Looking After A Best Friend - Your Cooling System!
Summer has arrived and with it sustained hot days:
And that means more cars, but not all cars, are going to overheat! Overheating cars cost money - big money sometimes so what can we do?
Oh and winter's just as bad, if not worse!:
Why?
Because if the anti-freeze is not up to the job, lower temperatures will soon find you out! You're just as likely to get a blown headgasket in winter, through no water being able to get through a frozen radiator, as you are with a lack of coolant or a dodgy water pump when it's a 100 in the shade!
Our car's cooling system can be a best friend if we look after it and a worst enemy if we don't!
The cooling system carries out a critical function - it maintains correct engine temperature by circulating coolant through the engine to collect heat and then runs it through the radiator, where it is cooled by a fan if it is static or by the airflow and/or the fan as the car moves.
There are three major sections:
Coolant Circulation
This function is handled by our old friend the water pump which keeps the coolant on the go! The (main) water pump is belt or gear-driven but in some case with high performance or serious 4 x 4s a secondary pump is utilised for better flow and cooling in extreme conditions, e.g. crossing the Sahara! In some cars, typically Mercedes of certain vintages, the water pump is a supplementary electric unit and I frequently fit these to endurance rally cars besides the mechanical unit.
I advisedly use the word critical again and the successful operation of a water pump is the condition of the belt that drives it. It is indeed critical. On most of today's newer cars this is done by the engine's cam/timing belt. On some older cars, such as my ancient Monza, the pump and belt are external and operated by a 'V' or flat belt run off the main crankshaft pulley.
Servicing of the cooling system is all about checking the strength and condition of the coolant and changing it as and when required (i.e at the scheduled service intervals). This also applies to the drive-belts and external tensioners. When you have belt-driven pumps replaced it is also a very good (if not mandatory) idea to replace the tensioner/s.
Hoses, Radiators, Heater Matrices, Expansion Tanks and Heater Control Valves
Other parts of the cooling system, which can be just as critical, are those mentioned in the above heading. The materials used are in constant contact with the coolant, which can be corrosive, so all the parts mentioned can suffer from time exposure as well as from day-to-day operation.
Servicing of the cooling system consists of regular coolant replacement and the checking and replacement (as required) of hoses and clips on a regular basis. You should also check for any leaking parts.
It is a good idea to flush out your cooling system every two years or so. Stergene Hand Clothes Wash (Lornamead) is very good for this though you must flush out finally with hot water until it runs clear! Use at least 500ml with the initial coolant and check just how much gunge does come out!
Hoses are like arteries and regular check-ups are mandatory. I do mine three times a year; Spring, Summer and Autumn. Look for abrasions (contact with other parts like an incorrectly adjusted bonnet or throttle linkage), cracks, flexibility and leaks. If you drain and replace the coolant for whatever reason, it is always a good time to check for leaks and doubtful hoses (a crazed appearance is always suspicious and I would chuck anyone like that out). I change hoses at least every two years but you could chance a longer period.
Radiators, heater matrices, heater control valves and expansion tanks should be replaced as and when necessary due to leaks or blockages. If you are not absolutely sure about this part of the cooling system operation, leave it to a pro!
Temperature Control
Cooling system temperature controls include coolant temperature sensors, both radiator and expansion tanks, electric or viscous coupling cooling fans and the electric fan relay. In the main these function separately from the engine but control its operation through cooling and/or by transmitting control signals to the engine management system(s).
The oft forgotten thermostat is a spring-loaded valve that opens and closes according to coolant temperature. A possible sign of a sticking thermostat will be a high temperature reading followed by a drop to normal running temperature or a continuously low temperature. Both these are common signs of a faulty thermostat.
Expansion and radiator caps are spring-loaded pressure relief valves which operate according to cooling system pressure. Both these should maintain coolant at pre-determined pressure settings. Faulty caps should always be replaced with caps of equal pressure setting or, in an emergency and as a temporary measure, one with a setting as close as possible.
Fans on the water pump pulley (beloved of GM) are nearly always of the viscous coupling type. At lower temperatures the fan will not lock up allowing quicker warming up and will only come into operation when temperatures have exceeded a certain level. Faulty units will either cause the engine to overheat in traffic or to run too cool at higher speeds increasing fuel consumption and emissions.
Electric fans are either run independently or in conjunction with a viscous coupling fan. Their efficient operation is controlled by a temperature sensor located in the radiator/radiator hose or on the thermostat or water pump housing and in certain cases a relay may be employed. Some may have variable speed setting sensors. There are exceptions to this but they are rare.
