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Autopapyrus · Subaru XV (GP) 2.0 FB20 (2014)
https://autopapyrus.com/guides/subaru/xv/cylinder-head-gasket-replacement-with-flatness-check/
Compiled automatically from service literature and owner experience. Specs are for the typical configuration — check them against your exact car before you start.

Subaru XV (GP) 2.0 FB20 (2014): Cylinder Head Gasket Replacement with Flatness Check

The FB20 is a horizontally opposed (boxer) engine with a chain-driven timing system and two cylinder heads. The gasket is usually replaced after overheating, a breach into the coolant or oil, or a leak at the joint. The keys to success: checking the flatness of both heads and the block mating surfaces, clean threaded holes, new bolts, and tightening strictly according to the specified sequence.

Difficulty: Hard Time: 2-3 days for an experienced shop (disassembly, inspection, reassembly, adjustments) Steps: 16 Tools: socket and ratchet set, torque wrench, angle gauge for torque-angle tightening, precision straightedge and feeler gauge set, plastic scraper, flat surface plate with sandpaper, compressed air, locking tools and marks for chains, oil syringe, service scan tool

Part

  • 🔩 cylinder head gasket set (separate gasket for each head), new cylinder head bolts (stretch bolts, not reusable), valve cover gaskets, spark plug well seals, new spark plugs, engine oil with filter, coolant, exhaust manifold and downpipe gaskets, intake manifold gasket if needed. Confirm exact part numbers for your VIN by part name in your supplier's catalog
There's a full repair manual for this car Every system, wiring diagrams and torque specs — not just this job. Haynes AutoFix (online) and 1 more. See manuals →

Step by step

16 steps
  1. Confirm the diagnosis before disassembly: test for exhaust gases in the coolant, measure compression, perform a cylinder leak-down test, and inspect the oil for emulsion. A failed gasket is often caused by overheating, so check the water pump, thermostat and radiator at the same time.
  2. Let the engine cool, disconnect the negative battery terminal, and drain the coolant and engine oil. Remove the engine undercover, air intake, air filter and air filter housing.
  3. Remove the ancillaries: intake manifold, fuel rail with injectors (relieve the fuel pressure first and wipe up any spilled fuel immediately), ignition coils, spark plugs, and any harnesses and sensors that are in the way. Label all connectors and hoses.
  4. Remove the exhaust manifolds or the downpipe, and disconnect the catalytic converter assemblies and oxygen sensors. Soak the exhaust fasteners with penetrating oil in advance, because the studs often seize and snap.
  5. Remove the valve covers. Set the crankshaft to TDC of cylinder 1 using the marks. Carefully mark the chains and sprockets (with paint or a marker), remove the tensioners, and release the chains according to the service manual. If the timing cover or other timing drive components must be removed, do so in the order specified by the manufacturer. The exact sequence for the FB20 depends on the specific version, so do not remove the sprockets without marks and position locking.
  6. Remove the camshafts and rocker arms from each head (mark their position and order). Loosen the cylinder head bolts in the reverse of the tightening sequence, evenly and in several passes: first 1/4 turn, then 1/2 turn, then remove them completely. Remove the heads by tapping lightly with a rubber mallet, not by prying at the joint with screwdrivers.
  7. Inspect the gaskets: burn-through spots, traces of coolant or oil, and stains in the combustion chambers will point to the cause. Check the pistons and cylinder walls for scoring.
  8. Clean the mating surfaces of the block and heads with a plastic scraper and a non-abrasive solvent. Do not use metal scrapers or an angle grinder, as they damage the aluminum. Make sure debris does not get into the oil passages and cylinders (cover them with a rag, then blow out with air, then vacuum). Carefully clean oil and coolant out of the bolt holes (liquid in a blind hole can distort the torque when tightening).
  9. Head flatness check: lay the precision straightedge along the length, across the width and along the diagonals of the mating surface, and check the gap with a feeler gauge. For Subaru aluminum heads, the typical warpage limit is about 0.05 mm, but verify the exact allowable value against the manufacturer's specification for the FB20. Check the block surface the same way. If the limit is exceeded, send the head to an engine machine shop for resurfacing, keeping the cut to the minimum (remove only what is necessary). Severe warpage or cracks are a reason to replace the head.
  10. Check the heads for cracks (especially between the valve seats and around the spark plug wells), and check valve and seat wear as needed. Also check the valve springs, valve stem seals and the condition of the camshafts. If the heads were removed with signs of overheating, have them inspected at a specialized shop (pressure testing).
  11. Install the new gaskets dry, strictly in the correct orientation (by the markings, with the passage holes aligned). Do not apply sealant to metal multilayer gaskets unless the manufacturer requires it. Place the heads on the dowel pins and install the new bolts (lubricate the threads and the underside of the bolt heads only as specified by the manufacturer, usually with engine oil).
  12. Tightening the cylinder head bolts: an approximate procedure for FA/FB series engines is about 34 N·m (25 lb-ft), followed by angle tightening (about 90°), with full loosening and repetition in cycles. Be sure to verify the exact values, the number of passes and the sequence (from the center outward, in a spiral) against the manufacturer's specification, as a mistake here is unacceptable. Tighten only with a torque wrench and an angle gauge.
  13. Install the camshafts, chains and tensioners strictly according to the marks, and check that the marks line up after turning the crankshaft by hand through two full revolutions. Install the valve covers with new gaskets and spark plug well seals, tightening to the specified torque.
  14. Reassemble everything removed in reverse order: exhaust (with new gaskets and fasteners), intake, fuel rail, coils, spark plugs, sensors, harnesses. Fill with new oil and filter, and coolant.
  15. Bleed the air from the cooling system (top off at the radiator, heater set to maximum, front of the vehicle raised). Crank the engine with the starter with the ignition disabled to build oil pressure, then start the engine.
  16. Warm the engine to operating temperature, check for leaks, check the coolant level, and scan for fault codes, clearing any stored codes. Monitor the coolant and oil levels over the first 500-1000 km, topping off if necessary. Re-tightening the bolts is not required unless the manufacturer's specification calls for it.

Common mistakes and warnings

  • This job requires solid engine repair experience: incorrect chain marks, reusing stretched bolts, or not following the tightening sequence will lead to repeat gasket failure and engine damage. If you lack the experience and tools, have a specialized repair shop do the work. Do not skip the flatness check and the cleaning of the threaded holes: this is the most common cause of repeat gasket failure.
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