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Autopapyrus · Mercedes-Benz B-Class OM608 1.5 CDI (2019)
https://autopapyrus.com/guides/mercedes-benz/b-class/cylinder-block-deck-resurfacing/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Mercedes-Benz B-Class OM608 1.5 CDI (2019): Cylinder Block Deck Resurfacing

Resurfacing the cylinder block deck on the OM608 (Renault K9K) is required when the deck is warped after overheating, or to restore sealing after an engine overhaul. The OM608 is an adapted Renault K9K 1.5 dCi with a cast iron block and an aluminum cylinder head. The work is done on a specialized machine and requires strict adherence to tolerances for flatness and surface finish.

Difficulty: Hard Time: 4-6 hours (cylinder head removal + machine resurfacing + reassembly) Steps: 18 Tools: torque wrench with angle gauge, socket set (8-19 mm), ratchet, extensions, screwdrivers, drain pan for oil and coolant, shop rags, degreaser, resurfacing machine (milling or grinding), metal straightedge (500 mm or longer), feeler gauges 0.03-0.10 mm, micrometer or dial indicator (for precise measurement)

Part

  • 🔩 cylinder head gasket (multi-layer metal composite), cylinder head bolt set (single-use TTY bolts), manifold gaskets, camshaft seals (if needed), oil filter and air filter (replacement after assembly is mandatory)
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes AutoFix (online) and 2 more. See manuals →

Step by step

18 steps
  1. Disconnect the negative battery terminal, drain the coolant through the drain plugs on the radiator and the block, and drain the engine oil.
  2. Remove the plastic engine cover, the air intake duct, and the air filter housing. Disconnect the fuel lines, the turbocharger vacuum lines, and the sensors (temperature, oil pressure, oxygen).
  3. Remove the intake and exhaust manifolds (tightening torque at assembly: 20-25 N·m (15-18 lb-ft) for the intake, 25-30 N·m (18-22 lb-ft) for the exhaust; exact values per the manufacturer's specifications).
  4. Remove the valve cover (tightening torque at assembly: 8-10 N·m (6-7 lb-ft)). Set the timing marks on the crankshaft pulley and the camshaft sprocket, and lock the flywheel with a locking pin through the hole in the clutch housing.
  5. Remove the timing belt (loosen the tensioner pulley and slide the belt off to the right), then remove the camshaft sprocket and the rear timing cover.
  6. Loosen the cylinder head bolts in the reverse order of the tightening sequence (from the edges toward the center), then remove the head together with the gasket. The cylinder head bolts on the OM608 are single-use TTY (torque-to-yield) bolts and must never be reused.
  7. Clean the remains of the gasket off the block deck with a plastic scraper (not a metal one, which risks scratching the cast iron), then degrease with acetone or solvent.
  8. Check the flatness of the block with a metal straightedge (500-600 mm) lengthwise and crosswise, using a 0.03 mm feeler gauge. A deviation of more than 0.03 mm over the full length is unacceptable. If you have a micrometer or a dial indicator on a stand, measure on a 9-point grid (corners, center, midpoints of the sides).
  9. Take the block to an engine machine shop with a resurfacing machine (surface grinder or milling machine). Milling is preferable: it gives Ra 1.6-3.2 µm (roughness grade 7-8), while abrasive grinding gives Ra 0.8-1.6 µm (grade 9-10). A multi-layer metal composite gasket requires a finish no rougher than Ra 3.2 µm.
  10. Remove the minimum amount of metal, usually 0.05-0.15 mm per pass, and no more than 0.3 mm in total over the whole life of the block (otherwise the compression ratio and the combustion chamber geometry will change). This is critical for a diesel: removing 0.1 mm raises the compression ratio by roughly 0.3-0.5, which can lead to knock and overheating.
  11. After resurfacing, check flatness again. The deviation must not exceed 0.02 mm over 500 mm, and locally within a 75 mm diameter circle not more than 0.025 mm.
  12. Wash the block with hot soapy water, blow out the passages with compressed air (to remove metal chips from the oil and coolant passages), and degrease the deck.
  13. Install the new cylinder head gasket without any lubricant (multi-layer gaskets are installed dry), set the cylinder head on the block, and thread in the new cylinder head bolts.
  14. Tighten the cylinder head bolts in three stages with a torque wrench (sequence: from the center outward, in a crisscross pattern): initial tightening 30-40 N·m (22-30 lb-ft), main tightening 60-70 N·m (44-52 lb-ft), then an additional 90° turn, and then another 90° (the exact tightening procedure and torque values are per the Renault specifications for the K9K or the Mercedes service manual for the OM608; values may differ).
  15. Install the camshaft sprocket (tightening torque 80-100 N·m (59-74 lb-ft)), the timing belt (tension per the tensioner indicator or by sound frequency; check the manual), the manifolds, the hoses, the sensors, and the valve cover.
  16. Fill with engine oil (4.3 L (4.5 qt) with filter) and coolant (the cooling system holds about 6.5 L (6.9 qt)), then connect the battery.
  17. Start the engine and warm it up to operating temperature of 90°C. Check for coolant and oil leaks along the cylinder head joint, and listen for abnormal noises (valve tapping, camshaft ticking).
  18. After 500-1000 km, check that the cylinder head joint is still sealed. On high-compression diesels, gasket settling is possible (if the bolts are TTY, retightening is not recommended; only check that there are no leaks).

Common mistakes and warnings

  • Resurfacing the cylinder block changes the compression ratio. Exceeding the allowable amount of metal removal (more than 0.3 mm in total) will lead to knock, overheating, and destroyed pistons. Use only single-use TTY cylinder head bolts. Reusing old bolts causes uneven clamping load, a blown gasket, and oil mixing with coolant. This job requires shop-grade equipment (a resurfacing machine, a torque wrench with an angle gauge, and measuring tools). If you lack machining experience and precise tools, take the job to an engine repair shop.