Need to flush my coolant system

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Tynan918

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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

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Aug 2, 2021
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The garden hose flush for the radiator and block is what I do, flush till it comes out clear, find the coolant capacity of the cooling system, put in half that amount in full strength coolant, then top off with water. For winter cars, I've had good luck flushing the heater core both ways with a garden hose. Had a Buick Roadmaster that I had to do that about every year, then I'd get good heat all winter.
How do you flush the block with the garden hose ?

Specifically the block, because I've already flushed the radiator and the heater core...
 

Bonnewagon

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Had a Buick Roadmaster that I had to do that about every year, then I'd get good heat all winter.
We have the same problem with a 2012 Jeep. Heater clogs on a regular basis. A quick flush and it's good for another year or so. Still can't figure out why. Without opening the block drains the only thing you can do is jam a garden hose into a radiator hose and blast as much out as you can. Remove the upper and lower and do it both directions. You will never get it all out but as long as it is looking clear that is the best you can do. I would not drive very far without a thermostat in place. The coolant will pass through so fast as not to have time to release the heat. EDIT: That rusty valve shuts off the coolant to the heater when the AC is on.
 
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How do you flush the block with the garden hose ?

Specifically the block, because I've already flushed the radiator and the heater core...

Stick a hose in the thermostat housing and and run it until the water runs clear out of the water pump. Just leave the freezer plugs in the block. Taking them out is just asking for trouble. Your never gonna get it perfect with a garden hose.


There. I tried to help.
 
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403Olds

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How do you flush the block with the garden hose ?

Specifically the block, because I've already flushed the radiator and the heater core...

Put the garden hose in the lower radiator hose, and let it run until clear water comes out of the thermostat housing, then run the hose thru the thermostat housing until it runs clear, repeat until it's clear both ways, or you get bored... usually about three times it's pretty decent.

Pulling the plugs is more thorough, but this has worked well for me.
 

Tynan918

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Aug 2, 2021
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Everything ran clear and no brown from the radiator, heater core, water pump, or engine (upper radiator hose). Ran it 45 mins. in idle like this and the water was clear the whole time.

Ready to dump the coolant mixture in...
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Tynan918

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Aug 2, 2021
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Everything ran clear and no brown from the radiator, heater core, water pump, or engine (upper radiator hose). Ran it 45 mins. in idle like this and the water was clear the whole time.

Ready to dump the coolant mixture in...
View attachment 206115
I have 3 questions before I start dumping in the distilled water and full strength green coolant...

1. How should I pour these to correctly mix 50/50 ?

2. As I was filling up the radiator by hand (before I used the water hose) after a couple of flushes, I can only get about 1 1/4 gallons before the radiator topped off ... How will I get 4 gallons of this mixture in the system if I'm only able to add 1 1/4 gallons ?

3. My overflow tank has a small crack in the passenger side upper corner, the threads on the neck for the cap are damaged, and it's pretty dirty inside. Should I be pouring in the coolant with it like this or should I replace it before pouring in coolant ? Also, if the salvage yard is where I can afford a replacement, what years and models of GM vehicles can I find one in ?
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Tynan918

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Aug 2, 2021
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Well I ended up taking off the reservoir and taking it to the car wash to power wash it with soap and water.. it had rust gunk all in it..

I went ahead and I had two empty gallon bottles and I put half of the full concentrate coolant and half of the gallon of distilled water and mix them together in one gallon. I did that for two bottles.

With the engine cold and not running I started adding the mixture to the radiator and cooling system this is how much I used of 2 gallons before it became full..

I turned on the engine and the coolant level went down so I started adding more until it was full again and this is where we're at...

Do I run the engine until it gets warm with the thermostat open and then add more ?... I have the engine running now and I'm going to run it for about 20 minutes and see where the level is and if I need to add more..

Getting hard to believe the cooling system holds 4 gallons of coolant..
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565bbchevy

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