South Africa

South Africa
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17 June 2013

Hevac and rocker cover oil control

Were on role here today.

This section is one that can confuse a little so may not be ideal for non technically mind people.

First up is the HEVAC unit, you know the unit that controls your interior fans and temp settings.
On later P38's, 1999 and up a different unit was used which did not power the AC unit directly to engage the clutch, later models did this via a relay but as the later units can be difficult to locate a early model (1995 to 1998) can be used but requires a daft simple mod.

The process requires you to remove the AC relay in the engine bay fuse box and add in a loop wire, yipe its that simple..
Thanks goes to "Handy Andy" in Johannesburg or "Jozi" as some call it, also not to be confused with "Little Johannesburg" in the USA, this is Johannesburg, South Africa

The next topic can always bring up a hot debate on this mod.
I agree manufacturers spend lots of money and time on development but do they always get every bit right.........NO, if you say yes we can argue till the cows come back from Neptune..

On the Famous Rover V8s oil consumption can be a issue, on some motors not so and it be original not ever opened, a head job or rebuild.....some motors will burn oil......why why why nobody seems to know... and it got me thinking.

Dip into a Range Rover classic and on the right side rocker cover is a fat vent tube sticking up, if you remove this tube inside it filled with a type of mesh, its not there for no reason.
Its job is to prevent oil being sucked into the inlet manifold the vent tube pipe is attached too.

On Disco II and P38's as the pictures show below there is a baffle plate to prevent oil being sucked through the vent pipe, if so then why is there oil in the inlet manifold....its simple really and its to do with oil vapour, oil companies and motor manufacturers alike call this "Inlet wetting".

In the first picture you can clearly see the plenum gasket is wet where the large holes are, this gasket seals up the upper inlet cover to the lower inlet manifold and the inlet ducts are where the large holes are wet, this wetness can only be caused by the vent system on the engine and occur on cruise and de-acceleration which in turn creates high vacuum on this vent circuit.

To possibly remedy this issue I came up with the idea in the pics below, I hope it works as the results are not in yet and will only know in a weeks time, if anyone does this mod please let me know your findings as I'm convinced it will work.

Please e-mail feedback to

Also note that this problem is notorious on VWs

On the Gems its a simple job but not so on the Thor engines (Disco II and later P38s)
A light coat of oil is clear, dark rings around the large holes

Inside the right side rocker cover, or some call it a "Tappet cover"
Seriously though its called a rocker cover.
Inside this cover is a baffle plate (Gold) and that's suppose to stop all the oil..

Remove baffle plate

Oh before you strip it down did you remember to buy brass pot scourer.
If you forgot I assume you have a bicycle.....

mmm do I need to say more, ok place the brass scourer around the vent tube section inside.
Before closing it all up remove the plastic bit inside the vent tube and make sure its clean, DO NOT FORCE IT OUT, IT WILL BREAK (Disco II and later P38s)

Do remember to install the baffle plate...
Here's hoping it does as it should and convinced it will.
(Update to follow)