D5 (2005 on) Oil Consumption & Soot Filter Full - THE TRUTH

[Nickthecook]

Mention the issue surrounding the Euro IV D5 (D5244T4) and stupidly high oil consumption and everyone shouts back 'Seized Oil Rings.' Well now you can shout back, 'Wrong Sucka.'

Maybe a little oil is getting past the rings, but the majority of it is actually being sucked from the engine. It took some working out and my head really hurts now. Ok, here goes......

Your oil is being pulled from the crankcase breather pipe where it enters the air intake, next to the turbo inlet. You see, the Euro IV uses what is known as an HPL EGR system, albeit a very poorly designed one. HPL stands for high pressure loop. Unfortunately, Volvo messed it up by

a) using a Pressure Only MAP Sensor (it bottoms out just below atmospheric pressure and therefore doesn't show if there's a Vacuum Present) But Diesels work with excess air? That's not strictly true of the Euro4, I'm afraid.

b) They put the MAP Sensor on the intercooler, when it should have been placed the other side of the EGR/Throttle body. Ever wonder why the hole's not been cut for the sensor on a new intercooler? Now you do.

c) Poor control systems in general, with no safety net. As one article stated, 'Using two separate closed control systems for the EGR Flow and the Turbo Control, risks serious consequences without adequate oversight.' HPL EGR was already 2-3 years old by the time the Euro IV was released, so I'm not sure why Volvo made such a mess of it.

The HPL system works by utilizing the VNT Vanes and throttle to alter air flow and create a Pressure differential between the fresh air going in and the Exhaust gases coming out. Done correctly, a high flow of EGR is drawn through to the intake side. Not done correctly, a Big Vacuum is created in the intake, which sucks open the CCV Valve, on the exhaust side you see the opposite occur in the form of high pressure exhaust gases, which causes the DPF pressure sensor to spit it's dummy out.

This isn't just a theory, I have diagnostic data to back it up. Basically, when pulling away after slowing down and using the engine to brake, I was billowing smoke out of the back. Not so much D5, as Bonds DB5 with the smoke screen switched on. This just didn't fit in with the 'Oil Ring' issue everyone said it had. VIDA of course didn't show the Vacuum, only the MAP sensor bottoming out. So I used Torque and set it to calculate boost with the MAF Data instead. My fist thoughts were.....WTF? A 16.2hg vacuum in a Diesel Intake, this can't be right, but then I remembered the reason I'd decided to use the MAF sensor, it was because the MAP value had suddenly dropped and bottomed out. Then I looked at the Air Intake Temp and saw a sudden, sharp drop in temperature. This of course fits with the sudden drop in pressure.

Now for the other side. I've recently purchased 2 x (non Volvo, but not cheap) Differential Pressure Sensors. Despite being the correct part, neither will adapt to within the specified parameters. I can only assume Volvo's attempt to rectiftly their design **** up through a software patch (DPF/Oil Level) changed the original specified values for the sensor. Worryingly, the old sensor never threw a code but the engine felt like it had reached the end of it's days. However, in between the relentless DTC's generated by the new sensor, The car was an altogether different beast. Smooth, quiet, responsive and **** me it's got some power back.

With regard to the 'Soot Filter Full' messages, I'm more likely at present to get the message during lift off, than under boost. Lifting off/ engine breaking, seems to very quickly turn 20psi boost, into a -10psi vacuum on the intake, this of course means a spoke in pressure exhaust side. As an after thought, the DPF system on the D5 has to be able to cope with the increased speed and pressure of the exhaust gases, generates by the HPL EGR system. This is probably another reason the original part doesn't adapt, as the other vehicles it also fits do not have this system.

As I've only just got to the bottom of this problem, I don't as yet have a solution. But I would suggest a new CCV Valve a good place to start. Followed by an EGR overhaul and a Turbo control overhaul. Then there's The DPF, which seems to play a major role in the problem, as the more restriction there is, the worse the intake/exhaust pressure differential becomes.

I would imagine the so called 'rising oil levels as a result of bore wash' was more than likely a vacuum in the crankcase, sucking the diesel past the rings.

Finally, I find it extremely hard to believe Volvo were unaware of their design error, so I may just contact them to ask why they let so many loyal owners waste their money, trying to resolve a problem they didn't understand. I even know of owners who have sold/scrapped their Pride and Joy, rather than waste anymore money. One poor Guy even said to me, 'I'm certain it has something to do with a Vacuum.' Volvo, you're utter B******S for keeping this one to yourselves.'

So there you go, finally the truth as to why some Euro IV's consume oil nearly as quickly as they do diesel. When I get a minute, I'll post some screen shots of my diagnostics to back up the above. But in the meantime, if you have one if these problem cars, try calculating boost via the MAF and see what figures you get. Rapid engine braking seemed to produce the biggest intake vacuum, although a long downhill section of road could draw a huge volume of oil from the crankcase. Please let me know how you get on, both with testing for the problem and also any fixes you may have found.