whoop
09-16-2007, 06:59 PM
My supercharged '93 Cobra is overheating, and I can't figure out why...?!! I've replaced the thermostat with a 180*, replaced the radiator with an aluminum 2-core (1" core), installed an electric fan, flushed the system & added water wetter.... It's STILL overheating!!
It's never pegged out the temp gauge, but got 1 notch from the top today, & lost all coolant through a blown water pump seal (while sitting still). Oh, yeah, I also had a shop tell me the water pump was working fine...
So..... once I replace the water pump seal, if it still overheats, what should I try next??? Anyone else have this problem?
Thanks, Dave
Dirty_SOHC
09-16-2007, 07:16 PM
My supercharged '93 Cobra is overheating, and I can't figure out why...?!! I've replaced the thermostat with a 180*, replaced the radiator with an aluminum 2-core (1" core), installed an electric fan, flushed the system & added water wetter.... It's STILL overheating!!
It's never pegged out the temp gauge, but got 1 notch from the top today, & lost all coolant through a blown water pump seal (while sitting still). Oh, yeah, I also had a shop tell me the water pump was working fine...
So..... once I replace the water pump seal, if it still overheats, what should I try next??? Anyone else have this problem?
Thanks, Dave
I'm gonna guess that the pump is bad. I would recommend an electric pump so that you have constant flow and it will free up some power also.
Masshole
09-16-2007, 07:22 PM
I'm gonna guess that the pump is bad. I would recommend an electric pump so that you have constant flow and it will free up some power also.
he did say a shop told him the pump was fine. but.... if he had'nt said anything about the pump, my first quess would be the pump. so with all of what you said has been replaced, and... AND... the pump IS fine, then it has to be an electical gremlin somoewhere. but i belive since you replaced the thermostat, the raditaor you shouls also replace the pump. replace it, and then if its still happening it has to be a short somewhere. check the wiring to the gauge its self first. that MIGHT... be the issue. let us know tho :mick:
Dirty_SOHC
09-16-2007, 09:21 PM
he did say a shop told him the pump was fine. but.... if he had'nt said anything about the pump, my first quess would be the pump. so with all of what you said has been replaced, and... AND... the pump IS fine, then it has to be an electical gremlin somoewhere. but i belive since you replaced the thermostat, the raditaor you shouls also replace the pump. replace it, and then if its still happening it has to be a short somewhere. check the wiring to the gauge its self first. that MIGHT... be the issue. let us know tho :mick:
EDIT'D- I'm sorry
Switch to the electric pump, hard wire the fans and pump to one switch. This will do tow things, first will guarantee they are both on, second will allow you to circulate coolant and have the fans running at a constant rate even if the engine is off if so needed(say at the track between runs).
whoop
09-16-2007, 09:46 PM
Wow, thanks for the quick responses! I'll definitely change the pump while I'm in there, since I'll have to take it off anyway. The fan's already hardwired & runs all the time, and is pulling air in (I checked that too), but all ideas are appreciated!
I figure the temp gauge isn't shorting or incorrect, since it is definitely overheating (I lost all the coolant when the water pump gasket blew, I'm just hoping all the internals are still ok........) I'm thinking all else is ok, since it never pegged out the temp gauge, it blew the gasket before that. But it did lose the coolant...
Anyway, I'll definitely keep you posted as to how it runs after the pump is replaced & re-sealed. Thanks again! Dave
speedfreak87
09-16-2007, 10:50 PM
if it still overheats when the pump is replace, pressure check the coolant system, chances are after that the head gaskets are blown...
My 87 was blown between a water jacket and cyl, and I lost coolant but it never blew smoke, go figure.
A lot of times, especially on older ones, a weak hose can actually cause this.
Does it seem to cool fine if from cold you start it, let it idle up to operating temp and let it continue to idle ? Then, if you get in the car and rev several times, the temp goes up(fairly rapidly)?
If so, or it exhibits the above while driving and hard acceleration events, I suspect a hose is collapsing on you(increased suction/vacumm as a result of more demand from the pump).
If you are changing the pump anyway, I'd recommend changing ALL hoses at the same time.
whoop
10-01-2007, 06:13 PM
Just following up on this, no more overheating!! The problem..? The fan was too small, wasn't pulling enough air. It was an aftermarket fan, but I never would've guessed the fan would be causing the whole issue. I also had the water pump replaced since I was in there, but had a stock fan put back on (they told me the stock fan will keep it at 185* all day long). Seems to be the case so far, I've run it hard & have yet to break the temp gauge over the 2nd line.
