2002 Chevy Tahoe How to Flush the Coolant System

2002 CHEVROLET TAHOE
150,000 MILES • V8 • 2WD • AUTOMATIC
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CCBRYAN
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I started to drain the coolant system for a system flush and could only get about 7 of the 14 quarts in the system to drain out. I poured the coolant back in until I figure out what's up, and the system shows to be full.

What do I need to do other than removing the reservoir cap and opening the drain valve?

I removed the upper radiator hose and it did not help.

I started the engine and ran it until the engine reached temperature - still nothing additional came out beyond a trickle.

I started this exercise because the system started running about 245 F under highway loads, and I thought the thermostat was stuck. Is the trickle I'm getting the flow through the thermostat air bleed valve?

How should the draining normally be done?
May 10, 2009 at 10:50 PM
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PEAR69
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In order to totally drain all the fluid out of the system you must remove the soft plugs in the engine block. The radiator holds about 1/2 of the coolant in the system (when full and running) and the engine block holds the rest.
To totally flush the system - remove the thermostat - drain the coolant in the radiator only - then put in some coolant system flush (prestone is the best) - and fill it up with DISTILLED WATER - run the engine (without a t-stat) as directed in the instructions of the flush. Then drain all the coolant out by first draining the radiator - then filling with regular water - run for a while - drain coolant from radiator...Keep doing this until the coolant is all water..
Next - drain as much water out as possible by removing the upper and lower radiator hoses and the radiator drain plug (as usual) - install a NEW thermostat - add coolant and be sure to mix coolant with DISTILLED WATER or just buy pre-mixed coolant.

I do not recomend removing the soft plugs in the engine block to drain coolant - unless you are rebuilding the engine. Flushing the system is the way to go.
May 12, 2009 at 4:21 PM