12/31/2025
Pulled from The Rumble Seat Reviewer, September 2025, this tech article was written by our club Technical Committee member, Vic Varady. Copies of our newsletter, The Rumble Seat Reviewer, are available for FREE download from our website at https://smokymountainmodela.com/newsletters
Radiator Temperature Check
Club President Tony Gardner spoke at [our monthly meeting] about losing coolant from his radiator on a run. He found the problem to be a partially plugged radiator, restricting coolant flow. I have experienced this problem before and used a different method to identify it a few years ago, before I sent the radiator out for cleaning. I wrote an article that was in the May 2009 Rumble Seat Reviewer covering Brake Adjustment. Coolant temperature and brake operation are temperature phenomena. This article can be accessed on our website. The tool I used for coolant work and brake adjustment was a Non-Contact Infrared Thermometer, which is readily available and not expensive from Harbor Freight and others. I have several, and I usually keep one in my toolbox on a trip. The last one was $10, purchased at a flea market, and it needed a battery.
To review the performance of your radiator, you need to take temperature measurements externally from the front at several points along a horizontal line on the radiator after driving the car for a few miles. The first level should be near the top of the radiator, about 1 inch below where the coolant enters the radiator. The second level should be 6 inches to 12 inches below that. Plot the temperatures on a chart. Do the next horizontal scan approximately 12 inches below the first one, then follow with another scan. Three or four scan levels will usually uncover the need for attention. I usually also record the temperature of the incoming coolant and the coolant discharge. This can be done with the hood opened, and you sight the instrument using the laser. Watch your hands. You do not need to wait for a problem to show itself. Keep a file with the results in your folder, which you put in a safe place that you can remember.
At Harbor Freight today, this tool is a laser-sighted instrument #3729, the cost is $23, and it should be readily available. My first one from another store came with a case and cost over $100 25 years ago.
You can use this tool to check temperatures around the house at heating/cooling vents, windows, walls, water delivery, and anything else you think of. I used it to check the exhaust manifold for cold spots where the combustion is compromised. You may find that there is a lot of heat coming from the muffler when you measure the passenger side floor. I have found that the muffler heat deflector is very useful. Mike’s in Georgia has this accessory (Part # A5230HS or A5230HSS). I wrote a post for this accessory in Ford Barn recently (Vic in E-TN), and if you have some metal-bending skills, there is a picture of this. I would rather spend a few dollars and get it shipped directly.
– Vic Varady, SMMAC Tech Committee Member
