COOLANT (Water and
Antifreeze mixture) is
initially supplied and/or replenished from the COOLANT RESERVOIR, (GREEN)
and after circulating through the RADIATOR is on its way into the ENGINE, via the LOWER RADIATOR
HOSE and the WATER PUMP. After circulating throughout the ENGINE the heated Coolant (RED) from the top part of
the ENGINE
passes
through the THERMOSTAT HOUSING, UPPER RADIATOR HOSE,
and enters the top part of the RADIATOR .
After being cooled down (YELLOW), by its passage through the RADIATOR CORE, the COOLANT is then returned via the LOWER RADIATOR HOSE into the WATER PUMP, which then pumps it into the passages surrounding the COMBUSTION CHAMBER, and throughout the hot sections of the ENGINE - the CYLINDER BLOCK and the CYLINDER HEADS.
After being cooled down (YELLOW), by its passage through the RADIATOR CORE, the COOLANT is then returned via the LOWER RADIATOR HOSE into the WATER PUMP, which then pumps it into the passages surrounding the COMBUSTION CHAMBER, and throughout the hot sections of the ENGINE - the CYLINDER BLOCK and the CYLINDER HEADS.
- COOLANT RESERVOIR
- RADIATOR
- WATER PUMP
- THERMOSTAT
- RADIATOR CAP
- RADIATOR FAN
- THERMALLY CONTROLLED FAN CLUTCH
- ELECTRIC FANS
- ELECTRIC FAN CONTROLS
COOLANT RESERVOIR
Its function is mainly to serve as a reservoir of extra Coolant and its level must also be carefully monitored to make sure that it has sufficient coolant - no more, and no less than indicated on the 'Full line' (when engine is hot). It is also important to make sure that the Coolant Reservoir does not have any leaks itself, or that the hose to the Radiator Cap is not clogged and that it is not leaking due to the cracks, or that there is no broken seal or a clamp of the Hose that connects it to the Radiator / Radiator Cap.
RADIATOR
Just like the other components, the Radiator is an essential part of the Engine Cooling System and it must be kept in good shape to ascertain the full flow of the coolant which in turn is fundamental for the proper cooling function. Its efficiency can also be hard to measure precisely, but it is a safe bet that if there is rust in the Cooling System the Radiator tubes might already be clogged. Another culprit for the clogged Radiator can be all the 'Stop Leak' chemicals which in general are a 'life saver' for a small Radiator leak... but if the condition worsens and the system starts to overheat, it is only a matter of time before another leak develops typically next to the one that has been fixed, or somewhere else where there is another week spot. Typically, more Stop Leak chemicals are added, and that stops the leak - until the next one. Several treatments like that will extend the life of the Radiator but will be constantly be decreasing the Coolant Flow...
One test that can be easily performed which will instantly help with the determination of 'sufficient' or 'insufficient' flow through the Radiator is as follows: With the COLD engine open the Radiator Cap, and providing that the Coolant does NOT have a Rusty Color, let out some Coolant out until it the Coolant level reaches about 2/3 of the level (or about 5 -6 inches below the Radiator cap opening - for 'Side Flow' type Radiators only). Start the engine and observe the Coolant in the Radiator as the engine temperature starts to rise. Very soon (as the Thermostat opens) the Coolant will be seen coming out of the Radiator tubes. If there is just a slow trickle there is a good chance that the Radiator tubes are sufficiently clogged and that the cleaning ('Rodding out') by the Radiator shop is required - if it is still in a repairable condition. If there are tubes that are so badly clogged that they can not be opened up without damage, that Radiator must be replaced.
Caution! The replacement radiator must be of the same COOLING CAPACITY as the original. It is essential, specially for the larger and high compression V-8 engines, that if the original Radiator is a Heavy Duty type - with 4 ROWS - that it must be replaced with the same! Replacing it with the 3 ROWS - in order to save money - is just NOT the solution! The Overheating problem can actually become worse!
WATER PUMP
Besides the Thermostat, there are other items on the 'Check List' that are just as crucial for maintaining the normal running temperature of an engine. Namely, even with the Thermostat functioning properly, for the coolant to circulate through the cooling system the Water Pump must be functioning correctly. Felling the pressure in the Upper Radiator hose is also one of the methods, but it is also easy to see if the Water pump is OK by just watching the coolant flow in the Radiator (of the 'side flow' type) - when a COLD engine is started., and after the Thermostat has opened.
WARNING! DO NOT OPEN the radiator Cap unless the engine is completely cold, or the Radiator has cooled off to where it can be touched by hand! Even then, there might still be pressure in the Cooling System so it must be opened with a Shop Rag or with a doubled up Paper towel. Heavy Duty Rubber gloves and safety glasses are also a MUST!
The coolant flow in the Radiator ( the 'side flow' type) will be visible through the opening with the Radiator Cap removed. Another easy way to establish that there is a Coolant flow through the system is when a cold engine starts to warm up, the top of the Radiator closer to the Upper Radiator Hose will start to feel much warmer, while the rest of the radiator will remain at the cooler temperature.
