Coolant Questions
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Senior User
Joined: Apr 2006
Posts: 201
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From: Hacienda Heights, CA
Coolant Questions
Its been two years since my Flathead was rebuilt (it is a 1950 I believe), and I figured it was time to change the coolant. I live in So Cal, and have NEVER had any overheating problems. The engine rebuilder just used water with soluble oil. I notice now that the water looks rusty! Whats best to use for replacement? Antifreeze/water, or Distilled water with soluble oil, or antifreeze/water with something like redline water wetter?
Also, I read the capacity is 23 quarts? WOW, what is the best way to drain as much of the old out as possible; I hate changing the coolant, but this has to be done. Any tricks or tips would be well appreciated!
Also, I read the capacity is 23 quarts? WOW, what is the best way to drain as much of the old out as possible; I hate changing the coolant, but this has to be done. Any tricks or tips would be well appreciated!
Fleet Owner
Joined: Jul 2004
Posts: 27,283
Likes: 1,046
From: NM
It's very hard to drain 100% of the coolant. The block is sloped 3 deg to the rear, so dirt and rust collect in the back of the block. If you face it downhill and pull off the lower radiator hoses, you'll get about as much as you can. Flush it while it's like that, vigorously. Best way is to pull the thermostats and stick the hose in there. Refill with 50-50 distilled water and antifreeze.
The only time I've been able to get 22 qts into mine is after an engine rebuilt, totally dry block.
The only time I've been able to get 22 qts into mine is after an engine rebuilt, totally dry block.
Cargo Master
Joined: Nov 2014
Posts: 2,442
Likes: 256
While changing the coolant do you also recommend a new thermostat and if so what temperature. I see they can range from 160 to 190 and I am sure there are all kinds of opinions on that and would like to hear them.
Lead Driver
Joined: Apr 2002
Posts: 8,813
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From: Littleton, New Hampshire
When replacing coolant it's always a good idea to include a couple of cans of anti-rust and water pump lubricant. These chemicals will keep rust formation in the cooling system to a minimum.
I'd use a 160 degree thermostat with the flathead.
I'd use a 160 degree thermostat with the flathead.
Senior User
Joined: Jul 2003
Posts: 322
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From: FL
The best way to keep a flathead cool is a topic like religion and politics...and engine oil!! 
My opinion is that water is the best transfer of heat. However, you also need a good anti-corrosion and a wetting agent. Glycol coolant does this for you and if you're not having any overheating issues, I'd run the minimum amount of coolant (10-25%) you can get away with and since you're in SoCal, there's no real danger of freezing either, so the coolant/anti-freeze is really just for lubrication and anti-corrosion - nothing more.
My opinion is that water is the best transfer of heat. However, you also need a good anti-corrosion and a wetting agent. Glycol coolant does this for you and if you're not having any overheating issues, I'd run the minimum amount of coolant (10-25%) you can get away with and since you're in SoCal, there's no real danger of freezing either, so the coolant/anti-freeze is really just for lubrication and anti-corrosion - nothing more.
Lead Driver
Joined: Jul 2011
Posts: 6,599
Likes: 34
From: Rockingham, VA
Glycol coolant does this for you and if you're not having any overheating issues, I'd run the minimum amount of coolant (10-25%) you can get away with and since you're in SoCal, there's no real danger of freezing either, so the coolant/anti-freeze is really just for lubrication and anti-corrosion - nothing more.
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Senior User
Joined: Jul 2003
Posts: 322
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From: FL
10% is good for about 20*F...not to mention, you'd have to have extended periods at that temp to even begin to worry about radiator or block damage...if you did nothing more than crank it up before going to bed, you'd never need to worry.
20% is good to about 10*F
But Glycol only has about 65% the heat capacity that water does at normal automotive temperatures...which means the least amount of antifreeze to protect against your coldest temps is the best ratio to run. Blanket ratios like 50/50 are usually good for most applications (because they're easy and cover most of the country), but with flatheads and their unique cooling challenges, the least amount of anti-freeze you can get away with, generally the better off you are.
EDIT - Found this webpage which explains it better than I can:
http://hellafunctional.com/?p=629
Last edited by Flat Ernie; Jan 9, 2015 at 10:26 PM. Reason: Added webpage
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Senior User
Joined: Oct 2004
Posts: 289
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Environmentally Friendly Antifreeze
Don't use the Propylene Glycol based "environmentally friendly" coolants. Use a major brand of good old Ethylene Glycol based coolant at whatever concentration you think you need. The propylene glycol based antifreeze will mix with and gel your motor oil if you get a coolant leak into the engine oil. Ethylene Glycol will separate, and can be detected in the oil.
