There is not scheduled replacement of the timing chain. It will normally last the life of the engine until the engine needs a complete overhaul. Replace it is it is noisy, or you cannot keep the engine timed correctly.
timing CHAIN
On a 1996 Mercury Cougar : The 3.8 liter V6 engine has ( 1 timing CHAIN ) The 4.6 liter V8 engine has ( 1 timing CHAIN to each cylinder head , so there are 2 timing CHAINS )
It must have a timing chain because Gates ( they make timing belts etc. ) only lists a timing belt for the 4 cylinder engine on a 2000 Mercury Cougar
The 4 cylinder has a timing belt
The 3.8 liter V6 engine in a 1991 Mercury Cougar has a timing CHAIN
It has a timing chain. No timing belt changes are mentioned in the maintenance schedule...
It has a cam chain that normally requires no maintenance.
Chain and it is a very (~1000.00) costly fix.
Timing Chains (2) with respective guides, tensioners and sprockets.
The 2.5 litre V6 engine in a 1999 Mercury Cougar has ( 1 timing CHAIN to each cylinder head , so there are 2 timing CHAINS )
Dual chains
The V6 uses chains. The I4 uses belts.