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Mercedes-Benz · Known Issues

2018 Mercedes-Benz B-Class Problems: 8 Known Issues

2018 model year · 970+ owner reports · Updated September 2026

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Issue summary

According to Au7o's analysis of 970+ owner reports, the 2018 Mercedes-Benz B-Class has 8 documented known issues, with 2 rated critical. The most serious are M270 Timing Chain Stretch and Cold-Start Rattle (Petrol) ($350-$1,800 repair) and OM651 Diesel DPF and EGR Clogging (B180 CDI / B200 CDI) ($200-$2,500 repair). The most commonly reported issue is Dual-Clutch Transmission (DCT) Shudder at Low Speeds with 680 owner reports. Across all issues with published estimates, repair costs range from $50 to $3,500. DIY maintenance guides at au7o.io.

In This Article

  • B-Class Engine2
  • B-Class Emissions1
  • B-Class Transmission1
  • B-Class Electrical1
  • B-Class Body/Panels1
  • B-Class Brakes1
  • B-Class Cooling1
  • FAQ
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In This Article

  • Engine2
  • Emissions1
  • Transmission1
  • Electrical1
  • Body/Panels1
  • Brakes1
  • Cooling1
  • FAQ

All 8 Known Issues

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On the 2013-2019 Mercedes-Benz B-Class, the turbo petrol M270 (and naturally-aspirated M270/M274 in B180/B200/B250) uses a two-stage timing chain whose plastic guide rails and hydraulic tensioner degrade prematurely. Owners report a loud metallic rattle for roughly 1-15 seconds on cold start that fades as oil pressure builds. Short-trip urban use accelerates the problem because the cold-start period (low oil pressure) makes up a large share of running time. Stretch typically appears from ~80,000 km (50,000 mi), with some city cars rattling from ~70,000 km. Left unaddressed, chain stretch alters valve timing, throws fault codes, and risks contact/wear on cam bearings and phasers.

Common Symptoms

  • Metallic rattle on cold start lasting 1-15 seconds
  • Rattle fades once engine warms
  • Rough running or misfire
  • Reduced power
  • Check engine light

How to Fix

Diagnose with a cold-start listen and read live chain/cam-position data via XENTRY. If only the tensioner is at fault, replacing the hydraulic chain tensioner first is the cheaper initial fix; if the chain is stretched, replace the complete OEM timing kit (chain, both guide rails, tensioner, and cam phaser sprockets if worn) to avoid consequential damage. Use the correct MB-Approval 229.5/229.51 0W-40 or 5W-40 oil and shorten oil-change intervals on short-trip cars.

Typical repair cost:$350 - $1,800

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Community Reported
High ConfidenceVerifiedReviewed Jun 2026
Community reported
290 owners

On the 2013-2019 Mercedes-Benz B-Class, the turbo oil feed line on the M270 engine in the B-Class develops leaks at the banjo bolt connection on top of the turbocharger. Oil drips onto the hot exhaust manifold, producing a burning oil smell and visible smoke from the engine bay.

This issue also affects: Alfa Romeo Stelvio

Common Symptoms

  • Burning oil smell from engine bay
  • Visible smoke from under hood
  • Oil drips on exhaust manifold
  • Low oil level between services

How to Fix

Replace the turbo oil feed line and both copper crush washers at the banjo bolt connections. Inspect the turbo for bearing play while the line is disconnected. Clean oil residue from the exhaust manifold to eliminate the burning smell.

Owner tips & cautions

  • WarningOil on a hot exhaust manifold is a fire risk. Address the leak promptly and monitor oil level weekly until repaired.
Typical repair cost:$300 - $900

Research This Issue

Based on 290 owner reports

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Community Reported
Medium Confidence290 owner reportsLast reported by owners Mar 2025Reviewed Mar 2026

On the 2013-2019 Mercedes-Benz B-Class OM651 2.1L/2.2L diesel, the 2.2L OM651 diesel in B180 CDI / B200 CDI variants is prone to diesel particulate filter (DPF) blockage and EGR-valve carbon fouling, especially on short urban trips where the exhaust never reaches regeneration temperature. Symptoms include reduced power (limp mode), increased fuel consumption, frequent failed regenerations, and warning lights. Carbon buildup in the EGR valve and intake also causes hesitation and rough running. The OM651 timing chain can also stretch and rattle, compounding diesel reliability concerns.

