Too Much Paint

J

jeepguy1948

Well-known member
My new to me ‘30 Phaeton came to me as a non running car. In the end I had to do an engine swap. While I was doing that and had to take the radiator out anyway I took it in to the radiator shop and had it flushed out and make any needed repairs. As soon as he saw it he said the it was a very old repop.
When I got it back I did a real nice paint job, something I could be proud of out there for all the world to see. Now I have overheating issues (remember, I don’t know if it had an overheating issue before it was parked). The water pump is new and the engine block has been flushed out. The only possibility that I can think of is all that paint I put on is blocking the passages and acting as an insulator. Have any of you heard of this happening?
 
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And you are geographically where? It helps if you put your state, or province in your profile.
 
Too much paint on the core's fins will interfere with the air dissipation they were designed to carry away excess heat. But the radiator core would have to be very borderline in efficiency to cause the overheating problems you describe.
Or... If you have one of those two-row core radiators sold by Rick's and J.C. Whitney in the 1970's, that thing will not cool a Model A engine in January during a blizzard in northern Alaska. While still learning about Model A's and with a limited cash flow, I didn't know there was a MAJOR cooling difference between a good four-row core and a two-row core radiator. So, I opted for the cheaper one - the two-row radiator. I could never keep the engine cool for very long and did a lot of pulling over to allow it cool down. Until I finally replaced that P.O.S. with a decent radiator, I could only drive my Model A on cool or cold days for a limited range. One of my first lessons learned about taking the cheap route when buying Model A parts: You usually get what you pay for. There's a reason why the four-row radiators are so expensive.
Your radiator guy may have cleaned out the core and sealed leaks, but if it is a two-row core from years ago, it is a designed failure that no radiator shop in the world can make function properly. That your new engine overheats since you got the radiator repaired tells me you might have one these Rick's rip-off specials that so many parsimonious Model A owners like me bought 50 years ago because of the low price. There are very few components in a Model A that can make your life more miserable than a bad radiator.
Marshall
 
It’s possible to put on too much paint, and/or to use the wrong type of paint. There is a specific type of radiator paint that ensures the tubes and fins aren’t insulated. When I have an old Ford radiator worked on, I always let the radiator shop do the painting; they have the proper paint and apply it sparingly. You can buy it at Eastwood. If you think you’ve insulated the tubes with the paint you applied, maybe a radiator shop can boil the radiator and remove your stuff. Good luck.
 
I don’t know how to tell a 2 row from a 4 row but peering in there with a flash light it kind of looks like maybe a 2 row (1 row in front and 1 row in the back with a hollow space in between?) My concerns are exactly as you describe Marshall, I have a radiator that is not up to the task no matter what I do. The problem is of course that it’s summer and Model A season now and I’m without a Model A to drive. I have been on the Brassworks waiting list for 2 months now but have another 2 months to go.
 
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Before you replace the radiator why don't you remove the paint and see if it will cool. Also make sure the timing is not set too retarded.
 
Bruce, Post #5 has the right response. Use a radiator paint and just enough to make it black. You may be able to remove the existing paint with a good paint remover.
 
What your radiator guy said "As soon as he saw it he said the it was a very old repop". Marshall hit the nail on the head. If you want to use that radiator you can't use your car over about 80F outside temp.

As far as Brassworks goes, you are paying a lot for that. What about the best radiator that Snyder's sells? That is what I have in my car.

Is your car a 29-29, or 30-31?
 
