During the recent hot spells we have sold more than usual number of radiators for these classic cars. High temperatures in the UK is a rarity, but when it does arrive it will show any weakness in these old car’s system with anything from a leaking hose to a catastrophic failure. Early Mustang radiators also shared cooling with the automatic transmission cooling lines at the bottom of the radiator, so in effect the cooling system can be working twice as hard. If the welds fail at the bottom end of the radiator you could get coolant into your gearbox potentially destroying the gearbox as well. A few radiators below we have stockpiled, not all are from our customer cars, but a number are recently.

To hlp out we have put together a quick reference giide for cooling. This doesn’t cover everything, but should help answer a few questions.
Keeping Your Classic 1964โ1973 Mustang Cool: A quick guide to cooling system care.
There’s nothing quite like cruising in a first-generation Mustang, that is until the temperature gauge starts creeping toward the red. These cars were engineered for the roads and traffic conditions of the 1960s, not modern stop-and-go driving or summer heat waves of today. With the right components, regular maintenance, and a little know-how, you can keep your classic running cool for many years to come.
Understanding Radiator Types and Row Configurations
Not all radiators are created equal, and when it comes to classic Mustangs, you have several options to consider. OEM-style copper-brass radiators were factory equipment and offer a period-correct look, but they’re heavier and less efficient than modern alternatives. Aluminum radiators have become the go-to upgrade for most enthusiasts as they’re lighter, dissipate heat more effectively, and are available as direct replacements that bolt right in.
When shopping for a radiator, you’ll encounter different row configurations. A two-row radiator was standard on most six-cylinder cars and works fine for stock applications with light use. Three-row radiators provide additional cooling capacity and suit mildly modified V8s or cars driven in warmer climates. Four-row radiators offer maximum cooling but come with diminishing returnsโthe added thickness can actually restrict airflow, and the extra weight strains mounts and brackets. For most builds, a high-quality two-row aluminum radiator with wide tubes outperforms a four-row copper-brass unit while weighing less and costing about the same.
| Radiator Type | Pros | Cons |
|---|---|---|
| OEM Copper-Brass (2โ3 row) | Period-correct appearance, easy to repair | Heavy, less efficient, prone to corrosion |
| Aluminum (2 row, wide tube) | Lightweight, excellent heat transfer, durable | Not original-looking, requires proper grounding |
| Aluminum (3โ4 row) | Maximum cooling capacity | Heavier, can restrict airflow, overkill for most builds |
The Often-Overlooked Radiator Cap
Your radiator cap does more than keep coolant from sloshing outโit’s a precision pressure valve that directly affects your cooling system’s efficiency. Pressurizing the system raises the boiling point of your coolant, allowing it to absorb more heat before turning to steam. For every pound of pressure, the boiling point increases by roughly 3ยฐF (1.7ยฐC).
Factory caps on early Mustangs were typically rated at 13โ15 psi, which was adequate for stock engines running on the highways of the era. If you’ve upgraded your engine, added air conditioning, or regularly sit in traffic, consider stepping up to a 16โ18 psi capโthis raises the boiling point enough to provide a meaningful safety margin. However, don’t go overboard: a cap rated too high can stress aging hoses, heater cores, and radiator tanks. Always ensure your entire cooling system is in good condition before increasing pressure. A failed cap that doesn’t hold pressure is a common culprit in overheating issues, so replace it every few years as preventive maintenance.
Radiator Cap Pressure Ratings Used on Classic Mustangs
7 PSI Caps
This rating was frequently paired with early 1964ยฝ to 1966 baseline inline-6 setups or low-temperature thermostats (like a 160ยฐF or 180ยฐF unit).
- Pros: Puts minimal physical stress on aged vintage components. It heavily reduces the risk of blowing out a fragile, 60-year-old original heater core or splitting a weak seam on a factory brass/copper radiator.
- Cons: Lowers the maximum boil-over threshold significantly. In modern stop-and-go summer traffic, a 7 PSI cap will prematurely vent expansion fluid out of the overflow tube onto the pavement, causing a persistent loss of coolant.
13 PSI Caps (The Factory V8 Standard)
This is a standard specification for most V8 Mustangs from Ford factory manuals between 1965 and 1973. It balances cooling capability with safety.