Common Symptoms

  • Reduced power / limp mode
  • DPF / engine warning light
  • Increased fuel consumption
  • Frequent or failed regenerations
  • Hesitation and rough running

How to Fix

Take the car for sustained high-speed driving to allow a complete regeneration; if the DPF is heavily loaded, perform a forced regen via XENTRY or a professional DPF clean, and in severe cases replace the DPF. Clean or replace a fouled EGR valve and clear intake carbon. Read soot-load and differential-pressure data to confirm. Diagnose and fix any underlying cause (failed glow plugs, leaking injectors, faulty differential-pressure sensor) before replacing the filter. Maintain with correct low-SAPS oil and longer drive cycles.

Typical repair cost:$200 - $2,500

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Community Reported
High ConfidenceVerifiedReviewed Jun 2026
Community reported
680 owners

On the 2013-2019 Mercedes-Benz B-Class 2.0L Turbo I4, the 7-speed dual-clutch transmission (7G-DCT) in the B-Class develops a noticeable shudder during low-speed maneuvers and from a standstill. The issue stems from clutch pack wear and adaptive software that struggles to compensate as the clutch material thins over time.

This issue also affects: Alfa Romeo Stelvio

Common Symptoms

  • Vibration during low-speed acceleration
  • Jerky takeoff from stop
  • Shuddering between 1st and 2nd gear
  • Hesitation when creeping in traffic

How to Fix

Start with a DCT adaptation reset via Mercedes XENTRY diagnostic tool. If shudder persists, the dual-clutch assembly requires replacement. Updated clutch packs with revised friction material are available and significantly improve longevity.

Owner tips & cautions

  • TipA transmission adaptation reset often buys time, but the clutch pack will eventually need replacement. Budget for it around 60,000-80,000 miles.
Typical repair cost:$200 - $3,500

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Based on 680 owner reports

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Community Reported
High Confidence680 owner reportsLast reported by owners Jun 2025Reviewed Mar 2026

On the 2013-2019 Mercedes-Benz B-Class, the W246 tailgate (boot) locking system is a frequently reported electrical weak point. Corroded contacts in the lock actuator, a defective interior release lever, or water ingress from a leaking rear-washer hose cause the boot to fail to open or lock. Keyless-Go interaction and a weak key battery can compound the symptom. Electrical faults account for a large share of W246 complaints, and the tailgate lock is among the most-cited. The emergency release cable behind the rear seat backrest is the temporary workaround when the boot will not open.

Common Symptoms

  • Boot/tailgate will not open from button or key
  • Boot will not lock
  • Intermittent operation in damp weather
  • Must use emergency release cable behind rear seat

How to Fix

Clean the actuator contacts with electrical contact cleaner and apply dielectric grease (preventive cleaning roughly every 30,000 km is advised). Repair or re-solder corroded wiring (a Mercedes repair kit with heat-shrink is commonly used). For a permanently defective actuator, replace the lock actuator and re-teach the component via XENTRY. Fix any leaking rear-washer hose that allows water into the lock mechanism, and dry/clean affected connectors.

Typical repair cost:$50 - $500

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Community Reported
High ConfidenceVerifiedReviewed Jun 2026

On the 2013-2019 Mercedes-Benz B-Class, w246 cars fitted with the panoramic glass roof suffer water ingress when the front-corner sunroof drain tubes clog with leaves and debris, or when the perimeter rubber seal wears. Owners report water entering at the front edge / A-pillar area and pooling in the footwell, with damp carpet, headliner staining, and musty smells. The drains are located at the right and left front of the sunroof. Trapped water can also reach electrical modules under the carpet.

