Archive for October, 2009
Most radiators in late model cars are aluminum. Years ago, they were mostly copper/brass. In the 1980s, only about 24 percent of all new domestic and import vehicles were equipped with aluminum radiators. Today, that percentage is almost 100 percent.
Why the change to aluminum radiators? Because an aluminum radiator is much lighter than a copper/brass radiator: 5 lbs. versus 15 lbs. Empty. Aluminum radiators also contain no lead solder (which corrodes and is an environmental pollutant). The average service life of a typical aluminum radiator is actually about 10 to 12 years, which is about two to four years longer than a copper/brass radiator. Also, aluminum radiators are cheaper to manufacture.
Copper/brass radiators actually cool better than aluminum (almost twice as good), but the added weight and higher cost of copper makes them too expensive.
Radiator manufacturers have developed new, lightweight lead-free brazed copper/brass radiators that weigh less than the traditional lead-soldered radiators, but the cost is still high. These new copper/brass radiators are about 7 percent lighter and 15 percent smaller than an aluminum radiator of comparable cooling capacity. The new brazing technology for joining the tubes uses a copper/nickel/tin/phosphorus alloy which provides a stronger connection and is more environmentally friendly than lead solder. Brazing the tubes also eliminate solder bloom corrosion that can form inside older copper/brass radiators if the coolant is not changed regularly.
The inside and outside of the new brazed copper/brass radiators are also electroplated to improve corrosion resistance, and the radiators are also easy to repair. Furthermore, the amount of energy needed to produce one ton of copper from copper ore is only about 40 percent of that needed to produce aluminum from its ore, so the overall energy picture for copper/brass is more favorable than that of aluminum. Both metals are also highly recyclable.
CAUSES OF RADIATOR FAILURES
The most common reason for radiator failure is internal corrosion, which can have multiple causes. If the coolant is not changed regularly for preventive maintenance, the coolant can turn acidic and eat away the radiator from the inside out.
The corrosion inhibitors in conventional green antifreeze are gradually depleted over time, and the recommended coolant change interval has traditionally been every two years or 24,000 to 30,000 miles. The new long life orange and yellow OAT-based antifreeze formulas can typically go 5 years or 150,000 miles between changes.
Aluminum is more vulnerable to electrolytic corrosion than either copper/brass or cast iron because aluminum is a highly reactive metal. When the corrosion inhibitors in the coolant are depleted and the pH of the coolant drops to 7 or below, aluminum becomes a sacrificial anode and is eaten away.
Checking the pH of the coolant with chemically-treated test strips can help you determine if the coolant is overdue for a change. The alkalinity of a typical antifreeze/water mixture will vary depending on the additives in the antifreeze and the ratio of ingredients, but is usually somewhere between 8 and 11. The average for most antifreezes is around 10.5, but when diluted 50/50 with water and added to the cooling system the pH drops to the 8.5 to 9 range. Higher is not necessarily better, though, because some of the new long-life coolants have a pH of only 8.3.
ELECTROLYTIC CORROSION
A different type of corrosion can also occur in the cooling system even if the coolant is in good condition. Electrolytic corrosion can occur if the engine does not have a good electrical ground connection. Voltage from the charging system and ignition system will flow through the coolant to ground, creating electrolysis corrosion that eats away at the metal components in the cooling system. This may eat pin holes into the radiator or heater core and cause coolant leaks. It can even eat away at the inside of rubber hoses and cause them to fail also.
This type of corrosion can sometimes be detected with a voltmeter. Place the positive test lead into the coolant, and touch the negative lead to battery negative terminal or body ground. If the voltmeter shows more than a few tenths of a volt, current is traveling through the coolant and may be attacking the cooling system. Check the engine ground straps for loose or corroded connections. If a ground strap is missing, replace it (or install an extra strap if one is not enough).
RADIATOR DAMAGE
Radiators can also be damaged by vibration that causes the end tanks or seams to crack and leak. Areas that are most likely to crack include the hose fitting connections, and the areas where the end tanks attach to the finned heat exchanger.
Radiators can also be damaged by freezing if the coolant does not contain a high enough concentration of antifreeze and the outdoor temperature drops below freezing. Ice expands as it freezes and can split out the tube or end tanks on the radiator.
Leaks may also occur in the automatic transmission oil cooler located inside the end or bottom of the radiator. ATF from the automatic transmission is circulated through a small loop of metal pipe inside the radiator to cool the fluid. Leaks here can allow coolant to mix with the fluid (which is bad for the transmission), or the ATF to mix with the coolant.