- Pros: Raises the coolant boiling point by roughly 39ยฐF above standard atmospheric pressure. This keeps a healthy vintage 289 or 390 V8 from “gurgling” or spitting out fluid immediately after hot shutdowns.
- Cons: Requires the entire cooling loop to be in decent condition. While it is a safe factory baseline, an original, corroded heater matrix or a dry-rotted bypass hose can still crack under a true 13 PSI load.
16 PSI Caps
Commonly introduced via aftermarket aluminum radiators or when upgrading classic Mustangs to high-performance configurations (like stroker builds or track setups).
- Pros: Substantially elevates the system’s thermal ceiling to handle heavy engine loads and high ambient temperatures without boil-over. Ideal if you are running modern air conditioning or a tight engine bay layout.
- Cons: Increases system stress across all old gaskets, water pump seals, and hose clamps. Never use a 16 PSI cap on an original 1960s brass-tank radiator, as the high pressure can balloon or burst the core seams.
Mustang Maniac sells many styles of radiator caps, make sure you choose the correct one for your vehicles setup.
Regular Maintenance: The Foundation of a Cool Engine
Even the best radiator won’t save you if you neglect basic upkeep. Establish a maintenance routine that includes:
- Coolant flush and refill every two years or 30,000 miles. Old coolant loses its corrosion inhibitors and becomes acidic, eating away at aluminum, copper, and iron components from the inside out.
- Inspect hoses and clamps at every oil change. Squeeze the upper and lower radiator hosesโthey should feel firm but pliable, not rock-hard, spongy, or cracked. Replace any hose that shows signs of swelling, softness, or surface cracking.
- Check the thermostat if you experience temperature fluctuations. A stuck-closed thermostat causes rapid overheating; a stuck-open one prevents the engine from reaching operating temperature. Replace it with a quality unit rated for your climate (180ยฐF for most applications, 160ยฐF for very hot regions or high-performance builds).
- Test the water pump for bearing play or weeping seals. Grab the fan (with the engine OFF) and check for wobbleโany movement means it’s time for a new pump.
- Clean the radiator exterior annually. Bugs, road debris, and corrosion can block airflow through the fins, dramatically reducing cooling efficiency. A gentle spray from a garden hose (from the engine side outward) clears most obstructions.
- Verify fan operation and belt tension. Check the radiator belt is not cracked or split. A broken radiator belt will stop water flow from the pump potentially causing serious damage within a short space of time.
- Electric fan conversions are popular upgrades, with manual override operating from the cabin can be great preventative measure.
- If you’re running a viscous mechanical fan, ensure the clutch engages properly when the engine warms up.
- To help with air flow fit a radiator shroud. This improves the efficiency of the fan pulling cool air through the radiator. The fan blade positioning needs to be set up correctly to get the full benefit.
- Fitting a better designed fan will improve air efficiency through your cooling system.
What to Do, and Never Do, When Your Mustang Overheats
If you see the temperature gauge climbing into the danger zone or steam escaping from under the hood, pull over safely as soon as possible and shut off the engine. Turn on your heater full blast while you’re still movingโthis draws heat away from the engine, but once stopped, shut everything down. Open the hood to let heat escape, but never remove the radiator cap while the system is hot. The pressurized coolant is well above 212ยฐF and will erupt violently, causing severe burns. Wait at least 30 minutes, or until the upper radiator hose feels cool to the touch, before carefully removing the cap.
Once cooled, check the coolant level and look for obvious leaks. If you must add coolant to get home, add it slowly with the engine running at idle to avoid thermal shock to the engine block. Better yet, call for a tow if the problem isn’t immediately apparent.
What you must never do:
- Never keep driving with the gauge pegged in the red. Even a few minutes of severe overheating can warp cylinder heads, blow head gaskets, score cylinder walls, or crack the engine block. These repairs cost thousands of dollars and may total a numbers-matching car in a worst case scenario.
- Never pour cold water into a hot engine; the sudden temperature change can crack the block or heads instantly.
- Never ignore the warning signs. If your Mustang runs hotter than normal, diagnose it now before it’s to late.
Driving with an overheating engine causes cumulative damage with every passing minute. Head gaskets fail, allowing coolant into the oil or combustion chambers. Aluminum heads warp and require expensive machining or replacement. Pistons expand and scuff cylinder walls, leading to oil consumption and loss of compression. In severe cases, connecting rods seize and punch through the block. The bottom line: an overheating engine is an emergency, not an inconvenience.
