MTFCA Forum

For the past several years I've been running a radiator on my speedster with unpainted fins; the idea is that bare metal transfers heat more efficiently than a painted surface. (This is a Southern California car so I need all the heat transfer I can get.) The problem is that now I'm starting to see blue patina forming on some of the fins. This obviously can't be a good thing.

My first question is of course how to remove the patina safely. Secondly, would it be better to just paint the core and not have to worry about it corroding again?

Any suggestions are appreciated.

If you do paint the core, you will lose some cooling ability. A very thin coat should be used. A good radiator shop might be able to remove the corrosion and paint it with the proper paint.
Norm

There are radiator paints that are thinner so they do not add a thick layer. Also, spray conservatively as to not cause build up.

10% pickling vinegar might remove the patina. Use full strength in someting like a pump sprayer. Spray the core to completely wet it, then keep spraying it every few minutes to keep it wet for half an hour or so. Rinse well, blow dry.

You didn't say whether the radiator is a stock Model T radiator or not. If it is a stock Model T radiator, and the engine is not modified, it should be able to handle California heat. If the engine is modified for more power, that is a different matter. For a stock, non-brass era Model T I would recommend a Berg's flat tube radiator, if it is a brass-era T I will defer to someone who knows more about it then I.

The core is a flat-tube core; the motor is mildly hopped up with a 'Z' head and slightly larger valves.

Eastwood offers a rattle-can paint product called "Radiator Black" which supposedly features a "heat dissipating formula." Has anyone tried this product on a "T"?

we have always used a black powder mixed with water and then sprayed on with a regular spray bottle . The water dries up and you are left with a flat black finish. We redo it every 10 years. I remember now it is called lamp black.

The correct spelling is Lampblack one word it is what they used back in the day ,it is made from soot . I don't know if you can still buy it Dad had a bag of it . First used in 1960 it will out last me as a 1/4 tea spoon will do a rad with left overs.

Amazon sells lampblack….
https://www.amazon.com/s?k=Lampblack&ref=nb_sb_noss_2

Stove blacking (?)

JMO, but if a coat of black paint is the difference between the radiator properly cooling the engine and not, you need a bigger or newer radiator (or both). Let's not overthink this.

I don’t believe anyone is worried about a one time application of thinned paint on an old radiator. It’s when multiple owners over the years have slapped layers on top of each other with a paintbrush and a can of enamel paint that happen to be on the shelf.

I agree about the multiple coats, but the OP states that the fins were unpainted; this will be a one-coat job.

Heat is dispersed by "conduction" by the transfer from one source to another - engine heat to the coolant: the motion of the coolant through the system is called "convection" (thermal siphoning) where the hot fluid/gases go to the upper part of the radiator, and as they are cooled fall to the lower part. Cooling is caused by "convection", which occurs when the surrounding temperature is lower than the internal temperature. The more exposed surface area (fins) and air flow through the radiator the greater its ability to dissipate heat through "radiation". When it comes to paint, there are two things that will affect radiation: color and air flow. Black is the best color used to radiate or absorb heat, thus it has been the color of choice. A thin coating should be viewed as not to clog or restrict the air flow through the system grid of tubes and fins; not as an insulator. So while the affect of a thick layer of paint may have on "conduction", transfer of heat from the surface of the radiator to the atmosphere, a thick layer of paint may have a greater affect on the ability of it to dissipate neat by "convection" by reducing or restricting air flow through the grid. (corrected)

Radiators are primarily heat exchangers. They do radiate some heat, but their design is aimed at warming the air that passes through them by getting as much heat as possible from the liquid coolant passing through the tubes into the air passing through the core. OE radiators all used to have a thin coat of some kind of cheap black paint.

Don’t waste your time screwing around with any of the “maybe this will work” answers.

Take it to a RADIATOR SHOP and have it prepped and painted. They can properly do it with the proper materials so the paint sticks, stays looking good, cools well, and has good longevity.

Professional radiator paint, properly applied, is heat conducive and won’t change the cooling ability of your radiator. If you have a new radiator that runs too hot, something is wrong that needs to be fixed... Likely not the radiator.

Also, the reason radiators are coated to begin with is because they loose efficiency as soon as they begin to corrode.