My heat has stopped working and the dash service lights ay check coolant. I just put coolant in 2 months ago? Could i need more and Must it be Dex?

You need to check the actual level in the rad. The engine can only pull fluid from the reservoir if your system is already full. If you have to much air in the rad/engine it will not work. Once your coolant level falls to or below the pump you will loose the ability to pump the coolant.No pump no coolant to the heater core, no heat. If your system is this low it will take a few shots to fill it up. You may need to find a way to bleed air out of the top of the engine. Coolant needs to touch the thermostat to open it and allow circulation, once the thermostat opens most of the air will be purged out. (An airlocked motor will eventually heat up the internal air enought to open the thermostat but the engine may get hot enough to cause damage. I've cooked one. Use caution)

You probably do have a small leak but fill the system first then try and find it.

Thk You. I'll try to check the level. This is a just purchased preowned Cadillac...Do I need to use a particular kind if coolant? I heard I should only use DEX but the 1st time I put coolant in I put regular all purpose Prestone (supposedly for all makes)?

All purpose should be fine. Most "all purpose" and "universal" antifreeze is compatible with the new motors. The only thing you should avoid is mixing grades. You already have both so add what ever. The main thing is concentration and if diluting use de-mineralized water or get pre-mixed antifreeze. I run 70/30 antifreeze to water which is liquid down to -45.

there is an arrow on your overflow tank cap make sure it is lined up with the hose coming out of it, that not lined up could in some cases cause that notification to come on for other reasons refer to the answers above me they are correct

oh you should use dexcool it's a good product for Cadillac to use

I have same problem I got it fixed. Cadillac between 1990 to 1995 they add hose for no reason. U can see three med hose on back engine u can see T hose. One left from heat core and one right from top engine. And one bottom from engine. I shut the bottom hose. And finally got hot heater in car I use nose visa grip to shut bottom hose