If you havent checked your thermostat I would pull it out, it may be stuck closed, yes, a t-stat lets the hot coolant flow to the radiator, if its stuck,the system is jammed and not flowing. Id replace it anyway since your doing the pump job as well.

Or just remove the t-stat and run it without it, if it still gets too hot there is a restriction somewhere other than the t-stat.

 

If the car over heats while in motion then you most likely have a restriction in the radiator. Depending on how many times you have overheated it ans how hot it has been you may have blown the head gasket.

 

We can rule out the T-stat. Replaced it, no difference. Removed it entirely, no difference.

 

Well then any thoughts on MDTAHOE's comments, he would know far more than me about your specific vehicle.

 

The car has never overheated to the point when it dies. It's gotten mighty hot before, but I've always pulled over and turned it off to let it cool off. So I don't think (pray) it's the head gasket.

I'm beginning to suspect the radiator as you do. One look inside it and you can see that it's full of gunk. That stupid dex-cool fouls up the coils on the inside really bad.

Maybe I'll drop the $130 for a new radiator. So help me, if that doesn't fix this, I'm going to go drive this car off the interstate. Preferably before it overheats.

 

Dex-cool does not cause problems. That is only assumed by misinformed consumers. The problem with dex-cool is that is air gets into the system it causes sludge. Air gets in by a bad rad cap (should be changed every year) or a slow coolant leak that is left to leak. Also people believe that it is good for 5 years or 150,000 miles but that is not completely true, it actually says up to 5 years or 150,000 ( in perfect situations) (no air getting in).

 

A car does not have to overheat until it quits to blow the head gasket. It could blow with even on time into the red (usually not), the more times it happens the more likely it will blow.

 

if the radiator is plugged up with **** and you dont see any signs of coolant in the oil or have not seen white smoke and the coolant is clean and after you have insured that exhuast gases are not entering the system by performing this test drain the coolant to a level just above the tops of the heads , remove upper rad. Hose , thermostat and fan belt start the car and have someone rev it up a few times while you look into thermo. Flange if the coolant rises quit a bit or you see bubbles it may be exaust gases leaking into coolant system if then and removing all the same crap thats in the rad.your satisfied that you dont have a wrecked head gasket or even if you do then you might want to consider flushing the block with a commercial strength scale removing rad. Flush. That way it is done and there are some passeges that are damn hard to get to !with car running add it to system and run car for 15 to 20 minutes if you are using a chemical solvent high strength i would remove and isolate heater hoses it will jack up the heater core after flush and a neutralizer and flush a couple times when you have put it all back together add a rust inhibitor and sealant pellets it will they will give pump and internal parts an extended life and help coat passages thats all i got bud, luck on the heads

 

As far as the thermostat feeding coolant to the block or the radiator...im not sure...try putting in a lower psi thermostat and make sure your thermostat housing is torqued to spec...double check the bottom of the radiator in the corners for minor leaks and that your coolant isn't rust colored. I'm having an overheating issue with mine as well and so far I can keep going on the highway if I put the heat on full blast. Your heater core is essentially a small secondary radiator. If you can't figure it out then it may be worth it to have a shop check it out or the dealership. Also check for TSB's or recalls on cooling system related parts. Let me know if the lower psi thermostat works.