How to Change the Starter Motor on a Porsche 911 G-Body (1974–1989)

How to Change the Starter Motor on a Porsche 911 G-Body (1974–1989)

Replacing the starter motor on a Porsche 911 G-Body (1974–1989) is a very achievable job for the competent home mechanic. This is laughable. It’s a horrible job! While access is tight and the hardware is often original, taking a methodical approach makes this a straightforward and satisfying repair. Ha ha I’m not sure I’ve ever been satisfied after this job , usually just glad it’s over  


This guide walks you through the process step by step, highlighting common pitfalls, tool tips, and best practice learned from experience.

 

 

 

Tools & Equipment Required

 

  • Axle stands or a lift
  • Wheel chocks
  • 13 mm socket or spanner
  • 17 mm socket and spanner
  • Allen (hex) socket (usually 10mm – always confirm)
  • Long extensions (various lengths)
  • Ratchet
  • Penetrating oil
  • Flat-blade screwdriver or 7 mm socket (heater hose clamp)
  • Torque wrench (for refitting)
  • shed load of hope
  • patience
  • double jointed fingers

Tip: A wobble or universal joint can make the top bolt far less stressful.

Step 1

Before touching anything near the starter motor, disconnect the battery.

The starter is permanently live and accidental shorting can damage wiring, tools, or cause serious injury. A great fireworks display  

• Disconnect the negative terminal first

• Removing the battery entirely adds safety and frees working space

Never skip this step.

Step 2: Disconnect the Starter Motor Power Leads

With the car safely raised and supported, locate the starter motor on the gearbox bellhousing.

On the rear of the starter you’ll find:

  • A 13 mm nut securing the main battery cables
  • One or more smaller trigger wires (spade or ring terminals)

Carefully:

  1. Undo the 13 mm nut and remove the main power cable
  2. Disconnect the smaller ignition trigger wire(s)
  3. Move all cables well clear of the starter - you can shove them up over gearbox. 

Workshop Tip: Take a quick photo before removal. It removes all doubt about wiring during refitting.

Step 3: Remove the Lower 17 mm Starter Fixing

The lower starter fixing is a 17 mm nut on a stud threaded into the gearbox.


Rather than removing just the nut, my preferred method is to remove the entire stud using the double-nut technique.

Double-Nut Method:

 

  1. Thread two 17 mm nuts onto the stud
  2. Lock them together by tightening them against each other
  3. Use the inner nut to wind the stud out of the gearbox

Why this works better:

  • Reduces stress on old gearbox threads
  • Makes starter removal easier, it’s a right pain to get past stud otherwise
  • Simplifies refitting and alignment

Tip: Use penetrating oil and steady pressure. These threads are often 40+ years old.

 

Once removed, support the starter motor — it is now only held by the dreaded upper fixing.


Step 4: Remove the Heater Hose from the Heat Exchanger

To access the upper starter bolt, the heater hose must be removed. This flexible duct runs from the heat exchanger to the body and sits directly in the tool and starter motor exit path  

 

Procedure:

 

  1. Loosen the hose clamp at the body end
  2. Gently twist the hose to free it
  3. Pull the hose clear and move it out of the way

Inspection Tip: If the hose is brittle or cracked, replace it now while access is good.


With the hose removed, you’ll have a clear line of sight to the upper starter fixing. This is obviously a joke unless you can see around corners or through solid steel.

Step 5: Remove the Upper Starter “Barrel nut”

The upper starter bolt, often called the barrel bolt, is the most awkward part of the job. It’s hellish! 

This fixing uses an internal Allen (hex) drive, not a conventional hex head.

Tools Required:

  • Allen key socket (usually 8 or 10 mm)
  • Multiple extensions
  • Ratchet with good control
  • knuckle protectors
  • large swear box and plenty of loose change. 

Removal Tips:

  1. Approach from the front end of the engine, you can just about get both hands in there. 
  2. Clean dirt from the bolt head before inserting the socket, this may seem pointless, but those barrel nuts get full of road dirt and your socket Alan key will not fit in there snuggly
  3. Fully seat the Allen socket — this is critical
  4. Crack the bolt loose slowly and evenly

Important: Rounding this bolt will turn a simple job into a nightmare. Take your time. If this goes wrong and you rounded the bolt, you will end up taking the engine and gearbox out

Once removed, support the starter motor and lower it clear of the bellhousing.

ta daaa you’ve done it! 

refitting is loads easier. I generally swap the old style starter for a newer lightweight high torque model  they are lighter and shorter  they fit much easier.

 

 

 

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