The Mercedes-Benz CLK W209 came on the market in 2002, when it replaced the previous Mercedes-Benz CLK W208. Although the model is generalized with the code W209, it actually took the code C209 for the Coupé and A209 for the Cabriolet. In 2005 there was a restyling that changed the design of the bumpers, the grille, the taillights and the rims. There were also modernizations in the interior and on the technical level. The CLK model remained on the market until 2009 when it was replaced by the next generation Mercedes-Benz E Coupè W207. Let’s see the Mercedes-Benz CLK C209/A209 review with the most important information, faults and common problems.
Table of Contents
- Impressions and Description
- Reliability and Issues
- Engines and their Problems
- Conclusions and Advice & Tips for buying used
Mercedes-Benz CLK C209 Coupé
Impressions, Interior and Comfort
Mercedes-Benz CLK W209 is an upper middle class model. The second generation CLK-Class is intended to contain the Coupé and Cabriolet versions of the Mercedes-Benz E-Class W211. Despite this however, the CLK is based on the smaller platform of the Mercedes-Benz C-Class W203. It’s basically like putting an E-Class on the platform of a C-Class.
For the coupe of the C-Class W203 however, the Mercedes-Benz C Sportcoupe/CLC CL203 was created. This is not to say that the CLK and Sportcoupe/CLC are the same. In fact, the CLK has been profoundly modified and engineering choices taken from the Mercedes E-Class and S-Class of the same period have been added. Furthermore, the Mercedes-Benz CLK is better in the cabin and also in terms of equipment.
Platform and Body
As already mentioned, the platform of the Mercedes-Benz CLK W209 is the same that we can also find on the Mercedes-Benz C-Class W203. Here, however, it has been improved and modernized with modern technologies that have led to an increase in torsional stiffness and have improved safety. This is a conventional platform for this manufacturer: engine installed longitudinally and rear wheel drive. However, all-wheel drive has never been mounted on the CLK W209, although it is present on the C-Class W203 and E-Class W211.
The front suspension is MacPherson, the rear is multilink.
The body design of the Mercedes-Benz CLK W209 maintains the same style as other models of the manufacturer. Aesthetically it is something between the C-Class and the E-Class of the same period. The aerodynamics are also very good with a Cx of only 0.28. The style is modern and elegant, with a feeling of lightness.
Mercedes-Benz CLK A209 Cabriolet
Aesthetically, the car is attractive, both before and after the restyling, especially in the more equipped versions.
The second generation Mercedes-Benz CLK W209 is available in two body styles: 2-door Coupé (C209) and Soft-top Cabriolet (A209). The German car has a length of 4638 mm, a width of 1740 mm and a height of 1380 mm. The wheelbase is 2715 mm. The weight of the car varies from 1550 to 1755 kg depending on the version.
The manufacturer has decided to make the CLK-Class slightly smaller than the E-Class W211. On the basis of the E-Class, a larger and more luxurious 4-door Coupé was created which took the name of Mercedes-Benz CLS C219. In a sense it can be considered the bigger sister of the CLK.
Comfort and Practicality
Mercedes-Benz CLK can not be called too spacious and practical car. It’s a car for selfish people. The interior space is more than enough for two people to stand in front. If necessary, people can also sit behind. But, in the back seats, tall people may feel insufficient legroom and headroom.
The trunk/boot has a volume of 435 l on the Coupé and 390 l on the Cabrio. Not a great result, but for this class of car it’s good.
The suspensions behave well, they manage to guarantee a good level of comfort. There are also comfortable seats and a comfortable driving position. Thanks to the large number of adjustments, anyone will be able to position themselves correctly. All together it makes the Mercedes-Benz CLK W209 an enjoyable car both in and out of town. Even longer journeys shouldn’t be too tiring.
Interior and Equipment
The interior has a nice design (it is not copied from any other model, but is individual to accentuate the class of the car), good ergonomics and a welcoming feeling. The materials are of high quality and pleasant to the touch. They are also quite resistant. On well-treated cars, there will be no particular signs of wear for at least 100,000 km (60 k miles). Very pleasant is the system that brings the seat belt closer, which gives a further feeling of luxury (the belt is approached by an electric motor to be able to find it more easily).
