W123 300D shudders when shut off? Check the engine damper
The five-cylinder OM617 diesel in the W123 300 D is considered nearly indestructible, but by design does not run as smoothly as a gasoline engine. If the engine visibly shakes on after shut-off, the steering wheel trembles when starting, or there is a thumping from the engine bay when pulling away, many owners first look at the engine mounts or the injection system. An often-overlooked component is the engine damper: a shock absorber that dampens the rocking movements of the engine. In this guide we show how to recognize a defective engine damper on the W123, how to check it yourself and which replacement part fits.
Symptoms
| Symptom | Likely cause |
|---|---|
| Engine shakes noticeably more than before when shut off | Engine damper without damping effect |
| Thumping or knocking from the engine bay when pulling away and lifting off the throttle | Worn rubber bushings on the engine damper or worn engine mounts |
| Oil film, dirty damper body | Engine damper leaking, damper fluid escaped |
| Strong vibrations at idle in the steering wheel and body | Engine mounts sagged, also check the engine damper |
| Vehicle jerks when lifting off the throttle on overrun (W124/W201 diesel) | Other cause: linkage damper on the injection pump – see Linkage damper guide |
Causes
The engine damper works much like a shock absorber on the suspension: it sits between the engine and the vehicle body and dampens the movements that occur when starting, shutting off and during load changes. Especially in a diesel with its high compression pressure, these forces are considerable. After decades in service, the damper loses effectiveness through internal wear and leaks. Added to this are heat from the engine bay, oil and diesel mist, and aging of the rubber bushings at the mounting eyes. The bushings become hard, crack or wear out – then the damper rattles instead of damping.
A worn engine damper is initially a comfort problem. Over time, however, more movement is transmitted to the engine mounts, radiator hoses, fuel and vacuum lines and the throttle linkage. Replacing it in good time therefore also protects other components.
Testing it yourself
- Visual inspection: Open the hood and inspect the engine damper with a flashlight. Oil film or a damper body caked with dirt indicates a leak.
- Check the rubber bushings: Check the bushings at both mounting points for cracks, hardening and play. Worn bushings can often be recognized by bare chafing marks.
- Start-stop test: A second person starts the engine and shuts it off again while you watch the engine. If the engine rocks noticeably and keeps oscillating, the damper is no longer working.
- Load change at standstill: With the parking brake applied and the brake pedal pressed, briefly shift between forward and reverse (automatic) or carefully engage the clutch (manual transmission). Thumping points to the damper or the engine mounts.
- Removed damper: If the damper can be moved by hand without even resistance or moves jerkily, it is worn. Take the opportunity to check the engine mounts as well.
Solution
A worn engine damper cannot be sensibly repaired, it is replaced. For the W123 300 D, 300 CD and 300 TD with OM617 we have the genuine engine damper with part number A 123 240 09 48 (1232400948) from Stabilus in stock. It is NOS (new old stock): unused and from old stock, in the original Mercedes box. Price: 64,90 €. When installing, it is advisable to check the condition of the mounting parts and rubber bushings and to tighten the bolts to the specified torque.
Engine damper W123 300 D / 300 CD / 300 TD
Part number: A 123 240 09 48 (1232400948) · Stabilus · NOS, unused
64,90 €
To the engine damperYou can find more parts for your Benz in our category Spare parts for the W123.
Compatible vehicles
| Model series | Model | Engine |
|---|---|---|
| W123 (Sedan) | 300 D | OM617 |
| W123 (Coupe) | 300 CD | OM617 |
| W123 (Wagon) | 300 TD | OM617 |
Fitment for other engine variants is not documented. Please compare the part number on your removed damper or ask us with your VIN.
Do you drive a W123 diesel and the key sticks when starting? Also read our guide Ignition lock and steering lock on the W123/W126 diesel.
FAQ
How do I recognize a defective engine damper on the W123 300 D?
Typical signs are noticeably stronger shaking when starting and shutting off the engine, knocking or thumping from the engine bay during load changes, and traces of oil or cracked rubber bushings on the damper itself.
What part number does the engine damper for the W123 300 D have?
The engine damper offered here carries the Mercedes part number A 123 240 09 48 (1232400948) and, according to the product data, is intended for the W123 300 D, 300 CD and 300 TD with OM617.
Can I keep driving with a defective engine damper?
In the short term yes, the engine is still carried by the engine mounts. Over time, however, more movement is transmitted to the engine mounts, hoses, lines and linkages, so the damper should be replaced promptly.
Is the engine damper the same as an engine mount?
No. The engine mounts carry the weight of the engine; the engine damper only dampens the rocking movements of the engine. Both components age, but they should be checked separately when troubleshooting.
Does the engine damper 1232400948 also fit other W123 diesels?
According to our product data, fitment is documented for the W123 300 D, 300 CD and 300 TD with OM617. For other engine variants, please compare the part number on your vehicle beforehand or ask us with your VIN.
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. Not sure whether the engine damper fits your car? Call us at +49 179 8991069 (Mon–Fri 8 am–6 pm) or write to us via the contact form.