I don't mean to step on any toes here and of course Model A owners should pursue every possible cause of overheating, but in my experience (and most old-timers here will back me up based on their own likewise futile attempts), trying multi-blade fans, using smaller diameter crank pulleys to increase fan speed, backing off service brake adjustment, running without front license plates or tilted at a 90 degree angle (cops LOVE that!), cutting down the size of the water pump shaft impeller blades, reducing the amount of coolant to keep the coolant from puking past the radiator cap, limiting the amount of paint on radiator fins, running snake oil cures such as Water Wetter, installing thermostats, and whatever else guilty man can think up is only dodging the cause of overheating in most cases.
Flushing the engine block is a recommended and time-proven procedure to help reduce restricted coolant passageways. But unless the block is boiled out in a hot tank, you're never going to completely open up the passageways with auto store chemical additives. Think "varicose veins" in the human body and how difficult it is to open them up after they've shrunken internally.
The MAIN culprit for overheating in Model A's that people dance around with all these efforts is the obvious one - the *&%# radiator itself! Whether the core size is incorrect and insufficient to cool the engine, fins have separated from the tubes, past tube leaks having been closed off or sealed with a stop leak, or just a simple lousy core to start with (such as a honeycomb design), of the many, many postings on this website over the years complaining about overheating, replacing the radiator or re-coring it has solved the problem in virtually every case. Everything else attempted is just putting a Band-Aid over an open cancer sore.
In all likelihood, "Jeepguy1948" is going to end up replacing his radiator or else he will be plagued by continual overheating problems. I am not saying in every case of overheating that the radiator needs to be replaced. What I am espousing is for chronically overheating Model A engines, the best course of action is to replace the radiator, expensive though it maybe. How much does it cost to replace a burned-up, overheated Model A engine by comparison??? $800 versus several thousand dollars...
Marshall, the Eternal Spender of Your Money
 
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When I refurbished the current babbetted engine for my '31 last year I installed a "Heavy Duty" radiator from Snyders that I got several years ago. I have heard that it was manufactured by Berg's, apparently no longer in business. I had previously run this same radiator on the same engine in my '30 for about 6 months prior to disassembling the car but pre-engine refurbish and had no issues.

When I was working on the block I did everything I could to open up the water passages short of boiling it (didn't want to boil it with babbett). Wire wheels, long screwdrivers, air flush, water flush, etc. It seemed pretty clean to me when I got done. Head was boiled and decked. I left the radiator alone.

I'm still having overheating issues - typically running 180-190 on the freeway and higher when I'm climbing, even with air temps in the 70's. Timing is good, carb jets blown out. I got the temps down maybe 10 degrees by putting in a new coil (I had an old Ford Script coil) thinking that the coil might have been weak at higher temps. My next step is radiator flushing and possibly rodding out. But day-yum, radiator work is expensive these days!

I do have a new Brassworks radiator on order to mate with the Burtz engine I just built. Not sure I want to mate the new radiator with the old engine, or vise-versa. But I'd really like to get this sorted out so I'm confident that when I reuse this combo of engine/radiator that I have a solid assembly.

An additional unknown is the aftermarket 5.2 head I'm running. I have no idea of the cooling efficiency of the water passages, but like I said, I boiled it out before using it.
 
Sourcing a used radiator is a big gamble. Is it really OK? Brassworks is the way to go if you have the money to spend and the time to wait. I ordered mine in early January 2026 and it arrived the middle of June 2026. The cost was high but radiator shops around here all went the way of the Dodo bird.
 
If you can, get your current radiator recored and have them install a 3- row core. Where is western Washington are you located?

Mike
 
A big Thank You to Marshall for taking the time to explain for me the problems caused by the 2 tube radiators (that’s exactly what I had, an old re pop 2 row radiator. Even though I had a radiator shop go through it (that’s exactly a couple hundred bucks down the toilet) it would never have done the job). A club member came to my rescue with a new in the box Brassworks radiator for a great price (and no waiting). The radiator is now installed and no more overheating issues! Thanks again Marshall!!!
 
The 4 row radiators were for trucks and take a different radiator shell for the thicker radiator. — original passenger car was 3 row
the fins can loose their connection to the tubes and make a radiator that is clean inside not work.
I have seen the small (steam?)holes in the block and head look open and be mostly closed off below the surface— I always clean them out with drill to their full original diameter.
 
Thanks for the kind words and I'm glad you isolated the cause of your engine overheating. The downside is you have an additional expense buying a new radiator, even with a favorable price. It will be a pleasure from here on out driving your Model A without dealing with radiator problems.
Marshall
 
Yes, Kurt in NJ is quite right. I really should have written "three-tube/row" core for passenger cars instead of four. The four-tube/row was for heavy duty use back in the day. My numbering was not accurate, but the meaning is the same. I was using the New Math in my figuring. :)
Marshall
 
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