Replaced water pump, new hoses, flushed system still overheats. Used 5 gallons in 650 miles of running. Blazer will run for about 300 miles on hiway spped. Than without notice will overheat. In city traffic will overheat in about 100 miles.No water on ground. Overfill takes a full fill when heat light comes on. Actually 'check gauges' lights up.

 

When i bought my 96 Blazer back in 2002 it used to do the same thing. Do you still have the stock cork intake manifold gasket, if so i bet thats it. Can you smell coolent while driving but not see anything leaking out, if so that's it. I think it cost me like 400 bils to have mind replaced. Then after about another 6 month's my radirator rotted out and that cost me about another 400 bills to replace, no over heathing since. Also if you are still running red coolent, flush it and switch to green. The red coolent just isn't anygood. Good luck to ya, you can't go wrong with any Blazer.

 

Make sure the engine is leaking coolant internally; as the previous writer posted, make sure you aren't having the engine leak into the combustion chamber. The exhaust odor (when engine is hot) will stink bad, and will pump out steam from the exhaust after it's fully warmed up. Only after you're sure it's not burning coolant, the radiator is probably clogged. After 5-6 years, it's not unusual for the radiator to be internally clogged. This will cause the overheating. It's then best to do this: pull the radiator, and have it "rodded out" or re-cored. Replace the thermostat then too; after any overheating, the spring device on the thermostat looses it's spring-y-ness, and will not regulate the engine heat properly. Flush out the cooling system too- get the old junky coolant out, and insure the heater core gets a good flushing too, if possible. In my past auto experience, radiators get clogged over time and need frequent flushing, or else they get clogged. Then your engine overheats like you've described it.