The up front location of the radiator also makes it (and the A/C condenser) vulnerable to any stones or road debris that comes through the grille. A stone impact can have the same effect as if somebody shot a bullet into the radiator, and puncture the tubing causing the radiator to leak.
Bugs, leaves and dirt can also build up on the face of the radiator and restrict airflow to the point where it may cause the engine to overheat. Spraying water or compressed air from the backside of the radiator can clean out the debris and restore normal airflow and cooling.
Internal clogging due to a buildup of lime deposits or gunk in the cooling system, on the other hand, is not so easy to remove. If tubes in the radiator become plugged, it creates dead zones that do not provide any cooling. Plugged tubes can be detected by scanning the surface of the radiator with an infrared thermometer. Any area that reads cooler than an adjacent area when the engine is hot and running is not flowing coolant. Adding a can of cooling system cleaner may help, but it usually requires professional cleaning by a radiator shop to remove the blockages. The shop has to disassemble the radiator and rod out the clogged tubes to restore normal flow.
Radiators can also be damaged in an accident. A frontal collision almost always damages the radiator. If the radiator is not punctured or crushed, it may be twisted, causing tubes or end seams to crack and leak.
Small pinholes leaks can often be plugged by adding a can of cooling system sealer to the coolant. But large leaks or leaks that cannot be stopped with sealer require taking the radiator to a radiator shop for repairs, or replacing it with a new one.
RADIATOR REPAIRS
Internal corrosion damage usually required replacing or rebuilding the radiator. But small leaks can be repaired a variety of ways depending if the radiator is aluminum or copper/brass.
The cheapest fix, of course, is to try adding a bottle of cooling system sealer to the coolant (via the radiator cap or coolant reservoir). If that fails to stop the leak, the radiator will have to be patched, rebuilt or replaced.
Solder bloom is a type of internal corrosion that can form when neglected coolant, rust and some types of leak inhibitor additives react with the soldered joints in a copper/brass radiator. White to green crumbly deposits begin to grow, which can block tubes and restrict the flow of coolant. A radiator with this kind of problem must be recored or replaced. The cooling system should be cleaned and flushed to remove deposits and sediment.
Leaks caused by punctures in an otherwise health copper/brass radiator can usually be patched by soldering, brazing or even sealed with epoxy or specially-formulated high temperature hot-melt adhesive (which is not the same kind of adhesive used in a home hot glue gun.
Aluminum radiators can also be repaired by soldering, brazing or welding, but it takes skill and special materials. Epoxy or a special high temperature hot melt wax (available from the Barbee Co.) are other repair alternatives that can achieve good results on aluminum.
Leaks in plastic end tanks can be filled with epoxy, covered with fiberglass and epoxy, or hot air welded using nylon plastic filler rod. Welding plastic takes some skill and requires careful surface preparation to get good adhesion. The leak must first be “V” ground and sanded, then cleaned with wax and grease remover to assure a strong bond. The other alternative is to simply replace the damaged end tank. But the job is harder than it looks because the end tank must be pressed down on the core with about 150 lbs. of pressure while the header tabs are clamped in place. Radiator shops have the proper fixtures for doing this kind of work.
REPLACING A RADIATOR
The first step in replacing a radiator is to drain the cooling system. Open the drain valve on the radiator, and catch the old antifreeze in a bucket. Then dispose of the old coolant properly. Some recycling centers accept used antifreeze. Do no dump it on the ground or pour it down a storm sewer. In many areas, used antifreeze can be safely disposed of by flushing it down a toilet (an added bonus with this method is that antifreeze kills tree roots and helps keep sewer lines open).
If the cold coolant contains any sediment or rust, the cooling system should be flushed with a chemical cleaner before any further disassembly. All of the cleaner should then be flushed out of the engine and cooling system with plenty of clean water.
The old radiator can now be removed by disconnecting the upper and lower radiator hoses, the ATF oil cooler lines (which requires using flare nut wrenches if you don’t want to damage the fittings), removing the fan shroud or cooling fan, then unbolting the radiator support brackets. On some newer vehicles, the radiator is attached to the A/C condenser, making it much more difficult and expensive to replace.
If the radiator is being replaced, the new radiator must have the same width and height as the original, and the same cooling capacity. Some replacement radiators may actually be thinner than the original because they use a more efficient tube and fin design.
When bolting the radiator in place, check for misalignment between the mounting brackets and radiator support. Misalignment can crease stress that may lead to fatigue cracking and radiator failure.
