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Range Rover (BMW M62) V8 PCV System
About
The PCV systems function is to re-cycle blow by gasses that find themselves in the crankcase, in the olden days these gasses used to be vented to atmosphere. In modern times this was deemed to be unacceptable so these gasses are now fed back into the engine via the intake manifold to be burnt.
The crankcase ventilation system is pressure regulated by a valve mounted at the rear of the inlet manifold. Vacuum supply ports are incorporated on the valve for the power brake booster and the fuel pressure regulator.
At idle when the vacuum is high, the valve closes down and only allows a small amount of blow-by vapours to pass into the manifold. At part to full load conditions, the spring opens the valve and additional blow-by gasses flow into the manifold.
The crankcase ventilation system uses a cyclone separator to purge the blow-by gasses of any oil vapours. The oil vapours condense in the separator and drain back into the sump.
The Problem
The gasses that pass through the PCV hoses are a nasty mixture of unburnt fuel, exhaust gasses and oil vapour. As such they attack the rubber PCV hoses and turn them to mush in about 5 years or around 60,000 miles.
Initially the hoses collapse under the vacuum, so they stop serving their purpose as they close up when the engine is running, particularly when the engine is under load. The next thing that happens is that the build up of vacuum causes the hose to pop (inwards), this then results in your vacuum system being completely open to the elements.
As a result the engine will often idle roughly, mpg will suffer and you will get condensation/water ingress. Common fault codes are, but not limited to P1174 and P1171. Land Rover dealers have been known to diagnose this incorrectly as a blown head gasket – as the symptoms (rough idle and water in the oil) are similar.
The Repair
There are four hoses in the PCV System, two large hoses running from one valve cover to the cyclone and from the cyclone to the PCV Valve. One small hose returns oil from the cyclone to the sump and one is the PCV Valve return.
Typically, the two large hoses fail and the cyclone hose is often not too far off. The two main hoses are fairly easy to repair as long as you have removed the engine cover and the pollen filter housing. The cyclone hose is difficult to reach and to get to the bonnet must be put into “Workshop Position” if you are to have any hope of reaching it.
