I really don't know where the problem is. I changed the thermostat and it's got coolant in it. Still overheats to the point of steam coming from the top radiator hose. It overheated last night and the temp gauge went to the top and then went down while steam poured from the hood. The fans are working. How can I tell if it's the head gasket or the water pump? All ideas are welcomed. I just replaced the harmonic balancer. The A/C is working, but I don't think the heater is.

Thanks

Justin

 

When was the last time the system was flushed? If you are getting coolent flow through the top hose, pump is working.

 

I've never flushed the radiator.

 

If you are unsure of when it was flushed, I'd start with that. With it cold, pull the radiator hose's (I think the bottom one is the supply to the water pump) that will drain it, or you can use the drain valve. I'd recommend after draining what you can, garden hose in the radiator statically flush what you can. Prestone makes a flush chemical, use it as per directions, with heat on during the process. Follow the directions. After the flush/rinse, add 50/50 concentrate anti-freeze back into the system. You also will have to (probably) burp the system. After you start it up, run it with the cap on loose till the thermostat opens, that should get the air out. Shut it off, let cool, and top off with 50/50 coolent.

 

Ok thank you. I'll give it a go tomorrow.

 

DONT DO THAT. first off, the lower hose does NOT go to the water pump. the lower hose goes to the thermostat housing, and coolant is pulled thru the engine, and exits thru the upper hose, on the right side of the radiator. DO NOT use a garden hose to backflush your cooling system. if you do, you stand a good chance of blowing up the heater core. then, you get to take out the dash to get at it. you ever take a dash out of a millenia? you REALLY dont want to. you might have air in the cooling system. here are some symptoms common to the 2.3. first, when the car is warming up, look at your temp gauge. it will slowly move, like always, then when it just gets into the warm zone, it will suddenly shoot up to near, or into the red. turn your heater on full blast, if you dont get heat, or just a tiny bit, you got air in the system. bleeding this car can be a nightmare. here is what MIGHT work for other cars, but i have never gotten these to work on the 2.3. car on an incline, engine higher than back. dont work. upside down coke bottle on coolant tank, run engine till bubbles go away, or this kit:
Lisle 24610 Spill-Free Funnel : Amazon.com : Automotive dont work. warm up engine, cool down, refill tank. dont work. here is what REALLY works:
UView 550000 Airlift Cooling System Leak Checker and Airlock Purge Tool Kit : Amazon.com : Automotive

you will need shop air to make this work, BUT, it is 100%. and, you do it cold. it will pull open the thermostat, and fill ever empty space in your cooling system. it will also tell you if you have a leak. if you dont have shop air, and your car dont pass the tests, look for a shop that can fill your cooling system using a vacuum. most shops have a tool similar, or the same one. i know of a couple of shops that will ONLY fill cooling systems using a vacuum, because it is fool proof, and the car dont have to come back to refill the coolant resevoir.

 

ok , I removed the radiator and flushed it. It was pretty gunked up. I found several holes along the plastic side near the upper hose outlet. Looks like I'm gonna need a new radiator. I guess I don't understand why there are holes. Seems like there was too much pressure and it blew. Could it be that the water pump needs to be replaced too? Maybe I'm over thinking it.

Thanks

 

You could have pulled the hoses off the radiator and flushed it with a garden hose.

 

They wear out. It isn't your pump. If you would have tried a leak stop, it would have just found another weak stop, and start leaking there.

 

first off, changing a water pump on the 2.3 is a HUGE job. and then, for SURE you will have to refill the cooling system by the vacuum method. now, if the car has more than 100k, and the timing belt has never been done, then yah, i would think about the pump, because you are due for a timing belt(105k, according to mazda fsm). think of the water pump as being behind the timing belt(which it is), so all of the timing belt parts have to be removed to get at it. also, if your car has a lot of miles on it, you should consider changing all the hoses, which is again a pretty big job. especially difficult is the oil cooler hoses. but with a new radiator, and cooling system up to pressure, any weak hoses might now not hold up, and if any of them go, the car will instantly become undriveable. be careful with a new radiator. the factory radiator is aluminum/plastic. the core is very thin(japanese car radiators are very efficient). there are some aftermarket radiators that are brass/copper, and are much cheaper. they will not be as efficient, they will be much heavier, and most do NOT come with a drain. and no drain on a 2.3 radiator can be a big pain in the butt.

again, the fact that your heater is not working tells me the system has air in it. even with a new radiator, you will have problems bleeding the air from it. just remember the vacuum system works, the others dont