the un-burnt diesel drains into the sump raising the oil level and thinning it meaning you're not getting the correct levels of lubrication thus causing the tapping noises, not good!

We have a Mazda5 diesel that is only used for around town driving (not recommended for cars with DPF, ie pretty much all diesels LOL) so had to have the 'things' modified and re-mapped, has been perfect ever since.

ALi-B

iTrader: (1)

Slight correction there it's not a failed regen that causes this, but the repeated active DPF regenerations which is occurring more often than normal (be it failed or successful). If there is a partial blockage in the DPF or there is a fault with engine making it produce excessive soot (you will not see the soot as its trapped by the DPF) it will perform active regens much more frequently. The same situation will happen if the engine is shut down before a active regen is complete; It will reattempt to regen next time the car is driven at operating temperature...if the engine is turned off again before it completed, it will keep on reattempting to regen until its eventually driven long enough for it to happen...meanwhile the oil level keeps going up and up....

As every active regen means the engine ECU post-injects extra fuel intended to be burnt by that catalytic converter. The problem is some of it ends up going past the piston rings and diluting the engine oil. So the more active regens, the more oil dilution occurs, this can be made even worse if there is a injector fault or piston ring fault allowing more unburnt fuel to get into the oil.

From my experience I seem to see this problem is more common on engines with Denso engine management...Mazda MZR-CD, Mitsi L200 etc..they all do it. Bosch EDCs do it too but I only usually find it on Ford/PSA DV6s with ash in the DPF.

Interestingly on the Mazda and Mitsi that get the oil dilution/high oil level fault codes logged in the ECU have no oil level or quality sensors!!! The ECU guesses it from the amount of active regens it's done. I'm fairly certain the Subaru diesel is the same in this respect as they use pretty much the same Denso engine management system. I could be wrong though as I'm lucky enough to not yet have a Subaru diesel in with this particular fault . And the L200s get shipped off to the dealers as our equipment won't properly talk to modern Mitsubushis (which I'm relieved to admit - the last one the dealers couldn't fix and ended up dropping in a new engine, I couldn't work out why they replaced the engine, I'm just glad it wasn't my responsibility ).

Bottom line is though..it's putting too much fuel in the oil. Be it from too many active regens or a injector/piston ring issue. Its usually the former.

It's not a quick one to diagnose, but I'd first be looking at the exhaust pressure before the DPF and log it, if it's not excessive (blocked), drive it until it does an active regen or manually force a regen and after completion compare the pressure as well as noting exhaust temperatures to see if anything abnormal is found. Be it a sensor fault or the DPF not fully clearing itself during regen due to containing non-combustable particles (ash). If the latter is the case then the DPF needs replacing or removed for cleaning.

If it's not the DPF but it's blocking up quickly then it's looking for what causing the engine to produce too much soot (air leaks, EGR, injectors, inlet restrictions, tuning boxes, dodgy remaps etc). If that can be ruled out it then it's looking at physical engine issues; injectors or rings...by then I think I'd have lost the will to live. LOL.

Obviously I'm talking from a technician's viewpoint: it would be easy just to say "ya DPF's buggered mate" and whilst its possible, but to be sure it needs to be proven that regens aren't clearing it- which is why the exhaust pressures and temperatures need to be logged before, during and after regen and during test drives....hence not a quick job.

The other concern is engine damage due to the diluted oil. If the level is too high the oil needs changing asap otherwise severe and permanent engine wear occurs. The Subaru diesel is well known for failed crankshafts, degraded oil will make this happen sooner.

Will it be expensive? Well firstly you are looking at a oil+filter change, test drives and a possible forced regen as a minimum at the very least just to find out what is going on. If you are lucky it will be just down to driving style and needing a extended drive, or maybe a faulty sensor. If this doesn't fix it then much bigger bills will be likely.

modrich

iTrader: (2)

exactly what I was trying to say...cough

Ali-B, what manufacturers use Bosch ECUs that don't suffer with DPF issues?

ALi-B

iTrader: (1)

Everything with a DPF has the potential to have a DPF issue.

What I meant was the raising oil levels. The worst offenders I've found on Mazdas and Mitsubushis (like in the worst case having to suck out 3 litres of excess oil/fuel before seeing a normal level on the dipstick after the oil was changed a month earlier).

