Tag Archive: 500SL

500SL Repairs

Our 1985 Mercedes 500SL has been undergoing some pretty extensive electrical work to address various issues and improve functionality:

• Dash Light Dimmer (Rheostat):
  The dimmer had failed, causing the dash lights to remain overly bright and reflect off the screen glass. Upon inspection, the rheostat was found to have no resistance across its rotation and was in poor condition. As this rare part is a sealed factory unit, replacement was not a viable option. Instead, the unit was carefully drilled open, disassembled, cleaned thoroughly, and reassembled. A broken wire connection was resoldered, and the original rivets were replaced with screws, converting it into a serviceable part. The rheostat now functions perfectly, dimming and switching off the dash lights as intended.
• Stereo and Speaker Installation:
  A new DAB stereo, speakers, and antenna were provided by the customer for installation. The old stereo and speakers were removed, but the new 180W speakers, with their larger magnets, required modifications to fit. Steelwork behind the mounts was adjusted, and the fascia fixing positions were modified to create sufficient clearance. New screw holes were drilled, and the fascia springs and brackets were adapted to ensure a factory-like fit. Although an antenna adapter is pending, the system was tested via Bluetooth, delivering excellent audio quality.
• Battery Clamp Replacement:
  The under-bonnet battery was previously secured with a makeshift softwood clamp. This was replaced with a custom-fabricated clamp made from 2mm sheet steel, which was drilled, shaped, and painted for durability. The new clamp provides a secure and professional solution.
• Heated Screen Issue:
  The heated screen for the hardtop was reported as non-functional. Testing revealed the switched 12V feed to be operational, but further investigation is not possible without the hardtop present.

Mercedes Work Begins

The first steps in breathing new life into our 1985 Mercedes 500SL have been successfully completed. The work done so far has been addressing a variety of mechanical, electrical, and general maintenance concerns.

Heater Blower Maintenance

One of the initial issues tackled by Pete was the squeaky heater blower. The blower was removed from the car for inspection and preventative lubrication. The cause of the squeak was traced to a loose fitment, which has now been addressed. While the blower was out, all loose debris was hoovered out of the heater box, and the seals were cleaned and reseated to ensure a proper fit. After reinstallation, the system is functioning perfectly without any noise.

Exhaust Repairs

The old exhaust rubber mount was replaced with a new one, ensuring the tailpipes are now securely and neatly positioned within the rear recess of the car. A rattling noise reported by the owner was diagnosed by Pete as a loose heat shield on the link pipe between the exhausts (a common area for vibration in V8 models). This was tightened, and a quick test drive confirmed that the rattle had been completely resolved.

Cooling System Refresh

The car’s cooling system received a thorough refresh. The dirty coolant was fully drained and replaced with a fresh 50/50 mix of antifreeze and water. The system was run up to temperature, bled of air, and tested to ensure the heater delivers warm air as expected – everything is now functioning perfectly.

Electrical Work Begins

Attention then turned to some of the electrical issues. The battery terminals, which were in poor condition, were removed and thoroughly cleaned, along with the posts on the battery itself. However, it was noted that the positive battery post is loose within its casing, meaning the battery will need replacing.

The heated seat switches were seized and inoperative. After disassembly, cleaning, and de-rusting the spring-loaded mechanisms, they are now working intermittently but will likely require further repair or replacement. These intermittent issues might also be linked to the battery post problem, which will need addressing before moving forward.

Brake Service and Hub Maintenance

The brakes were fully stripped, inspected, and cleaned. The wheel hubs were also cleaned, and anti-seize grease was applied to their faces, ensuring the wheels no longer stick to the hubs during removal. After reassembly, all components were torqued to Mercedes specifications.

Mercedes 500SL Basic Appraisal

The customer reported a few issues with our 1985 Mercedes 500SL, and Pete confirmed most of them during a test drive:

• Rattle & Knocking Sounds:
  A noticeable rattle occurs at very low speeds or from a standstill. Additionally, there’s a knocking noise from the passenger side, especially over uneven roads. This could hint at suspension or steering issues.
• Cruise Control:
  As reported by the customer, the cruise control wasn’t working.
• Brakes & Steering:
  The brakes functioned well, including the handbrake, which holds firmly and keeps the car straight. Steering felt fine overall, though the knock might still be related.
• Gearbox:
  The gear changes were slow at times and selecting “Park” resulted in a noisy shift.

Lighting Issues

While the external lights are fully operational, there were a few concerns with internal and auxiliary lighting:

• Courtesy Lights: Only work when the doors are opened, not via the dashboard switch.
• Dashboard Dimming: The instrument cluster doesn’t dim when adjusted.
• Park Brake Bulb: Fails to illuminate when the parking brake is applied.

Heated Seats

The heated seat switches are non-functional. They’ve completely collapsed in their housing, rendering them unusable and unlit.

Engine Bay

A peek into the engine bay revealed a mix of positives and areas needing attention:

• Oil & Fluids:
  • Oil level is fine, but the oil itself is slightly dirty.
  • Brake fluid is clean and at a high level.
  • Coolant is brown, although the level is okay.
  • The washer fluid reservoir is full of mould and gunk, which could block the pump.
• Filters & Belts:
  • Air filter is a bit dirty but still serviceable.
  • Auxiliary belts are worn and cracking—replacement is strongly recommended.
• Battery: The terminals are corroded and need cleaning.

Tyres

A close inspection of the tyres uncovered some concerning details:

• Spare Tyre: A 34-year-old Continental tyre that’s heavily cracked and perished.
• Driver’s Front Tyre: Dunlop, 5mm tread, with minor cracking. No DOT code was visible.
• Driver’s Rear & Passenger’s Rear Tyres: Both are Runway Enduro, 6mm tread, 15 years old.
• Passenger’s Front Tyre: Forcum brand, 5mm tread, also 15 years old.

Recommendation: All tyres should be replaced due to their advanced age and cracking.

Suspension & Steering

Several issues were noted beneath the car:

• Suspension:
  • Front lower arms have play, and the bushes are perished.
  • Rear exhaust rubber is beginning to split.
• Steering:
  • Minimal play in the driver’s track end.
  • Play in steering tie joints and the damper arm.
• Exhaust:
  • The heat shield is loose on the exhaust link pipe.
  • The exhaust has been repaired and painted, but the paint is now flaking, and rust is returning.

Underside Condition

There were signs of wear and tear under the car:

• Corrosion:
  • Slight underbody rust, with the driver and passenger sills showing small crusty holes. Pete wasn’t sure if these were factory imperfections or rust-through spots.
• Oil Leaks: Minor oil residue was observed on the sump and power steering pump, but no drips were evident overnight.

Additional Notes

• The steering wheel’s centre bolt is heavily damaged.
• Hardtop functionality couldn’t be tested as the soft top is currently fitted.

500SL Headlights

The headlights of our 1987 Mercedes 500SL have been stripped down by our workshop manager John.