What all needs to be replaced if the timing belt breaks on a 98 Cadillac catera?

A broken timing belt on a 1998 Cadillac Catera (which uses the Opel Omega engine) is a catastrophic event. It's *extremely* likely that you'll need to replace far more than just the timing belt. The interference engine design means the pistons can collide with the valves when the belt breaks, resulting in significant, and expensive, damage.

Here's what you're almost certainly looking at replacing:

* Timing Belt: Obviously.

* Timing Belt Tensioner: This needs replacing as it's likely damaged or worn out.

* Water Pump: Often driven by the timing belt, and should be replaced proactively to avoid future issues.

* All Valves: Very high probability of bent valves due to piston-valve contact. This is the most expensive part of the repair.

* Valve Seals: Likely damaged or compromised.

* Head Gasket(s): Could be damaged due to the impact of the pistons and valves.

* Possibly Pistons and Connecting Rods: In severe cases, piston damage can occur.

* Possibly Cylinder Head: In the most severe cases of damage, the cylinder head might be cracked or warped, requiring replacement or extensive repair.

In short: Be prepared for a major engine overhaul. The cost will likely exceed the value of the vehicle, depending on its condition and market value. It's crucial to get a professional mechanic to assess the damage before proceeding with any repairs. They'll be able to give you an accurate estimate of the repair costs.