MB Medic Mercedes-Benz Repair Guides, Service, How To DIY
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The R170 Mercedes-Benz SLK caused real excitement at launch thanks to its electric folding hardtop, and it sold in large numbers from the first year. It launched in Europe in 1996 and reached the US in 1997 as a 1998 model: a two-seat, rear-wheel-drive roadster, first offered as the four-cylinder SLK230 Kompressor. The V6 SLK320 arrived in 2001, followed by the SLK32 AMG. Automatic cars use the durable five-speed 722.6 transmission.
The 722.6 adapts its shift points to the way you drive. That works well most of the time, but it can also make the SLK change gears in the middle of a corner when you would rather it held the gear. If that bothers you, the SLK was also sold with a manual transmission. On an automatic, keep the fluid fresh with a 722.6 transmission fluid change.
Common Mercedes-Benz SLK R170 Problems
A few issues have been reported with the five-speed automatic, so make sure it shifts smoothly on the test drive. Keep in mind that the SLK has very little trunk space, especially with the top down. If you want a used SLK, check it carefully for rust, especially around the wheel arches and door handles.
Make sure the roof opens and closes properly, and run it through several cycles. A roof or window fault on an older SLK can cost more to repair than the car is worth, which makes it a good reason to walk away or negotiate the price down.
The lower ball joints on the R170 are a common weak point. This can be a costly repair if you take the car to a shop that charges over $100 an hour, but it is also a reasonable DIY job. A set of ball joints for the R170 costs less than $100 if you search online. For example, we found R170 Front Lower Ball Joint Set on Amazon. Front wheel bearings wear too, and our R170 front wheel bearing replacement guide walks you through that job.
The retractable top of the SLK is known to develop problems with age. Most often the hydraulic cylinders leak oil, so the top moves slowly. Eventually the leak gets large enough that the system loses too much hydraulic fluid to work.
If the hardtop does not work, check the hydraulic fluid reservoir first. If the level is low, top it up to the max line. You can use Mercedes hydraulic fluid Mercedes part#A 000 989 91 03 10 or Febi Bilstein # 02615 Hydraulic Fluid ZH-M.
If the fluid level is fine, check the convertible top relay next, then the roof microswitches. Our Mercedes convertible top troubleshooting guide shows you how to find a faulty microswitch and where the hydraulics usually leak.
A used Mercedes-Benz SLK R170 is worth buying, especially if you plan to keep it as a weekend car. If you find one in good condition, you get a roadster with an irresistible combination of speed and good looks. Before you pay, go through our used Mercedes-Benz buying checklist, and once it is yours, resetting the R170 oil service light is a quick job you can do yourself.
If you want to learn more about the SLK R170, visit these training manuals we found online. This is an external link, and you will leave MercedesMedic.com when you click.
Troubleshooting Mercedes-Benz SLK-Class Problems
To diagnose an R170 roof fault, scan the roof control module with the UCAN-II Pro. Read the stored fault codes, watch the switch and sensor inputs in live data as you operate the top, and run the active tests the module supports. That tells you whether the problem is a microswitch, the pump relay or the hydraulics before you spend money on parts. Some R170 models route body modules through the round 38-pin diagnostic socket under the hood, so you may need a 38-pin adapter to reach them.
Before you buy parts, scan every control module, not just the engine. It shows the root fault behind the warning lights and tells you whether the problem is still active. See how to do a full health check.