However, on some elements, serious signs of wear may appear at high mileage. First of all, of course, the most used elements wear out: the steering wheel trim, the gear knob, the climate control buttons and more. At high mileages, wear and tear on the seat upholstery is also unavoidable.
The good part is that all traces of wear and tear present in the cabin can be eliminated if desired. Some pieces can be replaced, others can be repainted or restored.
The soundproofing is very good and the interior remains silent in any situation.
The cars found on the used market are usually very well equipped. You can have leather seats with heating and electric adjustment, automatic climate control, cruise control, light and rain sensors, multifunctional steering wheel, Comand multimedia system and much more. Naturally, the large number of options further increases the pleasure of use.
The multimedia system is not very interesting on Mercedes-Benz CLKs produced before 2005. After this year, it has become more modern and functional. Audio quality is very good.
Safety
In the EuroNCAP safety test, the Mercedes-Benz CLK W209 got 5 out of 5 stars. Crash safety is quite good, but to decrease the risk you need good tyres. Tires are almost the most important thing for safety on the road.
Reliability and Issues
Gearbox and Transmission
The Mercedes-Benz CLK W209 can be equipped with a 6-speed manual gearbox, a 5-speed automatic gearbox (5G-Tronic of the 722.6 series) on the pre-facelift versions and a 7-speed automatic gearbox (7G-Tronic of the 722.9 series) on the restyling.
Manual transmission
The manual transmission is rare and quite reliable. Over time, gear engagement may not be very precise due to wear on the gear selection mechanism. The problem is most often encountered on cars of the first years of production. On the restyling versions the problem has been solved.
If treated well, the clutch can even last 300,000 km (185 k miles). With aggressive use it will obviously live less.
It is useful to periodically check the oil level in the gearbox. By changing the oil regularly and maintaining its proper level, the mechanical parts will live for many miles.
5G-Tronic automatic gearbox
The old 5-speed automatic transmission is the 5G-Tronic of the 722.6 series. It is a very interesting and widespread automatic transmission. It had been mounted on Mercedes for a long time and we can also find it on Mercedes-Benz E-Class W210, Mercedes-Benz E-Class W211, Mercedes-Benz S-Class W220 and others.
In general it can be defined as quite reliable, but in the first years of production it had some “childhood” problems which were then resolved. The Mercedes-Benzes produced before 2000 – 2001 suffered mainly. The already updated version was mounted on the Mercedes-Benz CLK W209 instead.
Due to the partial lockup of the torque converter, the lockup system of the converter can already be found worn out at 150,000 km (95 k miles) on some cars. At this mileage it usually happens on cars with powerful engines or those used aggressively. With quieter use, the torque converter will fail no earlier than 250 thousand km (155 k miles). The first signs of wear will be rough gearbox operation the inability to engage mode “D” until the car warms up. At first the problems only show up when the gearbox is cold, but as the situation gets worse they will also feel when the gearbox is hot.
After 150 – 200,000 km (95 – 125 k miles), in addition to overhauling the torque converter (due to the wear just mentioned), it may be necessary to change the solenoids and clean the hydraulic block where accumulations of dirt could be found if the oil has not been replaced regularly. For the same reason, the control board can also suffer and the speed sensors can fail. Many do not replace the gearbox oil at all and as a result its life is shorter than in gearboxes on which it is replaced regularly.
One of the most important things is to change the oil every 40 – 60,000 km (25 – 35 k miles) together with the filter. This will improve the operating conditions and therefore lengthen the life of the unit. If the gearbox breaks down, the cost of repairs will be large. If treated very well, it can even go 200 – 300,000 km (125 – 185 k miles) without major problems.
7G-Tronic automatic gearbox
After the restyling came the 7G-Tronic (722.9 series) 7-speed automatic transmissions that is much less reliable, but it’s much faster and helps save fuel.
Even this gearbox in the first period of production suffered from many “childhood” problems. However, this only applies to transmissions of initial production. Over the years, it has been repeatedly modernized and improved, so over time it has become more reliable.
One of the most famous weaknesses of this gearbox is the flimsy hydraulic block. Furthermore, these units can tend to overheat and the torque converter could not last very long. High operating temperatures ruin the electronics, solenoids and hydraulic block. The first interventions may be necessary even after 100,000 km (60 k miles).
