Thread: Oil in air intake duct

Originally Posted by glenhendry

Also, there is a 'drop tank' in the air duct (looks standard) where presumably fluids can flow to rather than making it back to the air filter box. Anyone know what that is for?

I think it's a resonance chamber to reduce induction noise.

My old P38 had oil on the butterfly at the throttlebody, this is caused by the PCV (Positive Crankcase Ventilation) valve on the rocker covers sending engine oil vapour back to the intake - it's a part of emission control. If you were keen to get rid of it you could find a spray of some sort to spray in while the engine is running that would no doubt remove it (throttlebody cleaner??). It may also be possible that your PCV is buggered.

Cheers
Keith

The oil is normal on anything other than a brand new condition engine. The mixer ring has a breather attatchment that connects to the fresh air side of the mixer as you can see. You could wash/clean/test the PCV valve, hose and port on the drivers side rocker cover. This is what normally manages the fumes and could be partially blocked by crud. The hose to the mixer is a fresh air inlet to the engine and an overflow during full throttle.

On another note I see your IAC valve (your first finger is pointing to it) doesn't seem to be connected to the gas side of the mixer. This is dead wrong as it now takes clean gas free air and adds it variably to the intake as the idle speed is controlled.



The proper position for the mixer (and the breather redirection) is before the IAC hose take-off so that your idling mixtures are not disrupted every time your idle speed changes. The above pic is of a D2 with a custom air intake and early RRC air cleaner, fitted after a series of backfires ruined a customer's original set-up. The fresh air breather comes out of the mixer to the passenger side before connecting back to the rocker cover.

The thing under your inlet hose is analogous to the muffler in your exhaust. If you remove and plug it you get a bit more induction roar. (V8 noise!)

It also does a half-decent job at collecting water that would otherwise go straight in to the throttle body.

Got half a cup of filtered muddy water out of mine after an unexpected swim a while ago, eh Dave (DT-P38)?

Cheers
Paul.