I own a 2006 Ford Expedition and I recently started having this knocking noise coming from the front of the motor when driving. I took the truck to my mechanic that I have been with for the past 6 years and he stated it was a timing belt tensioner and it would run from $1500.00 - $2000.00 for the job. I wanted to have another estimate and took my truck to Miguel and Ramon at Engine Rebuilders. Ramon checked my oil pressure and noticed it was a bit low. He added oil to the truck and changed filter and my $1500.00 problem is gone and so is my old mechanic. Thank You Engine Rebuilders.