As already mentioned, the complex electronic system suffers greatly due to the high operating temperatures. On the other hand, modern electronics offer the possibility of diagnosing the gearbox well. A good mechanic will be able to discover many problems just by connecting the computer and reading the various parameters.
The torque converter locks up very aggressively (acts almost like a wet clutch) and is almost always at least partially locked. This causes accelerated wear of the locking system. As a result, due to heavy wear, the oil becomes heavily soiled with wear fragments. Dirty oil can lead to the destruction of the oil pump (it can even happen at 100,000 km or 60 k miles) and accelerated wear of the entire unit.
As already mentioned, over time the 722.9 gearbox was updated and the situation improved. There have been recalls intended to fix the problems. In general, gearboxes manufactured after 2009 are more reliable. Better to buy a car with this gearbox only if it has participated in recalls or the previous owner has already modernized/repaired the gearbox. Otherwise it will almost certainly be up to the new owner to fix the gearbox.
The mechanical parts of this gearbox are well made and shouldn’t cause problems if you don’t drive with damaged hydraulic systems and if you pay attention to the quality and quantity of oil. Mechatronic can break, especially if the oil is not changed regularly. The symptoms of this problem are: difficulty downshifting, error message, gearbox in limp mode or complete blockage of the car.
A modernized 722.9 automatic transmission can live for many miles if well treated. To lengthen life, it is advisable to replace the oil regularly, fit a lower temperature thermostat, add a large heat exchanger and add an external oil filter. These recommendations are ultimately useful for any modern automatic transmission (they are all quite overloaded).
Drivetrain and Transmission System
As already mentioned, Mercedes-Benz CLK W209 can only have rear-wheel drive. With quiet use there will be no problems up to high mileage. The cardan shaft (drive shaft) lives at least 150 – 200 thousand km (95 – 125 k miles), the rear differential and the axle shafts only need periodic checks, maintenance of the correct oil level and protections in good condition.
Periodically it is important to check the drivetrain and see if there are any oil leaks. If the quantity and quality of oil in the various mechanisms is in order, everything will work for many miles.
Suspensions, Steering and Brakes
The suspension of the Mercedes-Benz CLK W209 has a simple and quite reliable structure.
The rear suspensions are resistant. Among the most common problems we mention those with springs that can break. On the front axle on the other hand, the elements are not so long-lived. The arms live about 50 – 100,000 km (30 – 60 k miles) on bad roads.
The silent blocks and stabilizers wear out quickly and the suspensions begin to rumble. Also, a loss of stability on the road will be felt. Cars equipped with large and heavy engines may have problems even every 30 – 50,000 km (20 – 30 k miles).
Over time there have been various modernizations that have improved the strength of the suspension.
Steering system
The steering rack is quite durable overall. Over time it may begin to leak and tend to make noises. It’s better to keep it in good condition since it costs so much. It is necessary to intervene and repair it after the first signs of wear.
The power steering pump can also stop working. When this happens, the steering wheel becomes heavy and has difficulty returning to the central position.
Brakes system
The brakes are effective and reliable. They are criticized for the small duration of the discs. This is not the fault of the discs themselves, but of the various safety systems that interact with the brakes. Because of this, the duration can be even half of what it should be. Obviously wear is accelerated if you have an aggressive driving style.
Electronics and Electrical System
The electronic system of the Mercedes-Benz CLK W209 is well done. As long as the car is still new, there must be no serious problems with the electronics, unless due to external factors. Among these we have: water infiltrations that come into contact with control units or cables, accidents that damage the system or interventions by unqualified people on the electronic system.
However, this model is not exactly new. Over the years, some problems may appear even for no particular reason.
The situation is very critical if the SAM control units are damaged in any way (for example if they come into contact with water). These have a central role and allow communication with the other control units and sensors scattered around the car. When a SAM ECU dies, it can also damage the other elements connected to it.
In addition to the SAM control units, there are also many other control units that control the large amount of systems. Virtually everything contains electronics. To understand the complexity, we can give the example of the wiper control unit which can lose its management firmware or be damaged in any other way. After replacement or repair, the ECU must be reprogrammed with the official Star Diagnose tool.