Other important sensors acting as part of the cooling system are:
Gauge sender unit
Warning light sender (red warning light: On/Off)
Thermo time switch (cold start control unit)
Lambda or variable control fuel injection sensor
Et al
Temperature control is absolutely critical with regard to emissions, good performance and economy. As many experts on here will know, this area is one of the most difficult to diagnose particularly where the engine management system is involved. As such this is one area that you cannot maintain and it is best left to those with the correct diagnostic and setting-up equipment. However if you try and keep the sensors clean internally and externally through the use of proper coolant and clean connections, you are a long way down the road to problem free motoring in hot weather.
Follow the above and hopefully you will reduce the chances of your car's cooling system burning a rather large hole in your pocket!
Below are a few tips that I've picked up over the years, particularly on the competition side.
TOP TEN TIPS WORTH REMEMBERING
1. Keep the engine and its bay clean - it's easier to spot leaks. An engine is also its own heat exchanger, so if it's covered in muck it will act like a winter coat in the summer! Use something like "Gunk" then wash off with a low pressure hose. DON'T STEAM CLEAN! It's more trouble than it's worth. Make sure that you protect the ignition system when you're doing this! Cleaning the radiator fins will help as well - "Gunk" or something similar is also useful here. But no high-pressure hoses or you can screw up a rad in short order!
2. Replace coolant at the intervals recommended by the manufacturer or before. Ascertain that the coolant is suitable for your car - if in doubt buy original. This is absolutely critical! Make a note of when it should be done by leaving a sticker in a prominent position in the engine bay. Always allow the cooling system to rid itself of air (air locks) before installing the radiator and expansion tank caps. I leave them off overnight to be on the safe side but
don't forget to put them back on the next morning!
3. Replace all your cooling system, heater, bypass, upper and lower radiator and manifold coolant hoses plus any others you come across at least every two years. Your manufacturer may not recommend this but it is always better to be safe than sorry. Just check up on the cost of a head gasket failure on your car!
4. It is essential that radiator and expansion tank caps are replaced with ones having the correct manufacturer pressure settings. I am always wary of aftermarket caps as they don't always seal correctly and will thus lose pressure AND coolant!
5. If and when you replace the thermostat use one with identical settings. This is most important as in today's cars the electronics and mechatronics frequently use the coolant temperature for other important functions - like climate control or cold/warm start operations. As with hoses it's worth changing thermostats using the same time scale.
6. Adjust or replace the drive belt(s) for the water pump at the recommended intervals. Failure to do so can lead to a new engine! If you prefer you may change it earlier as some manufacturers have been know to get their sums wrong! Never overtighten the belt as it can lead to bearing failure which can also be catastrophic. If in doubt invest in the appropriate Haynes manual for your car. This should give you the recommended tension settings. And very importantly always check the belts visually and by feel. If it looks shiny, it's probably slipping and that means it's been subjected to excess heat. Change it now - today; tomorrow may be too late! Also feel under the belt to see if there are any little bits coming away. A wipe with a clean white cloth is a good idea as it will show up any "crumbling". If there is evidence of this, it requires immediate replacement as above.
7. Change your water pump with an original or superior aftermarket one at the first sign of trouble. Initially this can be a slight screeching noise which will grow louder as the bearing failure rate increases. Also check for movement as with a wheel bearing. If you are changing the cam/timing belt and tensioner, it's always worth changing the pump at the same time as much of the work involved is duplicated if the changes are done separately.
8. Fan clutches (viscous) can be problematic and have a limited life. Change it and the fan blades (if required) if you suspect that it's not functioning properly. This is easy to check. If the engine is cold you should be able to turn the fan freely. It's just the opposite when the engine is hot - it should be "locked" in place. Inefficient operation of this is usually shown up by the car's temperature gauge.
9. Diagnosis of correct temperature sensor function is an area for the experts though it is possible to buy software to check this. But it's best left to guys who have the suitable equipment, backup data and diagrams.
10.
This should be a given: - Make sure that your car is correctly maintained in other areas such as ignition timing, idle speed and exhaust system. These can all have an effect on the running temperature of the engine and you should not expect the cooling system to try and compensate for their poor operation. And an occasional look at the temperature gauge (if you have one) is not a bad idea either!
I hope that this is of some help and will keep you off the hard shoulder! It's a really old cliché but it really is better to be safe than sorry. And cheaper too in the long run
Here's to cooler motoring this and every summer - and winter too!
Nullius addictus iurare in verba magistri,
Quo me cumque rapit tempestas, deferor hospes
(c)AntMat@automotiveforums.com
: Not much I can add, other than to say the corrosion inhibitors in the Ethylene Glycol mixes deteriorate, and therefore need that two year change interval. The OAT later long- life types are longer lasting of course. Oh! and the water impeller propels the coolant around the system, often misnamed a water pump! Impellers impel,pumps, pump!
! 
