The 3.0L V6 engine in 2003 to 2008 Mazda 6, MPV and Tribute models is nearly identical to the Ford 3.0L Duratec engine used in the Ford Taurus, Escape, Freestyle and Fusion, Jaguar S-Type and X-Type, and Lincoln LS. It is a dual overhead cam (DOHC) engine that has been in production since 1996. The engine has two timing chains (one for each cylinder head).
Replacing the timing chains is a difficult, time-consuming job that may take 9 to 12 hours to complete. Accessing the timing chains requires removing all of the accessories from the front of the engine, removing the front cover and oil pan, both valve covers, and the right halfshaft and crossmember! You also need a puller to get the water pump pulley and crankshaft pulley off. This is not a job for a novice.
Adding to the difficulty of the job is the fact that there is no Top Dead Center (TDC) timing mark on the crankshaft. This makes it tricky to align the camshaft sprockets to the crankshaft. The number one piston should be at Top Dead Center when the crankshaft pulley keyway is at the 11 o'clock position.
Rotate the crankshaft clockwise until crank pulley keyway is in the 3 o'clock position.
The timing mark for the intake camshaft should be pointing right, and the mark on the exhaust camshaft should be straight up.
Then remove the Right Hand timing chain components in the following order:
1) Chain tensioner
2) Tensioner arm
3) Timing chain
4) Chain guide
5) Timing chain crankshaft sprocket
Next, turn the crankshaft clockwise one and two-third revolutions. The crank pulley keyway should be at the 11 o'clock position again.
The timing mark for the Left camshaft should now be pointing to the left, and the exhaust cam timing mark should be straight up.
You can now remove the Left Hand timing components in the same order as before.
First, compress the right and left chain tensioners in a vice until the pistons are all the way in. Lock the pistons in place with a paperclip.
The new timing chains should have three marked links that will align with the marks on the camshaft sprockets and crankshaft gear. One link will align with the mark on the crankshaft gear opposite the keyway. The other two marks links will align with the intake and exhaust cam sprockets. How do you know which is which? Count the number of links between the marked links on the chain.
Mazda says there are 29 links from the crankshaft timing mark to the marked link for the exhaust camshaft sprocket, and 42 links from the crank timing mark to the intake camshaft sprocket timing mark.
Install the Left timing chain first, in the reverse order the components were removed.
Once the Left timing chain has been installed, rotate the crankshaft clockwise until the keyway is in the 3 o'clock position. You can now install the Right timing chain components.
After both timing chains have been installed, remove the paper clip from both chain tensioners.
Make sure you have the camshaft sprockets and crank properly aligned by rotating the crankshaft clockwise until the keyway is back to the 11 o'clock position again. The marked links on the Left chain should align with the left camshaft sprockets.