Mercedes Benz 107 Roadster Common Repairs & Guides

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Cruise Control Problems:

Go to  General Development Laboratories - Home Page

See trouble shooting.

and check the actuator and the amplifier. Then see Site Table of Contents for Replacing, Repairing, Rebuilding Amplifiers & Actuators

Engine Hard to Start when warm

There are many reasons why the engine would be difficult to start,

Some 450 SLs suffered from vapor lock and hard re-start because of the position of the catalytic converter.

Another possibility is the fuel filter and fuel accumulator may be at fault or the pump may be the cause.

The problem occurs particularly after the engine has been running due to the pressure relief valve located at the back of the pump inside. It is activated by a small spring and a metal cone which in time sticks and does not allow pressure to be relieved.
As the pump is driven by a permanently excited electric motor the pressure is reduced. After stopping, the fuel accumulator maintains pressure in the system to facilitate starting and with this pressure if the valve is stuck it develops an inner leak.
If you tap the pump firmly it releases the pressure valve and the engine starts again. When the tapping becomes frequent, it is time to replace the pump.

Mercedes knows this and they provide a Check Valve which is to be installed by replacing the existing hollow screw on the pipe connection to the pump, effectively providing a secondary pressure relief valve and avoiding having to buy a new pump.
(Check valve $12.98, cap nut $1.49

SL Window Switch Repair

Two 4" screwdrivers
One small file 6" or smaller
One brush for cleaning
One pair of tweezers 6" for replacing springs & balls
One Q-tip for cleaning
One 6" strip of emery paper (fine-grit)

Step 1. Take the switch out of the console by means of a 4" standard screwdriver. This can be done by lifting the switch part of the way up, and out, & unplug the wiring block. Some plug into the side, some into the back of the switch. The block plugs in only one way and switches are not interchangeable. With the switch in hand, take two screwdrivers, 4" type, & pry off the chrome cover. Do this slowly, as it holds the switch together and you want to see how it works for reassembly. (it's pretty simple) Two steel balls, two springs, two brass rockers. What goes wrong, is, the contacts on the switch get corroded and need to be cleaned for current to flow through.

Step 2. Take a small file, I carry a 6" jewelers file (fine-cut) and a piece of emery paper (fine-grit) to clean the contact points. Reassemble the switch and the window will work.
Note about the window switch: Do not hold the switch down any longer than to close or open the window. There is no limit switch on these cars. If your window moves slowly, clean the contacts to gain full power.
Should take about 20 minutes

Signal / Flasher Problems

Have your hazards or turn signals been problematic?
107.044 117.985 V8 450SL CIS fuel inj. years 1976-1980.
Hazards and turn signals share the same flasher.
Do your hazards works?
If not, then this flasher is likely to be the issue.
The flasher is part of the hazard switch.
You need to remove the ashtray, the mount for the ashtray, take out the two screws that hold the wood console in place, the shift boot (rubber around gear selector).
Carefully lift the front of the wood, roughly one half inch, then slide the wood section back and it should be off.
On the bottom of the hazard switch is the flasher.
You may be able to fix this by cleaning the corroded contacts inside, 50/50 risk that it repairs or breaks.

Center Console Removal:

1. Remove ash tray
2. Remove 2 screws from rear of ashtray holder
3. Remove ashtray holder. Pry out right side first and then disconnect electrical connector on left side.
4. Remove 2 screws from wood console
5. Remove wood by sliding to rear to disengage dowel.

Stereo Removal & Replacement

Pull the faceplate off the radio.
Remove the ashtray and tray holder. When removing the ashtray frame you have to twist from the passenger side toward the driver side because there is an electrical connection on the driver side. Remove the two screws in the back. Pull the wood fascia (of the AC controls) down and out from the bottom.

Push down the two tabs sticking up from the space where the wood fascia was and the radio unit slides out.
(remove the face plate from the radio and there are 2 locking bars holding it in place ,1 each side, straight screwdriver)
Go to Find Car Audio/Video Gear that Fits Your Vehicle at Crutchfield! and buy this wiring harness (again this is for my 560). Wire everything up and away you go.

I just pulled the 2 knobs off, and what I'm calling the 'faceplate' is actually a thin mylar type printed plastic insert . I just popped it off with a pen knife, and that exposed the 2 'locking bars' that were secured by the screws