Flushing radiator

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Michael Paul
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Flushing radiator

Post by Michael Paul » Sun May 12, 2019 6:24 pm

Hi all, just got a 22 touring running after many years of storage. With lots of electrical connection cleaning, new fluids, and battery, it fired up and ran great with a little coaxing.

I would like to flush the radiator, the former owner suggested using CLR. It's the stuff normally used for porcelain surfaces. Has anyone had first hand experience using it? It was touted as being just as good as a shop radiator flush.

Any comments or suggestions appreciated.
Michael Paul

Peter, Memphis TN
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Re: Flushing radiator

Post by Peter, Memphis TN » Sun May 12, 2019 7:14 pm

CLR has been widely touted on this Forum for that purpose.

There are three things you're trying to remove from the water passages -- Calcium and Lime from the water, because folks don't use distilled water as we all know we should, and Rust. That's what CLR stands for. There may be some oil and some plain dirt, but those are the big three.

The problem generally is not loosening the crud, it's flushing it out. That takes time and patience, and can make a big mess in your yard. What you'd like, is to be able to pressure wash the inside passages of the motor and radiator.

I believe Steve Jelf is the one who made up a rubber stopper with water hose and air hose connections, so you could use your compressor to add pressure to the water. Perhaps he'll re-post that thread.

Back to your original question, CLR is a good choice.

Jerry VanOoteghem
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Re: Flushing radiator

Post by Jerry VanOoteghem » Sun May 12, 2019 7:22 pm

Not necessarily trying to dissuade you from flushing your radiator as it's not a bad thing to do, however, I'm wondering if you're wanting to do this to solve some issue, or just because it seems like you should? Myself, if it's all currently working well, I would tend to leave it alone. Once flushed, you may "uncover" some leaks, (as I did with a 1912 Overland radiator, which then became a good lawn sprinkler). :)

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Re: Flushing radiator

Post by CudaMan » Sun May 12, 2019 7:34 pm

Mark Strange
Hillsboro, MO
1924 Cut-off Touring (now a pickup)

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Henry K. Lee
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Re: Flushing radiator

Post by Henry K. Lee » Sun May 12, 2019 10:10 pm

For years I have only used 2 gallons of White Distilled Vinegar, topped off with tap water. Run the vehicle around for about 30 minutes, let cool then drain. Really breaks up the deposits nicely with outstanding results. You may even wish to do this in cycles over a few days Sometimes if there are heavy deposits, remove the radiator and lay flat with the radiator cap installed and fill again with straight vinegar and let set for a couple of days. Pour out the the contents on a fence row as weed killer (does a nice job), back flush a couple of times. Done!

All the Best,


This method with Distilled Vinegar works very well if used in a 5 gallon bucket too, for cleaning electrical harnesses. Let set for about about 5 days and rinse off. You will be amazed.

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Michael Paul
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Re: Flushing radiator

Post by Michael Paul » Sun May 12, 2019 11:39 pm

Thank you for all the great info. The car sat for more than 15 years. I'm pretty sure the radiator was drained when it was stored. We have hot summers here so a good flowing radiator is a must. It does have an aftermarket water pump so that's good.

It did have symptoms, when I shut it down after a 10 minute try out, it was a little overheated. For a couple minutes, the overflow tube was blowing off. Seemed like air, not steam. No bubbles in the water while running so I don't think it is a head gasket. I used just plain distilled water

I imagine there's plenty of debris and scale in that thing after 98 years. Vinager sounds interesting, would do more than just the scale.... I like the idea of have some organic weed killer when I'm finished.

Vinager has amazing uses. In my younger days I was a race horse trainer. One of the best secret remedies was rapping sore tendons with gauze soaked in vinegar overnight. it would draw the inflammation out like nobody's business. You can even use that remedy on yourself if you don't mind walking around smelling like a salad. Lol.

Thanks again, Mike

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Steve Jelf
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Re: Flushing radiator

Post by Steve Jelf » Mon May 13, 2019 12:06 am

The presence of a water pump suggests an overheating problem. A good cleaning may fix it, or not.
The inevitable often happens.
1915 Runabout
1923 Touring

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George N Lake Ozark
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Re: Flushing radiator

Post by George N Lake Ozark » Mon May 13, 2019 12:51 am

I've used CLR, fine stuff. Drained the rad. fresh water and Cascade to remove any oil crud, Drove a few hours , let sit over night . In the morning drained ,rinsed with fresh water and add CLR drive for about an hour to circulate, let sit over night, drain , ran fresh water and baking soda to neutralize , drain and fill with coolant of your choice.

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Re: Flushing radiator

Post by Scott C. » Mon May 13, 2019 1:35 am

My 26 Roadster had a lot of sludge and rust in the radiator and block. I tried Dawn dish soap, Purple Power, vinegar and a lot of flush cycles. They all did a little bit of good, but not much. I then used Thermocure. It is a cooling system cleaner from Evaporust. Far better result. I had to buy a second bottle and do it twice to get it really clean. It really did the trick! Then I did my 26 Coupe and it came out really nice also. I bought it at Walmart for around $20.

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