Xantium

I remember hearing the story about the m3 owner a while back who lost his oil cap and plugged it with a sock only to get it sucked into the engine under the valve covers and cause thousands in damage.

What exactly would hapen to the renesis if the oil cap was forgotten (not on at all).
Would dirt just get into the oil or would there be low oil pressure?

TRZ750

Absolutly no affect on oil pressure. Yes there would be a chance of dirt in the oil. The main problem would be that the oil cap off would cause the fuel tank to not draw down in pressure, like the fuel cap off, and you would get a check engine light.

d j

did you lose yours? ...if you need an oil cap, I have a stock one that I don't need anymore. you can have it as long as you pay for shipping.

mazdatech177

sorry to correct but... the rx8 uses an electric pump to pressurize the evap system instead of the vacuum type systems of days gone. ive had some oil caps missing the rubber seal causing a rough idle. this allows unmetered air into the engine via the vent tube going from the oil fill to the intake air tube.

TRZ750

Thanks mazdatech177, but isn't that just used for the checking. Isn't there still a vent hose going to the engine so that the HC vapor off the fuel tank gets burned up? I didn't check the hose layout, but I would think that the evap canaster that traps the fuel tank HC can be smaller if the tank has a vent to the engine. Of course the cost of connecting the vent to the engine may be more than using a larger charcole canister. Again I didn't check the details, so your are probablly correct.

corners

The differance here is between BMW engines and the rest of the world. (I have owned and wrenched on several 6 cylinder BMW's)

BMW's don't actually use a PCV valve for crankcase ventilation, they hook the crankcase up to manifold vacuum right at the throttle body. This creates a somewhat unmetered vacuum leak to the intake but the ECU compensates for it. It also means the crankcase pulls about 16" of vacuum at idle. BMW's will stall out and throw a CEL when you leave the oil cap off or dipstick out due to this. This would easily suck in a sock.

The rest of the world uses PCV metering valves with only suck a half PSI or so on the crankcase. This would not suck in a sock.

Besides, the renesis doesn't have a valve cover. I don't know where it would end up but an ingested sock wouldn't tangle up in a rocker arm.

redcivic

In high school a buddy had a Yugo and he lost the oil cap and stuck a rag in it. His car die don the way home. It ate the rag and ruined the exotic Yugo engine

mazdatech177

yes the evap purges into the intake manifold via a control solenoid. but the oil cap seals in oil and crankcase vapors and is seperate from the intake manifold. so a missing oil cap would have no effect on evap system sealing or operation