2004 Chevy Tahoe. Heater working only at higher speeds.
My Tahoe heater only pushes warm air when my driving speed goes above 30 mph. My engine temp gauge fluctuates from normal to slightly higher as the heater goes in and out. While idling my engine temp gauge rises and my heater blows out cold air. Then when I start driving my engine temp gauge drops and my heater start blowing warm air again. Does anyone have an idea what might be going on? Thank you.
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Re: 2004 Chevy Tahoe. Heater working only at higher...
You have air trapped in the cooling system. A good indication is that one or both of your heater hoses going into the heater core are cold when they should be hot.
Park facing uphill, raise front of vehicle so radiator cap is higher than top of engine. (You want bubble to get to radiator and out the cap.)
Leave cap on but loose, so bubble can purge.
Turn heater on.
Fill radiator and reservoir with 50/50 mix of antifreeze.
Start engine and run at about 1500 roms until the engine warms up and thermostat opens.
You will know themostat opens when top radiator hose is hot indicating coolant is flowing.
Shut off engine.
Fill radiator and reservoir. Install cap.
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Sound's as though a previous owner installed a speed governor so that the engine would not exceed the nationwide 55-65 mph speed limit average. This most likely was a company owned vehicle or owned by someone concerned about speeding ticket's or excessive speed by a teenage driver. It can be uninstalled by an experienced mechanic. Unless this poses a problem while driving on an interstate, you may wish to leave it as is.
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.
hi from uk can i offer this advice ? when you start engine let it warm up a little then drive untill temp guage reads warm at least ? then when you put front screen defrost on only select screen and No 2 speed then as temp reaches normal screen will clear fully if you select full speed on heat blower to clear screen at first start it will not work because the coolant from engine passing thro the heater matrix/radiator will be rapidly cooled by fan of heater TRY IT? in years gone by it was common remedy if you were stuck in traffic and temp rose towards hot you could cool system down by putting heater on full heat and the fan on max this cooled the engines coolant as it passed thro the heater ?hope you understand how heater/fan should work for optimum efficiency my wife has owned 2 of these accents and never had heat/demist problems it is surprising how many people consider the demist/heater systems are poor on many cars not just hyundai hope this helps best wishes
This sounds like your automatic climate control is starting to malfunction. Check to make sure your coolant is full, and temp is not fluctuating, and when your vehicle is warmed up, try using the low setting and feel for air temp. Is it warmer than if you turn it up? When at idle the vehicle is not producing heat the same as if you are driving, putting load on your engine and more air/fuel combustion means more heat, which is why you can feel heat while driving. Ideally you should feel heat as soon as the engine is warming up, getting hotter as it reaches peak temp of 190-210 degrees. You can try to make sure your water control valve is not blocked, and all electrical connections are secure. This will be located close to your firewall and connected to the coolant tubes that run into your firewall to your heater-core. Also use recirc (setting)to try to summon as much heat as possible, however ultimately, you may need to take you vehicle in for service. If it only warms when driving defrost will be an issue. Good luck.
Notorious for plugged heater cores. Also updated plastic restrictioncouplers mounted at heater core available from dealer. Try back flushing heater core. Run engine till its at operating temperature then carefully hold the inlet and outlet hose breifly with heater fan on high if hoses are nearly the same temp then flow is good , if not then core is plugged.
there could be an air lock in the system, pluged heator core, a bad thermostate or control modual. try bleeding the air out through the bleeder screew if there is no heat after that have the control modual tested if its okay try having the cooling system flushed then if it still doesnt heat intall new termostate