BMW M51 connecting rod 11242243157 – buying guide E34 E36 E38
Anyone overhauling an M51 diesel quickly finds that new genuine connecting rods for this engine are hard to come by, and used rods from donor engines have an unknown history. This guide explains how to recognize connecting rod damage, what to look for when buying, and why the correct part number matters so much on the BMW diesel – because M41, M51 and M21 look alike but have different numbers.
How do you recognize wear or damage?
The connecting rod transfers the piston force to the crankshaft and converts the reciprocating motion into rotation. The split crankshaft bearing sits in the big end, and the bronze bushing for the piston pin sits in the small end. Damage usually only shows once the engine is disassembled – the following findings are the typical reasons for replacement.
| Finding | Meaning |
|---|---|
| Wear marks, scoring or discoloration on the bearing bore of the big end | Bearing damage, e.g. from lack of oil – measure the connecting rod; replace it if in doubt |
| Play or scoring on the bushing in the small end | Wear of the piston pin bushing; check bushing and connecting rod |
| Out-of-round or widened big end when measured | Connecting rod no longer within specification – do not reuse |
| Connecting rod bent or heat-discolored after engine damage (hydrolock, spun bearing) | Replace the connecting rod; also check crankshaft and cylinders |
| Oil consumption, blow-by and falling compression with intact connecting rods | Different cause, usually pistons, rings or cylinder bores – see Piston set guide: recognizing wear and choosing oversize |
Important: Whether a connecting rod can be reused is decided by the measurement carried out by the engine rebuilder. Visual findings are a guide but do not replace measurement.
Causes
After several decades and high mileages, the loads in the rotating assembly add up. The most common cause of connecting rod damage is disrupted lubrication: oil changes that are too infrequent, an oil level that is too low or falling oil pressure lead to bearing damage at the big end. Wear of the piston pin bushing adds to this. If a bearing seizes, the connecting rod is stressed thermally and mechanically to the point that it is no longer within specification. During an engine overhaul it is therefore standard practice to measure the connecting rods and replace damaged ones with genuine parts of identical dimensions.
What to look for when buying
- Identify the engine: The number 11242243157 belongs to the six-cylinder M51 diesel. The four-cylinder M41 in the 318 tds requires set 11242245435; the M21 in the 524 td is not covered either.
- Compare the part number: Compare the BMW number with the parts catalog or the removed parts – this is the cheapest and safest check.
- Clarify the quantity: The complete factory set 11242243157 comprises 6 connecting rods. The partial set offered contains 4 pcs. Anyone wanting to fit all six cylinders with new rods needs 2 more connecting rods of the same number.
- Check the condition: Look for unused bearing surfaces without wear marks and undamaged connecting rod bushings. Both points are met by the NOS set offered; age-related marks on the box are normal.
- Fit in the engine: Have the connecting rods measured together with the crankshaft and bearing shells before installation, and use new connecting rod bolts and bearing shells as specified by the manufacturer.
Solution
If the rotating assembly of an M51 is due for an overhaul, unused genuine connecting rods are the most reliable basis. We offer a BMW connecting rod partial set 11242243157 with 4 connecting rods from old stock: New Old Stock in the original BMW box, unused, bearing surfaces without wear marks, connecting rod bushings undamaged. Price: 800,00 €. The partial set is a one-off item – you will find more classic parts from other makes in our section Other makes.
BMW connecting rod partial set 11242243157 – 4 pcs
M51 diesel · 325 td/tds (E36) · 525 td/tds (E34) · 725 tds (E38) · NOS
800,00 €
View offer →
Compatible vehicles
| Model series | Model | Engine |
|---|---|---|
| BMW 3 Series E36 (sedan, 1991–1998) | 325 td, 325 tds | M51 (six-cylinder diesel) |
| BMW 5 Series E34 (sedan, 1988–1997) | 525 td, 525 tds | M51 (six-cylinder diesel) |
| BMW 7 Series E38 (sedan, 1994–2001) | 725 tds | M51 (six-cylinder diesel) |
Does not fit for the four-cylinder M41 in the 318 tds (11242245435 applies there) and the M21 in the 524 td.
FAQ
Does the connecting rod set 11242243157 fit the BMW 318 tds?
No. The 318 tds has the four-cylinder M41 diesel, for which the different number 11242245435 applies. The number 11242243157 belongs to the six-cylinder M51 diesel in the 325 td/tds (E36), 525 td/tds (E34) and 725 tds (E38).
Why does the set contain only 4 instead of 6 connecting rods?
The complete factory set under 11242243157 consists of 6 connecting rods. A partial set of 4 pcs is offered. To fully equip the six-cylinder engine you additionally need 2 connecting rods of the same number.
Are the connecting rods used or new?
They are New Old Stock: unused genuine BMW connecting rods in the original box, the bearing surfaces are free of wear marks and the connecting rod bushings are undamaged.
Does the set also fit the BMW 524 td?
No. The 524 td (E28/E34) has the older six-cylinder diesel M21. Set 11242243157 is not intended for this engine.
How do I make sure the connecting rods fit my engine?
Send us your VIN (chassis number) and model year before buying. We will check free of charge whether number 11242243157 belongs to your car. Also compare the number on your removed connecting rods or in the parts catalog.
KFZTeile-Thot is a specialist business for tested and refurbished Mercedes parts with its own test benches and also carries selected, tested classic parts from other makes; we have over 1,000 positive eBay reviews. Want to know whether the connecting rod set fits your engine? Call us: +49 179 8991069 (Mon–Fri 8 am–6 pm) – or use our contact form. You can find another BMW guide at BMW E28 heating not regulating – heater control valve 64111373188.