Pint Size Project — Cooling System

Memorial Day weekend usually signals the start of summer in this part of the country, and warm weather can be expected. If you drive a post sixties little British car, then you shouldn’t have much trouble with overheating as long as:

1) your cooling system is full of 2-to-1 mixture of  water and antifreeze

2) you have installed a 160 degree thermostat and the proper radiator cap

3) the fan belt is tightened properly

4) all the radiator ductwork and overflow/recovery system is in place

Regarding antifreeze, Texans obviously don’t have to worry about the radiator turning into a block of ice, even in January. The anti-corrosion properties are what should concern those of us south of the Snow Belt. The 1/3 mixture is fine for preventing rust in our cast iron (aluminum is another story) engines, and transfers heat noticeably better than a more concentrated mix. Distilled water should be used for best results.

Some engines won’t warm up in cold weather with a 160 thermostat, but it is worth the trouble to swap to the cooler stat once hot weather arrives. Thermostats have changed over the years. Many early cars, like the Sprite, AH3000 and TR3 have a bypass in the cylinder head for coolant circulation before the thermostat opens. These engines had a special stat with a sleeve that blocked the bypass after the engine warmed up and the stat opened. These stats are available once again from Moss, but most folks just use the modern version. However, some cooling action will be lost if the bypass is not blocked off. A sleeve (Moss again) is available to get this done, but a plug in the bypass hose works as well. Most modern thermostats do not have a vent like they did in the old days. I always drill a 3/16-inch hole in the flat part of the thermostat to make filling the system easier and prevent pressure build up. Caps have changed, too. Older ones are a little taller, and there are several pressure ratings, so order the correct one for your vehicle. Arbitrarily raising the pressure is a good way to blow a hose or a freeze plug!

Everybody knows the risk of poor charging due to a loose fan belt, but the same thing can happen with the water pump. A new belt will almost certainly stretch and should be checked often

When you are stuck at a traffic light the engine temperature may rise alarmingly. Some increase is to be expected, but can be minimized if everything is in order. While driving at highway speeds, your engine should be running at its coolest. If the temp jumps only at low speeds, you may have low coolant level, an antiquated fan, or missing/damaged ductwork. An overflow bottle will allow the maximum amount of coolant to be in the radiator. When hot, the excess will overflow, only to be recovered when the engine cools down. This action also allows the excess air in the system to be purged. The ductwork or radiator shroud prevents the hot air in the engine compartment from being pulled around to the front of the radiator when the car is moving slowly. It is very important that only outside air is pulled through the radiator.

Older LBCs may lack some of the more modern engineering found on the 1968+ cars. Lots of these improvements can be retrofitted to these clunkers! For instance, a late 1275cc Sprite cross flow radiator, ductwork and fan will bolt right on an early car. A TR6 fan can be made to work on a TR3, and its compact overflow bottle will fit just about anything. Aftermarket high performance fans are available (you guessed it, Moss!) for Austin-Healey 3000. A handy fellow can easily fabricate a radiator duct, if a new one is not available. A nice ABS plastic shroud is available for older MGBs. A new radiator is not all that expensive and probably more cost effective than a trip to the radiator shop. Consider losing the crank hole in the TR3 radiator, as that makes it about fifteen percent less effective.

Barring a bad head gasket, or some other dire problem, you should expect to run between 160-190 degrees Fahrenheit, regardless of the outside temperature. As a last resort, modern, all aluminum radiators are available for many British cars.

In my opinion, electric fans are of little use, unless they are specifically designed as a replacement for the original fan. They also put quite a load on the charging system; therefore, forget about using an electric fan on a car with a generator.

Don’t trust that temperature gauge, either. Laser thermometers are reasonably priced and using one for a second opinion may prove that your engine isn’t so hot after all! Of course, that’s what we suspected all along.

By Mike McPhail
Gulf Coast Austin-Healey Club
Hill Country Triumph Club

'Pint Size Project — Cooling System' have 6 comments

  1. July 9, 2013 @ 7:40 pm Gene Balinski


    You mention the use of a laser thermometer to validate the car temp gauge. Where would you suggest using the laser to get an accurate engine temperature measurement ?

    Safety Fast!

    Gene Balinski
    80 B


  2. June 26, 2018 @ 8:37 am Frank Stabler

    The overflow bottle is a great idea, but it won’t work without a radiator cap that is designed to work with that type of system.


  3. June 26, 2018 @ 11:48 am Haig

    To improve accuracy of the laser surface probe ,attach a piece of black tape to the area being tested. Shiny surfaces with reflect and change the reading. Test various areas. top hose bottom hose radiator top and bottom etc.


  4. June 26, 2018 @ 1:12 pm Richard Noar

    I have a ’67 E-type coupe that HAD all the usual over-heating problems associated with those cars. I solved them by installing an electric fan from a Ford Taurus and ditching the water/antifreeze mixture for Evans Waterless Coolant. The car can now sit and idle until it runs out of fuel and never overheat! The fan kicks in at 180 and shuts off at 160.
    The only modification I did to the Taurus fan was to trim about a quarter inch off the width of the fan’s shroud so it could clear the steering rack. A feature I like about using Evans coolant is there is now a zero-pressure cap on the radiator. I have been running this set up for the past four years with no cooling problems, including a trip through Red Bluff CA in 100 degree weather! The car ran very well even though I was tempted to carry a block of ice on my lap to hold down the temperature INSIDE the car. Almost forgot to add that the car has had a one-wire 150 amp Powermaster alternator for the past ten years.


  5. June 28, 2018 @ 11:08 am Andrei from the Great White North

    My experience with Minis showed that a lot of the overheating problems came from: 1) fan blades being installed backwards 2) intake system air leaks leading to a weak mixture and subsequent high burning temperatures 3) incorrect timing from worn distributor bushings, stuck bob-weights in the mechanical advance system, and punctured vacuum advance units.

    Without understanding the actual problem component, the engines were adjusted to compensate, but that only works at idle. Once driving around in traffic, the temperatures start to rise.

    Just a thought, check the action of the other components too.


  6. June 30, 2018 @ 9:12 am John Harrison

    Replacing the electric temp gauge with a Capillary one (usually a dual oil pressure /water gauge) will give more accurate reading of whats happening with the water temp and frees up the oil pressure dash gauge slot for Volt meter. On late MGBs any way.. maybe others.


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