Cooling System Upgrades

Here’s an example of a radiator gone sour. After many years and miles, the fins become bent and damaged from road debris hitting the radiator. The fins are the small inlets in the front of the radiator that allow air to flow through. After about 50,000 miles on a typical Mustang, these fins get clogged up and it gets harder for them to breathe in the fresh air—kinda like a water drain in your house that has built up many years of corrosion and garbage.

High-performance driving means lightweight, rugged, and efficient cooling. This reverse-rotation, low-profile flex fan (PN 2817 and 2818) from Flex-A-Lite is just that. Designed for high performance at normal, non-A/C driving applications, this fan is made out of aluminum, is available in 17- and 18-inch diameters, and can spin up to 8,000 rpm.

Yet another great Flex-A-Lite product is this direct-replacement Black Magic 175 electric fan for ’86-’93 5.0s. This unit has been increasingly popular in the 5.0 world, and now comes complete with custom mounting brackets to fit any 5.0 without drilling or modifications. The Black Magic 175 has a 15-inch diameter and reportedly pulls 2,800 cfm of air at zero degrees static pressure.

A good replacement for a stock radiator would be the nice, shiny, three-core aluminum one from Ford Racing Performance Parts (PN M-8005-C) for ’79- ’93 Mustangs. It provides great cooling efficiency and saves weight on the front end. It also features a cooler for auto transmission or power steering.

Other manufacturers of aluminum and copper/brass two-, three- and four-core radiators are Griffin and Be Cool. Pictured here from left to right, are Griffin's aluminum radiators for a ’94- ’95 Mustang, a ’96 Cobra, a ’79-’93 Fox-body, or a ’79- ’93 Mustang in copper/brass.

Both Griffin and Be Cool (shown here) are known for their excellent products which they can custom-build for any application. Many quarter-mile racers are using aluminum radiators because they weigh less than copper/brass. You early-model fans will be glad to know that these companies make radiators for your Ponies as well.

There are other factors that contribute greatly to a properly working cooling system. Just because they may be an inexpensive part of the package deal, doesn’t make them any less important. Shown here are three of Prestone’s best cooling system ingredients. Prestone’s Super Flush and Super Radiator Cleaner are two other respected products in preventative care for radiators which, if used continuously, will help prevent large deposits and give your radiator a longer life on the road. Stant, another maker of quality cooling system parts for your Mustang, also makes thermostats. They have a direct drop-in for your O.E. ’stat as well as 180- and 160-degree ’stats. A radiator cap is also inexpensive insurance against overheating because it acts as a pressure top for your radiator, keeping everything inside in balance. Caps are rated in pounds of pressure, and 5.0s typically like to run with 14 to 18 psi.

Stock water pumps on Mustangs aren’t bad, but as mentioned earlier, if you want to go with one that’s built stronger and will last longer, the Edelbrock Victor Series pump for 5.0L Mustangs is the way to go. The hub is machined from billet steel for strength, and black-oxide coated for corrosion resistance. Another cool feature is the curved impeller inside the pump. The curve design is said to vastly improve water pressure and volume, even at lower rpm.

Whether you live in sunny Los Angeles, rainy Seattle, or windy Chicago, the objective is the same—to keep your Mustang running its best. Part of that equation is an effective and efficient cooling system. Cool-running cars make more power (up to a point), generally get better mileage, and don’t cause your stress level to go through the roof due to a creeping temp gauge needle. Hot-running cars create a domino effect of problems, from detonation or pinging, to overheating and exploding radiator hoses.

This is particularly the case with many modified Mustangs, especially those built before 1994 with the wimpy two-row radiators. The stock cooling system is good for a stock engine, but not much more. High-performance engine parts increase the heat in the combustion chamber (that’s what makes power), which raises the coolant temperature; and the stock cooling system runs out of breath pretty quickly, leaving you stranded in the middle of the Ozarks with an erupting radiator.

We all know that factory gauges aren’t the most accurate, but they can still tell us a lot about how the car is running. Most pre-’94 Mustangs like to run (water temperature) between 190 and 200 degrees F, which translates into the water temp needle being at or around the M or A in NORMAL. SN-95s like to run a little hotter. The stock thermostats on the Fox bodies are 192-degree units, which means that as soon as the water/coolant reaches that temperature, the thermostat opens up to allow the water to circulate through the radiator and system. A popular mod is to swap out the stock thermostat in favor of a 180-degree ’stat, which is a quick and inexpensive way to knock off about 5 to 10 degrees.

In this story, we’ll shed some light on how your Mustang’s cooling system works, what products are out there to aid with cooling, and how to keep your cool the next time your radiator spills its guts out on the freeway.

The Thermostat
The reason that Ford installed 192-degree ’stats in the Mustang was purely from an emissions standpoint. A 192 ’stat keeps the engine-operating temp higher, which in turn helps the catalytic converters build up more heat, thereby generating a more efficient burning of hydrocarbons. As we mentioned earlier, a popular cooling system mod is installing a 180-degree thermostat in place of the factory 192-degree job. But if you’ve been to the parts store and noticed that they have 160-degree ’stats, you’ve probably been tempted to get one. The problem when you start getting into low-temp ’stats like this is that it stays open almost constantly, which makes the radiator’s job of transferring heat out of the water negligible. A little restriction through the thermostat keeps the water in the radiator longer, which lets it remove more heat before returning it back to the engine.

The same goes for removing the ’stat completely. We’ve had experience with this very thing and can tell you that the car will make some funky moves of the temp gauge without a thermostat. Editor Kinnan’s ’87 5.0 was continually having heating problems (the needle would rise and fall for no reason whatsoever). Thinking the thermostat was sticking, he removed the housing to find that a previous owner removed the ’stat. Installation of a 180-degree ’stat completely solved the problem.

Water Pump
The stock water pumps on most Mustangs do a fairly good job of pumping the coolant through the system, but if you want something a little sturdier and more reliable, look to some of the aftermarket companies like Edelbrock. Their Victor Series 5.0L Ford water pump PN 8840 is made of cast 356 aluminum, which is CNC-machined and heat treated to T-6 specs, making it strong and durable. The Victor’s water passages are also designed for max flow and pressure with equal distribution to both sides of the block, a big factor in efficient cooling.

Coolant
Although not an extremely detrimental issue, a good coolant-to-water mix can mean the difference between running at 200 degrees F or 10-15 degrees less. Most manufacturers and mechanics recommend that you use a 50/50 mix of antifreeze and water, a good tip. Many people don’t realize this, but adding more antifreeze will actually hurt cooling performance because of its lower boiling point than water. The main reasons that we are told to put in a mixture of antifreeze are because it has a lower freezing point (than water) and it prevents corrosion inside the radiator. So, if you’re one of those people who runs around town in a Mustang with a radiator full of coolant and wondering why the temp needle is too high, there’s your answer.