The inside heater temp is going up and down with the engine's rpm. At road speed temp is normal and at a stop sign cold air take over. There is a new thermostat, new fan belt and the engine temp is operating in the normal range no ups and down with its reading. How does the flow of hot coolant move through the heater core? is it with a vlave control through the front panel temp dial on the dash. or is there a vacuum hose some where involved.
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Re: inside heater temp
Some where on the heater lines or by the heater core there should be a gate valve. However is your heater fan fluctuating ( blower motor ) with your R.P.M.s ? if so then check the tension on your altenator belt.
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That sounds like a plugged heater core or heater hoses. At lower RPM there is not as much pressure from the water pump, so the coolant can't circulate through the heater core. Find the heater hoses (in and out) on the firewall. With the car running, engine warm to hot, squeeze the hoses - they should be hot and pretty tight. If they aren't, then something's probably blocking them. Then you'd just have to figure out if if it's the heater core that's blocked or the hoses. You can disconnect the hoses and blow compressed air in to the heater core. Probably a lot of crud buildup. It's messy but it can be done.
Hi, the likely problem is a bubble forming in the system, possibly due to a head gasket failure.
Try stopping on a steep incline--does the heater stay warm? If yes, what you have is an air bubble that hangs at the heater hose until pressure from the water pump blows thru it as the engine speeds up. Park on an incline, open the radiator cap, run the engine until the thermostat is open, turn the heater on, crack open any/all bleed ports to release any trapped air, and fill the radiator to the neck. Wait until the level stops dropping and make sure bubbles don't continue to come up. If they do, you may have a blown head gasket that will keep forming these bubbles until you change the gasket.
Heater control valve malfunction will not cause engine to overheat unless coolant is leaking externally...Overheating going down the road can be the result of a few different things...Partly clogged radiator...Insufficient air flow due to possible fan problem...External coolant leak...Make sure fans are operting properly and have cooling system pressure tested for leaks...Gaining and losing heat on the inside of the vehicle usually means system is low on coolant but you must find out where coolant is going
1st check the coolant level. Low level will cause a no heat situation as you describe. What does the engine temp. gauge indicate? Is it indicating on the low side of normal, or is it in the normal range? If it indicates a low operating temp. after car warm up, the thermostat may be stuck open, which would not allow the car to fully warm up, and again, result in the no heat condition. Let me know about checking the coolant level, and temp gauge info. Curt
I think you could be right about there being air trapped in the system. Or the heater core(radiator) is plugged. Either way you need a pressurized radiator coolant pump to put the coolant in without air being trapped. Although,i have seen it done by jacking the vehicle up high enough that the radiator was now higher than the heater core level, and then the coolant was put in. But this is dangerous to try.