Oil pump chain rattles on W124 W126: check & replace
A rattle from the lower part of the engine that lasts a few seconds after a cold start, or an oil pressure gauge that drops further than usual at warm idle: many owners of a W124 or W126 first think of the timing chain or a faulty gauge. One component that is often overlooked is the oil pump chain. It sits at the bottom of the engine and drives the oil pump. This guide shows how to recognize a stretched oil pump chain, how to check in a sensible order, and which chain fits your engine.
Unused iwis oil pump chain 0019970294: single-row, 52 links, endless-riveted.
Symptoms
| Symptom | Likely cause |
|---|---|
| Rattling at the front bottom of the engine, especially after a cold start | Stretched oil pump chain, worn sprockets |
| Oil pressure fluctuates at idle or builds up slowly | Oil pump drive with play, alternatively low oil level or worn bearings |
| Rattling at the top of the engine around the valve cover | More likely the timing chain, chain tensioner or guide rails – not the oil pump chain |
| Oil pressure gauge permanently reads zero or jumps, but the engine runs normally | Often a faulty gauge or sender – see Faulty oil pressure gauge on the W124 |
Important: If the oil pressure gauge suddenly shows no pressure and the warning light also comes on, shut off the engine immediately. Check first, then drive on.
Causes
The oil pump chain transmits the rotation of the crankshaft positively to the oil pump so that oil pressure builds up in step with engine speed. It sits at the front bottom of the engine behind the front cover, between the crankshaft sprocket and the oil pump sprocket, and is not to be confused with the upper camshaft drive.
After three or four decades and often several hundred thousand kilometers, the pins and bushings of the chain links wear. As a result, the chain becomes longer, runs over the sprockets with more play and starts to slap. Infrequent oil changes and long periods of standing accelerate this wear. Because the oil pump chain is easily forgotten when only the timing chain is replaced, the original chains are still fitted in many vehicles.
Testing it yourself
Work from the simplest step to the most involved:
- Check oil level and oil condition. Too little oil or heavily aged oil also leads to low oil pressure and noises. This is the cheapest thing to rule out.
- Watch the oil pressure gauge. Note the reading cold and warm, each at idle and at raised engine speed. A clear drop only at warm idle is an indication, but not yet proof.
- Cross-check the gauge. Have the oil pressure measured with a mechanical pressure gauge. This lets you separate a fault in the gauge or sender from a real pressure problem.
- Narrow down the noise. Listen with a stethoscope or a long screwdriver held to your ear: does the rattling come from the front bottom or from the top at the valve cover?
- Visual inspection after opening. If the front cover is open anyway, for example during a timing chain replacement, check the chain and sprockets for play and wear. Compare the number of links and the chain pitch of the old part.
For diesel engines with increased oil consumption, it is also worth a look at our guide OM601 smokes blue – valve stem seals, because oil loss past the valve stems lowers the oil level and thus the oil pressure as well.
Solution
A stretched chain cannot be adjusted – it is replaced. The most economical approach is to replace it together with the timing chain, since the front of the engine is open anyway. Also check the sprockets: heavily worn teeth shorten the life of a new chain.
We offer the matching chain with the part number 0019970294 : an unused iwis chain (NOS) in its original box, single-row, 52 links, endless-riveted. The box shows signs of storage. Price: 29,90 €.
Caution, risk of mix-ups: This chain is not suitable for OM615, OM616 and OM617 – the double-row duplex chain with 42 links and the number A0009978194 belongs there. Also does not fit M116, M117 as well as M104, M111 and M112, which require 46 or 48 links.
iwis oil pump chain 0019970294 – 52 links
NOS in original box · single-row · endless-riveted · M103, OM601, OM602, OM603
29,90 €
View offer →You will find more parts for your model series in the category W124 as well as under Other spare parts.
Compatible vehicles
| Model series | Models |
|---|---|
| W124 E-Class (1984–1997) | 260 E, 260 E 4matic, 300 E, 300 E 4matic, 300 CE, 250 D, 300 D, 300 D 4matic |
| W126 S-Class (1979–1991) | 300 SE, 300 SEL |
| R129 SL-Class (1989–2002) | 300 SL |
| W463 G-Class (from 1989) | 300 GE, 250 GD |
Engines per product listing: M103, OM601, OM602, OM603. Compare the number of links (52) and the chain pitch with your old part before buying. Not sure? Send us your VIN (chassis number) and model year via the contact form – we will check free of charge whether the chain fits.
FAQ
How do I recognize a stretched oil pump chain?
Typical signs are a rattling noise at the front bottom of the engine, especially shortly after a cold start, and oil pressure that fluctuates at idle or is noticeably low. Only a look at the chain and sprockets after opening the engine gives certainty.
Does chain 0019970294 also fit OM615, OM616 or OM617?
No. Chain 0019970294 has 52 links and is single-row. OM615, OM616 and OM617 require the double-row duplex chain with 42 links and the number A0009978194. It also does not fit M116, M117, M104, M111 and M112.
Should I replace the oil pump chain when replacing the timing chain?
Yes. If the front of the engine is open anyway, the oil pump chain should be included, likewise with a rattling oil pump drive. The additional effort is then small.
How many links does the oil pump chain for the W124 have?
Chain 0019970294 has 52 links and, according to our product data, fits among others the 260 E, 300 E, 300 CE, 250 D and 300 D. Compare the number of links and the chain pitch with your old part before buying.
What condition is the chain on offer in?
It is an iwis NOS chain in its original box: unused and endless-riveted. The box shows signs of storage.
KFZTeile-Thot is a specialist business for tested and refurbished Mercedes parts with its own test benches and has over 1,000 positive eBay reviews. Do you have questions about the oil pump chain or your engine? Call us at +49 179 8991069 (Mon–Fri 8 am–6 pm) or write to us via the contact form.