Would an oil catch tank work on my diesel T4

if it's non-intercooled, and you've disabled the EGR valve (if it has one??) Then it's really not going to make all that much difference

If it's intercooled, the extra oil film buildup can reduce the intercoolers efficiency after a long time. If it still has the EGR system enabled, the soot mixes with the oilly mist, and turns to sludge. Only have one or the other, don't try to have both (hint: get shot of the EGR system!)

The crankcase pressure itself pushes out the oilly mist via the breathers, and on a TD, the turbo will indeed "suck" the excess pressure out of the crankcase, and it will actually burn the oilly mist rather nicely.

On a petrol, the oilly mist just reduces the effective octane of the fuel, on a diesel, it just makes the inside of the pipes a bit grotty



A catch-tank WILL NOT remove the oilly mist from the breathers output, they're actually meant to catch any large amounts of oil encountered during hard cornering, when it finds its' way out of the breather pipes. Most modern engines don't have this problem, due to well-designed breathers


But if you like the way they look, fit one on the pipe that feeds the breathers into the intake manifold. After several hundred miles, you may get a small amount of condensed fluid, but not much else

My Peugeot Expert 2.0HDi is suffering from similar problem. It's comming from the turbo when "on boost" and not the breather. Simple case to rebuild turbo but if left the engine will eventually run on the engine oil until it seizes etc. In that situation turning off the ignition does nothing - you have to stall it. Better to sort out the problem as a matter of priority than add a catch tank.
My symptoms are visible when accelerating hard at any speed so turbo kicks in as there is clouds of black smoke (overfueling as the engine is burning it's oil). An OBD code reader diagnostic check showed nothing.

Paul H

not quite sure on your logic, of assuming a catch-can on the breather pipes, will cure an ovalled bore? (quite possibly something else going on instead)

ah well, as long as it works though eh?

and FYI, MAP = manifold absolute pressure

This will normally have some from of diaphragm, which is then pushed against the sensor. Specifically made to stop oil/petrol destroying the sensitive electronics.