It is very important that the Water pump is pumping at the full capacity though, and establishing this might be not be very easy without the specialized 'flow meter'. This can also be very tricky on a large engine which heats up very fast, especially in a hot climate, so an inspection by by a competent and knowledgeable Mechanic (or the Radiator Shop that is properly equipped), could help eliminate - or confirm - the Water Pump status.
THERMOSTAT
The most common cause of Overheating problem, and with the most drastic consequences, can be the Thermostat which is stuck in CLOSED Position! The function of the Thermostat is to act as a Temperature activated Valve - which in fact is exactly what it is. When functioning properly, the Thermostat should be in the OPEN position at the 'normal' Engine Temperature. There is a variety of temperature settings at which a Thermostat opens, and this is determined by the Manufacturer's specifications, and it varies from one Car or Truck model to another. Most common range is between 165 and 195 Degrees Fahrenheit. Below that threshold temperature the Thermostat should remain closed. This helps a cold engine reach the normal running temperature, as when it is closed there is no flow of coolant, and the engine of course warms up much faster. This is an important factor especially in the colder climates and it affects many aspects of the engine performance, fuel consumption, exhaust emissions, even how fast the shivering driver will start to enjoy the benefits of the warm air from the heater, etc.
As essential of an item that Thermostat is in the colder climates, it can actually be more beneficial to permanently remove it in the (very) warm and tropical climates. Just the absence of it in the Thermostat housing will leave more space for the coolant to flow, and with the increased coolant flow naturally comes the increased engine cooling efficiency!
The easiest and the safest way to ascertain that the Thermostat is functioning properly is to hold the Upper Radiator Hose as the engine is started and as it warms up 'feel' the warm water starting to circulate through it. Although there are other methods ... for example dumping a Thermostat in a pot of boiling water and watch it open up instantly - if functional... if there is any doubt, the safest thing to do is to just remove (and/or replace) the Thermostat.
RADIATOR CAP
Another relatively small item, but a very important item! They come in different Pressure Ratings, which vary with Engine size, Engine Compression rating, Vehicle use (Heavy Duty/Standard), climate, etc. and for the relatively low cost it is best and safest to replace any Radiator Cap that has the seals that look like they are worn out, or there are cracks, or debris on its sealing surfaces. Even if it does not look like it has an 'External' leak the Cap's function is to also 'communicate' (in both directions - 'in' and 'out') with the Coolant Reservoir so that when excessive pressure is reached in the system, it allows the return of the Coolant which is expanding under heat and pressure to return to the Coolant Reservoir. Likewise, it allows for the Coolant from the Coolant Reservoir to go back into the system when the lower level in the system creates the sufficient negative pressure to allow it to flow into the Cooling system. The best and the SAFEST type of Radiator Cap to replace the original Radiator Cap with is the one that has a "Pressure Release' lever on it! The Interlocking Lever designs assures that the cap can only be removed AFTER the lever has caused the pressure to be released back into the Coolant Reservoir. This is absolutely the safest way to prevent any hot water and steam 'accidents' which can result even in some serious skin burns! The minimal cost of only few Dollars extra is definitely worth it!
RADIATOR FAN
Although this is an EXTERNAL Component of the Cooling System, it is also a very important one. Its proper operation can make all the difference in how much Cooling takes place in the Radiator - if at all!
There are 2 types of Radiator fans - Mechanical and Electrical ones, with the Electric fans being on all newer cars from the late 1980s / early 1990s and later.
In either case they MUST turn fast enough when needed in order to do their job of simply moving the air through the Radiator fins. Again, different Engines have different requirements!
The Mechanical types are controlled with Thermal Clutches, which in response to higher temperature provide higher friction and thus the fan turns faster and closer to its maximum ratio in reference to the speed of the engine. Typically The Thermostatic Clutches go bad and that results in the slower than acceptable speed of the fan - which is especially critical when the Engine is idling, or running at the low RPM - such as being stuck in the Traffic... Or worse yet, stuck in the Traffic on a 100 degree day with the air condition at 'Full blast'. Fans, and Fan Clutches are NOT easy to be diagnosed either. The only 'sure fire' method is with an Optical Scanner but only a well equipped Radiator Shop will have them - they know one when they see one. An experienced ear (and eye ... and hand) can tell a good Fan Clutch from a bad Fan Clutch. There is one 'Do-It-Yourself test' though. But it is too dangerous to take a chance and risk some potentially serious hand injury. Do not try it unless you are sure you know what you are doing!
The Electrical types are controlled by the temperature sensors throughout the engine compartment and it is very easy to see if they are operating properly or not. Wait until the Engine gets very warm, if not HOT, and in the worst case turn the air condition ON. The Radiator Fan should eventually turn ON. If it does not this is an electrical type of problem and the Fan must be trouble-shooted first to see if it is operational at all. If yes, then the problem is with the Temperature control somewhere - anywhere - and this turn into a major job for a well equipped Auto electrician who knows what he is doing on that particular Model (all are different!)... There is however a relatively simple (and much cheaper) do it yourself solution to this, but that is something that is covered separately - for those 'in need' (see below)...
