R107 diagnosis & repair
Find out what's wrong with your R107 before you buy a single part.
Answer a few questions about what the car is doing. You end at the most likely cause, the cheapest test that confirms it, and only then the parts that fix it — 280 SL through 560 SL.
Start here
What is the car doing?
Search the symptom or pick one below. Each one opens a step-by-step decision tree that ends in a likely cause and the parts or tools to fix it.
Every R107 symptom we cover
The full index, grouped by system. Each entry opens its own diagnosis.
Engine — starting & running
- Cranks but won't start — Starter spins normally but the engine never catches — no run, no stumble.
- Engine won't crank — Turn the key and the starter doesn't spin — clicks, silence, or dimming dashboard.
- Excessive fuel consumption — Mileage has dropped noticeably — under 12 mpg city or under 17 mpg highway.
- Hesitation / flat spot under accel — Stumbles, bogs, or breaks up when you put your foot in it from low RPM.
- Pulling blink codes (pre-OBD-II) — Procedure for reading the diagnostic blink codes from the X11 connector under the hood.
- Rough idle when cold — Engine runs lumpy or hunts when cold but smooths out as it warms up.
- Rough idle when fully warm — Engine idles fine cold but gets rough, hunts, or shakes once warm.
- Stalls at idle — Engine catches and runs but dies at idle, especially at stops or when A/C engages.
Cooling, charging & oil
- Battery / charging warning light on — Red battery light on the dash with engine running, or you've found the battery flat in the morning.
- Engine overheats — Coolant temperature climbs above 100 °C in stop-and-go or up grades.
- Oil leak — where is it coming from? — You see oil drops on the garage floor or smell burning oil after a drive.
- Timing chain rattle at startup — Brief metallic rattle on cold start, lasting 1–3 seconds, from the front of the engine.
Transmission & drivetrain
- Harsh or late 1–2 shift — 722.3 transmission shifts hard, late, or with a clunk at the 1–2 upshift.
- Transmission slips or flares — RPM rises momentarily during shifts without a corresponding speed increase.
Brakes & chassis
- ABS warning light on — Yellow ABS lamp stays lit with engine running. ABS is disabled but base brakes still work.
- Brake pedal pulsates under braking — You feel pulsing through the pedal when slowing from speed, even with light pressure.
- Brake pedal soft / goes to the floor — Pedal feels spongy or sinks to the floor with steady pressure.
- Pulls to one side under braking — Steering wheel tugs left or right when you apply the brakes.
Body, top & electrical
- Dashboard clock dead or erratic — The analog clock in the R107 instrument cluster has stopped, runs intermittently, or jumps. Most commonly caused by a failed electrolytic capacitor on the small PCB inside the clock module — a well-documented DIY repair.
- Driver power seat won't move — Seat doesn't move in any direction, or only some directions.
- Soft top won't go up or down — Top motor doesn't run, runs but top doesn't move, or stops partway.
Climate control
- A/C blows warm — no cold air — A/C system runs but vents blow ambient or warm air on max cold.
- Heat blasts even when set cold — Vents blow hot air no matter what you set on the climate control panel.
- No airflow from vents — Set fan to high, no air comes out of any vent.
How it works
Diagnosis first, parts second.
- 1
Pick a symptom
Describe what the car is doing. Each symptom opens a hand-authored decision tree.
- 2
Walk the tree
Answer a few targeted questions. Each branch cites tonk.ca, MercedesSource, PeachParts, and the MBCA Star archive.
- 3
Get the right parts
End at a likely cause and a curated kit — OEM where it matters, with vetted suppliers.
Parts & tools
Curated kits
References & suppliers
We index the community, we don't replace it.
Decision trees cite tonk.ca (factory manual scans), MercedesSource (Kent Bergsma's DIY articles and kits), PeachParts (forum diagnostic histories), and the MBCA Star technical archive. Links open the source directly — no rehosting, no proxying.
Parts pills point at ECS Tuning, Amazon, eBay, and VEVOR. We tag fitment as R107-wide or 560 SL focused so you can confirm the part before you order it.
Got a symptom? Let's narrow it down.
Most R107 problems trace back to a small set of well-known root causes. Start from the symptom and skip the forum-trawling.