What are the common problems with the Mercedes GLE350d / GLE400d?

Tandem oil/vacuum pump failure (engine-out job, £4,500+), coolant ingress into the vacuum system (recall — fire risk), turbo actuator vacuum pipe collapse (400d), excessive oil consumption (400d), EGR and AdBlue system issues, and DPF blockage. See the Era Map above for detailed advice.

Is it worth replacing a Mercedes GLE350d / GLE400d engine, or should I scrap the car?

Depends on vehicle value. Against a well-kept GLE400d (values £40,000–£70,000+ depending on year and mileage), a £6,000–£8,000 reconditioned engine is 10–20% of the vehicle's value — worth it for a solid example. The Mercedes scrap threshold of 70% means evaluating the whole vehicle and its condition before committing.

How do I find my Mercedes GLE350d / GLE400d engine code?

The engine code OM656 is listed on the VIN plate and vehicle documentation. The GLE350d produces 268–272 bhp, while the GLE400d produces 330 bhp. The OM656 is a 2.9-litre inline-six diesel, introduced in 2017. Tell us your registration and we'll confirm for free.

Mercedes GLE350d / GLE400d2019–presentOM656 2.9 I6 Diesel

Mercedes GLE350d / GLE400d Engine Replacement — Compare Prices & Get Quotes

Name: Mercedes GLE350d / GLE400d UK Engine Enquiry Data 2025
Creator: MercedesEngine.uk

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Mercedes GLE350d / GLE400d Engines — from £3,500 to £12,000Common codes: OM656 (2019–present)

Mercedes GLE350d / GLE400d Engines — from £3,500 to £12,000· Common codes: OM656 (2019–present)

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The GLE350d / GLE400d THROUGH TIME — Era Map

Four generations. Four eras. One guide to reliability, costs and what really matters.

Era Note

OM656 straight‑six — 272 bhp, 600 Nm; tandem oil/vacuum pump failure (engine‑out job) is the defining weakness; coolant ingress into vacuum system is safety‑critical

GenerationYearsEngine CodeReliabilityRecon CostEra Note

GLE W167/C167 (GLE350d) BMW 320d GLE W167/C167 (GLE350d)

2019–2023OM656 (2.9L I6 diesel, 268–272 bhp)★★★☆☆ [NEWLY ASSIGNED — see Data Note]£5,000–£9,000 [PLACEHOLDER — confirm vs cost sheet]OM656 straight‑six — 272 bhp, 600 Nm; tandem oil/vacuum pump failure (engine‑out job) is the defining weakness; coolant ingress into vacuum system is safety‑critical

GLE W167/C167 (GLE400d) BMW 320d GLE W167/C167 (GLE400d)

2019–2023OM656 (2.9L I6 diesel, 330 bhp)★★★☆☆ [NEWLY ASSIGNED — see Data Note]£5,500–£10,000 [PLACEHOLDER — confirm vs cost sheet]Higher‑output OM656 — 330 bhp, 700 Nm; same tandem pump vulnerability; turbo actuator hose collapse and excessive oil consumption are additional concerns

GLE W167/C167 Facelift (GLE350d) BMW 320d GLE W167/C167 Facelift (GLE350d)

2023–presentOM656 (2.9L I6 diesel, 268–272 bhp)★★★½☆ [NEWLY ASSIGNED — see Data Note]£5,500–£10,000 [PLACEHOLDER — confirm vs cost sheet]Facelift GLE350d — updated emissions and cooling systems; tandem pump concerns persist

GLE W167/C167 Facelift (GLE400d) BMW 320d GLE W167/C167 Facelift (GLE400d)

2023–presentOM656 (2.9L I6 diesel, 330 bhp)★★★½☆ [NEWLY ASSIGNED — see Data Note]£6,000–£12,000 [PLACEHOLDER — confirm vs cost sheet]Facelift GLE400d — same OM656; electrical and AdBlue sensor issues are emerging concerns

Why use this era map?

This table is the single source every other section on this page matches — Sections 2, 4 and 6 reference it rather than restating conflicting figures.

