Recalls & faults: Mercedes-Benz R171 SLK-Class (2004-11)

Recalls: Mercedes-Benz R171 SLK-Class

Overview

Manufacturers, or importers, issue recalls for defects or faults which have the potential to cause injury. Generally, manufacturers will inform the original buyers if their vehicle is subject to a recall and of the steps required to remedy the defect or fault. Please note that the recalls below (if any) are for Australian-delivered vehicles only. Furthermore, the number of recalls should not be taken as an indication of a model’s reliability or its safety more generally.

Recalls: Mercedes-Benz R171 SLK-Class

Mercedes-Benz R171 SLK: Takata airbag recall

In May 2018, a recall was issued for Mercedes-Benz R171 SLK vehicles that were available for sale from 1 August 2006. In these vehicles, the airbag inflator contained propellant wafers that could degrade over time due to high temperatures and humidity. In the event of a collision, the airbag could deploy too aggressively such that the metal inflator housing could explode/rupture and cause metal fragments to be propelled through the airbag cushion and towards vehicle occupants. These metal fragments could cause serious injury or fatality. For the VINs of the recalled vehicles, please see PRA 2018/16775.

Problems and faults: Mercedes-Benz R171 SLK-Class

Overview

This section identifies potential problems, causes and fixes based on the experiences of owners and repairers, online sources and technical service bulletins. This information is provided solely for reference purposes and AustralianCar.Reviews recommends that only properly qualified persons carry out repairs or modifications. Furthermore, the number of items below should not be taken as an indicator of a model’s reliability or the frequency with which they may occur.

To report a problem or fault to the AustralianCar.Reviews team, please use the Contact Us form. Note that AustralianCar.Reviews does not offer advice on automotive problems or disputes; such enquiries will not receive a reply. For vehicles purchased from dealers after 1 January 2011, please see our Australian Consumer Law fact sheet.

Mercedes-Benz R171 SLK 200 Kompressor: M271 camshaft adjuster/sprocket failure

Background
For the M271 engine, each camshaft has a camshaft adjuster/sprocket mounted to the front of it. The camshaft adjuster is mounted on a bearing so that it can rotate separately from the camshaft and is driven by timing chain. Furthermore, a solenoid is bolted onto the camshaft adjuster and attached to the end of the camshaft. As the camshaft adjuster is rotated by the timing chain, the sprocket can control the offset of the camshaft.

Camshaft adjuster/sprocket failure
The camshaft adjuster for the M271 engine is made from cast iron and its operation against the single-row steel timing chain causes the teeth to wear prematurely; while the teeth can potentially break off, this is relatively rare. Wear to the camshaft adjuster can cause:

• The engine’s valve timing to be advanced or retarded;
• The timing chain to stretch; and,
• At worst, changes to engine timing can cause the pistons and valves to collide – such engine damage is extremely serious.

Merc271 provides re-manufactured camshaft adjusters in which the original gear face has been removed and a high-tensile, surface hardened steel gear profile has been applied to make it significantly stronger. Some owners, however, recommend replacing the timing chains and camshaft adjusters as a preventative measure every 130,000 kilometres.

Symptoms
Symptoms of camshaft adjuster failure include:

• A rattling noise on start-up caused by play of the timing chain and camshaft adjuster teeth;
• Uneven running and a rough idle;
• Diagnostic trouble codes (DTCs) related to camshaft timing.

Replacement
Replacing the camshaft adjuster requires:

• The solenoid and valve cover to be removed;
• The tension on the timing chain to be released; and,
• The camshaft adjuster to be removed from the camshaft.

2004-06 Mercedes-Benz R171 SLK 280 and SLK 350: M272 balancer shaft sprocket gear failure

In May 2011, Mercedes-Benz issued service bulletin LI03.30-P-050027 for Mercedes-Benz R171 SLK 280 and SLK 350 vehicles that had M272 V6 engines which:

• Had serial numbers prior to 2729..30 468993; and,
• Were manufactured prior to October 2006.

