Power Steering

Brakes and their relative components are always a plenty at scrapyards and well priced. Steering racks, pumps and steering boxes are usually the steering parts that get the most money for any scrapyard dealer, so expect to pay a little more for good steering parts and components

Don’t touch a steering rack if it has been involved in a front-end crash or collided with a pavement. You can’t be mistaken if you are viewing the vehicle at the scrap yard, the wheels will tell you a story by the way they are facing. If possible check if the steering wheel turns the front wheels ok.

If one comes off the shelf make sure the tie rod ends are not bent and the housing is not damaged. The steering shafts that travel up and down inside the steering rack housing are prone to leak very easily if anything is even slightly distorted. This is like measuring a piston with a mic, you can’t always see the fault with the naked eye.

If you do purchase a second hand steering rack and pinion have it checked by a professional brake and steering shop. They have specialise and have the right equipment to detect the slightest leak that will only become apparent once the steering rack is fitted, you will more than likely be buying into troubled waters, not to mention that you would be putting peoples lives at risk. A steering rack ior steering box is not an easy item to remove and refit although it may look easy, its not.

Steering racks, steering boxes and the pumps are a specialist field and best left to the guys that do this finiky job every day. I have tried reconditioning steering racks in my day with very little success. It’s pretty much like stripping 100 different gearboxes; it’s a whole new learning curve. My advice to anyone reading this, contact the experts that have been in the business half their lives like the pros at Brake and Steering, they will give you good sound advice and point you in the right direction. They also collect and deliver and are a nationwide setup.

Cylinder Heads and Pistons

For many years cylinder heads were made from cast iron and still is used for most diesel engines. However, in the 60’s aluminium took over, initially for it’s superior heat conductive properties, but these days also to reduce engine mass.

When you are looking to buy a cylinder head there are also important criteria to consider. Firstly you have the option of buying a cylinder head on an exchange basis with a guarantee. There are many exchange shops around that offer cylinder heads on an exchange basis. The cylinder head is a part on a motor vehicle that is vulnerable to drastic heat exchanges within an engine.

Cylinder heads are the first components that will let you down if you abuse them and this I mean they don’t like drastic changes in temperature all round. An engine is designed to run at between 80-89 degrees C and any more for a long period usually results in a blown cylinder head gasket if you are lucky and only get away with the head being skimmed and refitted with a new cylinder head gasket.

The not so lucky will endure the pains of replacing the cracked head with another one. Extreme overheating can also cause the block to crack or a combination of the two. Head and block sealer is an additive that can be used to temporarily seal a fine crack and maybe get you home. I have driven with head and block sealer from Harrismith to JHB without loosing too much water and only just made it home. Read the instructions carefully. The contents of the tin must be administered in a certain way for best results.

For the not so fortunate a cracked head is the result once it is determined by a compulsory pressure test. To have a pressure test the cylinder head must be removed from the sub assembly. I have witnessed desperate clients pleading to have the head stitch welded and machined. These guys usually take drastic measures only to sell the vehicle to some poor individual that buys it thinking he got a good deal on the car or bakkie, only to walk in weeks later with the same piece of junk and place it on the counter. When you see this go down you can only pitty the man and advise him accordingly.

Thermostats

Most modern day cylinder heads are all made from alluminium alloys, although most diesel engines still come with cast iron castings for the cylinder heads. Heads don’t like the heat to soar over the desired operating temp limit when driving so make sure your thermostat is replaced at regular intervals. Years ago I discovered and pointed out a faulty batch of thermostats supplied by Landrover.

We fitted one to a 4 cylinder turbo diesel that we had remanufactured the (head, block and sump), for a Landrover dealership. The vehicle overheated and had to be towed back from Central Africa somewhere. I couldn’t believe that a new engine we had remanufactured could overheat and seize. My gut feeling told me to remove the thermostat on inspection. If you place a cold thermostat in a kettle you will see it start opening before the kettle reaches boiling point, this one remained closed. The result was, we were off the hook and Landrover SA discontinued the batch of thermostats.

When overheating an engine not only do the cylinder heads become stressed, but the pistons also made from aluminium alloy collapse, distort and shrink slightly. The change cannot be detected with the naked eye but when measured with a micrometer these changes are magnified. An example would be a new piston measuring 91.88mm to fit a std bore of 92mm should not collapse more than anything under 3 hundredths of a millimeter. With a standard piston to bore clearance of 2 hundredths of a millimeter this would mean the piston to bore clearance is now borderline at 5 hundredths of a millimeter, providing the bore is still standard and ‘on size’, (give or take another 100 th of a millimeter for bore wear), and its over the top.