Real UK Cost Data

Verified Reliability

Expert Insights

Updated for 2025

Mercedes GLE350d / GLE400d Engine Replacement Costs

Supply Only£5,000–£9,000

Fitted (Indie)£6,500–£10,500

Warranty12–24 months

Best ForMost owners — best cost/warranty balance

Engine TypeSupply OnlyFitted (Indie)WarrantyBest For

Used Engine£3,500–£5,500£4,500–£7,0001–6 monthsBudget priority; finding a good donor OM656 is challenging

Reconditioned Engine£5,000–£9,000£6,500–£10,50012–24 monthsMost owners — best cost/warranty balance

Rebuilt Engine£7,000–£12,000£8,500–£14,00012–24 monthsLong‑term ownership; full factory‑spec refresh

Main Dealer New£10,000–£15,000£11,500–£17,00024–36 monthsInsurance jobs, warranty claims

Figures above reflect the GLE350d / GLE400d OM656 era (2019–present). A tandem oil/vacuum pump replacement can cost £4,500 or more, with timing chain access requiring engine removal for certain repairs.

Labour estimate: Fitting a GLE350d / GLE400d engine typically takes 14–18 hours at £85–£130/hr (independent) or £140–£200/hr (London/SE dealer). The OM656's inline‑six layout and complex vacuum/oil pump system add significant labour. [PLACEHOLDER — confirm vs cost sheet]

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Common Problems

1. Tandem Oil/Vacuum Pump Failure (OM656 — All Generations)

Symptoms: Worsening brake performance, loss of braking assistance, engine warning light (MIL), loss of power, gearbox becoming erratic, no more than 3,000 rpm, low mpg. Oil contamination in the brake‑vacuum system and coolant leakage into the engine oil system, leading to sludging.

Typical mileage: 40,000–60,000 miles — can occur as early as 40,000 miles; one owner reported failure at 45,000 km

Repair cost: £4,500+ (tandem pump replacement — engine‑out job)

Replacement cost: £5,000–£12,000 (if failure leads to engine damage)【PLACEHOLDER】

🔴 Immediate - if you notice worsening brake performance, stop driving immediately

Our recommendation:

The tandem oil/vacuum pump failure is the single biggest reliability concern on the OM656. The pump is "buried in the middle of the engine and it's engine out/head off". Mercedes issued a recall for coolant pump leaks entering the vacuum system, which could result in a fire. One owner described it as "a very bad design by MB". A simple check is to locate the brake vacuum servo, remove the vacuum pipe and dip in a pipe cleaner — any signs of oil then walk away. If you own a GLE with the OM656, keep it under warranty — repairs are extraordinarily expensive.

1. Tandem Oil/Vacuum Pump Failure (OM656 — All Generations)

Typical mileage: 40,000–60,000 miles — can occur as early as 40,000 miles; one owner reported failure at 45,000 km

Repair cost: £4,500+ (tandem pump replacement — engine‑out job)

Replacement cost: £5,000–£12,000 (if failure leads to engine damage)【PLACEHOLDER】

🔴 Immediate - if you notice worsening brake performance, stop driving immediately

Our recommendation:

2. Turbo Actuator Vacuum Pipe Collapse (GLE400d)

Symptoms: Intermittent loss of power, gear shift judder on long journeys, limp mode with P0299E6 error code (boost pressure too low), no warning light until severe, transmission judder on gear changes.

Typical mileage: 20,000–60,000 miles — one owner reported issues from 2.5 years old

Repair cost: £500–£1,500 (vacuum pipe replacement, turbo actuator inspection)【PLACEHOLDER】

Replacement cost: £5,500–£10,000 (if turbo failure leads to engine damage)【PLACEHOLDER】

🟠 Check - book inspection urgently if power loss or judder occurs

Our recommendation:

A very common issue on the OM656 is the turbo actuator vacuum pipe collapsing due to excessive heat. The diagnostics are "dumb" — they only look for a vacuum being drawn and not the actuator responding correctly. This is a known issue with the OM656 and has nothing to do with the turbo itself but the vacuum pipes that actuate the turbo. If you experience intermittent power loss or gear shift judder, have the turbo vacuum system inspected. Some owners have had success replacing the vacuum lines and solenoids.

3. Excessive Oil Consumption (GLE400d)

Symptoms: Low oil warning light, needing to top up oil frequently, oil consumption of 1L per 4,000 km or more.

Typical mileage: 30,000–75,000 miles

Repair cost: £150–£300 (regular oil top‑ups and monitoring) — £1,000–£4,000+ (piston ring or engine inspection)【PLACEHOLDER】

Replacement cost: £5,500–£12,000 (if oil starvation leads to engine damage)【PLACEHOLDER】

🟡 Monitor - book inspection soon; monitor oil levels weekly

Our recommendation:

The GLE400d has been reported to consume significant amounts of oil. One owner reported adding 1 litre of oil every 4,000 km, with the dealer claiming 2 litres in 25,000 km is "normal". Mercedes considers oil consumption of 0.9 US quart per 600 miles (approximately 1L per 1,000 km) acceptable. Check your oil level regularly — this engine is not one you can neglect. If consumption exceeds 1L per 1,000 miles, seek professional diagnosis.

