Re: Wandering Marquis; Possible Solution
I had the same problem and replaced tie rods, pittman arm, idler arm, ball joints, steering box, flushed and pressure tested the power steering pump, checked the u-joint on steering column, replaced all 4 tires and had 2 alignments changing toe and caster. Nothing effected the wandering at above 45mph.
Last week I heard the brakes squeak so I took my MGM in for pads. My mechanic informed me that the brakes had at some point overheated-especially in the front and the rotor surface was glazed and warped. The rotors could be turned but he said the warping could effect performance (I had not told him about the wandering!) He also showed me that Mercury had installed "dust shields" on the front to prevent brake dust from showing up on the fancy rims, but his theory is that these shields reflect so much heat that they cook the rotors and recommended not putting them back on. That is what I had him do. I had all 4 rotors replaced.
With the new rotors my MGM is now tracking straight and true at all speeds.