How to flush cooling system?

[wcbcruzer]

Hello folks, what's the best way to thoroughly flush out a cooling system? I'm not talking about draining the petcock valve on the radiator... I'm talking serious business like taking a garden hose to the block with the thermostat out. However, even then I don't think I'll be getting all the old coolant out from the back of the block and other hard to reach areas. I've heard of people having to drain and refill their cooling system 15 times before it starts coming out clear. I'm just trying to avoid having to do it that many times, unless there's no other way.

Reason I ask is because I've swapped radiators more than once already (which was grounded with a ground wire). I want to get all the old corrosive gunk out of there, otherwise it'll eat the metal on the new radiator too. Plus, there's Stop Leak in the system from the previous owner.

2008 Mountaineer V8

 

[410Fortune]

Drain radiator
Fill with distilled water (I filtered use well water for this as I don’t want to buy 20 gallons of distilled)
Run engine to temp heater on high
Drain radiator

Repeat this about 3-4 times
On the final one add some prestone cooling system flush and run it through

Drain radiator
Fill with clean water and run it one more time

Drain
Now you will still have distilled water in the heater core and engine
The system should be running clear now
A good cooling system flush can take all day with running the engine to temp several times waiting for it to cool and bit and draining

You will need to start mixing in full strength coolant in an attempt to match the amount of water left in the engine and heater. Burp the system, use a coolant tester to check the mix.. add water or coolant concentrate to bring mix to proper levels

 

[wcbcruzer]

Thanks for the reply. I was thinking about removing the upper and lower radiator hoses, putting the lower hose in a bucket of fresh water with a garden hose filling it. Then have the upper hose discard all the water coming out of the engine. Run it like that until everything is flushed out. Then drain and refill with distilled water, as you mentioned.

Not sure if this will work, but it seems to be the fastest way of getting all the old stuff out.

 

[410Fortune]

Good idea
I May try that next time
It’s also a good idea to remove the heater hoses off the heater core and backflush it with your garden hose… amazing how much sediment can come out of the core after 20+ years

 

[wcbcruzer]

Oh you're right. Can't wait until I do this. It'll be satisfying... The more GUNK comes out, the better. Although, I don't think I'll see anything lol.

That Stop Leak is some weird stuff. It runs clear until there's a hole, then it oozes out like foam-in-a-can. Unless, that's not Stop Leak that I'm seeing...