Also, inspect the condition of all belts and hoses. Now would be a good time to replace the hoses and clamps if they are more than six years old. Any hose that has cracks, bulges or soft spots must be replaced. Also, make sure hoses are properly positioned and supported to minimize stress on the radiator connections. Make sure you replace the fan shroud or any other ducting that was originally on the vehicle if it has a mechanical cooling fan. Leaving off a fan shroud can significantly reduce the radiator’s ability to cool the engine at low speeds when most of the airflow is generated by the fan.
A new cap is also recommended for a new radiator. Make sure it has the same pressure rating as the original.
If the engine overheated, the thermostat should also be replaced. Too much heat usually damages the thermostat. Note: Some thermostats have a jiggle pin or small bleeder hole that vents air making filling easier. Others do not, and can trap air causing the engine to overheat. I always use a jiggle pin thermostat, or drill a small hole to create a vent if a jiggle pin style thermostat is not available for the application.
When refilling the cooling system, use a 50/50 mixture of fresh antifreeze and clean water (distilled water is best). With older copper/brass radiators, green coolant usually provides the best protection. For newer radiators, use a green coolant with silicate inhibitors, or an OAT-based orange or yellow antifreeze.
Getting all the air out of the system is essential for proper cooling, so look for any air bleed valves on the thermostat housing, intake manifold or elsewhere that might need to be opened to vent air while you are refilling the cooling system with coolant.
When everything is back together, and the cooling system appears to be full, start the engine and check for leaks as the engine warms up. Make sure the cooling fan comes on when the engine reaches operating temperature. Then shut the engine off, let it cool for an hour or so, then add additional coolant if needed to top off the system.
If your radiator is leaking, you have several repair options:
You can try the cheap fix and add a bottle of cooling system sealer to the radiator. These products are designed to seal small leaks. They can also seal internal engine leaks. Some work better than others, but most provide only a temporary solution to your problem.
You can attempt to repair the radiator yourself. Copper/brass radiators on older vehicles can often be soldered to repair leaks. Cracks or pinholes in aluminum radiators in newer vehicles can often be repaired with epoxy glue. But if the core is severely corroded or damaged, the radiator may have to be professionally repaired at a radiator shop, or replaced with a new radiator.
FIXING A LEAKY HEATER CORE
As with a leaky radiator, you might try the cheap fix and add a bottle of cooling system sealer to see if that will stop the leak. If it does not, you will have to disassemble the HVAC case to replace the heater core. This is a nasty job and involves a LOT of labor on most vehicles.
If a vehicle has a history of repeat heater core failures (some Chrysler cars, for example), the problem may be electrolysis corroding the heater core. One fix is to attach a grounding strap on the heater core. Another is to replace the OEM aluminum heater core with an aftermarket copper/brass heater core.
COOLANT RESERVOIR
Another coolant component that sometimes needs attention is the coolant overflow reservoir. The coolant overflow reservoir does more than catch the overflow from the radiator. It’s main function is to serves as a storage tank for excess coolant. When the system is hot, coolant will be forced out through the radiator pressure cap and into the reservoir. Then as the system cools down, decreasing pressure will draw coolant back into the radiator.
On many newer vehicles, the coolant reservoir is pressurized and is an integral part of the cooling system. The filler cap for the cooling system is located on the reservoir tank, and the tank is connected to the radiator and engine with hoses. The reservoir is transparent plastic and you can see the coolant level inside.
If the coolant reservoir is cracked or leaking, the system may lose coolant every time the engine heats up. Eventually, this can cause the engine to overheat.
Small punctures or cracks in the overflow reservoir can usually be repaired with silicone glue. If the reservoir needs to be replaced, make sure the hoses are routed correctly between the radiator and the reservoir, and that it is free from kinks that could block the flow of coolant back and forth.
FIXING LEAKY FREEZE PLUG
There are several ways to repair a leaky freeze plug.
One is to clean the surface of the plug, then sand it lightly with sandpaper, and pack it solid with a high temperature two-part epoxy such as gas tank sealer. Let it cure overnight. This trick usually seals leaky expansion plugs that would otherwise be very difficult to replace.
Another is to use a hammer and drift to knock out the old plug. Pounding in on one side of the plug will usually cause it to twist. The plug can then be pried out with a large screwdriver. Clean the hole, then apply a liberal coating of sealer to the hole and carefully drive in a new replacement plug. The plug must go in straight or it may not seal. Another option is to install a repair plug that has an expandable rubber grommet to seal the hole. You simply place the plug in the hole and tighten the bolt until it seals tight.