In these vehicles, premature wear of a gear on the balancer shaft sprocket could cause the positioning of the camshafts in the right cylinder bank to be impaired (relative to the crankshaft). According to the service bulletin, this wear of the balancer shaft sprocket could cause the following symptoms:

• Illumination of the check engine light; and,
• Diagnostic trouble codes (DTCs) 1200 or 1208 stored in the ME-SFI control unit.

Owners have experienced failure of the balancer shaft sprocket gear after 95,000 kilometres, accompanied by rough running and illumination of the check engine light. From October 2006 production, a hardened material was used for the sprocket and the timing chain guide wheel (idler) was modified.

For the M272 V6 engine, the repair procedure is as follows:

1. Remove the right front camshaft adjuster cover;
2. Check the balance shaft sprocket for wear using a flexible borescope. In rare cases, a stretched timing chain may be the reason for the DTCs if the sprocket does not exhibit any signs of wear;
3. If worn, replace the balance shaft. Note: since the balancer shaft is located inside the engine block, repairs are expensive;
4. Replace the chain tensioner (part number A272 050 01 11);
5. Change engine oil and filter;
6. Drive with engine at high load and rpm for at least 20 km;
7. Change engine oil and filter once more; and,
8. Replace the camshaft adjustment solenoids.

Mercedes-Benz R171 SLK 280 and SLK 350: M272 cam plug oil leak

Mercedes-Benz M272 V6 engines that were produced prior to June 2008 may experience oil leaks (or ‘seepage’) from the round plastic expansion plugs (‘cam plugs’) on the back of the cylinder heads. There were two different size cam plugs:

• Part number A000 998 55 90: two small expansion plugs (approximately 2.5 cm diameter); and,
• Part number A000 998 56 90: one large small expansion plug (for engines without vacuum pump).

To fix, the existing plugs were to be removed, the opening cleaned and new plugs fitted; no sealer was to be used in the installation of the new plugs (new cam plugs that were not susceptible to oil leaks were phased into production in June 2008).

2004-11 Mercedes-Benz R171 SLK 280 and SLK 350: actuator cam for VIM

For 2004-11 Mercedes-Benz R171 SLK 280 and SLK 350 vehicles, the actuator cam for the variable intake manifold (VIM) in the M272 V6 engine is susceptible to failure. Symptoms of a broken actuator cam include:

• Rough idle;
• A loss of power (particularly at low and mid-range engine speeds);
• Illumination of the check engine lights; and,
• Diagnostic Trouble Codes (DTCs) such as P2004, P2005, P2006, P2187 and P2189.

Due to the venting of oil from the PCV (positive crankcase ventilation) system, carbon deposits can accumulate on the swirl flaps inside the variable intake manifold. These carbon deposits increase the resistance on the plastic actuator cam and this can cause it to break. Other parts can also fail as a result, including the swirl flaps, the actuator mounting arms and the vacuum diaphragms.

AustralianCar.Reviews understands that the original equipment supplier for the intake manifold is Pierberg and that Mercedes-Benz’s repair involves replacing the entire intake manifold since they do not supply replacement actuator cams. However, eEuroparts.com sell intake manifold repair kits that replace the plastic actuator cam with a metal component and can be used for DIY repairs. However, the intake manifold also needs to be cleaned as part of any repair. For further information about this problem, please see:

• eEuroparts.com: Fixing Mercedes-Benz Intake Manifold Woes; and,
• eEuroparts.com: Mercedes-Benz Intake Manifold Repair DIY.

Problems and faults: Mercedes-Benz R171 SLK-Class

• Rumbling or squeaking noises from the air conditioner compressor may be due to a bad pulley or bearings; revised components were subsequently released.
• The steering wheel buttons may stop working due to electrostatic discharge damaging the steering column module.
• The air conditioning (blower) motor may stop working or only work intermittently due to an internal circuit breaker in the air conditioning (blower) motor regulator that requires replacement.
• The ‘check engine’ light may illuminate due to a wiring harness in the engine compartment rubbing on a bracket, short-circuiting and causing a fuse to blow.
• The heated front seats may stop working due to the centre cushion heater failing.
• Water may leak from the windscreen or where the rear window meets the boot due to seal failures; revised seals were subsequently released.
• For early models, the steering rack boot was inspected during servicing due to possible damage during assembly.