The difference between Bosch and Denso I think is the way they calculate and sense oil level and quality (soot loading or dilution). They both do, but a lot of cars with Bosch systems have oil level and/quality sensors as a feedback; Volvo, merc, VAG, BMW, JLR so usually a service warning pops up long before any issues are noticed with the oil level.

The exception is the Ford/PSA diesels which are Bosch but have no sensors, instead they will chuck it into limp home if it thinks it's doing too many regens or they are taking too long (p2458 is very common associated fault code), I've had these do an active regen immediately after completing one!! You can imagine what that does to the oil, but the code and limp-home mode prevents it from going too far...I suspect some of the Denso systems don't do this and just keep on attempting regens even when the calculated oil dilution is too high.

tigerdurham

Thanks Ali-B. Just so you know, the car has 139,500 on the clock - and I average around the 30k mark most years - most done on longer journeys. Nothing has changed regards my driving distances for commute etc, yet this issue has only just started. I had the DPF filter forced regen'd at around 85,000, and then it's been removed, completely cleaned, and was reading less than 1% soot levels after the clean - this was at around the 135,000 mark (the DPF light came on). It has now developed this oil dilution problem (DPF was reading 35%) - I've discussed the regen scenario previously with my garage as they had the same experiences of why this typically happens, and they don't believe it's down to not reaching/aborting regens (as nothing has changed in my driving patterns since I got the car with 8,000 on the clock)......so the suspicion is on something else....which is worrying It seems strange that I've not had this issue until now

ALi-B

iTrader: (1)

It could still be a DPF regen issue, I'd say it needs re-checking to ensure the back pressure levels are acceptable after a regen.

Something that has occurred to me is "I think" these engine have the injector spill-pipes underneath the cam cover; if these leak, the fuel will go straight into the sump.

tigerdurham

UPDATE: So, the diagnostics in the Subaru garage on Friday showed all the pressures, pistons, DPF etc working just fine, and passing the tests. The main feeling from the garage is that it is possibly the crank, but in order to prove it they need to lift the engine out, and strip it to look...... £800 just for the diagnostic work on that. Car booked in to have that started on Thurs - will keep you posted

Smithys STI

iTrader: (1)

With regards to the engine sounding rough and noisey get the garage to remove the engine sump and check the oil pick up, my bet is that it is parshly blocked with carbon.
If it is then get them to remove the rocker covers and one or more of the injectors will have carbon around it,
This is were the injector seals are leaking and exhaust gasses are leaking into the oil causing the pick up to block.
Re seal the injectors and replace the oil pick up and it should sound loads better.
Had this a few times on legacy diesels.

tigerdurham

Hi everyone - so after having the engine lifted out and stripped, the garage have let me know that the big end has gone, and they have found fragments of metal in the engine, and also the DPF needs replacing. They have confirmed that my warranty should cover this, so this is now being referred to my warranty provider.....let's hope they don't argue too much

tigerdurham

Hi - before I start, please can I ask for helpful advice, and not people just slamming the warranty company!!


So the independent engineer has been. As a result, the warranty company are refusing to cover the damage. They are saying that the only way the damage could have happened is due to the DPF being completely clogged, there has been excessive back pressure in the engine resulting in the damage. However, I know, and have proof that there were no issues with the DPF a couple of weeks prior to this + the sensor was checked and working. No warning light was lit either. Please can you guys help me out? Is this the only way the damage could have happened? Or are they just tryng to pull a fast one? How do I best dispute and argue their decision?

ALi-B

iTrader: (1)

Assuming the engine is in bits I'd like to know how the "engineer" declared that the DPF is clogged...did he look down the down pipe and see some soot? well it's a diesel it will have soot And this is not a way of measuring severity of blockage. As I've said somewhere it's very easy to say "ya DPF is buggered". I'd want to see measured back pressure when the engine was running.

Secondly, if IIRC (not the re-read the entire thread), the oil was contamainated with diesel which in turn has caused bearing damage. Oil contamination happens for a number of reasons; internal spill pipes leaking, misfire, loss of compression, or excessive and repeated regeneration attempts. Have these other items been checked and ruled out?

Also the Subaru diesel has well known and documented issues. Internet search of "ee20 engine failure" will point you the right way.

Lucky_Joe

Hi guys,

I am having a similar problem...oil filling up with fuel (10% dilution within 1000km) in my YM11 outback 2.0D.

Just wondering if there was any outcome to this?

fpan

iTrader: (11)

Wait until they start putting particulate filters in petrol engines.