Complicated electronics (especially on heavily equipped cars) can start to “go crazy”. There are many small problems that could appear and they are different on each car. In most cases these do not completely prevent the use of the car, but they can annoy a lot.
Failures of alternators, ignition coils, parking sensors, xenon headlight ignition modules, body level sensors and other “trifles” can happen. Over time there may also be problems with the cables under the hood. Sometimes the ABS control unit may stop working. Light bulbs don’t always have a long life.
Before a possible purchase it will be useful to carry out a deep diagnostics, check the functioning of all the systems present, check the cables and their integrity (especially in critical points such as the doors) and look at the SAM control units. If you see traces of oxidation or humidity, it’s best not to risk it.
During the cold period of the year there can also be false alarms. For example, the ASR, BAS and SRS warning lights may come on. Generally it is enough to turn off the ignition for a few minutes and everything will be solved.
Electronics malfunctions can cause current leaks that completely discharge the battery even after a short stop.
Other
The corrosion resistance of the Mercedes-Benz CLK W209 is good, but not perfect. The situation has improved compared to the previous generation, but over the years the problem still becomes annoying. The same goes for the paint which is not very resistant on the cars produced in the period 2002 – 2004. Over time the situation has improved in both respects.
This is a common problem among models of that period. We have already talked about it in the article on the Mercedes-Benz E-Class W210, on the Mercedes-Benz E-Class W211 and also in the one on the Mercdes-Benz S-Class W220.
Be that as it may, only small traces of rust are acceptable on cars used in places with a particularly severe climate. If, on the other hand, the traces of rust are large, the car probably suffered some accidents and then was badly repaired.
Before buying a used car, it would be good to check the body well and see if there are any traces of rust in the welding points and under the car.
Engines and their Problems
Diesel engines list :
| Version | Engine | Power | Top Speed | Acceleration | Fuel Consumption |
| CLK 220 CDI | 2.1 l OM646DE22LA | 150 hp | 221 km/h or 137 mph | 10.2 s | 6,4 l/100 km
US: 36,7 mpg UK: 44,1 mpg |
| CLK 270 CDI | 2.7 l OM612DE27LA | 170 hp | 230 km/h or 142 mph | 8.6 s | 6,6 l/100 km
US: 35,6 mpg UK: 42,8 mpg |
| CLK 320 CDI | 3.0 l OM642DE30LA | 224 hp | 246 km/h or 152 mph | 8.2 s | 7,2 l/100 km
US: 32,6 mpg UK: 39,2 mpg |
Petrol/Gasoline engines list :
| Version | Engine | Power | Top Speed | Acceleration | Fuel Consumption |
| CLK 200 Kompressor | 1.8 l M271E18ML | 163 hp | 237 km/h or 147 mph | 9.3 s | 8,8 l/100 km
US: 28 mpg UK: 33,6 mpg |
| CLK 200 Kompressor | 1.8 l M271E18ML | 184 hp | 230 km/h or 142 mph | 9.3 s | 8,7 l/100 km
US: 28,6 mpg UK: 34,4 mpg |
| CLK 200 CGI | 1.8 l M271DE18ML | 170 hp | 231 km/h or 143 mph | 9.2 s | 7,8 l/100 km
US: 26,1 mpg UK: 31,3 mpg |
| CLK 240 | 2.6 l M112E26 | 170 hp | 236 km/h or 146 mph | 9.2 s | 10,8 l/100 km
US: 21,9 mpg UK: 26,4 mpg |
| CLK 280 | 3.0 l M272E30 | 231 hp | 250 km/h or 155 mph | 7.4 s | 9,2 l/100 km
US: 22,2 mpg UK: 26,6 mpg |
| CLK 320 | 3.2 l M112E32 | 218 hp | 244 km/h or 151 mph | 7.9 s | 10,5 l/100 km
US: 24,5 mpg UK: 29,4 mpg |
| CLK 350 | 3.5 l M272E35 | 272 hp | 250 km/h or 155 mph | 6.4 s | 9,9 l/100 km
US: 23,5 mpg UK: 28,2 mpg |
| CLK 500 | 5.0 l M113E50 | 306 hp | 250 km/h or 155 mph | 6 s | 11,5 l/100 km
US: 23,5 mpg UK: 28,2 mpg |
| CLK 500 | 5.5 l M273KE55 | 388 hp | 250 km/h or 155 mph | 5.2 s | 11,5 l/100 km
US: 22,8 mpg UK: 27,4 mpg |
| CLK55 AMG | 5.4 l M113E55 | 367 hp | 250 km/h or 155 mph | 5.2 s | 12,1 l/100 km
US: 24,2 mpg UK: 29,1 mpg |
| CLK63 AMG | 6.2 l M156E63 | 481 hp | 250 km/h or 155 mph | 4.6 s | 14,3 l/100 km