FIXING LEAKY HOSES
Do not waste your time trying to patch or wrap a leaky radiator or heater hose. Sealers do not work well with hoses either. Replace the bad hose with a new one, and inspect all the other hoses because if one has failed the others are probably reaching the end of the road, too. It is also a good idea to replace the original hose clamps, especially if they are the ring type. Ring clamps can lose tension with age and may not hold the hose tightly. Worm drive clamps are recommended.
FIXING A LEAKY WATER PUMP
No stop leak will seal a water pump that’s losing coolant past the shaft seal. Replacement is your only option here. But you can save some money on the job by using a remanufactured rather than a new pump.
Replacing a water pump is not too hard a job on most engines, but on some it can be tricky. On 2.8L GM V6 engines, for example, the bolts that hold the water pump also hold the timing cover in place. If you are not careful, the timing cover seal can be broken allowing coolant to leak into the crankcase. GM recommends using a special tool (J-29176 or equivalent) to hold the timing cover tight while the pump is being changed.
Check the fan clutch because a weak clutch can cause the engine to overheat.
If your engine has a belt-driven fan with a fan clutch, it is also a good idea to check the fan clutch when replacing the water pump. The lifespan of both is about the same, so the fan clutch may also need be replaced. If the clutch is leaking silicone fluid, or has any wobble in the bearing, it must be replaced.
Coolant leaks rarely pass unnoticed for long because sooner or later the engine will overheat from the loss of coolant. So if you are driving a leaker, keep reading because we’re about to tell you how to find and fix your coolant leak.
WHERE COOLANT LEAKS OCCUR
Coolant leaks can occur anywhere in the cooling system. Nine out of ten times, coolant leaks are easy to find because the coolant can be seen dripping, spraying, seeping or bubbling from the leaky component. So open the hood and visually inspect the engine and cooling system for any sign of liquid leaking from the engine, radiator or hoses. The color of the coolant may be green, orange or yellow depending on the type of antifreeze in the system. The most common places where coolant may be leaking are:
A worn seal on the water pump shaft can leak coolant.
Water pump. A bead shaft seal will allow coolant to dribble out of the vent hole just under the water pump pulley shaft. If the water pump is a two-piece unit with a backing plate, the gasket between the housing and back cover may be leaking. The gasket or o-ring that seals the pump to the engine front cover on cover-mounted water pumps can also leak coolant. Look for stains, discoloration or liquid coolant on the outside of the water pump or engine.
This radiator is badly corroded and is not worth fixing
Radiator. Radiators can develop leaks around upper or loser hose connections as a result of vibration. The seams where the core is mated to the end tanks is another place where leaks frequently develop, as is the area where the cooling tubes in the core are connected or soldered to the core headers. The core itself is also vulnerable to stone damage. But a major factor in many radiator leaks is internal corrosion that eats away from the inside out. That’s why regular coolant flushes and replacing the antifreeze is so important.
Most cooling systems today are designed to operate at 8 to 14 psi, so if the radiator can’t hold pressure your engine will overheat and lose coolant.
Pinch hoses to check for age cracks, hardening, soft spots, blisters or bulges.
Hoses. Cracks, pinholes or splits in a radiator hose or heater hose will leak coolant. A hose leak will usually send a stream of hot coolant spraying out of the hose. A corroded hose connection or a loose or damaged hose clamp may also allow coolant to leak from the end of a hose. Sometimes the leak may only occur once the hose gets hot and the pinhole or crack opens up.
Freeze plugs (casting plugs or expansion plugs in the sides of the engine block and/or cylinder head). The flat steel plugs corroded from the inside out, and eventually eat through allowing coolant to leak from the engine. The plugs may be hard to see because they are behind the exhaust manifold, engine mount or other engine accessories. On V6 and V8 blocks, the plugs are most easily inspected from underneath the vehicle.
Heater Core. The heater core is located inside the heating ventilation and air conditioning (HVAC) unit under the dash. It is out of sight so you can�t see a leak directly. But if the heater core is leaking (or a hose connection to the heater core is leaking), coolant will be seeping out of the bottom of the HVAC unit and dripping on the carpet. Look for stains or wet spots on the bottom of the plastic HVAC case, or on the passenger side floor.
Intake Manifold gasket. The gasket that seals the intake manifold to the cylinder heads may leak and allow coolant to enter the intake port, crankcase or dribble down the outside of the engine. Some engines such as General Motors 3.1L and 3.4L V6 engines as well as 4.3L, 5.0L and 5.7L V8s are notorious for leaky intake manifold gaskets. The intake manifold gaskets on these engines are plastic and often fail at 30,000 to 80,000 miles. Other troublesome applications include the intake manifold gaskets on Buick 3800 V6 and Ford 4.0L V6 engines.