Tip & How-To about Chevrolet Avalanche

How to Flush the Cooling System.

Normally the engine operates at 195F, unless you have replaced the thermostat with another one at 185F. If the temperature has a tendency to rise up, the reason is a partially obstructed cooling system or/and a bad thermostat.The first part of the cooling system that gives up is the heater core, because the coolant flowing channels are thin. It is the time for a coolant flush in your car. To do it right then you need time. Plan ahead for a weekend. With a cooled engine, start with the heater core hoses. Disconnect both of them, but the dirt has to go out of your car, so with a garden hose back flush it and let the dirt to get out of your cooling system. After you will get clean discharge,it is the time for coolant bottle, remove it, discharge the used coolant and clean it. The third to come is the radiator. Open the drain cook, or disconnect the lower radiator hose, and disposal used coolant properly. Now open the radiator cap and flush with water the radiator till discharge will be clear.You think that you are done? Not yet. There is half of old dirty coolant trapped in the system. Install everything, and connect all coolant system hoses, radiator, heater core and coolant bottle. Now you have to run your car with water. Fill out the cooling system with distilled water, start engine, turn on the heater high, and run till upper radiator hose get hot. That means the thermostat opens. Let the engine to cool down, open the radiator cap, and draining cook or lover radiator hose and drain everything. You can use flush detergent, if you wanted, at this stage, but flushing with detergent will add 4 more hours, because the detergent is colorless and you have to guess how many fill and drain processes to do, to get rid of it. I do not do it, but if your cooling system is very dirty you have to do it. After the last drain, fill the cooling system with concentrated antifreeze and 30% distilled water. The reason is because it is more water trapped inside the cooling system. The goal is to reach 50/50concentration. You need a coolant tester to find this. Start the engine and add coolant till radiator is full. Install the radiator cap and bleed the system. After driving you car for a day or so, let engine to cool down, open the radiator cap check the concentration of coolant with the tester, and add antifreeze or distilled water as necessary. It is a good idea to replace the thermostat while flushing the radiator. This procedure has to be done every 2 to 3 years. It is up to you to decide to use RED GM Dex-Cool or GREEN Prestone antifreeze. In all my cars I have replaced Dex-Cool with Prestone, but I flush the system every 2 years, and I never had a cooling system problem in all my cars.

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1 Answer

Is the thermostat easily accessable inside the engine compartment? My van over heats, has water in the radiator, when engine is started the level in the radiator rises as if the pump is turning but I don't have warm air at the blower as if the thermostat is closed.


its not easy. so make sure its bad. Have a shop scan the engine computer while you think the engine is at normal engine temp. it should be 190-195f if its lower than that, yes the thermostat may be bad. but its a job to replace.

Dec 02, 2010 | 1997 Chevrolet Venture

1 Answer

sometimes stalls or surges when hot, runs hot


Clean the temperature sensor wire connector.
Replace the temp sensor near the thermostat hosing.

Check the condition of the sensor wire cut(s) or short onto the engine block.

Monitor the fan operation with the hood open during warm up (0-15 minutes.) It should ran after the engine coolant temp get above 195F +.

Test fan relay.

Feb 10, 2010 | 1993 Buick LeSabre

3 Answers

How to reset Service Engine light? 2003 Envoy ... Autozone says engine temp too low was reason for light. That's silly. I have gages ... it runs at 180 degrees. I just want the light off.


Ok replace the thermostat which is stucked open, cuz the computer will not go into open loop unless the engine reaches normal operating temperature. You can disconnect the battery, to reset it, but untill you replace the thermostat, the check engine light will pop up again. Good luck

Nov 23, 2009 | 2002 GMC Envoy

1 Answer

sonata coolant temp at 61C at thermostat opening


If your positive that the reading is from coolant after the thermostat opens & on the return side of thermostat, as in flowing toward or into radiator, then that is too low. 61C/142F is too cool, even in summer. It should be coming out around 82C-90C.(180F-195F) I'd double check that reading and make sure it's coming from the discharge side of thermostat, and if it's correct, replace it with an 82C/180F thermostat, as this is what is recommended for 2.4L engine, but call Hyundai on the 3.3.L engine, as I am not getting a listing for thermostat on 3.3.L. Also keep in mind that during winter, your AC compressor is kicking in anytime your on defrost, as well as your normally running with heater on as well, if not defrost, which all contributes to lower gas mileage, add more fuel to get engine started when cold, and it will suffer some, but if running too cold, certainly will throw that all off as well.

Aug 11, 2009 | 2006 Hyundai Sonata

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