Every time i drive up to the lake my blazer overheats. Its a hill climb for about 45 mins. Roughly 10mins of it is really steep climbing. The car sits at about 215 until i hit the steep climb, then it jumps to 230. Once i get back to the normal climb and i get higher up in elevation it overheats to 260. The temperature outside is in the 70s when it overheats. In town the car never goes over 210. Last time it overheated i flushed the radiator and changed out the thermostat hoping that would fix it but i guess not. I also checked and the clutch fan works fine and the heater works well so the heater core doesnt seem to be clogged.

Could it be altitude related?

 

can you hear the clutch fan roaring when it starts getting toward overheating? if not, then either the clutch isn't engaging, or the radiator isn't getting the hot water through it to engage the fan. Might be an idea where to check.

 

have you washed the radiator out? I would put a hose on the fan side and flush to through the radiator and a/c condensor. We had the same issue with a 07 van. It was packed with bugs. Just an idea.

 

The fan clutch seems to be working fine, when i open the hood and rev the motor the fan spins faster which means its working, correct? I just cleaned the radiator and condensor out before i took the trip. Im still stumped.

An 04 should not have overheating issues.

 

did you do an infared read? the guage or sensor may be off. If water is moving thru and air is not blocked you would think all is good.

 

Just because the fan clutch appears to be working when you rev it up when it gets hot it may not be fully engaged. It should pretty much roar when the engine gets to the point of over heating. Running it at 260 degrees is NO GOOD. I shut an engine down to an idle stop the vehicle & let it cool when it gets up in the 230 area. Much over you risk damaging an engine. Remember when NASCAR runs an engine up in the 250 area they start to worry. They rebuild the engines completely after each race.

 

This sound very similar to things that happened with my 99 over the years. First thing to do is check to see if your radiator is cooling properly. I'm not one of the experienced mechanics like others here so all I know is what happened with my truck. Anyway...get the car warmed up then turn it off and feel the radiator. Mine was hot at the top and cool at the bottom four years ago which told me that hot water wasn't flowing through the bottom chambers and I replaced the radiator. Once you get those small slots clogged up normal flushing will not clear them. I don't know if you can "Rot Out" the aluminum cores at the radiator shop like we used to. Are you loosing any coolant and can't find any leaks? I was loosing about a pint a week. In my case it was going into the intake manifold which led to catastrophic failure last week and 3 gallons of water/coolant in the engine. Since it's a very slow leak and the engine is hot it pretty much evaporates and you don't see it in your oil.

 

Is the radiator cap new?

 

maybe you should upgrade to some nice e fans???

 

Good post. I have seen that also. There are shops that replace the plastic tanks & rot out
these radiators, but in my opinion a new radiator is the best way to go & probably the cheapest in the long run.