THANKS for all your ideas & suggestions! Now that I can run it, I'm looking forward to getting together at some local events & meeting y'all!
Dave
FrEvrNLv
10-01-2007, 06:16 PM
Just following up on this, no more overheating!! The problem..? The fan was too small, wasn't pulling enough air. It was an aftermarket fan, but I never would've guessed the fan would be causing the whole issue. I also had the water pump replaced since I was in there, but had a stock fan put back on (they told me the stock fan will keep it at 185* all day long). Seems to be the case so far, I've run it hard & have yet to break the temp gauge over the 2nd line.
THANKS for all your ideas & suggestions! Now that I can run it, I'm looking forward to getting together at some local events & meeting y'all!
Dave
Awesome! Glad you got it all taken care of! Now come out to the Sonic meet to meet a few of us (for more than the 15 seconds we met initially :lol: ) this Saturday ... :woot:
Info for SA Chapter Sonic event here (http://www.unitedstangs.com/forums/showthread.php?t=19201)
TT_GT
10-08-2007, 07:18 PM
heres some thing that may be of help
Troubleshoot Overheating
writer: Jim Smart
Overheating problems are as Mustang-specific as leaking cowl vents, squeaky upper control-arm bushings, rattling doors, and crummy drum brakes. Some of us blindly accept overheating problems as typical old-car shortcomings, but it doesn't have to be that way. When these cars were rolling off three assembly lines four decades ago, they didn't overheat. It became a problem as our classic Mustangs got older, which should tell us something about cooling systems and how little we understand them.
Cool: How Does It Work?
Your engine's cooling system is designed to carry operational heat away from the engine to the slipstream roaring through the radiator. Operational heat comes from fuel/air combustion and internal friction. Heat is transferred from the engine's components into the coolant that flows through the water jackets to the radiator. As air flows through the radiator, heat is transferred from the coolant to the atmosphere via the tubes and fins that connect the radiator's top and bottom tanks. The engine's thermostat controls the flow of coolant out of the engine's water jackets into the radiator via the upper radiator hose. Coolant that's been cooled in the radiator flows into the engine's water jackets via the bottom hose into the water pump. It's a continuous cycle of removing heat from the engine via liquid, pumping it into the radiator, cooling it down, and returning it to the engine to continue the process.
Cooling systems fail to do their job when we don't do ours. Regular preventive maintenance is the first step toward reliability. Under ideal circumstances, you should drain, flush, and service your Mustang's cooling system every spring, and properly dispose of the old coolant via local recycling efforts. Always maintain the appropriate balance of antifreeze and distilled water (yes, distilled water to keep mineral content down). Keep an anticorrosion additive in the coolant along with additives that help transfer heat to the coolant. Most of us, with our busy schedules and lifestyles, understand this isn't realistic. Who has time?
Radiator Facts
Classic Mustangs didn't suffer from overheating problems when they were new because their radiators provided just enough cooling capacity to keep them out of trouble. As these marginal radiators took on scale and corrosion during use, their cooling capacity dipped to inadequate. This was especially true with those tin-can Falcon/Comet radiators common to pre-'71 Mustangs without air conditioning. Beginning in 1967, Ford used a higher-capacity radiator in air-conditioned and high-performance Mustangs, which helped cooling issues considerably. But, it didn't eliminate them entirely.
Radiators, under ideal circumstances, have a big job. They have to transfer a tremendous amount of thermal energy to the atmosphere. Your Mustang's engine generates a lot of heat energy under normal operating conditions. When outside air temperature skyrockets in summertime, it becomes more challenging to transfer heat to the atmosphere.
If it's hard to understand the radiator's job, think of yourself as the radiator and the engine as a demanding boss who just laid a huge stack of paperwork on your desk. The faster you weed through it, the more your boss adds to the stack. Think of engine heat as the paperwork. A new radiator is like your mind first thing in the morning with a fresh cup of coffee. As the radiator ages, however, it becomes more like your mind at the end of the workday. For the radiator, it's scale and rust inside the tubes and tanks. For you, it's burnout from the workload. Eventually, the paperwork overwhelms you, just like excessive heat overwhelms an aging radiator.
New radiators do a good job transferring heat. The tubes, filled with hot coolant, transfer the heat to the fins surrounding the tubes. Air flows over the fins, designed to create as much surface area as possible, and carries heat away from the radiator. Think of the fins in your Mustang's radiator like the fins on your air-cooled lawnmower or motorcycle engine. Fins carry heat to the atmosphere through the increased surfaces and sharp edges.
