Hi, can anyone enlighten me of the purpose of this mysterious box? Of course I understand that the crankcase needs to breathe, just wondered what part this box plays. My 2l type4 doesn’t have one. Where this box is usually located I have a vertical exit which is connected to a vertical rubber pipe and crappy mini pancake filter. I’m currently about to plumb this crank vent to my air filter so loose the mini pancake. I can see why this is a much better idea. Just curious what part the oil breather plays?? Ta So item 7 in the photo
I presume if yours just goes up you have a CU code t25 crank case, same difference really. Just plumb it into the air filter
Great, yeh mine hasT25 CU (Jimmy) block, so plumb back to air filter - great. It’s what people in the know have said. Just wondered what it did- for me it’s the human equivalent of appendix!
It is meant to ensure that the air pressure in the crank case is controlled to be slightly higher than atmospheric pressure , so that as the pistons move in and out, the pressure never gets so high it forces oil out through cracks. The stuff that comes out is a mixture of air, combustion products and fuel leaking past the piston rings and oil droplets thrown around by moving parts. The best thing to do with oil droplets is to catch them in a filter like a sponge that drains back into the crank case. The best thing to do with the gases is to feed them back into the inlet manifold to burn them. On a T4 engine this was done in the plastic box on top of the engine containing a sort of spongy matrix with a one way valve into the breather hose and then into the inlet manifold. Best place for a breather is back into the inlet manifold if you lost the proper breather arrangement, through quite a fairly large diameter hose. The one way valve breaks and so they throw it away. On a T1 with an oil bath filter, spewing the breather into the air intake downstream of a flap that stops it leaking out with the engine stopped, and which causes a slight vacuum to make it spray down into the oil bath, keeping it topped up and allowing the volatile chemicals to go into the engine to be burnt. T1 positive crank case pressure is partly down to an air pump made from a spiral groove cut in the boss of the rear pulley. A lot of science, a bit of 13mm ID hose and a filter definitely is not it, setups that let the oil spray drain back are better. 1960's tin pipes pointing down from the oil filler with a rubber valve are primitive ...
The PCV valve is a fuel injection thing I believe. Type 4 cases have a few baffle plates cast into the breather "tunnel" in the case and the usual metal box on top is just more baffles. I expect the CU case has more cast baffles in the case instead as the breather part sticks up further.
