FAQ

A water pump pulls fluid from the radiator. It circulates the fluid through the engine block passages. When the thermostat opens, the fluid passes into the upper radiator hose. If the impeller on the water pump is too worn, not enough fluid is pumped throughout the system. If the bearing housing is leaking, not enough fluid pressure can be created for proper circulation. A water pump has a “weep” hole next to the bearing housing, if the bearing begins to fail, fluid will leak out of the hole. This is an early warning sign that the water pump is going out. Call or e-mail Thermalweld Technical Support for a free consultation. We can determine if the head gasket is damaged. After a short conversation, we will give an honest assessment of the condition of the vehicle and if a head gasket repair is required. For the best and most experienced head gasket repair technician in the world!!

Radiator caps are spring-loaded devices, designed to relive internal coolant system pressure. When an engine reaches operating temperature, the fluid begins to expand by about 30%, which creates pressure. The pressure from the expanded fluid must be relived. When the fluid expansion occurs, a spring in the cap compresses and sends fluid into an overflow tank. The fluid in the overflow tank will remain until the engine cools down. After the engine cools down, the fluid in the engine goes back to its normal volume. This creates a back pressure in the coolant system. An inner second spring in the radiator cap opens and draws the fluid in the overflow tank back into the radiator. A vehicle coolant system is a sealed closed-loop system. Water boils at 212° F, the boiling point temperature is raised if the fluid stays under pressure. A pressure cooker is a good example of a system under pressure. A pressure cooker raises the boiling point to allow food to cook faster. If the pressure is released in a hot pressure cooker, the fluid will instantly boil. The same is true with a coolant system. 1 PSI of cap-rated pressure increases the boiling point by approximately 3°F. Most radiator caps pressure rating is between 12 – 16 psi. The boiling point of the engine coolant is raised to about 250°F to 260°F with a 50/50 antifreeze to the water mixture. If a coolant system has an external leak, like a radiator hose or a bad seal on the radiator cap, the system is no longer under pressure. Which will cause an overheating problem. If an overheating occurs just once, the need for a head gasket repair is probable. The radiator cap is one of the main components that fail.

Every component in a vehicle’s coolant system must work together. If only one of the components fails, overheating will occur. When an engine overheats the need for a head gasket repair is probable. Over time the cooling fans wear out. As a vehicle is driven down the road, the air is being forced into the front of the radiator. The fan helps draw air through the back of the radiator. The fan is especially important if the vehicle is stopped in traffic. No air is being forced into the front of the radiator when a vehicle is stopped. If the fan is not functioning properly overheating will occur. If overheating occurs, it is probable that a head gasket repair will be necessary. There are two different types of cooling fans. Direct drive and electric. The direct-drive fan is powered by the engine with pulleys and belts. A question that is asked often: If the engine is running and the fan is turning, how can the fan be defective? Most direct-drive fans have an internal centrifugal clutch that wears out over time. The experienced Technical Support Staff at Thermalweld can give advice on how to perform a simple test to determine if the direct drive fan is operating properly. If the fan is not turning properly. Not enough air is being pulled through the radiator to cool the coolant before it goes back into the engine. The same is true for electric fans. An electric fan plays an important role in cooling an engine, the same as a direct drive fan. Often when an electric fan gets old, the temperature sensor or the relay quit working properly. If the temperature sensor is malfunctioning the fan will not come on at the proper time. Sometimes the relay switch gets a signal from the sensor but the switch has corrosion and cannot make good contact to activate the fan. It is common to bypass the sensor/relay components and direct wire to the fan. When a fan is directly wired, the fan comes on as soon as the engine is started. There are kits at the local auto parts stores to bypass the fan system.

A thermostat is a heat-activated gate. When an engine is first started, the fluid inside the engine is cold. The thermostat will be closed. The water pump will be pumping, but no fluid will be pushed into the radiator. When the fluid inside the engine block heats up, the thermostat should open. When the thermostat opens, fluid is pushed into the radiator. During this time the cooler fluid is being pulled from the lower house of the radiator. As the cooler fluid reaches the thermostat, the thermostat will close again. This cycle continues until the engine reaches operating temperature. When the engine is at operating temperature, the thermostat will stay open. The fluid will circulate through the coolant system constantly. Thermostats can become defective and stay partially open. Sometimes a defective thermostat will become completely closed, thus not allowing fluid to pass into the radiator. If this happens the engine can overheat in a very short period of time. One overheating incident can cause a blown head gasket. It is easy to determine if a thermostat is opening. When the temperature gauge indicates that the engine is at normal operating temperature, feel the upper radiator hose. If the upper radiator hose is not warm, that is an indication that the thermostat is not opening properly.

