98 saturn radiator leak

You are going to have to pressurize system to find leak rec shop takes special tool to pressurize and test system sorry

I'd have to see it in person to comment. The water pump is on the passenger side of the van.
A mechanic would fill the cooling system then pressure test it for leaks.

It's likely the radiator, like you think.

The water pump is on the passenger side of the engine.

If you are saying that it comes on now and then, and goes off, your may just need to add Anti-freeze/boil to the overflow tank. Does it come on when you're coming to a stop or going up or down a hill, if yes, add coolant to the overflow tank to bring it up to the correct level, not the radiator.

A small loss over a long period of time is acceptable, but constant refilling, indicates a leak either internally, with the coolant exiting through the exhaust, or one that you should see under your car occasionally. Sometimes you'll find your coolant leak in the floorboards if the heater core or hose leaks.

If your sensor comes on after driving a while & goes off as a result of adding coolant, then you'll probably need to pressure test the cooling system to identify where the coolant is going. Bad hose, seal, headgasket, head, etc.

Good luck !

Sounds like it's low on coolant. Check radiator. If low on coolant, heater may not get hot & temp gauge will read hot. The leak could possibly be a coolant leak..? Anti-freeze has a distinct odor when leaking from a hot engine. If that's the case, find the leak and have it repaired.

Either the coolant is escaping, or not circulating. If there is coolant in a puddle under where the car is usually parked, then I would look above that point, track the leak back to its origin and fix the leak. If the exhaust smells of coolant, then you need a real shop repair for a gasket or worse.
If the coolant is not circulating then I would check for a bad water pump or a blocked radiator. Lots of the L Saturns had leaking heater cores, a slippery wet passenger floor and stink was the indicator.

Do you have any coolant on the passenger side floor board? Coolant causing the radiator to fog up is a symptom of a leaking heater core.

Your heater core is in need of replacement.

mmmmmmmm they are really hard to replace but most likelly is goin to be a intake gasket, i do recomend you to call arrown the auto repairs and ask for a pressure test to the cooling system
this test is not that expensive and will tell you exactly where is the leak coming from, but on this type of vehicles i badly see a freeze plug leaking.