I saw this " environmentally friendly" antifreeze ruin a Caterpillar V12 diesel engine in an off road haul truck. The engine oil turned into black Jello when the engine developed a head gasket leak, putting coolant into the oil.
I saw this " environmentally friendly" antifreeze ruin a Caterpillar V12 diesel engine in an off road haul truck. The engine oil turned into black Jello when the engine developed a head gasket leak, putting coolant into the oil.
Senior User
Joined: Jul 2009
Posts: 321
Likes: 0
From: Vancouver WA
Don't use the Propylene Glycol based "environmentally friendly" coolants. Use a major brand of good old Ethylene Glycol based coolant at whatever concentration you think you need. The propylene glycol based antifreeze will mix with and gel your motor oil if you get a coolant leak into the engine oil. Ethylene Glycol will separate, and can be detected in the oil.
I saw this " environmentally friendly" antifreeze ruin a Caterpillar V12 diesel engine in an off road haul truck. The engine oil turned into black Jello when the engine developed a head gasket leak, putting coolant into the oil.
I saw this " environmentally friendly" antifreeze ruin a Caterpillar V12 diesel engine in an off road haul truck. The engine oil turned into black Jello when the engine developed a head gasket leak, putting coolant into the oil.
Fleet Owner
Joined: Jul 2004
Posts: 27,283
Likes: 1,046
From: NM
Don't use the Propylene Glycol based "environmentally friendly" coolants. Use a major brand of good old Ethylene Glycol based coolant at whatever concentration you think you need. The propylene glycol based antifreeze will mix with and gel your motor oil if you get a coolant leak into the engine oil. Ethylene Glycol will separate, and can be detected in the oil.
I saw this " environmentally friendly" antifreeze ruin a Caterpillar V12 diesel engine in an off road haul truck. The engine oil turned into black Jello when the engine developed a head gasket leak, putting coolant into the oil.
I saw this " environmentally friendly" antifreeze ruin a Caterpillar V12 diesel engine in an off road haul truck. The engine oil turned into black Jello when the engine developed a head gasket leak, putting coolant into the oil.
Logistics Pro
Joined: Feb 2005
Posts: 3,952
Likes: 117
From: Upper Left Coast
I would also suggest you flush the system and refill with a 50/50 mix of distilled water and an ELF OAT type coolant like the following.
You can get it at Napa and other places.......
Regards,
Rick
EDIT: My Gross error!!
Senior User
Joined: Jul 2003
Posts: 322
Likes: 0
From: FL
As far as heat transfer itself goes, one of the key reasons I recommend a surfactant (ie - water wetter) when using straight water is the only advantage coolant has over water - it is a surfactant. So, yes, adding coolant to water will improve cooling...to a point....and then you begin to dilute the water too much and cooling performance goes down...but not very much.
Normally, most systems are operating with excess cooling capacity, so these types of minor issues never really matter. However, in a stock flathead cooling system, it's operating at its margins in many cases, so every little bit helps!
And coolant has improved dramatically...as long as you stay away from the environmentally friendly stuff!
Just filled up my '54 today...25-30% coolant...but I'm in the south!
Logistics Pro
Joined: Feb 2005
Posts: 3,952
Likes: 117
From: Upper Left Coast
Well, the specific heat capacity of water is 1 - pretty much everything else is less...including antifreeze/coolant. Consequently, all else being equal, for a given quantity/volume of water, you'd need a greater quantity/volume of coolant to carry off the same amount of heat.
I hate when I screw this stuff up
(OK.....37 years ago, I got a "B" in Engr Thermodynamics!)
Ethylene Glycol Heat-Transfer Fluid
However, I think I'll stand by the "One should never use pure water in any automotive cooling system!"
Last edited by HT32BSX115; Jan 14, 2015 at 11:47 PM. Reason: AND I'll do my homework a little better next time!!
Posting Guru
Joined: Sep 2004
Posts: 1,616
Likes: 3
From: Sapulpa OK
Good stuff here. I agree water is the best for heat transfer. Not the best though for corrosion protection. I also found the info about a 20% mixture being good down to 10*very useful. Central California rarely sees temps below 25* unless you are up in the mountains.
Would 20% give adequate corrosion protection? If so then I will begin using a20% ratio.
Would 20% give adequate corrosion protection? If so then I will begin using a20% ratio.