This is the limit and experience has show that any more than this, results in an engine that uses oil and will show signs of loss in power. In most cases severe overheating will cause the rings to glaze the bore and collapse, thus loosing power due to the tension loss in the spring qualities left in the piston rings. Rings also tend to seize within their ring grooves of the piston due to the lack of spring tension forcing themselves outwards against the bore of the sleeve and sometimes break the ring land. You will immediately notice a nice constant stream of smoke emitting from your exhaust as you drive and guess what, your sub assembly will now have to be removed to replace the pistons, which ultimately means it’s time for an engine change or complete engine overhaul.

My advise is not only replace your thermostat on a regular interval but change all your hoses when they have reached the 100,000 km mark and always fill the radiator with at least 50%, good anti freeze-anti boil additive.

Viscous Fan Coupling

Another cooling component that is most often overlooked is the viscous fan coupling or clutch fan coupling. It is important to understand how it works. This component is probably responsible for more engine failures than any other cooling part on a vehicle simply because it’s failure is so gradual and unnoticeable. I have seen guys build up a new engine and not bother to replace the viscous coupling. Manufacturers fit them to most model cars and trucks as they are fuel savers and they allow the engine to produce more power. A fixed fan will also drain horse power from an engine powerplant.

The viscous fan is free to turn on it’s axis as the motor revs. In other words the engine RPM and the viscous RPM differ in their speed of rotation. It is designed to start locking-up at round about the time the engine reaches it’s desired temperature range which is controlled by the thermostat. The thermostat actually controls the viscous fan in principal because it regulates the engines expected temperature range. As the radiator cools the hot water from the engine, the thermostat allows only enough water in at a time, keeping the water at a constant temp within the head and block. The viscous coupling will then only engage again once the temperature rises again.

The problem arises however when the viscous comes to the end of it’s life span which is difficult for most people to understand because it always appears to be spinning in time with the engine revolutions. There is only one way to check it and that is when it is cold, on start up in the morning. You will hear the distinct rush of air as you rev up the engine. This noise will then fade away and quieten down completely after a 30 seconds or so. Watch the temperature climb on the temp guage, listening all the time. Once the temp reaches the half way mark after a few more minutes, the viscous fan coupling will reengage itself and you will again hear the wooosh of air being propelled through the fan blades as you rev the motor.

This indicates that the viscous coupling is working. If the temp guage reaches the half way mark and I mean, not a hair over the half way mark and the guage keeps climbing over the half way mark then you know it’s time to replace the coupling. They don’t come cheap so what a lot of guys do is remove them and fit solid fans adaptors. The problem with these are that when the vehicle attains a speed of lets say 110 km/h the fan reaches a static condition whereby the fan actually slows down the air flow through the radiator. Fixed fans are fine for round town vehicles that don’t exceed this kind speed. They are however very reliable in that they never give up sucking air and are great for traffic congested driving as they are constantly working whereas a viscous coupling only starts to really work when it gets to the desired operating temperature.

OIL PRESSURE

The Idiot Light

I have seen many a motorist drive his or her vehicle regardless of any warning signals. Even when the red light on the dashboard comes on they still keep on driving as if the light were a disco light. This light is often referred to as an ‘idiot light’, the red one with the outline of an oil can on it, it’s unmistakable, you can’t miss it, it’s bright red and red means stop. You should pull over and immediately switch off the car. Get a tow truck, no matter where you are; the costs incurred will leave you flat broke and carless for weeks unless you have a Motorite Insurance policy.

Oil pressure failure is usually attributed to a faulty oil pressure switch, a loose or severed wire and ultimately oil pump failure or a lack of oil channeled through to a particular part of an engine. Sometimes one of the oil channels gets a particle usually like a dislodged piece of matter large enough to partially block the oil channel causing the flow of oil to drastically slow down to a particular area of the engine. This may stop oil flow to a single crankshaft journal for instance and cause the crank bearing to seize thus damaging a big end or main bearing journal on the crankshaft.

Why a piece of debris can become lodged or dislodged is besides all logic if the engine was assembled by the original manufacturing engine builder at the assembly plant, but these things can happen, no one is perfect. Usually one would expect the oil filter to filter everything that passes through it. Change your oil and oil filter every 10,000 km’s without fail. Oil is the life of an engine so use good multi-grade engine oil. Filters can be purchased at your local motor spares shop. Here you can purchase excellent quality filters and engine oils.