Common Symptoms

  • Water in driver/passenger footwell
  • Damp or wet carpet
  • Headliner water stains
  • Musty/damp smell in cabin
  • Dripping at A-pillar or front roof edge

How to Fix

Inspect and flush the four sunroof drain tubes with low-pressure compressed air or a gentle water stream to clear debris; verify water exits at the rocker/sill outlets. Inspect and replace the perimeter sunroof seal if cracked, shrunken, or deformed. Dry the carpet/headliner and check underfloor connectors for corrosion. Periodic drain cleaning is the key preventive step.

Typical repair cost:$0 - $400

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Community Reported
Medium ConfidenceVerifiedReviewed Jun 2026

On the 2013-2019 Mercedes-Benz B-Class, w246 owners report the electronic parking brake (EPB) sticking or showing a malfunction warning on the dashboard. The fault is typically a failing parking-brake actuator motor, corroded cables/connectors, or a software glitch in the control module. The brake may fail to release, refuse to apply, or trigger an EPB warning, which can immobilize the car or require service before driving.

Common Symptoms

  • Electronic parking brake malfunction warning
  • Parking brake will not release
  • Parking brake will not apply
  • Brake fault message on dashboard

How to Fix

Fault-read the EPB control module with XENTRY/STAR. Inspect and clean cabling and connectors, update/recalibrate the EPB control-module software if a glitch is found, and replace the parking-brake actuator motor if it has failed. Recalibrate the system after any actuator or cable replacement.

Typical repair cost:$200 - $900

Research This Issue

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Community Reported
Medium ConfidenceVerifiedReviewed Jun 2026

On the 2013-2019 Mercedes-Benz B-Class, the M270/M274 petrol engines use a map-controlled, electronically actuated thermostat integrated into a plastic housing that cracks or warps with age and heat cycling, becoming a common slow coolant-leak point. Early symptoms are a sweet coolant smell from the engine bay and a gradually dropping coolant level with no visible puddle (it evaporates on hot surfaces), plus temperature-gauge fluctuation or slow warm-up as the thermostat starts sticking. On a cold-day test drive the car should reach ~80 C within 10-15 minutes; if it hovers below, suspect the thermostat. It is an expensive, dealer-favored repair because of access.

This issue also affects: Infiniti Q50, Infiniti Q60

Common Symptoms

  • Sweet coolant smell from engine bay
  • Slowly dropping coolant with no visible puddle
  • Temperature gauge fluctuation
  • Slow warm-up / engine not reaching ~80 C
  • Coolant warning

How to Fix

Pressure-test the cooling system and inspect the thermostat housing for seepage. Replace the complete thermostat/housing assembly with the genuine Mercedes part (aftermarket replicas have a high repeat-failure rate on M270), refill with the correct MB-spec coolant, and bleed the system. Address any concurrent water-pump weep-hole leak at the same time.

Typical repair cost:$300 - $1,000

Research This Issue

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Community Reported
High ConfidenceVerifiedReviewed Jun 2026
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Frequently Asked Questions

What are the most common Mercedes-Benz B-Class problems?

According to Au7o's analysis of 970+ owner reports, the 2018 Mercedes-Benz B-Class has 8 documented issues. The most frequently reported are: M270 Timing Chain Stretch and Cold-Start Rattle (Petrol), OM651 Diesel DPF and EGR Clogging (B180 CDI / B200 CDI), Dual-Clutch Transmission (DCT) Shudder at Low Speeds. Of these, 2 are rated critical and should be addressed promptly.

Is the Mercedes-Benz B-Class reliable?

The 2018 Mercedes-Benz B-Class has 8 known issues documented across 970+ owner reports. 2 issues are rated critical: M270 Timing Chain Stretch and Cold-Start Rattle (Petrol) and OM651 Diesel DPF and EGR Clogging (B180 CDI / B200 CDI). Prospective buyers should inspect for these issues and factor potential repair costs into their purchase decision. Regular maintenance following the manufacturer's schedule helps prevent many common problems.

How much does it cost to fix common Mercedes-Benz B-Class problems?

