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Coolant questons on a 1999 Pontiac Sunfire


Around a year ago, my 1999 Pontiac Sunfire had a problem that it spilled out all the coolant without any other known reason. (Right now the car only has 23,000 miles on it). I flushed the radiator, put new mixed coolant in it and it worked ok.

I have noticed that the coolant/ reservoir is a little dirty and that the coolant is not green anymore., so I do not know if I should flush the whole system using one of those “reverse flush kits” or if I should use a regular flush, water and replace with 50/50 coolant.

I do not know what kind of maintenance was given to this car prior to my getting it, and since I live in Puerto Rico we dont have to worry about the coolant in winter. So I dont know if he just kept adding water to the system or else.


Where is the peatcock located in tis car’s radiator?

The "reverse flush kit"is a good idea? All the units at my local auto parts have tons of dust over them, so I wonder if I will be wasting my money. If I do it, where do I connect it? (because the radiator do not have a cap, just the coolant reservoir) any graphic or label on the hose?

Should I replace the reservoir cap also? It is dirty with rusty water.

Your car probably came with a coolant called DexCool. DexCool is problematic (turns to a sandy,syrpy mixture,clogs heater cores).This is probably why the resivoir is discolored. Now at 23,000 miles DexCool probably hasnt had time to do its worst damage. I would instead of messing with the radiators petcock just disconnect the radiators lower hose and let everything drain. Shelve the idea of “reverse flush” (mileage low). I would replace thermostat and radiator cap (time). You must always use a 50/50 coolant mixture even if freeze is not a concern (rust inhibitors and pump lubrication) Dont ever get in the habit of using plain water.Take some time making sure you get the radiator full (there is a special funnel that helps with this)After complete check for proper heater operation if OK no damage from DexCool. If you wanted You could run the garden hose through the system while the thermostat and lower hose is off, this would be a nice touch. Dont know the rules about flushing radiators onto the ground where you live so Iam going to leave that decision up to you. I didnt tell tou that the clamp on the lower hose could be a type that is hard to get off without a special tool,it is possible with various plier designs,I would still try to get it off ,radiator petcock (it could just be a plastic screw in plug is at the bottom of the radiator (Ibelieve your radiator has tanks on the sides. Use green coolant

Your dad definetly used plain water in the engine. I wouldn’t do anything with the cooling system unless it is overheating. To be honest, I wouldn’t do anything with this car but sell it because it is a GM product.
The pitcock has to be on the lowest extreme part of the radiator and will need to be loosened with pliers. The car has to be warmed up enough to make sure that the thermostate is open and water is flowing through the engine, but you don’t need to run the engine while draining the radiator, and you really shouldn’t. Keep in mind that because water has been added to the system, you will never be able to get all the rust out of the system, and a small amount of rust wont hurt anything. The cap on the over flow bottle can only retain an insignificant amount of rust so I would just wash it out by hand as best you can and not worry about it.