I have a Mustang GT with a five liter engine...

Dear Car Talk

Dear Car Talk | Jan 01, 1996

Dear Tom and Ray:

I have a 1985 Mustang GT with a five liter engine. If I drive for a short distance (2 miles) and turn off the motor, when I start it up again the oil light comes on and there is no oil showing on the dipstick. The first time it happened, I added three quarts of oil, and when I got home later, the oil was way over the full mark on the dipstick. If I let the car sit for 30 minutes or more, the oil seems to reappear. The service department is stumped as to where this oil is hiding. What could be going on?

RAY: That oil is orbiting the earth with the Van Allen radiation belts.

TOM: Just kidding, Ric. The oil is hiding under the valve covers. When the engine runs, oil gets pumped up into the valve train, which is at the top of the engine. Then it's supposed to drain back down into the oil pan where it gets recirculated. But if the drain holes are plugged up, the oil just stays up there.

RAY: It happens to older engines--especially older engines whose oil hasn't been changed regularly. Gunk and crud build up on the inside of the cylinder head, and every so often, a piece of that crud breaks free, flows "down stream" with the return oil, and gets stuck in one of the drain holes. It's kind of like when the gutters on your house get plugged up with leaves and the water pours out over the sides because it can't get through the downspouts.

TOM: Eventually, the oil seeps back down to the oil pan, which is why it reappears after half an hour.

RAY: You need to remove the valve covers and clear out those drain holes so the oil flows down freely, Ric. This is an operation that your mechanic will do with a precision tool... like a coat hanger.

TOM: And when you install your next engine in this car, change the oil and filter every 5,000 miles, OK?

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