US: 22,6 mpg UK: 27,1 mpg |
| CLK63 AMG Black Series |
6.2 l M156E63 | 507 hp | 300 km/h or 185 mph | 4.2 s | 15,4 l/100 km
US: 20,4 mpg UK: 24,5 mpg |
| CLK DTM AMG | 5.4 l M113E55 | 582 hp | 320 km/h or 198 mph | 3.8 s | 14,5 l/100 km
US: 20,4 mpg UK: 24,5 mpg |
Diesel Engines
The diesel engines showed up quite well. These can be 4-cylinder (2.1 l CDI OM646), 5-cylinder (2.7 l CDI OM612) and 6-cylinder (V6 3.0 l CDI OM642).
2.1 l CDI OM646 diesel Engine
The 2.1 l CDI engine (also known as 2.2 l CDI) featured here is from the OM646 family.
The 2.1 l diesel engines are quite reliable and basically they don’t have any particular weaknesses. The fact is that by now they are all of a great age and generally also great mileage, so it is almost inevitable to encounter some annoying problems as well.
At high mileages the injectors and the high pressure injection pump could cause problems. There are cases where it is difficult to disassemble the injectors if this work has not been done for a long time. Sometimes, to take them apart you have to damage the cylinder head. A faulty pressure regulator in the injection system can also lead to misfiring or erratic operation.
On cars with a manual gearbox, the engine often spins at low revs under load, so difficulties may appear with insufficient oil pressure. This can lead to the failure of the bushings with subsequent deformation of the cylinder block and other similar problems. It happens more often on commercial cars with this engine, but here, too, it cannot be ruled out.
You may encounter engines with oil leaking from under the cylinder head. The EGR valve and intake manifold can become clogged with soot and this will lead to a loss of power and increased stress on the engine.
Otherwise, these are very robust aggregates. Paying attention to the aspects indicated above, the engine can even reach 500,000 km (310 k miles) without fatal failures.
2.7 l CDI OM612 diesel Engines
The 2.7 l CDI OM612 is an interesting 5-cylinder in-line engine which is very reliable and resistant.
The OM612 series engine has good power and does not cause many problems. Over the years and the miles passed, the plastic elements could crack and the rubber elements of the crankcase ventilation system wear out. Leaks can be seen due to wear on the engine gaskets.
The timing chain lasts at least 150,000 km (95 k miles). However, under certain conditions, even 300,000 km (185 k miles) can be exceeded with the original chain. Its duration depends on several factors. The most important is proper maintenance, with oil change intervals that are not too long.
You can rarely have problems with the cables under the bonnet and there are cases in which the block head cracks. It may also have small problems with some sensors, but everything can be easily resolved.
It will be best to keep an eye on the intake manifold. If this is in bad condition, it can be destroyed and cause damage to the engine. A new intake manifold has an acceptable cost.
You also need to pay attention to the injection system. There are engines with dirty injectors, but this is solved relatively easily. Fortunately, the mechanics are now familiar with these systems and have no problem repairing them. These, without much effort, will be able to solve the problems of the pressure regulator or the fuel leak from under the injectors. If the latter problem is not solved in time, the cylinder head will burn out.
3.0 l V6 CDI OM642 diesel Engines
The OM642 3.0 L CDI V6 engine is a well made engine, it has been produced for many years and has received great popularity.
The OM642 6-cylinder diesel engine mounted on the CLK 320 CDI versions will be a good choice. This 3.0 l was Mercedes’ first diesel V6. It is a modern and complex engine, with an aluminum cylinder block and cast iron liners, aluminum heads with hydraulic compensators, a complex Common Rail injection system with piezoelectric injectors, a turbine with variable geometry and much more.
