Alright, I found some brown gunk on the top of the radiator cap [before I read the forum on this]. So, my Dad and I tried flushing the coolant system. We bought a Prestone kit that comes with a T-connector for the engine inlet heater hose. We screwed the garden hose to the T-connector and flushed out all the dexcool and let it drain out from the bottom right radiator hose.

When we went to refill the coolant at the radiator cap, we were only able to put about 2.5 quarts of dexcool in.This is the total after the second refill. So, I'm guessing there must be about 7.5 quarts of water still in the system... so about 2.5 quarts too much of water. I'm not sure, I just think that's the problem. But now, the car overheats after about 10-15 minutes. The heater does not work anymore. The T-connecter seemed a little small. It fit without wiggling, but it was not tight and snug. I noticed that the heater wasn't working all that great before, so I don't know if it's just the coolant system that's the cause.

Anyone know what to do?

 

sounds like it just has air in it. take off the cap, add coolant as needed, open the air bleed(little brass bolt on the pipe over the water pump, 7mm i think) untill coolant comes out then close it. top off with coolant, put your cap back on and try it out.

to be more thougough, if you have a funnel adapter for your radiator, or dont mind making a huge mess, you could go ahead and run it with the cap off untill it gets up to operating temp, to make sure that you get all the air out, and check that the heater works, then just put the cap on, and turn it off with the res. full.

 

That does make sense because when I turned the car off, the radiator and resevoir were bubbling inside.

I will give it a try tomorrow - thanks.

 

you most likely got air in the system would be correct.
ok take the cap off the Rad.
turn on your heat full blast . the area where it should get it's hottest.
KEEP A EYE ON THE TEMP GUAGE!!! DO NOT LET IT OVER HEAT TO MUCH OR IT WILL BLOW A HEAD GASKET AND MOST LIKELY WARP SOMETHING TO BOOT!!

with the cap off run the car. Watch it till you see the water start moving in it. so it will cicrulate in the Rad. and the block, even if you use straight water to start off with. you need to ge tthe air out of the system.
once you have the air out you can start to ad din the coolent to make it to your 50/50 mix.

honestly i would not use dexcrap in my car. if you do a serch on here you can find a big ol long thread full or reasons on why i say this.

just rember the biggest thing is to watch the heat guage you dont want to get it so hot it will warp anything like the head.
Also the brown crap in the Rad. is mostly likely the leak stop that G.M. put in the rad. they did this as part of a recall on a few years of the Montes. cant remeber all of the years for it.

Good Luck

 

Works right as rain and so does the heater. I opened the bleed valve and poured dexcool in until it came out the valve. Ran it with the cap off for fifteen minutes - it drained enough out that it headed down the path of overheating again [my car never actually overheated at any given time] Bleed it, more dexcool. Closed cap. Ran it for fifteen minutes.

Thanks guys!!