Easy Breathing

filter intake and blanked breather port

A very simple little modification, this one.  I have been using a K&N air filter since well before the rebuild, which has the advantages of not needing servicing anywhere near as often as a standard paper filter, being cleanable and allowing better breathing (it did make a small but noticeable improvement when I first fitted it with the 12J engine).

The problem I have been having since the Tdi retro-fit is the engine’s oil breather.  With my 12J, I had the old breather system where the breather connected directly to the inlet manifold, so all oil mist and vapour was sucked directly into the cylinders.  That ran the small risk of an engine runaway should the engine start breathing particularly heavily, so LR changed the design so that the breather routed to the filter on later 12Js and all 19Js.  This protected the engine but resulted in clogged filters.  When the Tdi was introduced, the breather was connected to the induction system between the air filter and turbo charger, eliminating the filter clogging but allowing the turbo,  intercooler and air ducting to collect the oil.  The only problem with that is the oil collecting in the intercooler, eventually blocking it.

12 filter with Tdi breather running into intake (thinner hose)

My induction system uses the 12J’s air filter between a snorkel and the Defender turbo charger, running via a standard intercooler to the manifold.  The ducting is not standard, being made of sections of duct and hose from Tdi and TD5 Defenders and Discoverys to suit my engine bay.   The snorkel is attached to a 200Tdi Defender wing intake, which runs to the air filter via the Defender flexible pipe.  To join the pipe and filter housing I used a 19J’s adapter, which is just a steel pipe of changing diameter, the large part of which clamps around the filter intake and the small section of which is inserted into the flexible pipe.  This adapter has the engine breather inlet port, so my breather is just upstream of the air filter just like the 19J (this had been blanked with the 12J, but my Tdi induction tract has no other possible connection).

So, the air filter has been getting continual oil contamination from the breather.  The standard 12/19J paper element filters have a plastic shield around their top half, with stator vanes at its bottom edge to generate a vortex inside the filter housing, centrifugally throwing out any oil and dirt to trap it on the filter housing and keep the filter as clean as possible.  The K&N filter is plain and unprotected, so the top area was getting significant oil contamination from the inlet air rushing straight into it.

modified K&N (plastic shield from 12J filter)

The good news is that a quick test fit with an old but relatively clean spare paper filter’s plastic shield onto the K&N worked – it fits perfectly.  So, the K&N has been given a wash and re-oil, and has been fitted with the shield before re-installation.  The filter should stay much cleaner from now on.  I’m surprised that K&N don’t mention in their fitting instructions that you should remove the shield from the old filter and fit it to theirs, but I thought I’d share that tip with those of you running 12Js and 19Js with that filter.