The MG ZR, ZS and ZT cover six engine families. The Rover K-series powers the ZR (1.4, 1.6, 1.8) and ZS (1.6, 1.8), and the entry petrol ZTs (1.8 NA and 1.8 turbo). The 2.5 KV6 powers the ZS 180 and ZT 160/180/190. The L-series 2.0 turbodiesel powers the ZR TD and ZS TD; the BMW M47R common-rail diesel powers the ZT CDTi 116 and 135; the 4.6 Ford Modular V8 powers the rear-wheel-drive ZT 260 alone.
Engine number prefix and VIN are the essential ordering references, the K-series alone covers four capacities and a turbocharged 1.8, with non-VVC, VVC and turbo head castings that are not interchangeable.
The Rover K-Series and the MLS Head Gasket Fix
The K-series is the most widely fitted engine in the section: an all-aluminium DOHC 16-valve four-cylinder with damp cylinder liners, used in the ZR 105 (1.4, 14K4F), ZS 110 (1.6, 16K4F), ZR 120, ZS 120 and ZT 120 (1.8 non-VVC, 18K4F), ZR 160 (1.8 VVC, 18K4K) and the ZT 160 from mid-2003 with a low-pressure 1.8 K-turbo (18K4F THP) unique to the ZT. VVC and turbo head castings are not interchangeable with non-VVC components. Service items overlap with the Rover 25, 45, 75 and Land Rover Freelander 1, but ancillary brackets, looms, manifolds and ECU calibrations are model-specific. The K-series head gasket is the most discussed maintenance topic on these cars.
The original elastomer gasket is prone to failure on engines run cold or with a neglected cooling system. The well-established fix is the multi-layer steel (MLS) gasket, originally developed by Land Rover for the Freelander, fitted with 10.9-grade head bolts and a strengthened lower oil rail as a complete kit. Cylinder liner protrusion must be checked: liners must stand proud of the block face by 0.05 to 0.13mm and the protrusion must be even across all four cylinders. The further-uprated NAC-era 'N-series' kit refines the same MLS principle.
Correctly fitted to a sound bottom end, the head gasket issue is considered definitively resolved.
The KV6 V6 in ZS 180 and ZT 160/180/190
The 2.5-litre KV6 (90-degree, 24-valve, four-camshaft V6) powers the ZS 180 (177 PS) and three states of tune in the ZT range: a software-detuned 160 PS unit used until replaced by the 1.8 K-turbo in mid-2003, the 177 PS ZT 180 Auto from January 2002, and the 190 PS 'Plus' specification with bespoke camshafts, air intake and throttle body. The KV6 has a serpentine front timing belt driving the inlet cams and water pump, plus two short rear link belts driving the exhaust cams via floating pulleys requiring special setting tools. Cambelt service is labour-intensive; the recommended interval is 60,000 miles or five years, with front belt, rear link belts, water pump and tensioners as one. The plastic inlet manifold and plastic thermostat housing are routine wear items on high-mileage cars.
The L-Series and BMW M47R Diesels
The Rover L-series 2.0 turbodiesel (1,994cc, VP30 pump, Garrett GT1549 turbo) is the diesel of choice for the ZR and ZS, in two states of tune: TD 100 (99 bhp, 240 Nm) and TD 115 (111 bhp, 260 Nm). It is widely admired for its tunability, manual boost, SDI injectors and a remap can lift output toward 150 to 160 bhp without bottom-end work. Service items overlap with the Rover 25 and 45, but the Freelander 1 SDi uses a VP37 pump and is not interchangeable. The ZT CDTi 116 and 135 use the BMW M47R, a Rover-specific common-rail turbodiesel engineered jointly by Rover Group and BMW's Steyr plant for transverse installation.
The 1,951cc unit shares its core block and head castings with the longitudinal M47D20 fitted to BMW's 3 and 5 Series, but differs in injection (common-rail against VP44 distributor pump), turbocharger (Mitsubishi with wastegate), engine management and exhaust routing. The CDTi 135 was introduced in 2002 with the X Power software upgrade and intercooled specification. Injectors, fuel rail, turbochargers and management parts should be verified against the M47R designation rather than the broader BMW M47 family.
The Ford Modular 4.6 V8 in ZT 260
The ZT 260 and ZT-T 260 use a 4,601cc SOHC two-valve-per-cylinder Ford Modular V8 from the 2004 Mustang GT, producing 256 bhp and 302 lb·ft (409 Nm), with cast-iron block and aluminium heads. Mounted longitudinally, it drives the rear wheels through a Tremec TR-3650 5-speed manual gearbox (the only non-Ford OEM application) feeding a Dana Hydratrak limited-slip differential via a two-piece propeller shaft. The conversion was developed by Prodrive with input from Roush, with a unique exhaust, relocated battery, new heater installation and substantially revised chassis structure. Engine ancillaries (intake, exhaust, cooling, mounts and accessory drive) are MG-specific even where the engine is shared with the Mustang.