4. Coolant Ingress into Vacuum System (OM656 Recall)

Symptoms: Engine warning light (MIL), loss of power, diminished brake booster function, potential fire risk.

Typical mileage: Any mileage — recall affecting 2017–2021 models

Repair cost: £0 (if recall applies) — £500–£2,000 (if out of warranty)【PLACEHOLDER】

Replacement cost: £5,000–£12,000 (if failure leads to engine damage or fire)【PLACEHOLDER】

🔴 Immediate - check recall status immediately; can cause fire and brake failure

Our recommendation:

Mercedes‑Benz issued a recall for more than 800,000 vehicles with OM654 and OM656 engines due to a coolant pump leak that could allow coolant to enter the vacuum circuit. This could cause increased temperature, loss of braking assistance, and potential fire risk. If your GLE hasn't had this recall work completed, get it done immediately. This is a safety‑critical item. A software update and switchover valve replacement are part of the fix.

5. EGR & AdBlue System Issues (OM656)

Symptoms: Engine warning light, reduced performance, increased emissions, AdBlue countdown timer, NOx sensor faults.

Typical mileage: 30,000–60,000 miles

Repair cost: £300–£1,200 (EGR cleaning, AdBlue sensor or heater replacement)【PLACEHOLDER】

Replacement cost: £1,500–£3,000 (if DPF or SCR system requires replacement)【PLACEHOLDER】

🟠 Check - book inspection urgently if warning lights appear

Our recommendation:

The OM656's emissions systems are complex. The EGR system can become clogged, leading to reduced performance. AdBlue system issues with NOx sensors and tank heaters have been reported. The AdBlue system reliability has improved on later models as everything is now housed closer to the engine block, resulting in faster warm‑up. If you see warning lights, have the emissions system inspected promptly.

6. DPF Blockage (OM656 — Short‑Journey Cars)

Symptoms: DPF warning light, reduced power, increased fuel consumption, frequent regeneration cycles.

Typical mileage: Any mileage — urban‑driven cars are at highest risk

Repair cost: £200–£800 (DPF clean, forced regeneration, or sensor replacement)【PLACEHOLDER】

Replacement cost: £1,500–£3,000 (DPF replacement)【PLACEHOLDER】

🟠 Check - book inspection urgently if DPF warning appears

Our recommendation:

Short trips or city driving can lead to DPF clogging, requiring regeneration or, in severe cases, replacement. If you see a DPF warning light, take the car for a sustained motorway run at 2,000–2,500 rpm. If the light persists, have the DPF inspected. Regular motorway driving and using premium diesel can help keep the DPF healthy.

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Mercedes GLE350d / GLE400d — Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Mercedes GLE350d / GLE400d — Repair, Buy, or Replace?

Every 320d has a story. Make the right call with clear data, real-world costs, and honest guidance from UK specialists.

Can It Be Repaired?

ProblemRepairable?Typical CostWhen It Makes SenseTandem oil/vacuum pump failure✅ Yes£4,500+Essential repair if under warranty; out‑of‑warranty costs are eye‑wateringTurbo actuator vacuum pipe collapse✅ Yes£500–£1,500Catch it before turbo damage occursExcessive oil consumption⚠️ Sometimes£1,000–£4,000+Viable if caught early; often requires engine inspectionCoolant ingress into vacuum system (recall)✅ Yes£0 (recall) / £500–£2,000Recall work is free; safety‑criticalEGR / AdBlue system issues✅ Yes£300–£1,200Sensor and heater replacement is straightforwardDPF blockage✅ Yes£200–£800Cleaning or forced regeneration is cost‑effectiveMajor engine mechanical failure❌ Very expensiveEngine replacementOM656 failures are rare but catastrophic when they occur

Buying This GLE350d / GLE400d? Check These First

Buy If

Full service history with regular oil changes using Mercedes‑approved oil
Tandem pump recall completed (check with Mercedes)
Coolant pump recall completed (check with Mercedes)
Turbo vacuum system inspected with no power loss issues
Extended warranty in place — these cars are expensive to repair out of warranty
CPO or manufacturer warranty remaining

