i have a 2001 blazer with 4.3 vorteck at idle it gives off little heat but when it is running at anything above 50 kph it gives off alot of heat does any one what is wrong

 

What does the coolant temp gauge show at idle and also when driving?

Could be as simple as a stuck open thermostat or a vacuum leak. Check the vacuum lines under the hood for splits, especially at the connectors.

 

when it idles and when it is on the highway it is about the same the only different is at idle it is cold but when u rev it up it starts to give off heat the gauge shows about half way

 

Probably just low on coolant. Remove the radiator cap, operate the engine at 1500 rpm at normal operating temperature, and fill up the radiator with Dexcool coolant only. Then make sure the coolant reservoir is at the full line. FYI: These engines are known for coolant leaks from the lower intake manifold gaskets.

 

thats true about the lower intake gasket,replaced mine 3 weeks ago,,