Of course, the great complexity also increases the number of possible problems and defects. At large mileages you must be prepared for the expensive repair of the injection system, turbine and intake manifold. Timing chain lengthening is almost inevitable after 200 – 250,000 km (125 – 155 k miles).
Among the most famous problems that can happen at smaller mileages are leaking heat exchanger gaskets. New parts are cheap, but due to the inconvenient location, replacement work will be expensive.
Engines with heavy oil leaks are encountered. Plus, the oil pump isn’t too reliable. Both of these aspects must be kept in mind, the engine cannot handle oil pressure losses well and in these conditions the bushings can fail.
Otherwise the OM642 engines are still very reliable. Thanks to their good characteristics in terms of power, reliability and consumption, they have been mounted on many models of the brand. Knowing the weak points and taking care of these units, it is possible to reach even 450,000 km (280 k miles) without fatal defects. Badly treated engines, on the other hand, will give serious problems already at 200,000 km (125 k miles).
Common problems of diesel Engines
Modern diesel engines equipped with anti-pollution systems can have the usual problems with the EGR valve getting dirty and stopping working and the DPF filter getting clogged and giving problems.
Petrol/Gasoline Engines
Petrol/Gasoline engines can be 4-cylinder, 6-cylinder and 8-cylinder.
Before the restyling the V6 and V8 petrol engines fitted were of the M112 and M113 series. Later came the new engines of the M272 (V6) and M273 (V8) series. Only the larger 6.2 l V8 AMG is from the M156 series. The 4-cylinder engines are from the M271 series.
1.8 l M271 Engine
The 1.8 l M271 engines are modern and complex, with an aluminum cylinder block and cast iron liners, they are equipped with an Eaton mechanical compressor, timing chain, phase variators and balancing shafts. They are compact, lightweight aggregates that consume little and offer relatively good power. The bad part is that complexity can lead to big maintenance costs.
The timing chain and camshaft gears almost always wear out already at 100 – 150,000 km or 60 – 95 k miles (in some cases even at 60,000 km or 35 k miles).
The signs that the chain has stretched are: loud noise for a few seconds when starting the engine, irregular running of the engine and engine failure warning light on. Camshaft sprockets generally wear only if you continue to drive with a stretched chain, so you can avoid this problem by replacing it early. The replacement of the gears also involves the replacement of the phase shifters and the costs are very high. Even the phase shifters themselves do not demonstrate great reliability, have a fragile structure and are particularly sensitive to poor maintenance.
A chain that is too stretched could also slip and cause pistons and valves to crash. If this happens, in the worst cases the damage is so serious that it is now advisable to change the engine. A used engine in good working order may cost less than repairing the defective engine.
The mechanical supercharger, due to the large noise, could hinder the diagnostics of the stretched timing chain. Unfortunately the chain stretch problem occurred on both newer and older cars.
The mechanical compressor itself has a good life. If it starts rattling, it’s most likely time to change the bearings. Better not to wait too long, otherwise you risk breaking the compressor itself.
On these engines of the first years of production, there may also be problems with the crankcase ventilation system (the valves of the system get stuck and the pipes get dirty). It is a defect that should not be underestimated, in the worst cases it can lead to serious damage. It has been improved over time, so you can also fit the modernized system which is much better.
For the rest it can be said that the 1.8 l M271 are quite reliable and robust. With correct use, they can live even more than 300,000 km (185 k miles) without fatal failures.
M112 and M113 Engines
Of the large M112 family, only the 2.6 l and 3.2 l engines are mounted here. The 5.0 l and 5.4 l are mounted from the M113 family. The problems are about the same for all of these engines.
Among the 6 and 8 cylinder petrol engines, the most reliable are those of the M112 and M113 series. They are robust and long-lived units, but obviously they are not ideal.
Over time, the extended timing chain and the intake manifold will need to be changed (around 200,000 km or 125 k miles). The same goes for valve stem seals and other worn seals. Crankshaft pulley failures are frequent.
