Mercedes SLK R170 Buyers Guide


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Jan 25, 2014
Nuneaton, Warwickshire
Lots of Mercedes!
Hi All,

Over the years I have written some buyers guides for the popular magazines. I thought they may help here.

I hope these is no issue with that.

If there is anything wrong, please dont hesitate to correct me. The final printed versions were heavily scaled down by the magazines. These are my raw words and my opinions based on my experience only.


[FONT=&quot]- [/FONT]The mechanicals of the SLK are very similar to the W202 C- Class. The W202 was one of the most reliable cars Mercedes have made in my opinion.
[FONT=&quot]- [/FONT]All engines are timing chain driven in this range. Reported issues with timing chains are low, however we have seen timing chain issues with the M111 engine which is the engine code for the SLK200 and 230 engines. Most issues are down to either tensioners failing or lobes on the drive sprockets wearing down, causing slipping of the chain. Early stages should cause the engine warning lamp to illuminate bringing up a fault relating to timing such as “camshaft position fault” or similar.
[FONT=&quot]- [/FONT]On the M111 engine, The variable timing gear is prone to issues. If there is a rattle when the engine is revved, this indicates an issue with the timing advance mechanism. This could be down to a failing magnet, a relatively cheap fix, or it could require replacement of the complete timing adjuster mechanism, which is over £1000 job if using new parts.
[FONT=&quot]- [/FONT]We have had many issues in the past of engine lights illuminating. When fault code is read it points to an intake air leak or mass airflow sensor issues. This can be as simple as a perished hose, or can require intake manifold stripdown to find the fault. In some cases a modified air intake is required to relocate the Mass Airflow Sensor. This modification is reported to provide around 4-5 bhp improvement as well as fixing the issue discussed above.
[FONT=&quot]- [/FONT]If the Mass Airflow Sensor is faulty, these are over £200 for a good after market replacement. Never be tempted by cheap pattern parts as they simply don’t last. A failing MAF sensor is normally indicated by the car exhibiting a very sluggish acceleration.
[FONT=&quot]- [/FONT]The cam magnet mechanism can leak engine oil into the wiring loom. Capillary effect causes the oil to travel into the ECU. This will cause a misfire. The cure is a modified piggyback loom from Mercedes which has an oil blocker built in. The magnet housing should also be resealed. The loom is very cheap at around £20, but labour for cleaning all the oil out of the ECU and wiring could take a few hours. In severe cases the oil could cause permanent damage to the ECU requiring replacement.
[FONT=&quot]- [/FONT]Otherwise, the M111, which is the most common SLK engine, has very few major issues.
[FONT=&quot]- [/FONT]If the check engine light it on, or worse, someone has obscured it, investigation should be carried out before purchasing.
[FONT=&quot]- [/FONT]The 320 engine is fantastic, smooth and powerful. There are very few reported issues with the M113 engine. The only real common issues are leaking camshaft covers and failed crank position sensors. Neither are major issues and could be considered routine maintenance.
[FONT=&quot]- [/FONT]Transmission Service is recommended at around every 40K miles. An independent will charge around £200-300 depending on transmission type.
[FONT=&quot]- [/FONT]Coolant Renewal is due every 3 years, around £80 at an Independent.
[FONT=&quot]- [/FONT]Brake Fluid Renewal is due every 2 years. Around £80 at an Independent.
[FONT=&quot]- [/FONT]By now, all R170’s are aged enough to warrant a close inspection. We always recommend a full inspection prior to purchase. A full service history is only a starting point and does not guarantee that the owner has had the car meticulously maintained. We see cars with a full service history that have been neglected in key areas and we have seen cars with absolutely no paperwork that we haven’t been able to fault. The only way to know the condition of a car is to have it checked over by someone who knows these cars expertly. A Mercedes Independent Specialist is usually a good bet.

[FONT=&quot]- [/FONT]No specific common issues to the SLK, but a check over on the ramps is important as ball joints, bushes and other components can be worn not just with mileage but due to age too.
[FONT=&quot]- [/FONT]Subframe bushes should be given close attention. If these require changing, it is at least a days work for a garage to replace all four.
[FONT=&quot]- [/FONT]We recommend Mercedes braking parts, they are good value and we never have any come back from them.
[FONT=&quot]- [/FONT]Steering dampers normally require replacing at around 100K miles or 10 years in our experience. They are relatively cheap and help to regain steering feel and stop any wandering or vibration.

[FONT=&quot]- [/FONT]Wheels, as with many Mercedes may come with a diamond cut finish, particularly the AMG style that are standard on the sport models. These peel and corrode requiring refurbishment at between £2-300 for the set.
[FONT=&quot]- [/FONT]The SLK R170 is notorious for rusting, especially around the arches. Close attention needs to be paid in this area. If you are not confident, a technician needs to inspect the car to ensure it is not full of filler. As these cars get older, we see cheap repairs being carried out. These simply don’t last.

- [FONT=&quot]Check for Roof Rattles or creaking when operating. There aren’t any serviceable items on the roof, however as with most convertibles, seals can become hard or even dislodged causing wind or other noises.[/FONT]
- [FONT=&quot]Roof Operation must be nice and smooth. Issues are rare, however the system is complex with many switches and sensors![/FONT]
- [FONT=&quot]Check the roof does not leak, any leaks could mean replacement of seals which are not cheap. A leaking roof can also lead to expensive electrical problems.[/FONT]
- [FONT=&quot]PSE pump – The pump that supplies vacuum to operate the locking system is known to be problematic. The issue arises due to its location deep in the spare wheel recess. Any water in this area causes this pump to fail and the electrics to burn out. We have had to replace complete wiring looms for this pump. Spares are available second hand and there are now companies out there repairing these pumps. However its very easy to check the pump. First check that locking works. Then remove the spare wheel and the pump is located in a insulated compartment on the right hand side. If this is wet, there could be problems here. [/FONT]
- [FONT=&quot]Roof pumps have been known to fail. I wouldn’t say they are problematic. However the SLK R170 is now almost 20 years old so all items can fail. Pumps seem to be readily available second hand and should only be replaced by a competent mechanic. Mixing up the myriad of hydraulic hoses for the roof operation can lead to disaster![/FONT]
- [FONT=&quot]Interior plastics have a coating which has been known to peel. These will need replacement if this is the case[/FONT]
- [FONT=&quot]Rear light bulbs known to fail. These usually require holders to be replaced. In some cases, complete lamps required. [/FONT]
- [FONT=&quot]Indicator stalks are a common failure. These are still reasonably priced at around £80 from Mercedes. Fitting should cost around the same at a local specialist. [/FONT]

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