Author Topic: Flush an engine and radiator?  (Read 721 times)

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Offline priceless

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Flush an engine and radiator?
« on: June 05, 2018, 09:13:13 pm »
I've heard all the stories about flushing an engine and radiator completely. Getting all the rust colored water out.

Does anyone here have a tried and true way that is fairly simple without cutting hoses or having to punch out the freeze plugs or when flushing with pure water, does not mess up the bearings in the water pump?

Has anyone ever used one of the Prestone flush & fill kits?

It's come time to flush both my 67 and 69  V-8 Mustangs. 67 Mustang is a 289 and the 69 Mach is a 351W.

Any help and advice is deeply appreciated,

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Re: Flush an engine and radiator?
« Reply #1 on: June 05, 2018, 11:08:13 pm »
My research led me to Oxalic acid its what (some) rad shops use to clean copper radiators  the acid attacks only oxidized iron commonly known as rust. Easily found on line.
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Offline 69cobrajetrugae2

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Re: Flush an engine and radiator?
« Reply #2 on: June 18, 2018, 12:36:20 am »
I ruined a otherwise healthy engine in an ill fated attempt to clean the cooling system.  I collapsed a mud lined cooling passage in a head and the coolant velocity was insufficient to clear the blockage when the engine was restored to service and I cracked the head.

Old coolant should be yellowish in comparison to new coolant in routine coolant change.

Rusty colored coolant indicates that metal inside your engine has been transformed to rust.  Damage has been done.

The idea is to arrest the corrosive process however removing the corrosion through a chemical assault is in my opinion a very bad idea because the metal which has been converted to corrosion is usually located in a critical area such as a gasket interface, head, intake, freeze plug or radiator and is doing the job of the metal which it replaced, that is to hold a seal.

I would drain the radiator and replace the old coolant with 50/50 antifreeze and 6 "bars leak" tabs and repeat every 1000 miles or three months, whichever comes first. Bars leak tablets is simply rosewood and expands with contact to air but will not get hard and cause other problems like sodium silicate "Glass" based stop leaks will.  Only use the tabs not the bars leaks liquid.

Chemicals will stir up and release rust fragments which in our engines are located in the block's water jacket.  Once liberated the rust fragments will take flight up through the heads and their cooling passages.  If the rust does not dam up in the heads they will likely dam up in the radiator causing a partial restriction which did not exist before the cooling system service.  Removing the block drains and thermostat and running the engine at idle adding water at the radiator at same rate that is flowing from both block drains sounds good but again in my opinion, the best approach is to slowly add fresh antifreeze as outlined in paragraph 5 and let sleeping dogs lie...   
« Last Edit: June 18, 2018, 07:37:59 am by 69cobrajetrugae2 »

Offline b--r30

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Re: Flush an engine and radiator?
« Reply #3 on: June 20, 2018, 08:19:49 am »
My radiator guy removes the thermostat and then replaces the therm housing. Removes the lower radiator hose from the radiator and has an adapter to connect this hose to a garden hose,hooks another hose to the rad for a drain to...I didn't ask where. Turns on the faucet and runs the motor for a short while till the drain runs clear. I'm sure it doesn't really get everything clean but I'm happy with the fresh antifreeze and the good feeling that I'm actually trying to to do something.

Offline redscj

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Re: Flush an engine and radiator?
« Reply #4 on: June 20, 2018, 10:04:49 am »
     In the past, I've flushed several heater cores in a similar manner. Disconnect both hoses, attach hose fittings with hose clamps. One hose to an outdoor faucet & another away from the area. Let her rip. It's amazing the dirty water that comes out. Seemed to really help the heat output back then.
     As a side note, when I've done this there normally wasn't much antifreeze in the system. Not very eco friendly in todays world. I guess the first gallon or so of water should be ran into a bucket that can be better disposed of.
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Offline RoyceP

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Re: Flush an engine and radiator?
« Reply #5 on: July 02, 2018, 05:54:55 pm »
I've used vinegar for this. First you take the upper and lower radiator hoses off and remove the thermostat. Flush the block and radiator as much as you can with a water hose. Then reinstall the thermostat hosing and hoses, leaving the thermostat out.

Fill the cooling system with vinegar. Let it sit overnight, then drain the vinegar and repeat the flushing with a garden hose. You won't believe how much crud will come out!
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