Mercedes M274 Rattle on Cold Start: What It Means and What to Do

By Shlomi Kuba, Co-Founder and Head Mechanic, K&G Automotive. Published October 2026.

Good news first: a rattle on a cold start is something Shlomi Kuba, owner and head mechanic, and the team at K&G Automotive know well, and when it is checked early the cause can be found and fixed properly. Having it looked at promptly can save you money and prevent more serious engine damage.

Shlomi Kuba inspecting a Mercedes-Benz C-Class on the hoist at K&G Automotive in Underwood
Shlomi Kuba inspecting a Mercedes-Benz C-Class in the K&G Automotive workshop

Quick answer: A metallic rattle on a cold start in a Mercedes-Benz M274 engine usually points to the timing system, such as the timing chain tensioner, a worn timing chain, the camshaft adjusters or oil pressure. These symptoms do not necessarily mean the timing chain needs replacing. The right diagnosis finds the actual cause before any parts are replaced.

Which Mercedes Models Have the M274 Engine?

The M274 is a four cylinder petrol engine commonly found in selected Mercedes-Benz C-Class, E-Class, GLC, GLK and SLK/SLC models. If you are not sure which engine your car has, call us on 07 3341 2008 and we will happily talk it through with you.

What Causes the M274 Timing Chain Rattle?

Several components can contribute to a rattling noise when the engine starts:

  • Timing chain tensioner: if there is not sufficient tension on the chain when the engine starts, it can make a metallic rattle.
  • Timing chain wear: a worn chain can affect the engine timing and trigger fault codes.
  • Camshaft adjusters: worn or malfunctioning adjusters can cause abnormal noises and timing problems.
  • Oil pressure: low oil pressure or poor lubrication can affect the hydraulic timing parts that rely on oil to work.

These symptoms do not necessarily mean the timing chain needs replacing, which is why the right diagnosis matters.

What Warning Signs Should Mercedes Owners Watch For?

A rattle that lasts a second or two and then stops is the early stage. Book an inspection if you notice any of these:

  • The rattle lasts longer than a few seconds, or you hear it when the engine is warm
  • The engine warning light comes on
  • Rough idle, hesitation or a loss of power
  • Fault codes P0016 or P0017

Your engine computer checks that the crankshaft (which the pistons turn) and the camshafts (which open and close the valves) stay lined up. If they are out of alignment, a warning light may appear with fault codes such as P0016 or P0017. The code tells us where to look, not which part has failed.

How We Diagnose an M274 Rattle at K&G Automotive

We specialise in diagnosing and repairing complex Mercedes-Benz engine problems, which is why other workshops refer difficult diagnostic and repair work to us. Our philosophy is simple: diagnose correctly, repair professionally and avoid unnecessary parts replacement.

Our workshop is equipped with professional diagnostic equipment, including the Autologic diagnostic tool for European vehicles, and the dedicated Mercedes-Benz special tools needed to carry out timing repairs accurately and professionally. This is how we work through it:

  1. We talk to you first. When does it rattle, how long does it last, and when was the car last serviced?
  2. We read the fault codes and live timing data with our diagnostic equipment.
  3. We investigate the timing chain, tensioner, camshaft adjusters and associated systems, using proven testing procedures.
  4. We check the oil level, condition and grade.
  5. We explain what we found in plain English, and agree the work and an upfront price with you before we start.

“I had a engine light issue that Mercedes couldn’t seem to remedy. At short notice Shlomi was able to identify and solve the issue”

David, Mercedes owner, Google review

How Regular Servicing Helps Prevent Timing Problems

Parts of the M274 timing system rely on oil pressure, so oil does more work here than most owners realise. Servicing on time with oil that meets the Mercedes-Benz specification is the simplest way to protect the timing system.

Our Mercedes servicing and logbook servicing follows the manufacturer’s specifications, and it does not affect your new car warranty.

Why Choose K&G Automotive for Your Mercedes?

When you bring your Mercedes to K&G Automotive, you talk directly to the mechanic working on your car, and you get an honest, upfront price before any work begins.

We are European car specialists with deep Mercedes-Benz experience, and we have been looking after customers across Brisbane Southside for 18 years. We are a multi award winning business, with five Logan Business Distinction Awards, including Logan Business of the Year in 2018 and the Automotive and Transport category three years running in 2024, 2025 and 2026.

Our customers rate our care 4.7 stars from more than 600 Google reviews, and our prices are up to 50 percent lower than dealer group pricing.

About K&G Automotive

K&G Automotive is a family owned, multi award winning European car specialist in Underwood, Brisbane, established in 2008 by Shlomi and Einat Kuba.

  • Address: 1/20 Ferguson Street, Underwood QLD 4119, next door to Springwood
  • Phone: 07 3341 2008
  • Opening hours: Monday to Thursday, 7:30 am to 5:30 pm
  • Labour rate: $180 per hour including GST
  • Specialists in: Mercedes-Benz, BMW, Audi, Volkswagen, Mini, Skoda and Land Rover
  • Services: logbook servicing, advanced diagnostics, brakes, wheel alignment, batteries, starting and charging, engine cooling, climate control and pre-holiday servicing

M274 Rattle FAQs

Yes. It is a known symptom of this engine and usually points to the timing system. It is worth having checked early, because the cause is usually easier and less expensive to fix before it gets worse.

Your engine computer checks that the crankshaft and camshafts stay lined up. If they are out of alignment, it can turn on the warning light and show a P0016 or P0017 fault code. The code tells us where to look, not which part has failed, so the next step is a proper diagnosis.

Not necessarily. The tensioner, camshaft adjusters and oil pressure can all cause a similar noise. Replacing a timing chain is a big job, so we confirm the actual cause before recommending it.

A short rattle that stops straight away is not an emergency, but it is worth booking in. If it is getting longer or louder, or the engine warning light is on, have it inspected soon rather than waiting for your next service, as certain timing faults can lead to serious engine damage if left.

No. Using an independent repairer does not void your manufacturer’s new car warranty, as long as the work follows the manufacturer’s specifications using suitable parts, which is exactly how we work. Tell us when you book if your Mercedes is still under warranty.

Book Your Mercedes-Benz Inspection

If your Mercedes has a rattle on start up, an engine warning light or a suspected timing problem, call K&G Automotive on 07 3341 2008. You will talk directly to our mechanics, who are happy to talk it through with you, and you will get an honest price before any work begins.

Ready to go ahead? You can also book online.

Written by Shlomi Kuba, Co-Founder and Head Mechanic at K&G Automotive.

With over 25 years of hands-on experience and a background in mechanical engineering, Shlomi specialises in servicing and repairing European vehicles including Mercedes, BMW, Audi, VW, Mini, and Skoda. He is known for his expert diagnostics, high-quality workmanship, and genuine commitment to customer care, always taking the time to explain repairs clearly and offer honest, practical advice.

Shlomi holds a Bachelor of Mechanical Engineering, trained at automotive centres in Germany, and worked for Mercedes-Benz dealerships in Israel and then the Mercedes-Benz Brisbane dealership before founding K&G Automotive with his wife Einat in 2008. He was named Best Technician in Europe at the 2002 Mitsubishi Motors European Technician Olympics.

Read more about Shlomi