Determining Mileage when buying an Engine or Gearbox

The suppliers of used parts should try and enlighten their customers as to what type of mileage the accident damaged vehicle had on the instrument cluster if the vehicle has not been stripped yet. Although most new vehicles have digital clocks nowadays it is hard to determine the amount of kilometers the vehicle has traveled in its day.

This is always a sore point when buying from a scrap yard or used parts dealer. The battery is always dead and the guys selling the engine or gearbox have no inclination whatsoever to fit a battery with spark and check for mileage, but most don’t mind if you have a try under their supervision. It’s always clear to see if the wiring harness battery terminal has been severed. Sometimes the fire and rescue teams at the scene of an accident will cut the battery terminal to prevent an electrical short which can cause the vehicle to go up in flames, especially when there are injuries and a threat to life.

This has happened to the poor bloke towing the vehicle away from the scene of the accident who has had to contend with not only his tow job burning out but his tow truck also goes up in flames if he doesn’t have a suitable fire extinguisher! This guy did.

If you are laying out big money and have your heart set on something then have a go at fitting a battery, you may be pleasantly surprised at what you find on the instrument cluster kilometer reading if it all comes to light. But you can usually tell what sort of k’s a vehicle has done.

Kilometers vs Rands When Buying 2nd Hand Parts

I always put a little pressure on the used part salesman over the phone in this way when it comes to buying an expensive gearbox or engine, it’s a big sale for them and for you, and knowing in your heart if the kilo’s are low, like 55000 km’s on a late model Mercedes Benz ML 500 for example, you’ve got a great deal and must seriously not waste any time because those engines and gearboxes fly out the shop within a week. You could be looking at an engine with 155000 km’s on the clock! Generally you pay a bit more for the newer stuff with the least kilo’s. If the particular engine or gearbox you are purchasing is complete with the turbo charger, turbo intercooler, wiring harness and computer boxes etc. and have suffered little damage, especially when the vehicle has been rolled and not been in a head on collision, you have found an absolute gem.

Insurance assessors write these accident damage vehicles off and then they land up back on the road? I always like to punt on the ones still in the twisted vehicle. An engine or gearbox on the floor is like a horse with no name. Unless proof can be produced, steer clear of these items unless you are buying for resale purposes only. Always make sure that the engine at least turns over and check for excessive rust, some vehicles can stand in the rain for weeks at a time without any cover to the engine components that have been damaged and water will find its way in, and this will result in a complete engine rebuild.

One thing is for sure, the kilo’s on most cars are stamped and registered on the service book and computer database and can always be tracked back to the dealership where it was serviced. This would take some doing, so long as you’ve got the time and resources to do the spadework. If you are buying for keeps look for the number plate number or check for the number on the licence disc, then do it, as this exercise will allow you to sleep better at night.

‘Blueprinting’ is without question the most used and abused term in engine building. In a very strict sense, every engine is blueprinted. By what we simply mean that before an automaker introduces a new powerplant, the design engineers must transfer their ideas into drawings that will guide the pattern makers and tooling specialists. But this is an imperfect world, and not every component that falls off the end of the assembly line meets the engineer’s exact specifications. Drill bits and machine tools become dull. Grinding stones wear out. Gauges don’t always read properly. Lathes run untrue, and mills flex.

In any piece of machinery as complex and complicated as the internal combustion engine, all these inaccuracies add up. Sometimes the mistakes cancel each other out, and the finished part is just what the original blueprints called for. More often, they combine to produce a component that is often somewhat less ideal.

An assembly line is no place for a perfectionist. The vehicle manufacturers are willing to accept parts that are ‘almost right’ or ‘pretty close’. There has to be a reliable means of determining whether the part is ‘close enough’, and that’s what a tolerance figure does.

Which brings us back to the blueprints. All the critical dimensions are assigned to tolerance. Some tolerances are more critical than others. Machine tools and their operators occasionally have bad days. When this happens the problem of tolerance stack-up against the process. It’s possible for the individual machine operations to be within tolerance, yet the final part may be far out of spec. In many instances the acceptable tolerances cover such a wide range, it’s a wonder that any production engine is able to live a long and a productive life and yet millions do. Engines have an amazing tolerance for abuse.

The most basic form of blueprinting, then, is simply making sure that all of the factory tolerances fall within factory specifications. In the eyes of most knowledgeable enthusiasts, blueprinting an engine means not only checking clearances but correcting them as well. Careful blueprinting demands that the engine builder pay attention to how the hundreds of parts in an engine all work together. The engine builder must then recognize that changing one component has an effect on many other pieces. The term ‘blueprinting’ embraces a tremendous range of engine building skills. Even the most competent and professional engine builder continually discovers new tricks and techniques that will make his motors more powerful and more reliable.

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