3 replies to this topic

[lotusk]

i've been investigating the oil leak on my '98 Mpi a little further this evening and decided to check the breather hoses were not blocked. Should the hose from the timing chain cover to the throttle body be blowing or sucking air at the throttle body end? Currently I can feel a very faint blow of air when I put my finger over it at idle.

On the other hand, the other hose into the throttle body (connected to the inlet manifold, i think) has a large suction force. Apologies for the random questions - this is my first mini and i'm still trying to fully understand how it works

Thanks, Kieran.

[chris_gilly]

i've been investigating the oil leak on my '98 Mpi a little further this evening and decided to check the breather hoses were not blocked. Should the hose from the timing chain cover to the throttle body be blowing or sucking air at the throttle body end? Currently I can feel a very faint blow of air when I put my finger over it at idle.

On the other hand, the other hose into the throttle body (connected to the inlet manifold, i think) has a large suction force. Apologies for the random questions - this is my first mini and i'm still trying to fully understand how it works

Thanks, Kieran.

yer i think it should be blowing, so the breather goes to the throttle body manifold air box etc... then into the intake to slow combustion down. i think!!

[Sprocket]

They blow and suck, but blow more than suck

The whole purpose of the breathers is to allow blowby gasses from the sump to escape and also reduce the hydrocarbon emissions of the engine. These are fed back into the intake of the engine and burned. The system is called a Posative Crankcase Ventilation system PCV for short. what this means is that it uses the posative pressure in the crankcase, and the vacuum of the inlet manifold to evacuate the blowby gasses. This is why when you remove the rocker cover cap while the engine is running, the engine is heard to change tone. There is a slight vacuum in the engine. This is also why you have to replace the rocker cover cap regularly, as that in itself is a filter for air that is being drawn in, down through the engine into the sump, out through the breathers into the inlet manifold and into the combustion chamber, and then out the exhaust.

[lotusk]

They blow and suck, but blow more than suck

The whole purpose of the breathers is to allow blowby gasses from the sump to escape and also reduce the hydrocarbon emissions of the engine. These are fed back into the intake of the engine and burned. The system is called a Posative Crankcase Ventilation system PCV for short. what this means is that it uses the posative pressure in the crankcase, and the vacuum of the inlet manifold to evacuate the blowby gasses. This is why when you remove the rocker cover cap while the engine is running, the engine is heard to change tone. There is a slight vacuum in the engine. This is also why you have to replace the rocker cover cap regularly, as that in itself is a filter for air that is being drawn in, down through the engine into the sump, out through the breathers into the inlet manifold and into the combustion chamber, and then out the exhaust.

Perfect explanation guys, many thanks! I think i'll take the hoses off and check they are not blocked anyway but at least I now know what they are supposed to be doing