My 2003 Mercury Grand Marquis (4.6l) has developed a continuous rattling
noise in front when operating temperature is reached and the car is stopped
in drive with my foot on the brake. I believe I have narrowed down the
source of the noise to the Accessory drive belt and belt tensioner. The
rattle disappears when I put pressure (either way) on the belt tensioner.
The noise also disappears when the air conditioner is turned off.
Can the tensioner be lubricated or adjusted or otherwise fixed?
Try a blast of silicon spray on the belt and tensioner. I know, the idea of
putting lube on a belt is just wrong, but a mechanic shared this with me
some time ago - just for the flat serpentine belts. It quiets them down and
makes them last longer (anyhow, that's what he said.) Often the noise if
from the edge of the belt just touching a pulley and that is the fix. I
start the engine, than carefully use the spray. It is easier with the
little wand on the can because you can get it right into everything. Load
it up, excess blows off, tho.
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