Coolant Flushing Procedure on a 5.3

Hammer33 · August 23, 2004

According to my owners manual, my 2002 Tahoe should have 16 qts of coolant. I recently drained the coolant and only got about 10 qts out? I assume the difference is stuck in the heater cores.

My Helms manual gave the following instructions to flush:

1. take out the thermostat

2. replace the thermostat housing

3. connect a garden hose to the upper radiator inlet

4. let the water run through the engine and heater cores and come out the upper hose.

The problem is that the thermostat is integral to the housing – it does not come apart. Any ideas?

I also could not find the engine block drains? Where are they? Do your reach them from the top or from underneath?

Thanks,

Walt

asilverblazer · August 23, 2004

I know using a garden hose to add fluid is a bad idea so how do you flush everything out old water and anti-freeze and re-fill it with strictly dis-stilled water and anti-freeze (not leaving any garden hose water in it)? Sorry I can only post another question.

joefixit · August 26, 2004

Yea - I had this same problem. Where in heck are the block drains? Do you reach them from the top or the bottom? I would assume the bottom, but where?

I have no idea how to drain the coolant from front and rear (Tahoe) heater cores. I just figured I would drain the engine every year and hope that over time all the old stuff would get purged.

Joe

JimG · August 26, 2004

For what it's worth:

I checked my GM Service book for the 2003 5.3L engine. According to the book to drain the block you must "remove the left and right engine block coolant plugs". Boy, if that ain't helpful right there.

I took digi pics of the illustrations - hopefully you guys can match them up to your engine. I'll mention it for the sake of saying it: Arrow direction is towards the front of the engine. The manual does not reference the engine size to an illustration, that's why I'm posting all four. Generally it appears the plugs are at the rear of the engine and towards the bottom.

Images are here:

asepgrad98 · August 26, 2004

i suggest taking the upper rad hose loose and running the truck untill only clean water comes out(adding only water to rad). then drain rad, put 8 quarts of 100% coolant in. taht way you dont have to drain the engine.

asilverblazer · August 26, 2004

Thanks for the pics will definetly help out if I drain the block. I already removed the upper radiator hose and flushed that way. I guess for sake of simplicity I'll continue doing it that way.

Valsport · October 26, 2005

someone said the block drain plug on the passenger side is the knock sensor, but I found the sensor and it is on the oil pan, not the block (its right below the starter). Could coolant flow through a passage in the oil pan?

Bish · October 27, 2005

I use the following method stolen from another board a while back.

Get some garden hose fittings, some PVC plugs or adapters and some hose.

Connect garden hose sprayer to a short length of hose to a large hose that fits on the upper radiator connector. Take the radiator hose that was there and hang over the front into a 5 gallon bucket. Apply low to moderate pressure with the spray. I use clear hose so I can see the water flow making sure not to over-pressurize.

I get about a bucket and a half until it starts running clear. Then reconnect and run up to temp with all heaters on full. Repeat the procedure until it runs clear. Drain radiator and overflow and refill with 1/2 colling capacity of straight anti-freeze and top if necessary with water.. I have continued to use Dexcool, I just change it every 50K. The flush procedure works pretty well as I can flush mine in under 30 minutes now.

Too funny. I just noticed there are three threads on the exact same topic.....ALL with responses by me. Guess I should have just pointed to them

Valsport · October 27, 2005

I use the following method stolen from another board a while back.

Get some garden hose fittings, some PVC plugs or adapters and some hose.

Connect garden hose sprayer to a short length of hose to a large hose that fits on the upper radiator connector. Take the radiator hose that was there and hang over the front into a 5 gallon bucket. Apply low to moderate pressure with the spray. I use clear hose so I can see the water flow making sure not to over-pressurize.

I get about a bucket and a half until it starts running clear. Then reconnect and run up to temp with all heaters on full. Repeat the procedure until it runs clear. Drain radiator and overflow and refill with 1/2 colling capacity of straight anti-freeze and top if necessary with water.. I have continued to use Dexcool, I just change it every 50K. The flush procedure works pretty well as I can flush mine in under 30 minutes now.

Too funny. I just noticed there are three threads on the exact same topic.....ALL with responses by me. Guess I should have just pointed to them

<{POST_SNAPBACK}>

you're still not evacuating the coolant from the block, trying to find plug locations on the block.

az'03Silverado · October 27, 2005

The block drains are the big, brass-colored (maybe they are brass?), hex-head plugs towards the back of the engine near the tranny. They're close to the oil pan on the block. They require a big-a** hex key. Something along the lines of what is required to undo a manual transmission drain plug.

Bish · October 27, 2005

I use the following method stolen from another board a while back.

Get some garden hose fittings, some PVC plugs or adapters and some hose.

Connect garden hose sprayer to a short length of hose to a large hose that fits on the upper radiator connector. Take the radiator hose that was there and hang over the front into a 5 gallon bucket. Apply low to moderate pressure with the spray. I use clear hose so I can see the water flow making sure not to over-pressurize.

I get about a bucket and a half until it starts running clear. Then reconnect and run up to temp with all heaters on full. Repeat the procedure until it runs clear. Drain radiator and overflow and refill with 1/2 colling capacity of straight anti-freeze and top if necessary with water.. I have continued to use Dexcool, I just change it every 50K. The flush procedure works pretty well as I can flush mine in under 30 minutes now.

Too funny. I just noticed there are three threads on the exact same topic.....ALL with responses by me. Guess I should have just pointed to them

<{POST_SNAPBACK}>

you're still not evacuating the coolant from the block, trying to find plug locations on the block.

<{POST_SNAPBACK}>

Not true. The first time I did it, I pulled the block drains after flushing and saw nothing but clear water come out. Same with heater core lines...nothing but clear water after a flush. The next 2 times I did it I did not bother with the block drains.