2008 Mercedes-Benz SLK350 Problems

RepairPal has identified the most common problems with the 2008 Mercedes-Benz SLK350 as reported by actual vehicle owners. We'll tell you what the problem is and what it'll take to fix it.

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11
Known Problems

Vehicles equipped with a 7-speed automatic transmission may develop a rough shifting condition, most commonly going up from first to second gear and going down from third to second or second to first gear. Our technicians tell us this is due to an internal component failure. Mercedes has released updated parts; the transmission will need to be removed and disassembled to complete the necessary repairs.

The Mercedes Benz SLK350 may have engine oil seeping or leaking from the back of the cylinder heads. This is commonly misdiagnosed as leaking valve covers.

On the back of the cylinder heads there are three, in total, plastic expansion plugs that plug access ports to the camshafts. These plugs are well known for seeping oil, and leaking if left unattended. The oil will run down the back of the engine and eventually make it to the ground. 

Replacement of these three plastic plugs is extremely simple, and should be done as regular maintenance. The recommended interval for replacement is every 60,000 miles.

The engine in the SLK350 is known by Mercedes Benz to have issues due to a poorly manufactured gear on the balance shaft (also known as the counter-rotating assembly). Since the balance shaft gear is driven by the timing chain, which keeps the engine rotating synchronously, when it fails, the timing of the engine will change causing:

-Illumination of the Check Engine Light

-Rough Running Conditions

-Stalling

-Loud Rattle or Slapping Noise

-OBD Trouble Code P1200 and P1208

Correction for this issue is replacement of the balance shaft, or balance shaft gear. Replacement of the timing chain and tensioner should be done as well. The Mercedes Benz dealer may cover some or all of the repair cost on select vehicles as a result of a class action settlement.

The power steering reservoir designed for the Mercedes Benz SLK350 commonly leaks power steering fluid causing a screeching sound when turning the steering wheel, especially when the vehicle is stopped. The power steering light may illuminate on the dash for more severe leaks.

This is caused by cracking in the plastic reservoir, or a hardened, brittle seal between the power steering reservoir and power steering pump.

Remediation involves replacing the power steering fluid reservoir, power steering fluid, bleeding the system of air, and replacement of the seal between the reservoir and power steering pump.

When starting the engine after sitting for several hours, a knocking sound may be heard for several seconds. This is a common issue with the 2004-2010 Mercedes Benz SLK350. There are three common problems that can cause this sound to occur:

-Oil pressure building too slowly, allowing for movement between the crankshaft and crankshaft bearings

-Stretch or wear of timing chain and components

-Balance shaft (counter rotating shaft) gear wear

The remediation for these problems can be crankshaft bearing replacement with correct size, replacement of timing components, or balance shaft replacement.

A vibration felt through the center floor of the vehicle can be caused by driveshaft flex discs, which crack and shred, causing excessive driveshaft movement. Not repairing these can cause damage to the driveshaft center support bearing, or, in the worst case scenario, damage to the transmission or differential.

The camshaft adjuster solenoid (which is related to the variable valve timing system) may fail or timing chain/balance shaft components may wear, resulting in illumination of the Check Engine Light and various drivability issues. Mercedes-Benz has released a service bulletin outlining specific repair instructions depending on fault codes stored.

As a way to increase braking performance, the brake pads and rotors are make of a softer material and may be in need of replacement after approximately 20,000 miles; owners should be vigilant about getting their brakes checked.

The engine may develop a stalling and/or no start condition due to a failed crankshaft position sensor.

High mileage or older vehicles commonly develop leaks from the differential seals and/or cover. Our technicians recommend a complete reseal of the differential unit whenever these leaks are repaired.

The anti-lock brake system (ABS) modulator assembly may fail due to dirty brake fluid. Our technicians recommend a complete brake system flush every two years in order to help prevent this problem.