Yes my 1997 deville runs hot some times i flushed out the radiator i changed the thermostat and dex-cool antifreeze and no one at the auto part store seems to know what type of sealant solution i should add to the antifreeze

they say you cant mix different coolants but you can go to auto-zone etc, and buy a cheaper anti-freeze for general motors products. its a 50/50 mix for all gm cars and trucks.you can add this coolant to any brand of anti-freeze. its called universal type anti-freeze. to run a differant anti-freeze in it, you have to flush out complete engine and radiator because the dex-cool and the green stuff do not mix well and cause engine corrosion etc. dex-cool is reccomended for all chevy engines. good-day !

Two things are possible. Air in the cooling system, or the system needs to be flushed. You didn't say what year your van is, but I'm sure it use dexcool antifreeze. Dexcool is the orange antifreeze recommended by GM for all their vehicles. The problem is that dex cool attacks gaskets causing gasket failures, especially the intake gaskets. It also can cause buildup in the cooling system causing overheating, or plugging up heater cores. We'll try the easy solution first.We need to get the air out of the system. First, the radiator needs to be higher than the engine. If it isn't, either use drive on ramps or raise the front end with a jack, Remove the radiator cap, put the heater controls on hottest setting, start the engine and let it run. When the coolant gets hot enough, the thermostat should open allowing the coolant to circulate. When it opens, the coolant level will drop in the radiator. Add antifreeze to make it full again. The coolant will drop again and may do so several times. Just keep adding antifreeze each time. continue to do this until the coolant level stabilizes. If the thermostat closes momentarily it will cause coolant to overflow. Not to worry, wait til it opens again and top off the antifreeze. Put the cap back on the radiator and check the heater for heat. If it' still not warm, you may have to flush the radiator.

You may have to flush the system again. Did you use a commercial flush such as Prestone Super Flush? Plain water won't remove the rust and sludge. The Dex-cool antifreeze that GM recommends for their cars is bad about forming a gummy sludge in the cooling system. It clogs radiators and heater cores. I would suggest another flush with the Prestone product. Follow the directions closely for best results. One thing that will help is. after you drain the radiator, refill with clear water and let the engine run until the coolant is circulating good, then drain it again. Do this three or four times. This will ensure that all the antifreeze has been removed from the engine block. When you refill the radiator, use a green antifreeze that is compatible with aluminum radiators and aluminum engine parts. Do not use Dex-cool. Dex-cool can also cause the intake gaskets to fail. Make sure the new thermostat is at least a 195degree unit and that it is installed correctly. you would be surprised how many thermostats get installed upside down. After refilling the radiator, leave the radiator cap off and let the engine run until the coolant is flowing. Keep adding antifreeze each time the coolant is pulled down into the radiator. Use full strength antifreeze because the water that is retained in the block will dilute it. A 50/50 mixture won't protect below freezing.

Normally the engine operates at 195F, if you did not replaced thermostat with another one at 185F. If the temperature has a tendency to rise up, the reason is a partially obstructed cooling system or/and a bad thermostat.
The first part of the cooling system that gives up is the heater core, because the coolant flowing channels are thin. You got a good advice but not the best one. It is the time for a coolant flush in your car. To do do it right then you need time. Plan ahead for a week end. With a cooled engine, start as your friend advised you with the heater core hoses. Disconnect both of them, but the dirt has to go out of your car, so with a garden hose back flush it and let the dirt to get out of your cooling system. After you will get clean discharge, it is the time for coolant bottle, remove it, discharge the used coolant and clean it. The third to come is the radiator. Open the drain cook, or disconnect the lower radiator hose, and disposal used coolant properly. Now open the radiator cap and flush with water the radiator till discharge will be clear. You think that you are done? Not yet. There is half of old dirty coolant trapped in the system.
Install everything, and connect all coolant system hoses, radiator, heater core and coolant bottle. Now you have to run your car with water. Fill out the cooling system with distilled water, start engine, turn on the heater high, and run till upper radiator hose get hot. That means the thermostat opens.
Let the engine to cool down, open the radiator cap, and draining cook or lover radiator hose and drain everything. You can use flush detergent if you wanted at this stage, but flushing with detergent will add 4 more hours, because detergent is colorless and you have to guess how many fill and drain processes do do to get rid of it. I do not do it, but if your cooling system is very dirty you have to do it. After the last drain, fill the cooling system with concentrated antifreeze and 30% distilled water. The reason is because it is more water trapped inside the cooling system. The goal is to reach 50/50 concentration. You need a coolant tester to find this. Start the engine and add coolant til radiator is full. Install the radiator cap and bleed the system. After driving you car for a day or so, let engine to cool down, open the radiator cap check the concentration of coolant with the tester and add antifreeze or distilled water as necessary. It is a good idea to replace the thermostat while flushing the radiator. This procedure has to be done every 2 to 3 years. It is up to you to decide to use RED GM Dex-Cool or GREEN Prestone antifreeze.
In all my cars I have replaced Dex-Cool with Prestone, but I flush the system every 2 years, and I never had a cooling system problem in all my cars.

yes and also have your thermostat changed. but heres a way you can check before you buy these things:
#1 car must be cool
#2 let car warm up with hood open
#3 find upper radiator hose and put hand around it...you should feel any water running through it!
#4 after car warms to normal op temp, put hand around hose again and give it a squeeze...it should feel Hot and you should be able to detect a slight water back pressure..this will mean that both your pump and thermostat are working correctly. Also it is imperative that you read my tips and tricks on Dex-cool antifreeze, please, you could save thousands of $$$.

get the antifreeze that mixes with any color you should be fine also make sure you bleed the system get the air out of the cooling system there should be a petcock to bleed it with,crank let get operating temp.open petcock till steady stream runs out close pc your done.

buy you a new temp sensor from the dealer not autozone,try that,my suburban did the same thing cause i got a cheap piece of **** sensor from az

replace that thermostat again...flush radiator any way...then see how it runs...

The major reason for using dex-cool is that antifreeze is often neglected as a service item. If neglected, it becomes acidic over time which is particularly important with the use of aluminium in most major components which are served by antifreeze. Acid causes etching and premature failure of gaskets and permanent damage to blocks, heads and especially the radiator and heater core, which are not vert thick to begin with.
Since "normal" antifreeze acidifies faster than does dex-cool, mixing both together causes a change in breakdown rate...the more "normal" coolant added, the faster it breaks down.
Both coolants do not react chemically with each other and therefore retain the same ability to prevent boil over and freezing.
In reality, normal coolant can be used with little or no effect on components, provided that you change it every year. (that's where the EPA gets involved) They do not want people dumping this stuff into the ground, so they push for extended service intervals. Since dex cool has a longer service life, that's what they want you to use.
As far as how you chasnge the coolant, it is always a good idea to flush system during a change, regardless of antifreeze type. This removes solid particles which can plug radiator core. Radiators are much smaller than their older counterparts. Loss of even a small portion of cooling area can cause overheating. Engine running temps are also higher than older vehicles (heat=power output). Therefore most systems have a much smaller margin of error than before. What I find though is that regular flushing can also be bad for the system as the chems eat away at metal components in order to clean. I recommend regualr or dex cool antifreeze systems be flushed with water only, once a year, but retaining what you removed and filtering it through a coffee filter, using it during the year to "top off" the system. To retain effectiveness of coolant, use a hydrometer to check concentration, adding new coolant to bring reading to proper protection level.Then, every three years, do a complete chem flush and change entire batch. This keeps your system clean and the epa happy!