Need to flush my coolant system

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Tynan918

Royal Smart Person
Aug 2, 2021
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How do I flush my whole coolant system?

I know that there are drain plugs on the side of the engine to drain the water out of the engine block and there are plugs on the radiator and I can remove all the hoses, but how should I flush it out?

With a garden hose ?
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Tynan918

Royal Smart Person
Aug 2, 2021
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I have not had one that bad but my method has always been dead simple and the coolant looks clean when done.
1. Disconnect the lower radiator hose and let everything drain.
2. Flush the radiator out with a garden hose. Gets all the junk I can out of it first.
3. Hook the lower hose back up, fill the system with water and run it till it is up to temp.
4. Disconnect the lower hose, drain, re-connect, fill with water, run and repeat till the water coming out is acceptably clean.
5. Fill with alternating gallons of water and antifreeze.
Does this routine get out what's in the engine block as well? Without removing the drain plugs from the engine block?
 

SSMonteMan

Greasemonkey
Jun 12, 2015
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Does this routine get out what's in the engine block as well? Without removing the drain plugs from the engine block?
Yeah, that method will clear out all the fluid in the system, but it's a slow process. It's what I would do, though, as it's pretty easy.

Be careful with the flushing additives. Some of them can be corrosive.
 
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Tynan918

Royal Smart Person
Aug 2, 2021
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Yeah, that method will clear out all the fluid in the system, but it's a slow process. It's what I would do, though, as it's pretty easy.

Be careful with the flushing additives. Some of them can be corrosive.
Does sound pretty easy because I don't have to use a water hose or remove the drain plugs on the engine..

I'll do it this way and I'll do what the other guy said bye using a gallon of distilled water, a gallon 50/50 diluted green antifreeze, and a gallon of non-diluted green antifreeze... So that way I'm saving 20 bucks instead of paying 50 or 60 on 3 gallons of 50/50 green antifreeze.
 

tkruger

Master Mechanic
May 6, 2015
358
310
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NY
While your at it you might want to replace all of you radiator and heater hoses. Also do not reuse the hose clamps. Not worth the risk of loosing all your coolant while out driving around and having your motor over heat.

Keep the heater on when you do the flush and get everything out of there too.
 
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SSMonteMan

Greasemonkey
Jun 12, 2015
111
225
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I just buy 2 gallons of straight antifreeze and 2 gallons distilled water. Add 1 gallon antifreeze, 1 gallon of water, mix half a gallon of antifreeze and water in the now empty first gallon, then fill the second gallon, too, making 2 50/50 gallons. Saves a few dollars that way.

I also recommend new hoses and clamps. The right constant tension clamps are a bit more expensive than worm gear style hose clamps but are going to be better in the long run. New hoses, after the flush, will be nice and clean and last a lot longer than the old ones will.
 
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Tynan918

Royal Smart Person
Aug 2, 2021
1,136
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While your at it you might want to replace all of you radiator and heater hoses. Also do not reuse the hose clamps. Not worth the risk of loosing all your coolant while out driving around and having your motor over heat.

Keep the heater on when you do the flush and get everything out of there too.
The hose clamps I can afford to replace but I'm not so sure about the hoses...
 

Tynan918

Royal Smart Person
Aug 2, 2021
1,136
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I just buy 2 gallons of straight antifreeze and 2 gallons distilled water. Add 1 gallon antifreeze, 1 gallon of water, mix half a gallon of antifreeze and water in the now empty first gallon, then fill the second gallon, too, making 2 50/50 gallons. Saves a few dollars that way.
That's enough for the reservoir overflow tank too ?
 

tkruger

Master Mechanic
May 6, 2015
358
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NY
With the coolant as bad as your picture shows you might want to do the thermostat too. They cheep. If you don't replace the hoses, thermostat etc. you will need to re-buy all of the coolant if one goes. I understand that they may look good now but I have been in that situation where three months after doing a job I halve to redo 50% of it because I saved a buck not replacing a part. Pay more now or more later is the question.
 
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Tynan918

Royal Smart Person
Aug 2, 2021
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One more thing, my reservoir tank has a small crack in the corner and when I have it filled up with water it doesn't really leak but it drizzles.. can I put some gasket on this small crack or should I just buy another reservoir?

And if I need to replace the reservoir, which years and models of GM vehicles would I find one or are these Monte Carlo specific ?
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