S UMP VENTILATION

For a good working engine it is of great importance that your sump ventilation is working properly. A bad working system is bad for the environment but can also be an influence on the consumption of fuel.
The purpose of sump ventilation is to overcome exhaust gases, which have escaped from the liner walls, and prevent them entering the environment.
These gasses from the sump will be sucked back into the engine.
Most cars and particularly with most Rover V8 engines this will be done as follows.

On top of the engine, usually on the camshaft cover there is a hose (1.), which is connected to the engine side carburetors.
With the engine running a vacuum pressure is created which takes care of the gasses, both in the sump and on top of the engine, any they are sucked back into the engine again. The gasses will now get burned again.
With a good running engine doing the following can check this ventilation system.
If you remove the filler cap on top of the engine you will hear a sucking noise and the engine will run rough. Or it could possibly stop. Fresh air is supplied from the air filter to the camshaft cover or a special filter on top of the filler, which is the case in most injection systems. Basically there are two main reasons which will cause the ventilation to fail, a blockage or a leak.

Blockage in the system is visible by removing the filler cap. You should now see blue smoke and the engine will run as per normal instead of running rough, which it should do. If this occurs you have a big chance that the tubes to, or the airways inside, the carburetors are blocked.
In a bad situation over pressurization in the sump can cause oil leakage through various seals or can even blow the dipstick out.

Cleaning out the tubes, the flametrap (2.) and the airways inside the carburetor carefully, will overcome this problem. Make sure you put on a new O-ring (3.) An overhaul is needed when blue smoke is still coming from the engine after cleaning the tubes.

The ventilation system has only a small capacity but normally this is enough to get rid of the gasses. However if the piston rings are that bad that so much gas is going into the sump the only solution will be a complete overhaul of the engine.

Blockage is caused by the use of poor quality oil, not changing the air filter regularly. The effect of this is the "black sludge", a tar looking substance, which will cause blockage. Also driving only short distances, where the engine is not heating up to its working temperature, will be a possibility for blockage. The moisture from the sump can not be burned completely which gives you an oil based water emulsion, which looks like mayonnaise, which can block the ventilation system.

Leakage of the ventilation system can be detected from by noting a sucking noise around the engine when running at idle speed. The leakage will also cause the engine to use more fuel. This is because fresh air will be sucked into the engine through these leaks. Mostly a poorer fuel mixture will cause the engine to have less power, and to compensate you will automatically press the accelerator more as necessary. The solution for this is simple. Just check all tubes and hoses for leakage and replace the defective parts. Also check for hard and damaged hoses.

D.I.Y. Rene Winters.

Special thanks to Garry Beattie