M104.98x Motor Swap in a 190E

One of the most common engine swaps for a 190E is the installation of the bigger M103 3.0L motor. The swap from the smaller 2.6L M103 to a 3.0L M103 is a direct bolt-on swap (assuming the engines from the same cutoff years are used) and gives a small increase of around 30HP. Another option is to swap in the CIS version of the M104 engine found on the earliest M104 powered cars (1990-1992 300CE and 1990-1993 300SL). The injection system is still CIS and the ignition system is still EZL, but additional work is required to make the swap complete.

1. Disconnect battery
2. Remove front bumper
3. Remove air filter
4. Remove upper radiator support
5. Vacuum lines
   1. EGR, 2 lines
   2. Smog pump
   3. EZL
   4. Check valve at driver fender
   5. Two at the rear of intake manifold
   6. Black striped white vacuum line for throttle body
   7. Brake booster line
6. Cooling System
   1. Drain and remove radiator
   2. Disconnect water heater lines
      1. Supply at passenger fender
      2. Return at rear lifting hook
   3. Remove overflow pipe to coolant reservoir
7. AC System
   1. Vacuum AC system and remove condenser
      1. Wiring under both headlights and loom ties
      2. Bolt on driver side securing pipe to chassis
   2. Disconnect AC hose on driver fender
8. Power steering
   1. Siphon/extract power steering fluid
   2. Disconnect supply and return lines on pump
9. Disconnect fuel lines
   1. Supply at fuel distributor, 2x 17mm
   2. Return behind ignition coil, 17mm and 14mm
10. Disconnect throttle cables
11. Disconnect main engine wiring and set aside
    1. 4 prong CIS
    2. 1 prong temperature sensor
    3. 2 prong temperature sensor
    4. Cold start valve
    5. EHA
    6. Idle microswitch
    7. Airflow potentiometer
    8. IACV
    9. AC compressor
    10. Throttle position switch
    11. Ground wire at intake
    12. 2 plugs at the EZL
12. Disconnect auxiliary wiring and set aside
    1. Oil level sensor
    2. Oil pressure sensor
    3. Starter
    4. 10mm bolt at rear of intake manifold
13. Other wires
    1. Cruise control servo (8 pin connector under ABS pump)
    2. Disconnect alternator
    3. Crankshaft position sensor (rear) at EZL
    4. Crankshaft position sensor (front) underneath X92
    5. Ignition coil
14. Disconnect exhaust downpipes from exhaust manifold
15. Transmission
    1. Remove transmission mount
    2. Disconnect driveshaft from flex joint
    3. Disconnect transmission shifter linkage(s)
       1. Suggest removing entirely to avoid bending the rods accidentally
    4. Disconnect transmission slave cylinder fluid line (manuals only)
    5. Unbolt ground from bell housing
    6. Disconnect speedometer cable
16. Unbolt engine mounts from chassis
17. Secure engine to hoist and lift to remove. Remove with transmission attached.

Removed the front bumper, upper radiator support, radiator, condensor, and engine harness.

Engine hoisted out.

1. Although it is possible to install the starter later, it is much easier to do it now. Bolt starter to the engine before lowering.
2. Lower engine from hoist into engine bay and align motor mounts. Install without transmission.
3. Connect fuel lines
4. Main wiring harness
   1. See conversion task below
5. Auxiliary wiring harness / Starter
   1. Set starter in place if it isn't already and reconnect wires. Bolt starter to transmission later.
   2. Connect oil pressure and oil level sensor wires
   3. Bolt wire bracket to rear of intake manifold (10mm)
6. Other wires
   1. Connect alternator wires coming from right fender
   2. Connect 8 pin cruise control wires
   3. Connect rear crankshaft position sensor wire
   4. Connect front crankshaft position sensor under X11 diagnostic port
7. Connect throttle cable
   1. Readjust idle position
8. Connect power steering hoses
9. Cooling System
   1. Connect heater return hose at back of engine
   2. Use W124 water reservoir overflow hose and 190E valve from thermostat cover
   3. Drop in radiator and connect hoses
10. Vacuum system
11. Use T connector at front vacuum nipple to connect to EZL and EGR/Smog pump solenoid
    1. Connect black striped white vacuum line from throttle body to check valve at fender behind headlight
    2. Connect brake booster
    3. Connect 3 vacuum line at rear of intake manifold
       1. The M104.98x introduces a new vacuum nipple. Use it however you wish or block it off.
12. Fluid fill
    1. Power steering fluid
    2. Motor oil
    3. Coolant
    4. Brake fluid
    5. Charge AC