Engines may have problems with crankcase ventilation and piston rings. These little problems can lead to an increase in oil consumption. Also there may be oil leaking from under the valve cover and from the oil cooler. To have a leak-free engine it is important to periodically replace the gaskets and clean the crankcase ventilation system. Furthermore, it is advisable not to increase the engine revs up to the red zone of the rev counter.
These engines generally do 250 – 300,000 km (155 – 185 k miles) without major problems (when used and treated correctly). Among the weakest parts we can mention the catalytic converter which over time could cause problems and need to be replaced. For the long life of these engines it is advisable to change spark plugs and oil regularly.
M272 and M273 Engines
The 3.0 l M272 and 3.5 l M272 engines are mounted from the M272 family. The 5.5 l is mounted from the M273 family. The problems are about the same for all of these engines.
After the restyling, the reliable M112 and M113 engines were replaced by the new M272 V6 and M273 V8. In theory, the engines of the new series should have been better, but in fact they turned out to be just as greedy in terms of consumption, they have a little more torque, but at the same time they are much more expensive to maintain and have many weak points.
These engines may have problems with the ECU. The reason for the malfunctions of the control unit are the high temperatures under the hood which lead to a loss of impermeability and consequently oxidation. Driving with a malfunctioning control unit can also cause damage to the mechanical parts of the engines which are quite fragile.
Other weak points of the petrol engines of the M272 and M273 series are: small longevity of the mechanical parts, short-lived timing system and its high cost, problematic intake manifold, weak catalytic converter, occurrence of oil leaks and the risk of occurrence of scratches on the cylinder walls.
If the timing chain is not changed at the right time, there is a risk of damaging the balancer shaft on V6 engines and the chain pads on V8 engines. To change the balancer shaft, the V6 engine will have to be extracted. To replace the pads on the V8, you will need to disassemble the cylinder head. In both cases the cost of the works will be very high.
The entire timing mechanism must be replaced if there is wear on the balancer shaft gears on V6 engines and on the idle gear on V8 engines. On some engines this can happen as early as 100 thousand km (60 k miles).
There are problems with the electromagnets that control the operation of the camshafts and the intake manifold.
Furthermore, overheating can occur due to a dirty cooling system and broken fans. All of this can lead to detonations and damage to the cylinder walls which in turn lead to oil consumption. A consumption of around 1 – 2 liters per 1000 km (600 miles) can be reached. This consumption is also accompanied by a more or less evident smoke. The easy appearance of scratches is given by the use of Alusil as a material for the surface of the walls. Alusil does not tolerate any kind of dirt. To avoid problems you need to change the oil often, avoid overheating and avoid driving with dirty air filters, worn catalytic converters or intake manifold.
For some interventions it is necessary to extract the engine from the car and this considerably increases the cost of the works. These engines have also brought many problems to the owners of Mercedes-Benz S-Class W221 and Mercedes-Benz E-Class W211.
They don’t have only negative points though. They are more ecological (they comply with the Euro 5 and some even Euro 6 regulations), they have slightly better performance and the newer (more modernized) engines, if treated very well, can also reach large mileages without major problems.
M156 Engines
The M156 series engines are those mounted on the CLK 63 AMG sports versions. These are sports engines that are not exactly very reliable. In fact, American buyers have denounced the brand twice, complaining of the insufficient reliability of these engines.
The big engine fitted to the AMG sports versions is fun and interesting. If treated well and cared for carefully, it could even live for a relatively many miles.
The problems are given by the use of unsuitable materials in some points, which lead to a loss of resistance (for example in the case of the camshaft). In addition, scratches on the cylinder walls can appear on these engines over time. Even the cooling system is not effective enough for this big engine, especially in summer.
Conclusions and Advice & Tips for buying used
Mercedes-Benz CLK is a car that can give a lot of satisfaction and pleasant emotions. It is suitable for entertainment or for people who do not carry many passengers.
Conveys a feeling of luxury and individuality. In the right version, it will also be very reliable. It’s not a very popular car and can still attract attention.
The main competitors of the Mercedes-Benz CLK W209 are: BMW 3 Series E46 Coupe, BMW 3 Series E92, BMW 6 Series E63/E64, Lexus SC, Audi A4 Cabrio, Audi A5 and other cars of the same type.
The most important thing is to find a car in good general condition.