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How to clean corroded coolant system in a 4.3L 2000 GMC sonoma

Replaced thermostat and heater core. Now when driving engine gets hot and blows out cold air. Guess all that is left to change is the water pump right? Also noticed the coolant system had a corroded build up while changing other components. What is the best method for cleaning it up

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All that needs to be done is "burp" the system of the air bubble inside the heater core.(be sure that the vacuum lines are connected to the heater control valve)


This works for most cars and trucks:
Park the truck on a steep incline so the front is angled up at about a 30* angle.
Rev the engine a few times and then run the truck VERY hard for a few times at higher RPM.
That usually purges the air bubble out and you should get heat.
Check the coolant level in the radiator when it cools down.
Fill the resevoir ,again and see how much it takes.
Usually about 2 quarts.
After one cycle of hot and then cool,the resevoir/overflow bottle will cycle and pull the bubble out of the system.

The cheap/easy way to get the coolant clean is just to use the garden hose.Fill the radiator and then run the truck and drain it a few times.
If you do this,you will need to purge the system again.

Please recycle the old coolant. Sears and O 'Reilly's will take it,free.

Posted on Jan 19, 2013

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Posted on Jan 02, 2017

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SOURCE: 04 civic heater blows cold air at idle

you should have hot water on all rad. hoses when the motor is running at a norm. temp. the water is not going through the heater core like it should. you have cutoff valve bad low water are a stopped heater.try a hoter thermostat if none of the above are true.

Posted on Jan 18, 2009

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SOURCE: GMC Sonoma SLE 4.3L 1991- Coolant Temp Gauge Not reading

there are 2 coolant sensors one for gauge and one for ecm

Posted on Jul 23, 2009

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SOURCE: My 2000 GMC Jimmy has been blowing cold air. We

airjoc does not have a clue to your problem, I take you want to have warmer air not cooler ac. check the control system, if you have a vacum system tou may have a leak, if it is controlled by voltage, check the control panel and the control box. Also open the hood, place the heater on high but not on any defrost setting preferrably on just the floor setting. Start the engine and see if the ac compressor is running. If it is, the control panel is bad.

Posted on Oct 09, 2009

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SOURCE: heater blow cold air in my 1994 Honda Accord (4

Yes clogged heater core may be the answer in your case .


Posted on Dec 11, 2009

baugh55grfmj
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SOURCE: Hey Chevy Minivan heater dont work properly

Chevy made some weak intake gaskets on 3.1 and 3.4. My guess is that the intake gasket is weak and/or leaking and it is letting pressure out somewhere. At idle maybe the system pressure is to little to push hot coolant into the heater core.

Posted on Dec 22, 2009

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My 99 GMC sonoma with a 2.2L is not warming up properly


Possibly plugged or inerporable heater core. Possibly heater core valve (this diverts hot air through your heater system) When you flushed the block, was there a lot of contaminant? 95% of the time, cold heat means thermostat. Also there are a lot of really cheap after market thermostats, you can buy one as low as $6.00. That being said, just because a thermo is new doesn't necessarily mean it opens/shuts when it should. You can look on You Tube on how to test one in your kitchen with boiling water,.

So three basic things affect interior heat temps. Thermostat, plugged heater core/.valve, and insufficient coolant or liquid to tranfser heat. If your interior coolant (engine temp) is working normally and your vehicle reaches operating tempature according to the needle, your thermosat is probably not the cause.

My bet is somehow, your heater core is plugged so that their is not enough "flow"

Feb 28, 2013 | 1999 GMC Sonoma

1 Answer

98 gmc sonoma heat works of and on


All kinds of things to look at.
Start with coolant level in radiator. Very often if the radiator is low, the heater will not work, or work well, because if there is air in the system, air will rise to the top, leaving the heater core with an air bubble.
Whenever you replace any hose on the car, you must run the engine with the heater on at a medium high RPM (1500 RPM) for a while (5-10minutes) to "burp" the air from the system.
You'll need to make sure the system is full of coolant after that.
Then there could be a partly plugged radiator, a pinched or crimped heater hose, or the heater control might not be allowing the hot water to flow fast.
Be sure to test the temperature of the radiator, to be certain the thermostat is keeping the radiator coolant at near 200 degrees. A thermometer in the top of the radiator will tell you.
If you have a sealed system, you might VERY carefully feel all the hoses to determine the heat inside the radiator after the motor has been running for 10-15 minutes.
Thermostats can get stuck in the "open" position, requiring replacement before you will get heater heat.

Jan 05, 2013 | 1998 GMC Sonoma

2 Answers

I have a 1999 sierra 1500 4 w drive truck and my heat core blows only gold air. can anybody tell me what is the problem?


Before assuming the heater core is blown check the following.

1. Check coolant level while engine is cold.
2. Leave the radiator cap off and let the engine run. See if you can see the coolant circulate
when the engine is brought up to temperature.
3. Check the temperature gauge inside and note if the engine temp is correct.
4 Does the engine overheat?
5. Feel the heater hoses and check if they get hot.
6. Can you smell antifreeze inside the cab?

Start here and let me know.

Oct 31, 2011 | 1999 GMC Sierra

2 Answers

NO HEAT BLOWING COLD AIR


Make sure the coolant level is full. If coolant levels are ok you made need to replace the thermostat .You can disconnect the heater hoses going to the heater core and flushing water through with a garden hose at low pressure. If the vehicle has the 4.3L engine these are quite prone to heater cores plugging up. Would try flushing the heater core first.If that does not work most likely the thermostat is causing your issue. Be sure to fill coolant back up after servicing and allow air to bleed from the cooling system.

Dec 01, 2010 | 2003 GMC Sonoma Extended Cab

1 Answer

Heater not blowing warm air. Thermostat has been


Check the water control valve behind the engine close to the firewall. This valve opens and closes to allow hot coolant to enter the heater core. It is usually connected to the heater controls with a cable. When you adjust the heater control for heat, a cable activated lever on the valve should move and allow coolant to move through the valve. The cable from the heater control can come loose from the lever, or the valve itself can become corroded and hard to move.

Oct 16, 2009 | 1993 GMC Sierra

2 Answers

GMC Sonoma SLE 4.3L 1991- Coolant Temp Gauge Not reading


there are 2 coolant sensors one for gauge and one for ecm

Jul 23, 2009 | 1991 GMC Sonoma

3 Answers

Heat


Considering the age of the car, your heater core could be partially stopped up. Check the coolant in your radiator and see if it is a rusty color. Flushing the coolant system might help get your heat flowing again.

Jan 01, 2009 | 1995 GMC Sonoma

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