Generally, there are two types of coolant systems:
1. A radiator with a pressure cap
2. A radiator without a pressure cap.

A coolant system with a radiator cap has an overflow/recovery tank. It is a common component found in most automotive applications. They are typically connected by a tube to the radiator neck, and it serves as a place for excess fluid to be captured when the pressure release valve in the radiator cap gives way. When the engine cools down the pressure normalizes within the coolant system, and the fluid is pulled back into the radiator. If the radiator cap is defective overheating can occur resulting in a blown head gasket. If the tube is blocked a head gasket can be damaged.

A coolant system without a radiator cap has an expansion tank off to the side. Unlike the overflow/recovery tank, an expansion tank has a pressure cap. The pressure cap must be functioning properly or an overheating can occur. If an engine overheats damage to the head gasket is possible. Thermalweld provides an alternative to a complete teardown of the engine with a blown head gasket.

A coolant system is a sealed closed-loop system, which will raise the boiling point as long as it stays under pressure (think cooking a chicken in a pressure cooker). Water boils at 212° F. The boiling point can be raised to approximately 250° F, as long the coolant system stays sealed. If a coolant system has an external leak such as a leaking radiator, a hose, or even a bad seal at the radiator cap, the pressure is lost. The boiling point is lowered. In addition, vital fluid is lost with an external leak. As the fluid leaks out, there is less fluid to help cool the engine. Manufacturers design coolant systems to have a reserve cooling capacity of 30%. This means that the coolant system is built 30% stronger than what it needs to be. Over time the reserve capacity goes down due to normal wear and tear on the coolant system. A water pump impeller gets worn. A radiator has some of the cooling passages clogged up by minerals and sediment. If the cooling capacity goes too low an overheating will occur. If an overheating occurs only once, a head gasket repair could be needed. Exchanging antifreeze periodically is suggested by all manufacturers.

With millions of cars in the United States on the road, each one is a source of air pollution. The amount of pollution, especially in large cities, can create big problems. The federal government, states, and cities created clean-air laws that restrict the amount of pollution that vehicles can produce. Auto manufacturers have made many refinements to fuel systems to keep up with these laws. Around 1975 a device called a catalytic converter was introduced. A catalytic converter is a device that converts toxic pollutants in exhaust gas to less toxic pollutants. Catalytic converters are amazingly simple devices, so it is incredible to see how big an impact they have. Catalytic converters are used with internal combustion engines, fueled by either gasoline or diesel. If an engine needs a head gasket repair, coolant passes through at least one combustion cylinder, and out the exhaust pipe. Before exiting the exhaust pipe, the coolant must pass through the catalytic converter. The internal components of a catalytic converter have a series of plates with many small holes and are extremely hot. As the coolant passes through the catalytic converter, the residue of the water and antifreeze will get “cooked” on the plates. If a head gasket repair is not performed, over time the residue of the antifreeze and water will begin to build up and clog up the small holes in the plates. If exhaust gases cannot pass freely through a clogged catalytic converter, the heat from the exhaust will go back into the engine and cause the vehicle to overheat. Without a timely head gasket repair, the catalytic converter will become damaged and need to be replaced.

Hot fluid enters the radiator from the upper radiator hose. The hot fluid goes down through the passages in the radiator. To cool the fluid as it passes from the top of the radiator to the bottom hose, the air is pushed through the front of the radiator while driving. Hot air is also pulled from the radiator with a fan in the engine compartment. If the radiator passages are clogged, fluid will not be cooled properly. The uncooled fluid will be recirculated back into the engine. Overheating will occur. Also, a water pump requires a steady flow of fluid to operate properly. If fluid cannot get to the water pump fast enough because of a clogged radiator, the water pump will cavitate. When a water pump cavitates, instead of steady flow through the engine block, short bursts of fluid will occur. If an engine is allowed to overheat the head gasket could be damaged. At the first signs of an overheating engine, pull over the vehicle immediately. Sometimes an engine overheats without the driver even knowing it. Sometimes a driver sees that the engine is overheating but keeps driving. The best advice is to stop the engine as soon as possible. Once an engine overheats, the need for a head gasket repair is probable.