I replaced my idler arm bushings in October after seeing some play. After replacement there was still a good bit of play (movement) in the idler. The old bushings didn't look that old I had only had the car for a few months at this point and the PO had done done a bunch of work to it over the years. It appears to be that the mounting tube is out of round, has anyone else experienced what seems to be an out of round idler arm mounting tube.

No, but I have experienced a bad new idler arm bushing. It was allowing the arm bolt to tilt and therefore the arm to tilt up and down. Seems there's some substandard bushing kits out there. No, I didn't get the substandard part from MercedesShop, and the replacement (which didn't allow the tilting) was provided by my indie so I don't know its source.

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'83 300DTurbo http://badges.fuelly.com/images/smallsig-us/318559.png

Broadband: more lies faster.

If you actually managed to insert a bearing into an out of round tube and it conformed to the tube. The shaft should bind or be very tight. Thats if there was a reasonable tollerance between the inside diameter of the bearing and the idler shaft before installation.

Sounds like either the shaft is worn or the bearings where really oversize. Some measuring seems required. Or a new set of bearings for fit comparison with the shaft before their installation. Sounds like you have a lot of clearance at present. You might want to compare the shaft with oem bearings from a dealer. Sounds like possible aftermarket problems.