Heater blows warm air at idle speed but when you increase engine R.P.M. heater blows hot probable causes?

Question

98 Chevy Ventura van Bleed air out of system already also replaced thermostat can water pump be the problem or the reason only blows hot air when rev ed up

Answer 1

Obviously at idle you are not getting enough water flow to maintain the heat..could be a bad waterpump or possibly a water control valve that is controlled by vaccum that would change from idle (full manifold vaccum) to driving (reduced manifold vaccum) affecting water flow..

Answer 2

offering the heater substitute into working ok previous to the coolant point going low there's a sturdy hazard you have an air lock interior the equipment and consequently no coolant circulate interior the process the heater middle. additionally pay interest to the coolant close of valve . those in basic terms pertain offering the thermostat is great. With a foul thermostat you may a minimum of get a touch warmth. Bob

Answer 3

That's a sign of low coolant. Heater core is the highest item in the cooling system. So when you rev it up is the only time the water is pump up that high. Check and refill accordingly............md

Answer 4

have you tried tighten the fan belt or the timing belt if not your water pump is on its way out