This is the high-capacity Mustang radiator found on '67-'70 small-block Mustangs with A/C and all big-blocks. It's retained with saddle brackets at the bottom and a single top bracket.
A radiator is comprised of tubes that run vertically ('65-'70) or horizontally (cross-flow radiators from '71-'05 Mustangs). These tubes connect the top and bottom tanks (or left and right tanks with crossflow radiators). In conjunction with the cooling fins that surround them, these tubes carry heat away from the coolant inside. This is the Griffin aluminum radiator from Mustangs Plus.
Cooling systems are happiest with the 60/40 antifreeze/water mix most antifreeze manufacturers recommend. This ensures protection against freeze-ups down to -34 degrees F and protection against boilovers up to 230 degrees F. Don't forget anticorrosion additives, especially if you're running aluminum heads and intake. Coolant enhancers, like water wetters, help improve cooling efficiency.
We often expect too much of older radiators. The tubes become filled with scale, and they also get clogged with iron particles from the engine's water jackets. Proper cooling comes from good coolant flow through these tubes. When tubes become clogged, the radiator doesn't get rid of heat. Also, old radiators are often clogged with dead bugs and other debris in the fins and around the tubes, which further hinders cooling.
Whenever you're shopping for a new radiator, go for the most cooling capacity possible. If you're doing an original-type restoration, opt for the four-row-core, desert-cooler radiator, and specify automatic or manual transmission. They look dead stock and offer more cooling capacity than original equipment. If you're restoring a '67-'70 Mustang, opt for the largest radiator possible: the high-capacity version used on air-conditioned and big-block models. These radiators, especially with a four-row core, offer outstanding cooling capacity.
This is a typical thermostat housing and thermostat, normally located at the upper radiator hose at the intake manifold, cylinder head, or block.
Here's a poppet-design Stant thermostat used in most Fords. The spring holds the valve closed. Inside the copper actuator in the center is wax, which expands to open the poppet valve to allow coolant flow into the radiator. Copper is used for the actuator because it conducts heat well.
A cutaway view of a typical thermostat, courtesy Stant, shows the spring, poppet valve, and wax/copper actuator. The actuator works against the spring pressure to open the poppet valve. Thermostats fail when the valve sticks or the wax leaks out, rendering the valve closed and useless.
Thermostat
The thermostat is a small, temperature-activated poppet valve inside a small neck at the upper radiator hose. It controls engine coolant temperature by opening and closing as coolant temperature warrants.
Thermostat design has been virtually the same for nearly a century, and its function is simple. The spring keeps the poppet valve closed, and a wax-filled actuator opens it when things get hot. As the coolant inside the engine reaches operating temperature, the wax inside the actuator expands, pushing the poppet valve open against the spring pressure, which determines the opening temperature. The stiffer the spring, the higher the opening temperature.
Radiator Pressure Cap
The radiator cap keeps coolant inside the radiator and relieves pressure as necessary. Think of the radiator cap as a pressure-relief valve if coolant temperature becomes too high and pressure becomes unsafe. Radiator caps are also known as pressure caps because they relieve excess pressure at a given number of pounds per square inch (psi). This keeps us safe because it doesn't allow cooling-system pressure to become unsafe, possibly endangering anyone nearby. Older Mustangs call for radiator caps in the 7-pound range. Newer Mustangs use higher pressures in the 13-16-pound range because their engines run hotter at 192-195 degrees F.
Radiator-cap pound ratings tell us at what pressure the cap will unseat and release cooling-system pressure. A 7-pound cap will begin relieving pressure at 7 psi.
There are two types of radiator caps. Conventional caps have to be turned counterclockwise to the first stop to relieve pressure when hot. Safety caps, like Stant's Lev-R-Vent, relieve pressure when the lever is lifted. This keeps us safe from scalding-hot coolant. A hot engine generates a lot of cooling system pressure and heat--hot enough to cause severe burns. If you experience an overheated engine, allow it to cool before opening the radiator cap.
Cooling systems have to maintain a certain amount of pressure to keep the coolant from boiling. A good antifreeze/water mix helps raise the boiling point. But, when pressure is allowed to build inside the cooling system, it raises the coolant's boiling point even more. Unpressurized, the coolant will boil at a much lower temperature. This is why coolant explodes from a hot radiator when we remove the cap.
