Cadillacs and the northstar engine are notorious for squeaky belts. if i were you i would not do it yourself. take it to a dealer mechanic.
How to replace the belt
loosen the tensioner bracket, remove old belt. replace with new belt. tighten with tensioner. job complete!
The cam on this engine is driven by a CHAIN and not a belt. Therefore, It has no timing belt.
I t is either a 79 or an 85mm belt
Use a socket and ratchet and place on the 95 Deville's belt tensioner pulley. Pull to the side to release tension on the belt. Remove the belt and replace it, then lower the pulley back into place.
changing serpentine belt and pulley 90' sedan deville
Check all your accessories pulled by the belt. There are a lot of bearings in these accessories that can cause the " chirping noise".
There should be a sticker under the hood that shows the routing of the belt. Look on the hood or on the radiator support area
The 2000 General Motors/Cadillac Deville came equipped in the 4.6L Northstar engine. Removing the main belt will require depressing the tensioner to free it. The new belt can then be routed across the accessory drive pulleys. The OE AC Delco belts for this application are 6K815 and 3K243.
chain
Chain.
Timing Chain.