THERMALLY CONTROLLED FAN CLUTCH
This is found on practically all engines starting from the Mid 60s to the mid/late 80s until they were mostly replaced with the Temperature Sensors which control Electric fans. The Thermally Controlled Clutch is designed to ascertain the minimum RPM of the Radiator Fan during the startup and while the engine is still cold. As the engine temperature increases and it reaches its operating temperature, the friction within Thermally sensitive fluid within the Clutch housing increases, and the end result is also the increased RPM of the Radiator Fan. It is a very important part of the 'external' cooling system as insufficient friction when hot can cause the fan to rotate at a reduced speed and cause insufficient flow of air through the Radiator finns. The safest and easiest 'test' is when the engine is hot (and Turned OFF) to try to move/rotate the Fan by hand. If there is no resistance to turning it, and the Fan continues to turn when 'spinned' by hand, this is a definite indication that it is NOT functioning properly and that it MUST be replaced. If there is resistance to rotating / spinning it by hand, it is an indication that it 'might' be OK, but it is not the 'final word' on its condition. The only sure test is by specialized RPM (optical) test using professional equipment. Any better equipped Radiator Shop should be able to test it properly.
ELECTRIC FANS
Electric Radiator Fans are the latest and the best (also the most power efficient) method of creating the sufficient air flow through the Radiator finns - which results in the fastest drop in temperature of the Coolant flowing through the Radiator. They are ON only when they are really needed - when the radiator/engine temperature are high enough to require it. Therefore these Electric Motors are NOT of a 'Continuos Duty' type, and they should be also checked frequently, both when the Engine is Cold, and when the engine is Hot. With the engine Cold, they should be checked Manually, by rotating / spinning the Fan - to make sure that it is NOT frozen-up. When the engine is Hot it should be checked Visually only to ascertain that it does run when the engine is Hot, and especially when the Air Condition is On. This might require some persistence as unless the specific Temperature is reached it will NOT go On and it might create a wrong impression, especially in a cold weather. In this case the engine should be run at a High RPM (even for up to 10-15 minutes) and Radiator Temperature (and the Temperature Gauge) should be observed. If the (properly functional) Temperature Gauge goes above the 'Normal' Temperature, and the Electric Fan still does not intermittently go ON and OFF, indications are that there is a problem with the Temperature Control.
ELECTRIC FAN CONTROLS
This can be the 'Trickiest' part of the Vehicle Cooling System, and under the 'least control' of the driver. Since it is basically a Temperature Sensor, which activates the Fan Relay, and the Temperature sensors (and circuits) vary widely from Model to Model, it is the hardest part to analyze. First step is to check the FUSE BOX and see if any of the 'large' (High Current - typically 20 -30 Amps -depending on the Model) Fuses are not blown. If the Fuse is OK, following the Circuit backwards from the connector on the Electric Fan to the Relay is the next step in order to establish if the problem is somewhere in the cable Harness between the Fan Motor and the Fan Relay, also to ascertain that the Relay itself IS functional properly - which is to turn ON the Motor when it is energized. Since the Relay itself is energized in accordance to the preset Temperature level of the Sensor and the Control circuit, this process becomes progressively harder and requires the electrical troubleshooting skills of a knowledgeable 'Pro'.
However, this is where the entire Circuits Diagnostic / Repair process can really get 'out of control' - Price-Wise! It can 'branch-out' into the Air Condition System, and/or its Sensors or Control Circuits, and as far as even the Car's Engine Computer!
In short, it can turn into an open ended 'Cost Augmentation exercise' - as truly there are so many things that can go wrong here!
But, the Properly Functional Fan Control is ABSOLUTELY ESSENTIAL!
If the Fan Controls are not functional, it is a SURE THING, the Engine WILL Overheat!
If the Engine Overheats, especially if it Overheats REPEATEDLY, and if not cooled down right away, it is also a SURE THING, that the head Gasket will be damaged! Potentially the Head(s) will crack, too - depending on the severity of the Engine Overheating!
Therefore, the results can be definitely disastrous!
So, is there an economical solution as an alternative to the potentially costly repair of the Fan Controls ?
NO, There is NONE - if you ask your Car Dealer!
MAYBE, if you ask a 'CREATIVE' Auto Electrician!...
ABSOLUTELY! if you ask the ..."knowledgeable expert with the lifetime Automotive and Technical experience"! ...
For more details about a CUSTOM DESIGNED THERMOSTATIC UNIVERSAL FAN CONTROLLER KIT - WHICH CAN BE INSTALLED ON ANY CAR - AND AT THE COST OF LESS THAN THE AUTO ELECTRICIAN'S 'DIAGNOSTIC FEE' ... click on the button below.