Boiling Points & Pressures
Pressure Boiling Temp. (Deg. F)
0 212
4 224
7 232
9 237
13 246
14 249
Note: Boiling point drops with altitude. At 2,500 feet, water boils at 207 degrees; at 5,000 feet, 202 degrees; at 7,500 feet, 198 degrees; at 10,000 feet, 193 degrees. Sea-level atmospheric pressure is 14.7 psi. By contrast, at 10,000 feet, atmospheric pressure is 10.0 psi.
Coolant Recovery
Beginning in the '70s, automakers started installing coolant-recovery systems to catch any coolant vented from the radiator. The coolant-recovery system is little more than a reservoir tied to the radiator overflow. The hot engine vents excess coolant to the reservoir. As it cools, it draws the excess coolant back into the radiator. This prevents coolant loss and contamination of the environment.
Water Pump
Like the radiator, the water pump loses its effectiveness with time and use. The impeller blades gather corrosion and scale, making them less effective. When you replace the radiator, replace the water pump too. Opt for one of the high-flow pumps, which looks stock depending on where you buy it. Edelbrock and Weiand offer good-looking pumps that will improve your cooling system's effectiveness. With a high-flow water pump, you increase the number of gallons per minute circulating through the cooling system. Keeping coolant on the move reduces an engine's operating temperature considerably.
Aftermarket coolant recovery systems are available in a wide variety of types and styles. This one catches the modest overflow from a classic Mustang radiator and keeps it safe until cool-down draws the coolant back inside the radiator.
We spotted this custom coolant recovery system that employs a '67-'68 windshield-washer reservoir. It looks factory-installed and gets the job done.
Edelbrock's aluminum high-flow water pumps are designed especially for Ford small- and big-block engines to move more coolant through your Mustang's cooling system than original equipment. Paint it engine color and it blends right in.
Fan Club
The fan is one of your cooling system's most important assets. Yet it seems we choose cooling fans for all the wrong reasons--for the way it looks or because it's the correct original equipment. But, if you're going to drive your Mustang regularly, choose a fan because it works well. The most effective is the luxury-car thermostatic clutch fan, which works only when it's needed. It's quieter because it doesn't spin as fast as the water pump. Clutch fans, as their name implies, slip most of the time, engaging as often as a hot radiator and engine need them. Clutch fans go bad when they lose their hydraulic fluid, which is used to engage them. Without the fluid, they freewheel and don't cool anything. This causes overheating, especially when you're idling in traffic.
Also common is the flex fan. As its name implies, the flex fan moves big gulps of air at low engine speeds. As rpm increases--meaning the car is moving faster--the blades flex and flatten out to consume less power. Flex-A-Lite is best known for pioneering the aftermarket flex fan, hence the name. These lightweight fans haul down plenty of air at idle while consuming less power than a conventional steel fan as rpm increases.
This is a fan clutch controlled by a coiled bimetallic spring that works the control valve. Hot air coming through the radiator causes this spring to expand and move the control valve, which engages the fan. As things cool, the spring contracts, disengaging the fan clutch.
Here's a thermostatic clutch fan from a '69 Mustang GT390 with air conditioning and automatic transmission. This seven-blade fan has a tough job, especially in hot weather. The number of blades, coupled with blade width, determine cooling effectiveness. The wider the blades, the noisier they are. However, what do you prefer--quiet or cool?
This is Ford's flex-blade fan used from 1967 through the early '70s. Failure issues make these fans a bad gamble.
Beginning in the '67 model year, Ford used flex-blade fans as original equipment. Unlike the Flex-A-Lite version, the Ford flex fan is noisy. The Ford fans often failed, which makes them risky to use. If you want a flex fan, opt for one from Flex-A-Lite.
Outside of engine-driven clutch fans, electric fans are the most efficient. The downside is having to create a dedicated circuit for them via the ignition switch. The key element with electric fans is getting the airflow needed to keep the radiator cool. If you install an electric fan, wire it with a relay and thermostat via the ignition switch so it comes on as needed with the ignition on. This eliminates the risk of leaving the fan on and running the battery dead.
When you're choosing a fan, don't forget to use a shroud. Not all Mustang fans were shrouded. However, when the fan is properly spaced, shrouding improves airflow velocity through the radiator at slow or no speed. Watch out for proper fan depth, which is halfway into the shroud for maximum effectiveness.
