This bulletin applies to 2010 Mazda Tribute models. Some vehicles may exhibit an intermittent knocking or thumping noise from the left cylinder head. After the engine temperature reaches 210-220 degrees Fahrenheit, the noise is typically heard from the rear of the engine as the vehicle comes to a stop.
An example would be coming to a stop at the end of a highway exit ramp. Noise will continue 45-60 seconds and then diminish. Noise will occur again once the engine reaches 210-220 degrees F and the vehicle comes to another stop.
1. Is noise a 45-60 second knock/thump from a hot engine as the vehicle comes to a stop? If yes, go to Step 2. If no, proceed with normal diagnosis.
2. Using chassis ears or a stethoscope, listen to the cylinder 4 and 6 valve cover fasteners (6 is near the coolant pump). Is there significant difference in transmitted noise between the cylinder 4 and cylinder 6 fasteners when the noise is present? If yes, go to Step 3. If no, proceed with normal diagnosis.
3. Remove the LH valve cover.
4. Rotate the crankshaft clockwise until cylinder number 6 exhaust cam lobes are pointing up and valves are fully closed. The exhaust camshaft needs to be left in this position for all bearing caps. Each cam cap must be completely removed and installed, per manual instructions before proceeding to the next cam cap or damage will occur.
5. On the LH exhaust camshaft only, starting at the front of the engine with the thrust bearing cap (1L), perform the following on all 5 camshaft bearing caps:
a. Loosen both bolts.
b. Remove cap.
c. Install the cap and push the cap toward the intake camshaft while tightening the cap bolts, excluding the thrust bearing cap (1L).
d. Torque bolts to 89 in.-lbs., starting with the bolt closest to the intake camshaft.
e. Proceed to the next cap.
NOTE: Cylinder head camshaft bearing caps must be assembled in their original positions and orientation. Failure to do so will result in severe engine damage.
Install the LH valve cover. A new LH valve cover gasket should be installed (P/N ZZC4-10-2D5).
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