Repair costs for known Mercedes-Benz B-Class issues range from $0 to $3,500, depending on the specific problem and whether you choose DIY or professional repair. The most critical issue, M270 Timing Chain Stretch and Cold-Start Rattle (Petrol), typically costs $350-$1,800 to repair. Au7o provides step-by-step DIY maintenance guides that can help reduce repair costs.

What is the 2013-2019 Mercedes-Benz B-Class M270 Timing Chain Stretch and Cold-Start Rattle (Petrol)?

The turbo petrol M270 (and naturally-aspirated M270/M274 in B180/B200/B250) uses a two-stage timing chain whose plastic guide rails and hydraulic tensioner degrade prematurely. Owners report a loud metallic rattle for roughly 1-15 seconds on cold start that fades as oil pressure… Repairs typically run $350-$1,800. Severity: high.

What is the 2013-2019 Mercedes-Benz B-Class OM651 Diesel DPF and EGR Clogging (B180 CDI / B200 CDI)?

The 2.2L OM651 diesel in B180 CDI / B200 CDI variants is prone to diesel particulate filter (DPF) blockage and EGR-valve carbon fouling, especially on short urban trips where the exhaust never reaches regeneration temperature. Symptoms include reduced power (limp mode), increased… Repairs typically run $200-$2,500. Severity: high.

Content on this page was compiled with AI assistance using NHTSA complaints, TSBs, owner reports, and public automotive data. While we strive for accuracy, this information may contain errors. Always verify repair procedures and specifications with your vehicle's service manual or a qualified mechanic.

Data sourced from 970+ owner reports, NHTSA recalls, TSBs, and automotive forums.

What is the 2013-2019 Mercedes-Benz B-Class Dual-Clutch Transmission (DCT) Shudder at Low Speeds?

The 7-speed dual-clutch transmission (7G-DCT) in the B-Class develops a noticeable shudder during low-speed maneuvers and from a standstill. The issue stems from clutch pack wear and adaptive software that struggles to compensate as the clutch material thins over time. Repairs typically run $200-$3,500. Severity: medium.

What is the 2013-2019 Mercedes-Benz B-Class Turbocharger Oil Feed Line Leak?

The turbo oil feed line on the M270 engine in the B-Class develops leaks at the banjo bolt connection on top of the turbocharger. Oil drips onto the hot exhaust manifold, producing a burning oil smell and visible smoke from the engine bay. Repairs typically run $300-$900. Severity: medium.

What is the 2013-2019 Mercedes-Benz B-Class Tailgate / Boot Lock Actuator Electrical Failure?

The W246 tailgate (boot) locking system is a frequently reported electrical weak point. Corroded contacts in the lock actuator, a defective interior release lever, or water ingress from a leaking rear-washer hose cause the boot to fail to open or lock. Keyless-Go interaction and… Repairs typically run $50-$500. Severity: medium.

What is the 2013-2019 Mercedes-Benz B-Class Panoramic Sunroof Drain Clog and Water Leak?

W246 cars fitted with the panoramic glass roof suffer water ingress when the front-corner sunroof drain tubes clog with leaves and debris, or when the perimeter rubber seal wears. Owners report water entering at the front edge / A-pillar area and pooling in the footwell, with dam… Repairs typically run $0-$400. Severity: medium.

What is the 2013-2019 Mercedes-Benz B-Class Electronic Parking Brake Actuator Malfunction?

W246 owners report the electronic parking brake (EPB) sticking or showing a malfunction warning on the dashboard. The fault is typically a failing parking-brake actuator motor, corroded cables/connectors, or a software glitch in the control module. The brake may fail to release,… Repairs typically run $200-$900. Severity: medium.

What is the 2013-2019 Mercedes-Benz B-Class Plastic Thermostat Housing Coolant Leak (M270)?

The M270/M274 petrol engines use a map-controlled, electronically actuated thermostat integrated into a plastic housing that cracks or warps with age and heat cycling, becoming a common slow coolant-leak point. Early symptoms are a sweet coolant smell from the engine bay and a gr… Repairs typically run $300-$1,000. Severity: medium.