M103 crankshaft 103 031 05 – Buying guide W124 W126 R107
If you are overhauling a W124 300 E, a W126 300 SE or an R107 300 SL with the M103, you often face this question after disassembly: can the old crankshaft still be ground, or do you need a different shaft? New crankshafts for the M103 are expensive, and on the used market M103 and M104 shafts are often mixed up. This guide shows how to recognize crankshaft damage, what to look for when buying a used M103 crankshaft, and which numbers belong together.
How do you recognize wear or damage?
The crankshaft converts the reciprocating motion of the six pistons into rotation and drives the timing chain and oil pump via the sprockets. In the M103 it runs in seven bearings. Whether it can be reused is usually decided only once the engine is disassembled.
| Finding | Meaning |
|---|---|
| Deep scoring or discoloration on main or rod journals | Bearing damage, usually after oil starvation – shaft must be measured and, if necessary, ground undersize or replaced |
| Journals already ground to the last repair size | No further grinding possible – replacement shaft required |
| Runout error or crack found during inspection by the engine rebuilder | Shaft no longer usable |
| Missing or damaged teeth on the starter ring gear of the drive plate | Replace the drive plate; the crankshaft itself may be fine |
| Rattling at the front of the engine, especially on a cold start | Often not the crankshaft but the chain drive – see Oil pump chain rattles W124 W126 |
| Blue smoke and oil consumption | Usually valve stem seals or piston rings, not the crankshaft – compare Replacing valve stem seals |
Causes
After three decades and often several hundred thousand kilometers, the bearing surfaces are the main issue. Oil starvation, overly long oil change intervals or worn bearing shells leave scoring on the journals. On engines that have been overhauled several times, the shaft has sometimes already been ground undersize, so no further grinding remains. In addition there is consequential damage from bearing failures that makes a shaft unusable. On vehicles with automatic transmission, the starter ring gear on the drive plate also wears. A used genuine shaft with clean journals is therefore an economical basis for many overhauls – provided it is measured before installation.
What to look for when buying
- Identify the engine: The casting number 103 031 05 belongs to the M103 in 2.6 and 3.0 liters – both have the same stroke of 80.25 mm. The four-valve 300 E-24, 300 CE-24, 300 TE-24, 300 SL-24, E 280 and E 320 have the M104 with its own crankshaft. It does not fit the four-cylinder M102 or diesels.
- Compare numbers: Compare the casting number with your old shaft or send us the engine number. For reference: the current Mercedes spare part number of the M103 crankshaft is A 103 030 08 01.
- Mind the transmission: The drive plate A 102 032 06 06 is for automatic transmissions. With a manual transmission you need a flywheel instead of the drive plate – then the shaft without drive plate is the right choice.
- Assess the condition: Look for shiny main and rod journals without deep scoring. Light surface rust on the raw-cast webs is normal for stored shafts.
- Have it checked before installation: Our shafts have not been measured and have had no crack or runout inspection. Have the bearing journals, runout and freedom from cracks checked by an engine rebuilder before installation.
Solution
If the old shaft cannot be saved, a used genuine 103 031 05 crankshaft is the obvious route. We have three units in stock – each used and removed, with sprockets and hub including center bolt, without bearings, belt pulley and vibration damper:
- Crankshaft with drive plate (Edding no. 3) for automatic: 199,00 €
- Crankshaft with drive plate A 102 032 06 06 (Edding no. 8) for automatic: 179,00 €
- Crankshaft without flywheel/drive plate (Edding no. 12): 149,00 €
Because of their weight and size, the shafts are available for pickup only. We arrange the appointment after purchase; by arrangement, you can inspect the part beforehand. You can find more parts in our categories Mercedes W124 and Mercedes W126.
M103 crankshaft + drive plate A 102 032 06 06
Casting no. 103 031 05 · Automatic
179,00 €
View offer →
Compatible vehicles
| Model series | Models (only with M103 engine) |
|---|---|
| W124 / S124 / C124 (1985–1995) | 260 E, 260 E 4MATIC, 300 E, 300 E 4MATIC, E 300 4MATIC, 300 TE, 300 TE 4MATIC, 300 CE |
| W201 (1986–1993) | 190 E 2.6 |
| W126 (1985–1991) | 260 SE, 300 SE, 300 SEL |
| R107 (1985–1989) | 300 SL |
| R129 (1989–1993) | 300 SL, 12 valves |
| W463 | 300 GE, G 300 |
Does not fit for the M104 (300 E-24, 300 CE-24, 300 TE-24, 300 SL-24, E 280, E 320), four-cylinder M102 and diesel engines. The drive plate only fits with an automatic transmission.
FAQ
Does crankshaft 103 031 05 fit the 300 E-24?
No. The 300 E-24 has the four-valve M104 with its own crankshaft. The 103 031 05 is for the two-valve six-cylinder M103 in 2.6 and 3.0 liters.
Does a shaft from the 260 E also fit the 300 E?
The M103 in 2.6 and 3.0 liters has the same stroke of 80.25 mm, and crankshaft 103 031 05 is specified for both displacements. Still, compare the casting number with your old shaft or send us the engine number.
Are the crankshafts measured or inspected?
No. The bearing journals have not been measured, and there was neither a crack nor a runout inspection. In the photos, the main and rod journals are shiny and without deep scoring. Please have the shaft checked by an engine rebuilder before installation.
Do I need the variant with drive plate?
The drive plate A 102 032 06 06 connects the crankshaft to the torque converter and is for automatic transmissions only. With a manual transmission a flywheel is required – then the shaft without drive plate for 149,00 € is the right variant.
Are the crankshafts shipped?
No. Because of their weight and size, the crankshafts are available for pickup only. We arrange the pickup appointment by message after purchase; by appointment you can inspect the part beforehand.
KFZTeile-Thot is a specialist company for tested and refurbished Mercedes parts with its own test benches and has over 1,000 positive eBay reviews. Want to know which crankshaft fits your engine? Send us your VIN (chassis number) and model year, and we will check it free of charge: +49 179 8991069 (Mon–Fri 8 am–6 pm) – or use our contact form.