* Vacuum Pump: The vacuum pump on these models is often located near the firewall on the driver's side. If it's leaking oil, it could drip down and accumulate under the dash. This is a more likely suspect than the master cylinder being the *only* source. Vacuum pumps use engine oil for lubrication.
* Transmission linkage: While less likely to be *oil*, some transmission linkage components or seals might have developed leaks and are dripping transmission fluid. Transmission fluid is often reddish in color, but in older vehicles it can get darker.
* Steering gear box: Though usually associated with power steering fluid, a leak in the steering gear box could potentially mix with engine oil in rare cases and the result could appear as oil. Power steering fluid is usually a reddish hue.
* Engine oil leaks near the firewall: A small leak from higher up on the engine, perhaps from a valve cover gasket or even a rear main seal (though less likely to drip that far forward), could run down and pool under the dash.
* Previous repair: Something may have been repaired or replaced and wasn't properly sealed, resulting in a leak that only shows up under the dash.
Troubleshooting Steps:
1. Thorough visual inspection: Carefully examine the entire engine bay on the driver's side, paying close attention to the vacuum pump, steering gearbox, and areas near the firewall. Look for oil stains, dripping, or weeping.
2. Trace the leak: If you can find the source of the leak, follow the path of the oil to pinpoint its origin. A clean engine bay makes this much easier.
3. Check fluid levels: Check the engine oil, power steering fluid, and transmission fluid levels to see if any are low. This will help narrow down the potential sources.
4. Consider professional help: If you can't locate the leak yourself, a qualified Mercedes-Benz mechanic will have the experience to diagnose and repair the problem accurately. They'll have tools to help them pinpoint the leak much more effectively.
It's crucial to identify and repair the leak promptly to prevent damage to the vehicle's interior and to avoid further mechanical issues.
