Wheels: Joe and Bob write by e-mail:

“Jim, we sure enjoy your weekly articles in the DDN. My neighbor, Bob, and I are a couple shade-tree mechanics and manage to keep six vehicles going to save money wherever we can. Since you seem to excel at the unusual problems in the ‘little guy’ world, we’d like to share a recent mystery with you. Maybe you can shed a bit of light on the puzzle.

One of the six vehicles is a 2002 Mercury Sable GS with 185,000 miles. This is a one-owner car and still runs and looks great. A couple days ago, we noticed transaxle fluid under it. The car was parked in the driveway facing the street at about a 20 degree angle and had not been driven for 36 hours. Fluid leaks drive us nuts! We found the fluid coming out of the dipstick hole. Removing the dipstick, the fluid was at the top of the tube and just overflowing. Lots of head scratching and theorizing at this point. We started it up and, of course, the fluid receded back to whence it was useful. After warming it up, we put it in Joe and Bob’s garage for further investigation — NOTHING. The fluid was slightly down on the dipstick; we had lost only about four ounces. We haven’t a clue as to what caused the tranny to just start pushing its life-blood out the fill hole. Over the past three years, the car has been parked in this same location too many times to count, without incident. We also can’t be sure the dipstick was fully seated, but the rubber seal is still round and supple. Does this seal prevent fluid from leaking out or is it more of a dust catcher? Do you have any thoughts on how to solve the mystery? Thanks for your time.”

Halderman: I did not know off-hand so I asked Dick Krieger, from the Michigan Institute of Technology, for his opinion. Almost immediately he wrote back to me that he found a technical service bulletin (TSB) that addressed this exact issue. The Ford TSB 06-18-13 states that “erratic fluid level reading on transaxles dipsticks and/or leaks” can be caused by a clogged or restricted vent line. The vent hose needs to be replaced and secured so it cannot be restricted to solve the problem.

Thanks, Dick, for your help solving this seemingly strange problem.

James D. Halderman is an ASE-certified master technician, a member of the Society of Automotive Engineers and the author of 12 textbooks. Submit questions to jim@jameshalderman.com or follow him on Twitter @jameshalderman, or write him in care of: Wheels, Marketing Publications Department, Dayton Daily News, 1611 S. Main St., Dayton OH 45409.