Td5 D2 engine - ProVent, a better breather

Have been thinking about how to improve the engine breathing to ensure that only clean cooled air enters the intake manifold.

All running engines internally produce 'blow-by' gases that need to be vented safely otherwise the build up of pressure inside the running engine will only lead to blown gaskets and broken parts. 

These 'blow-by' gasses are mostly hot oil-mist particles suspended in air.

Most engines achieve this by installing an outlet on the rocker cover that directs the blow-by gasses back into the intake system. It relies on the intake depression to help evacuate these gasses, but some systems simply vent the gasses to the atmosphere and rely on the 'blow-by' pressure to evacuate them.

Putting dirty, oily air into the engine intake stream may well satisfy environmental concerns but it is not good for the engine 'breathing' and just leads to the oil-vapour particles condensing, collecting and coating the inside of the air intake manifold, the hoses and the Intercooler.

In extreme cases this can lead to the 'Runaway Diesel' syndrome, where the engine will continue to run on these vapours alone.

Manufacturers are aware of this and design a crankcase venting system that incorporates some kind of filtration designed to catch the oily vapour and in theory allow only cleaned air to pass into the intake stream.

The Td5 apparently has specially designed 'swirl-chambers' built into the rocker cover that are designed to remove excess oil from the oil-mist before it leaves the rocker cover. As Rave puts it...

... " The rocker cover features circular chambers which promote swirl in the oil mist emanating from the cylinder head and camshaft carrier. As the mist passes through the series of chambers between the rocker cover and oil separator plate, oil particles are thrown against the separator walls where they condense and fall back into the cylinder head via two air inlet holes located at each end of the rocker cover" ...

All that happens inside the rocker cover and it is maintenance free for life. Unfortunately, despite the good intentions, oil particles are still carried out of the rocker cover to be deposited into the intake stream and given time, the oily gunk will coat the insides of the intake manifold and the Intercooler leading to reductions in their thermal properties. 

Once the blow-by gasses leave the rocker cover they are directed into the intake airstream via a one way Depression Control Valve (DCV) mounted downstream of the MAF sensor but upstream of the turbo.

It is highlighted in the above image and the trailing hose leads back to the rocker cover.

Reckon some people mistake this unit for being an oil separator. All that it does is regulate the flow of the oil bearing gasses into the intake stream. 

When the turbo spools up and the suction pressure increases, the turbo will draw heavily on the rocker cover gasses and if unchecked could suck out all the oil! This 'depression' valve responds to the increased vacuum draw and closes off the outlet to the Turbo intake till the pressure returns to a set level. In doing so, the unit is able to maintain 'positive crankcase venting' at an acceptable level.

I wonder if there is a way (other then sucking on it) to check the operation of this valve or to find out at what pressure it operates? 

Perhaps its safer to just replace it with a new unit. There is no maintenance procedure for it other then replacement. The unit can fail in use with little visible warning. The ProVent unit I intend to fit has its own version of this valve so I have the option of removing this LR part..

At the very least I intend to remove it from Hx and give it a good clean through with meths. I have already removed it once and the pipework that it attaches to when working on the MAF sensor and discovered a trail of oily deposits inside the intake pipe obviously emanating from the valve outlet. 

More alarmingly, I took this photo of an oily deposit in front of the turbo inlet.

I can see that after fitting the ProVent and getting it up and running, I will have to clean all the components  downstream of the Turbo including the Intercooler and the intake manifold.....

Hopefully the installed ProVent will in future clean up the oily mist coming from the rocker cover before it enters the intake stream. The easiest method is to just vent the pipe to the atmosphere. But that does away with the 'positive venting' that the intake air-stream encourages and is not recommended.

The unit I decided to fit is a 'ProVent 200' made by 'Mann Hummel'....

They are not cheap and they never have been. Also, they are not readily available and my research only produced a couple of suppliers who seem to even know it exists.

I ended up getting one from an Industrial Filtration specialist 'MFE' based in the UK.

It is a lot bigger then it looks! It's instillation is a custom fit and a suitable location in the engine bay must be found. Luckily the Td5 Discovery has enough space on the bulkhead alongside the turbo. (Assuming the 'fuel burn heater' is not fitted!). Hx has its fuel cut-off solenoid mounted here on a convenient and accessible bracket welded to the bulkhead and I decided to fabricate a mounting for the Provent that will 'piggy-back' onto it.

The other concern is that the Td5 pipework is 19mm ID where the main inlet and outlet on the ProVent is 25mm. Reducers can be bought to accommodate this.

I ended up needing the following for the plumbing :-

  -  1 metre of 19mm ID clear reinforced hose

  -  500 mm of 13mm clear reinforced hose

  -  Two 25 to 19mm reducers 

  -  Two 19mm straight plastic connectors 

  -  One 19mm 90° bend connector 

  -  Hose clips x8

I opted to get clear hose just so any deposits can be seen inside them. The 13mm hose is for the 'oil drain outlet' on the base of the unit.

I tried to get this stuff in the local DIY stores, but it was just a waste of time and effort. The Internet won again..

See Also  - "Td5 D2 engine - Fitting the ProVent (1 - 4)"  for a description of fitting the ProVent 200 to a Td5 engine...