Cooling System Additives: Do They Actually Help?
Some are snake oil; others offer genuine benefits. Here’s what could work for you.
Wetting agents can reduce the surface tension of coolant, allowing it to make better contact with hot metal surfaces. This can lower operating temperatures by 10โ20ยฐF in some applications and is especially useful if you’re running straight water for racing. For street-driven cars running a proper coolant mix, the benefit is more modest but could still be worthwhile.
Corrosion inhibitor additives replenish the protective chemistry that breaks down over time, extending the life of your coolant between changes. These are particularly valuable for cars that sit for long periods or have mixed-metal cooling systems (iron block, aluminum heads, copper-brass radiator).
Stop-leak products are temporary sticking plasters at best. While they may slow a minor seep, they can also clog heater cores, thermostat passages, and radiator tubes. Use them only in emergencies to limp home, then repair the leak properly.
For most classic Mustangs, a correct mix of a quality antifreeze and distilled water, refreshed every two years, provides all the protection you need. If you want extra insurance, a wetting agent may be a reasonable addition.
Do your homework for the driving environments and what works best for your car. No single answer is the correct answer.
Evans Waterless Coolant: A Modern Solution for Vintage Iron
One product that deserves a mention is Evans Waterless Coolant. Unlike conventional antifreeze, Evans contains no water at allโit’s a propylene glycol-based fluid with a boiling point above 375ยฐF and no vapor pressure at normal operating temperatures. This means your cooling system runs at near-zero pressure, dramatically reducing stress on aging hoses, gaskets, and radiator tanks.
The benefits for classic Mustang owners are worth noting:
- No corrosion from water-induced electrolysisโa major plus for cars with original copper-brass radiators and iron blocks.
- No boil-over in extreme heat or high-altitude driving.
- Eliminates cavitation damage to water pump impellers.
- Never needs changing under normal use, making it ideal for collector cars that see limited miles.
The downsides? Evans is significantly more expensive than conventional coolant, and converting requires a thorough flush to remove all traces of water from the systemโresidual moisture compromises performance. You’ll also need to use Evans-compatible prep fluid and follow their specific procedure. For a daily driver, the cost may be hard to justify. But for a show car, weekend cruiser, or any Mustang with an original, irreplaceable cooling system, Evans offers peace of mind that’s hard to match.
Keeping a classic Mustang cool isn’t complicated, but it does require attention. Choose the right radiator for your build, maintain the system religiously, and respect the warning signs when something goes wrong. Your first-gen pony will reward you with countless miles of trouble-free cruising if you keep on top of the maintenance.
We stock a huge range of cooling parts, click here for the link.
Customer Cars
We have been working on a customers Falcon, creating a unique set of rear LED lights for him. A Falcon first that we know of. The interior has a knew four part dash fitted.


Under the hood has been tidied up and cured a couple of running issues.
WebShop
We are in a good mood due to the recent hot weather, so Adam has decided that the next few customers who make a nice order from us will get a little free gift from us. It’s a mini all in one spanner, stick in your glove box as an emergency or quick fix tool. It’s no Snap On giveaway, but it’s a little something from us to say thank you.

Coming Soon
As one of the original and leading suppliers of Mustang parts in the UK we’re often asked about fitting of some of the more complex parts or kits we sell. As we have mentioned many times before, we won’t divulge all our secrets, but we want to help out. With that in mind Adam is in the process of creating a walk-through guide for converting drum brakes to discs. It’s a common question, not only for Mustangs but also Falcons. We will be creating a page guide for that process and uploaded on here soon. Depending on how it’s received we may post more user guides in the future.
Stay Safe, Keep Cool & Take Care!


































































































































































































