Mazda 6 Service Manual: No.20 noise occurs at idle when vehicle is stopped in all positions/ranges

No.19 excessive shift shock on torque converter clutch (tcc)

No.21 noise occurs at idle when vehicle is stopped in d, s, l ranges, or in r position

Other materials:

Mazda 6 Service Manual: Inspecting Electrolyte Level
A low level of electrolyte fluid will cause the battery to discharge quickly. Inspect the electrolyte level at least once a week. If it is low, remove the caps and add enough distilled water to bring the level between the upper and lower level (illustration). Do not overfill. Examine the sp ...

Mazda 6 Service Manual: Oil cooler
LF, L3 1. Remove the under cover. 2. Drain the engine coolant. (See ENGINE COOLANT REPLACEMENT.) 3. Remove the oil filter cover, and drain the engine oil into a container. (See OIL FILTER REPLACEMENT.) 4. Remove in the order indicated in the table.   5. Use a clean rag to wipe off the m ...