OM656 vs D5 5 cilindros: which engine is more reliable?

The OM656 and the D5 5 cilindros tie on our risk index: 39/100 (moderate risk). The OM656 has 2 documented serious faults, the main one being «Leak in the vacuum-driven coolant pump (fire risk)»; the D5 5 cilindros has 1 documented serious fault, the main one being «Auxiliary belt breakage that takes the timing with it».

Risk index

OM656

Moderate risk · 2 serious faults

Risk index

D5 5 cilindros

Moderate risk · 1 serious fault

The index (0–100) weights the severity and frequency of the three most serious documented faults. How it is calculated

Reviewed on 9 October 202616 sources How we work

Is the OM656 reliable?

The OM656 is the roughly 3.0-litre in-line six-cylinder diesel with which Mercedes-Benz replaced the OM642 V6 from 2017 in the S-Class, E-Class, CLS, GLE, GLS and G-Class (350 d, 400 d and 450 d). It has few documented faults: the known campaign is the coolant pump one of 2021-2022, and the timing chain recall that circulates belongs to the OM654. Guides warn about the AdBlue/SCR system, the EGR and, in isolated cases, the roller rocker arms, without figures.^{[1][2][3][4][5][6][7][8]}

See the 4 of the OM656 faults

Is the D5 5 cilindros reliable?

Volvo's five-cylinder D5 (2.4 D3/D4/D5 and 2.0 D3/D4) has no documented systemic fault, but it does carry one serious risk: several owners report that a snapped auxiliary belt took the timing belt with it. The rest is EGR, DPF and the odd turbo.^[9][10][11]

See the 4 of the D5 5 cilindros faults

Side-by-side comparison

Comparison of OM656 and D5 5 cilindros
Item	OM656	D5 5 cilindros
Technical data
Type	Engine	Engine
Fuel	Diesel	Diesel
Displacement	2,925 cm³	2,400 cm³
Timing	Chain	Timing belt (dry)
Power	272–367 hp	126–215 hp
Production	since 2017^[1][2][12]	2001–2015^{[13][14][15][16]}
Reliability
Risk index (what is it?)	39Moderate risk	39Moderate risk
Documented faults	4	4
Of high or critical severity	2	1
Worst severity	Critical severity	Critical severity
Main faults	Critical severity: Leak in the vacuum-driven coolant pump (fire risk) Medium severity: NOx sensor failure and AdBlue (SCR) system warnings Medium severity: EGR valve clogged with soot after short journeys	Critical severity: Auxiliary belt breakage that takes the timing with it Medium severity: EGR valve and EGR cooler clogged with carbon Medium severity: Clogged diesel particulate filter (DPF)
Most expensive documented repair	No reliable data	up to €1,400Turbocharger failurePublished figure^[11]
Which versions to buy
BuyRecommended versions	OM656 3.0 diesel with electric assistance (D 30, from 2023)^[4][5][7]	None
With cautionVersions to be cautious about	OM656 2.9 diesel 350 d (OM 656 D 29 R SCR, from 2017)^[3][4][5] OM656 2.9 diesel 400 d (OM 656 D 29 SCR, from 2017)^[3][4][5][7]	2.4 D and D5 of 130-163 hp (D5244T, 2001-2009)^[9][10] 2.4 D5 of 175-215 hp and D4 of 181 hp (D5244T4/T10/T11/T14/T15, 2005-2015)^[9][10] 2.0 D3/D4 five-cylinder (D5204T, 2011-2016)^[10][16]
AvoidVersions to avoid	None	None

Severity of each fault: green, low; amber, medium; red, high; dark red, critical. How we rate them

Cars that each one is fitted to

OM656

See the 11 models with the OM656

D5 5 cilindros

See the 10 models with the D5 5 cilindros

Other comparisons

With the OM656

With the D5 5 cilindros

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Sources

Every fact on this page links to its source. If you find an error, let us know.

Mercedes-Benz OM656 engineWikipedia · Other source · consulted 9 October 2026
Mercedes-Benz OM 656Wikipedia (alemán) · Other source · consulted 9 October 2026 · in German
Rückruf für OM 656 und OM 654 Motoren wegen KühlmittelpumpeMBpassion · Motoring press · published 9 December 2021 · consulted 9 October 2026 · in German
Mercedes-Rückruf: Kühlmittelprobleme bei DieselautosAUTOHAUS · Motoring press · published 5 January 2022 · consulted 9 October 2026 · in German
DVSA – base de llamadas a revisiónDVSA (Reino Unido) · Other source · consulted 9 October 2026
Mercedes-Benz GLC (X253): Alle typischen Probleme & MängelGebrauchtwagenberater · Motoring press · consulted 9 October 2026 · in German
Mercedes OM656 Diesel: Häufige Probleme, Ursachen & Tipps zur Vermeidung von MotorschädenMBpassion · Motoring press · published 19 February 2026 · consulted 9 October 2026 · in German
Mercedes-Benz OM656 Engine Guide: Reliability, Common Problems & Tuning PotentialEuro Premium Parts · Technical documentation · consulted 9 October 2026
Fiabilidad Volvo S60 (2010-2017): averías y testimoniosFiches-auto.fr · Other source · consulted 5 October 2026 · in French
Fiabilidad Volvo XC60 (2008-2017): averías y testimoniosFiches-auto.fr · Other source · consulted 5 October 2026 · in French
Problemas Volvo XC90 D5Total Renting · General press · consulted 5 October 2026 · in Spanish
Mercedes-Benz S-Class (W222)Wikipedia · Other source · consulted 9 October 2026
Volvo D5 de 185 CV para S60, V70, XC70 y XC90Autopista · Motoring press · published 27 July 2005 · consulted 5 October 2026 · in Spanish
Volvo V70 (motorizaciones por generación)Wikipedia · Other source · consulted 5 October 2026
Volvo S80 (motorizaciones por generación)Wikipedia · Other source · consulted 5 October 2026
Volvo V60 (motorizaciones de la primera generación)Wikipedia · Other source · consulted 5 October 2026