Oil Is A Coolant
Did you know engine oil isn't just for lubrication? Engine oil cools where it counts--at moving parts, carrying excessive heat away from critical parts like bearings, piston skirts, and cylinder walls. As oil travels over these high-temp surfaces, it's your engine's front-line defense against overheating. Main and rod-bearing temperatures can rise as high as 400 degrees F, which makes coolant temperature pale by comparison. Whatever your coolant temperature is, add at least 100 degrees for the oil temperature. This is why we suggest the use of synthetic engine oils like Mobil 1, Redline, Royal Purple, and Castrol Syntex. These oils stick around when conventional oils begin to break down.
Antifreeze And Coolant Additives
The marketplace overwhelms us with choices when it comes to antifreeze and coolant additives. For years, conventional ethylene glycol antifreeze and water was used to keep our engines happy. Today, there are all kinds of antifreeze types, including water and antifreeze already mixed in one-gallon bottles. There are also environmentally friendly antifreezes designed to keep things safe for ground water and pets. Prestone offers a long-term antifreeze that lasts five years. There are antifreezes designed for severe-duty applications. Cruise the Internet and you'll find all of them.
This six-blade fan is common with add-on air-conditioner packages. However, it's noisy and not as efficient as a flex fan.
Did you know the four-blade 289 High Performance cooling fan is available from Tony D. Branda Shelby & Mustang Parts? It's authentic in every way and works like a champ. We like the powdercoat finish.
Flex-A-Lite has an extensive line of electric fans for classic and late-model Mustangs. Twin fans are good for crossflow and wide radiators. Single fans, like this one, are good for the lighter-duty Mustang operation.
Fan depth inside a shroud is important to cooling. Go too deep and you lose effectiveness. Make sure the fan is half inside the shroud, with half of the blades showing.
Cylinder-head gaskets in all applications must be installed with the end passages at the rear of the block. "Front" means front in all instances.
Compression height can and will affect engine temperature. Confirm compression ratio anytime you're building an engine. A miscalculation can bite you because you're unaware there's too much compression. Check this out during the building process, even with engine kits.
Air-conditioning condensers are one of the biggest overheating culprits because they get hot during use, which causes warmer airflow into the radiator. Make sure your radiator is up to the task if your car has air conditioning.
A blown head gasket did this damage to a problematic 289. Symptoms were overheating and sluggish performance.
Additives like Water Wetter and Hy-per Lube Super Coolant improve the effectiveness of your engine's coolant. Add a bottle and watch engine temperature go down. It also helps prevent corrosion.
Likely the most revolutionary antifreeze is from Evans Cooling. Evans NPG antifreeze is expensive at nearly $30 a gallon, but worth every penny if you want foolproof corrosion protection and maximum cooling effectiveness. The Evans nonaqueous coolant requires no water--you run 100 percent of the stuff in your Mustang's cooling system. Expect to use at least two gallons for most Mustang applications. Your Mustang's cooling system must be completely void of water before servicing with Evans coolant, which offers a corrosion-free environment, a higher boiling point (369 degrees F), and a lower freezing point. It also conducts heat better than any coolant in the marketplace. Using it is foolproof if you follow the directions.
If Evans NPG seems like an unnecessary investment, consider this: It never has to be replaced, and cooling system flushing and servicing never has to be performed. A radiator should last the life of the vehicle with Evans inside. Evans NPG has been tested to last 500,000 miles in diesel trucks. After more than 500,000 miles, it was tested and proven to show no chemical deterioration. Consider it an investment you make once. Install it and forget it.
Water wetter additives improve the heat conductivity of your coolant. All it takes is one bottle to improve cooling-system function (when everything is working as it should).
Reasons Engines Overheat
Engines overheat for all kinds of reasons, both inside and outside the cooling system, including:
Cylinder-head gaskets installed backwards
Crumpled or pinched exhaust pipes
Improper ignition timing
Any airflow restriction in front of the radiator (such as a dirty air-conditioning condenser)
Lower radiator hose missing the anti-collapse spring (overheating happens when you hit the freeway, and goes away when you get off)
Belt slippage (yes, it happens)
Improper water-pump-pulley sizing
Blocked cooling-system passages (corrosion, gasket sealer, stop-leak, and so on)
Improper fan for application (such as a reverse-rotation fan installed in error or fan installed backwards)
Improper valve timing (cam sprocket installed improperly)
Improper engine building clearances (too tight)
Fuel mixture extremely lean (carburetor jetting)
Blown cylinder-head gasket (especially with unexplainable coolant loss)
Coolant in the engine oil
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