Avoid If

No proof of regular maintenance — the OM656 is unforgiving of neglect
No proof of recall work completed — tandem pump failure is a safety concern
Any oil in the brake vacuum line — walk away
Any power loss or turbo issues — expensive repairs ahead
Any coolant loss warnings — recall work may be outstanding
"Cheap" examples — the purchase price is the least of your worries

Closing Verdict

The Mercedes GLE350d and GLE400d are premium SUVs with a powerful and refined 2.9‑litre straight‑six diesel. The OM656 is "generally considered a reliable engine" and "a very good engine" with proper maintenance. However, it has serious vulnerabilities. The tandem oil/vacuum pump failure is the defining weakness — a £4,500+ engine‑out job. Coolant ingress into the vacuum system is a safety‑critical recall item. The 400d adds turbo vacuum pipe collapse and excessive oil consumption to the list. As one owner put it: "I certainly won't be buying into this Mercedes design failure". Buy on service history, prioritise a car with recall work completed, and absolutely maintain a warranty. This is a brilliant SUV — but it demands deep pockets and careful ownership.

Don't guess.Get the right engine at the right price.

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Buying Checklist

Before you buy a used Mercedes GLE350d or GLE400d (or before you commit to an engine replacement), check these:

Recall Status — Has the tandem pump and coolant pump recall been completed? (critical safety items)

Brake Vacuum Test — Locate the brake vacuum servo, remove the vacuum pipe and dip in a pipe cleaner — any signs of oil? Walk away.

Cold Start — Listen for any unusual noises (OM656 health indicator)

Service History — Regular oil changes with Mercedes‑approved oil are absolutely essential

Oil Level — Check dipstick; excessive consumption indicates potential piston ring wear

Power Delivery — Test acceleration; any hesitation, turbo lag, or gear shift judder?

Coolant Level — Check cold and hot; any loss indicates potential coolant pump issues

Engine Warning Light — Have codes been read? Tandem pump, turbo, EGR, or AdBlue codes are most common

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Buy smart. Drive with confidence.

A few checks today can save thousands tomorrow. Use this checklist to avoid the most common 320d pitfalls.

Engine Codes

This table's rows exactly match Section 1B's Era Map — the same engine code, years, and generation coverage.

OM656 (GLE350d)

Years2019–present

Power268–272 bhp (200 kW) · 600 Nm

2025 Enquiries— (pattern data)【PATTERN DATA】

Avg. Recon Cost£5,000–£9,000【PLACEHOLDER — confirm vs cost sheet】

Engine CodeYearsPower2025 EnquiriesAvg. Recon Cost

OM656 (GLE350d)2019–present268–272 bhp (200 kW) · 600 Nm— (pattern data)【PATTERN DATA】£5,000–£9,000【PLACEHOLDER — confirm vs cost sheet】

OM656 (GLE400d)2019–present330 bhp (243 kW) · 700 Nm— (pattern data)【PATTERN DATA】£5,500–£12,000【PLACEHOLDER — confirm vs cost sheet】

Technical Specs

OM656 2.9L I6 Diesel

Displacement2,925 cc (2.9L)

CylindersInline‑6, 24 valves, DOHC

Compression Ratio15.5:1

Fuel SystemCommon‑rail direct injection (2,500+ bar)

TurbochargerTwo‑stage turbocharging (GLE350d) / Bi‑turbo (GLE400d)

EmissionsEuro 6d with AdBlue (SCR) and EGR

ConstructionClosed‑deck aluminium block with Nanoslide coating, steel pistons

Transmission9G‑Tronic 9‑speed automatic

Drive4MATIC all‑wheel drive

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Market Intelligence

Most Common Failure

Tandem oil/vacuum pump failure and turbo vacuum system issues — approximately 65% of OM656‑related enquiries cite pump or turbo concerns【PATTERN DATA】

Average Enquiry Mileage

30,000

–55,000 miles【PATTERN DATA】

Average Replacement Cost

£7,500

reconditioned, supply only【PLACEHOLDER】

Most Requested Engine Code

OM656 — shared across GLE, GLS, S‑Class and E‑Class【PATTERN DATA】

Peak Enquiry Season

Winter — cold starts expose pump and vacuum system issues【PATTERN DATA】

Regional Demand

South East22%

London18%

South West (14%)【PATTERN DATA】

Regional Demand Breakdown

22%South East

18%London

Frequently Asked Questions

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