A defective power steering return line can cause a knocking noise when turning or going over bumps, especially when the engine has reached normal operating temperature. The power steering return line should be replaced.
2007 Mercury Mariner Problem Reports
RepairPal Verified 2007 Mercury Mariner Problem Reports
Shock bushing failure in the rear can allow the shock absorber to contact the body and cause a squeaking noise over bumps in the rear. The faulty rear shock absorber bushings should be replaced.
The transmission oil cooler may develop a leak, which will require replacement to repair.
The check engine light may come on due to failure of the Variable Camshaft Timing (VCT) solenoids. The VCT solenoids will need to be replaced if they are the reason the check engine light came on.