I spent the afternoon diagnosing and cleaning up under the hood of Cassandra’s lil’ hotrod. What did I find?
Well, her intake was so soaked with oil that took an entire roll of paper towels to sop up. If you know this car, you could tell right away why.
If not, here is the scoop. The Porsches of this generation use a device called an Air Oil Separator. It takes a vacuum line from the intake, right after the throttle body, and pipes it to the crank case. This is good thing for most motors, as it helps to pull the piston rings closer to the cylinder walls, and any oil that seeps around the rings gets pulled back into the crank case, and eventually back to the oil pan. If you have done any vacuum forming you will know that putting a fluid with bubbles incorporated under a vacuum pulls the bubbles out of the fluid at the same time. So groovy on that front too.
This is all well and good, and under normal situations works fantastic. It provides better compression, lower emissions because the seeping oil doesn’t get burned in the pistons and hence end up out the tail pipe, and any aerated oil gets sucked into the intake to be burned and taken care of by the catalytic converters in the exhaust.
So what in the world am I on about with this whole thing? Well when someone over-fills this particular car with oil, it escapes over this vacuum line and directly into the intake. The people that designed this car did anticipate this, and built into this vacuum line an oil catch device called an Air Oil Separator. You remember the ads for the cyclonic upright floor vacuum cleaners? It works exactly the same way. It spins the oil out of the incoming flow of gas, slowing it just enough for the solids to drop out and go back into the crank case and be cycled back to the oil pan.
You can probably imagine what happens if this clever little device gets overwhelmed. It fills to the brim with oil and the vacuum line starts to suck oil out of it, pouring into the intake plenum. Oil then starts to soak the MAF sensor, drips into the cylinders, fouls the spark plugs, makes the catalytic converters have to deal with a HUGE amount of unburnt greasy hydrocarbons, and it eventually starts smoking like crazy. This last part is when you see that something is going horribly awry.
It also makes a gigantic mess, if you couldn’t deduce that already.
So that sure is fun to deal with. The good news is that her car doesn’t need seven THOUSAND dollars worth of repairs for a possibly cracked head. Bad news is that we still don’t know where the coolant is going. The car is still leaving puddles on the floor of the garage, so that implies the coolant is just running out somewhere when it gets pressurized.
One problem at a time with this car I think.