The three biggest problems with SWR are tight bends, looping the cable and poor ground. Tight bends compress the dielectric foam core and cause variations in the distance between the center conductor and outer braid. Looping (or running back-and-forth in a confined space) allows cross-inductance. A poor ground is a poor ground.
Once you've had a tight bend in the coax, straightening it out might not correct the problem, as the foam has already been compressed. Heat and vibration will cause that foam to permanently be deformed. Coax is relatively inexpensive, I would replace it. Get a piece of coax with a PL259 pre-attached on only one end and then a solder-on PL259 for the other end. Avoid tight bends (less than 3" radius), pinching or sharp edges while routing the cable. Cut the cable to length (leave enough to put on the connector and a little wiggle room), strip off 2" of outer jacket, separate and fold-back the braid and then strip the foam about 1/8" higher than the braid. Make sure none of the braid can touch the center conductor. Then trim the braid, screw-on the connector and solder/trim the center conductor.
If the mount is actually connected to the chassis then make sure you remove the paint from the frame and back of the mount, attach the mount, then spraypaint the mount and frame to prevent rust. If it's on a tire carrier, bumper, tailgate, etc., run a braided ground strap from the frame to a screw on the mount, removing paint for good contact on both ends.
Hope this helps