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oil in airbox

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Im getting a small pool of oil in my airbox. Is this normal? It has now soaked into the filter


When you consider how much oil is flug around and the air turbulence and pressure variances that can exist inside a crankcase.. its surprising that there isnt more oil in the airbox. It is possible, if the oiling is unusally high, that excess crankcase pressure, caused by combustion pressure bypassing the rings, is forcing excess oil mist/vapours thru the vent pipe.. a leakdown test may show the condition of your ring seal. In any case if the engine is tight, I would fit an oil/vapour catch tank in the line.. oil vapours in the intake charge promote detonation and alter fuel burn rates...

.. hope this helps. Jan

If you set no goals you shall surely reach them..

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A bit of oil is acceptable but I would not have thought it should be enough to soak in to the air filter element. Is there an oil separator in the breather hose line? It may be blocked. Some of these use a wire gauze which gets clogged over time. It may be worth removing one, if it is fitted, to have a look at the state of it. A replacement might help. I think a bit of investigation is required, just in case your engine is breathing heavily because of wear.

If it really bothers you and you can't stop it, redirect the breather to the road or a catch tank.

"If everything seems under control, you're just not going fast enough."

- Mario Andretti

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Thanks all for your reply's. Compression test is ok. Oil level is spot on. I have yet to check to see if the tube is blocked. An oil catch tank may well be on the orderbooks.

Thanks again!

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This setup is called a PCV system (Primery Crankcase Ventillation)

Its designed to do 2 things.

Any oil vapours and blowby) produced in the crankase are sucked back into the cumbustion chambers and burnt (for lower emmisions)

A slight ammount of negative pressure can be induced into the crankase, lowering the chance of pressure induced oil leaks.

By by-passing the airbox, you are tampering with the emmisions system, and will probably get a fail if its smog tested (visual non-compliance) if you have to have an inspection.

Its normal to have a little oil present in the airbox, and obviously as the engine wears the ammount will increase, and as long as the ammount isnt any more than a tablespoonfull, I wouldnt be unduly concerned. :P

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Thanks Wayne.

Im only getting a small amount of oil so i'll sleep better tonight!

Thanks again all! :P


My Excel has done this for the last 85k miles ... now at 135k and still pulling strong. You can go back to counting sheep instead of repair costs to send yourself to sleep :-)

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Guest Troy Halliday

As we are on the subject can I have some opinions please. I aam just about to order my catch tank but can't decide between anodised red, or Ali finish Mocal oil catch tank see pics below. I am going to fit it to the back of my custom airbox. I personaly think that the anodised red would be to much red. What do you think?




Oh and if I go for the Ali version it will be polished to a mirror finnish.

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I don't know if it would be too much red but it probably would be a different shade of red, so I would go for the aluminium finish.

S4 Elan, Elan +2S, Federal-spec, World Championship Edition S2 Esprit #42, S1 Elise, Excel SE


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