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Fox Body Mustang Cooling Issues, Problems & Solutions

Fox Body Mustang Cooling Issues, Problems & Solutions

Fox Body Mustang Cooling Issues, Problems & Solutions

Created by Jeff Jimenez
Last Updated 12/7/2016

Are you having cooling issues & problems with your Fox Body Mustang? Check out our solutions guide.

Viewing this install and using the information shared is subject to the terms set forth here - View the LMR Install Instructions Disclaimer.

FOLLOW: mustang , 79 93 mustang , fox body mustang , tech guide , engine , cooling system

We are going to take a look at some of the key components of the Fox Body Mustang cooling system. I am going to quickly highlight some of the most common issues that lead to over heating as well as some insight on when it is best to upgrade your cooling system components. We will start by evaluating the radiator in your Stang!

Fox Body Mustang Radiator Tech

Let me just come right out and say it! If your Fox Body Mustang has any engine mods at all, the stock radiator is already over capacity. It is barely adequate for a bone stock engine. Every Fox Body on the road really needs a larger radiator. Especially if you don’t know the maintenance history of your cooling system. Shop our complete line of radiators here: Fox Body Radiators. We carry a complete line of factory replacement and aftermarket radiators from brands such as SVE, Ford Racing and Fluidyne.

Physical Blockage

Inspect the front of the car! This is an easy fix. Check the A/C condenser and the radiator for visible external blockage such as grass, mud, inspects, plastic bags, cardboard, etc. Scrubbing with a soft bristle brush or cleaning with a power washer will do the trick.

Another form of blockage can come from inside your radiator. Pop the cap and look in the radiator. If you see significant scaling on the core tubes, you probably need to remove the radiator and have it professionally cleaned or simply replace it as the coolant cannot flow through a sealed off passage. This is one of the most over looked reasons for overheating issues in Fox Body Mustangs.

Fox Body Mustang Cooling Issues, Problems & Solutions - Fox Body Mustang Cooling Issues, Problems & Solutions

Fox Body Mustang Radiator Hoses

It's no secret that factory radiator hoses tend to wear and tear over time leaving your motor with weak or leaking hoses. A leak in your cooling system can eventually cause your motor to overheat over time which will lead to more costly repairs. You check out our complete line of replacement hoses here: Fox Body Mustang Radiator Hoses

Our SVE radiator hose kits are a great way to replace and upgrade your engine cooling components. Offered in black and blue finishes, these kits feature high quality silicone hoses that work great for factory or aftermarket radiators.

Fox Body Mustang Cooling Issues, Problems & Solutions - Fox Body Mustang Cooling Issues, Problems & Solutions

Fox Body Mustang Fan Tech

The factory cooling fan set up on your Fox Body Mustang is more than adequate to handling the everyday demand of a full-bolt on Stang – especially if you have added an aftermarket radiator. When it comes to maintenance on your factory cooling fan, make sure the shroud is in place and fully intact. Inspect all the fan blades for cracks and damage. Do not forget to check the fan clutch for signs of leaking. Any signs of residue on the fan clutch means it needs to be replaced.

The fan and fan clutch setup does have it’s limitations. It does rob some power from your engine because it is driven by your engine’s accessory system. For many, upgrading to an electric fan set up will free up this horsepower, give more room for turbo kits and provide more cooling power by moving more air. When it comes to maintenance for your Fox Body electric fan system, make sure it is actually coming on at the desired temperature. All of the common aftermarket fan upgrades have an adjustable thermostat that does need to be properly set after installation. Also, if it is wired properly, it will come on full time when the A/C is turned on, regardless of temp.

NOTE: Proper installation of an electric fan should include an upgraded alternator. A popular upgrade is a 130 Amp Alternator. Check out our complete line of alternator upgrades here: Fox Body Alternators.

Fox Body Mustang Cooling Issues, Problems & Solutions - Fox Body Mustang Cooling Issues, Problems & Solutions

Fox Body Mustang Radiator Air Deflector

The radiator air deflector is probably one of the most overlooked causes of over heating in most Fox Body Mustangs. If this is missing, you'll typically get overheating issues while cruising. Having this deflector in place allows proper airflow distribution through the radiator at cruising speeds when the clutch fan is typically not doing much work.

Luckily this is an easy fix! Check out our installation video here: Fox Body Air Deflector Install Video

Fox Body Mustang Cooling Issues, Problems & Solutions - Fox Body Mustang Cooling Issues, Problems & Solutions

Fox Body Mustang Coolant Tech

Coolant is a critical part of your Fox Body’s cooling system. There are many components and factors that go into keeping your coolant operating at an optimal level. We will look at everything from your thermostat to coolant levels in the information below.


An old thermostat is prone to sticking, and if it sticks shut, you'll of course overheat at all conditions. Having your thermostat stick open can also cause cooling issues in your Fox Body Mustang. If it stays open, this will allow the coolant to pass through the radiator too quickly and not dissipate enough heat, thereby causing an overheating condition.Check out our complete line of thermostats and housings here: Fox Body Thermostats & Thermostat Housings.

Low Coolant

Having a low coolant level of course means a diminished cooling capacity due to a lack of volume as well as a lack of flow. If your coolant is low, you obviously have a leak. Fix the leak and refill the coolant. Check after a few drive cycles and top off again as needed.

Age/Condition of coolant

Old, nasty, brown coolant cannot transfer heat well and therefore does not allow proper engine cooling. This also means the engine block and radiator are coated in the nice slime of decomposing ethylene-glycol. A full flush with fresh water is needed before replacing the coolant. Another issue with old coolant is that it develops an electrical charge over time. This charge causes electrolysis which is the #1 cause of cooling system corrosion and heater core failure.

Don't forget to add coolant additive such as Royal Purple Purple Ice when refilling your cooling system. This synthetic additive further reduces engine heating by reducing the surface tension of the radiator fluids and improves heat transfer.

Blown Head Gasket

This one is typically associated with the cooling system constantly "boiling over" because of compression escaping in to the cooling system and the cylinder/cylinders affected will typically exhibit a miss. This failure is most prevalent on power-adder cars.

Fox Body Water Pump Tech

If your coolant matches the description above, it is possible that the impeller on your water pump has corroded away and is no longer properly moving coolant through the system. This is not a very common failure and the pump tends to develop a leak before this takes place. If you have replaced and checked everything above, this should be the next step in your overheating evaluation.

Installing the wrong water pump is another major cause of overheating in Fox Body Mustangs. 5.0 Mustangs using a serpentine drive belt need a "reverse" rotation water pump. This is because the back (slick, non-ribbed) side of the belt is what makes contact with the pulley spinning the pump in the opposite direction as the rest of the pulleys. If a standard rotation pump is installed in a serpentine application, coolant will be flowing backward through the system and proper cooling cannot be achieved.

More Fox Body Cooling System Tech

Upgrading Your Fox Body Mustang’s Cooling System

The cooling system on your Fox Body Mustang is extremely critical to maintaining its performance and longevity. With the Fox Body being 20+ years old, the factory components (if they are still in place) have seen their best days and should be replaced. We get a lot of questions about what cooling modifications are nee... more

Fox Body Mustang Cooling Issues, Problems & Solutions Tech Info

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