How Do I Inspect And Replace My Land Rover Cylinder Head?

Few jobs make a Land Rover owner's heart sink like a suspected cylinder head failure. Whether you run a Series III on the 2.25 petrol, a 300Tdi Defender, a TD5 Discovery 2 or a Puma era 2.2 TDCi, the head governs how your engine breathes, seals and cools, and when it warps or cracks, the symptoms escalate quickly. The good news: with the right preparation, diagnosis and replacement are well within reach of a competent home mechanic. Here's how to inspect a suspect head, decide between skimming and replacement, and fit the new one properly.

Why Land Rover cylinder heads fail

Overheating is the biggest killer. A blocked radiator, failed viscous fan, tired water pump or slow coolant leak lets temperatures climb, and the head, clamped rigidly to the block, distorts as it expands. Cast iron heads, as fitted to the 2.25 and 2.5 four cylinders and the 200Tdi and 300Tdi, tend to crack, most often in the narrow bridges between the valve seats or around the injector and pre combustion chamber openings. Aluminium heads, used on the TD5 and Rover V8, warp more readily and can suffer casting porosity, a known weakness of the original TD5 head.

Age matters too. Decades of thermal cycling fatigue the casting, neglected coolant corrodes the waterways, valve guides wear until the engine smokes on start up, and petrol heads designed for leaded fuel suffer valve seat recession unless hardened seats have been fitted. Often a 'head gasket failure' turns out to be the gasket and the head, which is why inspection matters before you rebuild.

The warning signs to watch for

Head and head gasket problems share a family of symptoms:

•         Unexplained coolant loss with no external leak, or an expansion tank that pressurises quickly and bubbles at idle

•         White, sweet smelling exhaust smoke that persists after warm up

•         A creamy 'mayonnaise' emulsion under the oil filler cap or on the dipstick

•         Overheating under load, misfiring, rough running or hard starting on diesels

•         Oil or coolant weeping along the head to block joint

One of these justifies investigation. Two or more? Stop driving before a warped head becomes a ruined engine.

How to inspect a Land Rover cylinder head

Tests with the head still fitted

Start with the checks that need no dismantling. A cooling system pressure test, pumping the system to the cap's rated pressure and watching for a drop, confirms pressure is escaping. A combustion leak ('sniff') tester draws air from above the coolant through a chemical that changes colour if exhaust gases are present, proving a breach between a cylinder and the water jacket.

Next, compression test every cylinder: through the spark plug holes on petrol engines, or the injector or glow plug apertures with the correct adaptor on diesels. Two adjacent low cylinders point strongly to failure between the bores. A leak down test then pinpoints the escape route, hissing at the exhaust or intake means a valve, hissing at the oil filler means rings, and bubbles in the expansion tank mean the head or gasket. While you’re there, check the dipstick and the coolant itself: oil floating in the expansion tank, or coolant droplets in the oil, settle the question of whether the two systems are mixing.

Inspecting the head on the bench

With the head off, clean the mating face with chemical gasket remover and a plastic scraper, never an abrasive disc, which ruins an aluminium face in seconds, then work through four checks.

Flatness. Lay an engineer’s straight edge along both edges, both diagonals and across the centre, and try to slide feeler gauges beneath it. The workshop manual gives the exact limit, but more than a few thousandths of an inch means machining.

Cracks. Examine the bridges between the valve seats and around injector, pre chamber or spark plug openings with a magnifier and strong light, the classic failure zone on 300Tdi and TD5 heads. Hairline cracks hide easily, so a machine shop pressure test or dye penetrant check is the only certainty, particularly on the porosity prone TD5.

Valves, seats and guides. Look for recessed or pitted seats, and rock each valve sideways in its guide, perceptible movement means worn guides, and explains oil smoke.

Faces. Check for erosion around the fire rings and corrosion at the waterways, and inspect the block face with equal care.

Skim, repair or replace?

A head that is warped but crack free and within thickness limits can be skimmed flat. Skimming has limits, though: every casting has a minimum thickness, machining raises the compression ratio, and on the Tdi engines the head gasket comes in three thicknesses, selected by measuring piston protrusion and identified by one, two or three holes. A head that has been skimmed before may have nothing left to give, a machine shop can measure the casting and tell you whether there is meat left before you spend anything.

Cracked heads are another matter. Small cracks in cast iron can sometimes be repaired, but once a specialist has pressure tested, machined, re seated and re valved a decades old casting, the bill often exceeds the cost of a remanufactured head, with none of the warranty. On the aluminium TD5, cracking and porosity are effectively terminal: the standard fix is a new AMC head, LDF500160 for early engines or LDF500170 for late.

This is where remanufacturing earns its keep. Turner Engineering rebuilds heads in house to original specification with new valves, guides, springs and core plugs, seats cut on Serdi three angle equipment, and new pre combustion chambers and injector shrouds on diesels, every head carries a 12 month unlimited mileage written warranty. For the earliest Series castings, remanufacture is carried out on your own head.

How to replace a Land Rover cylinder head, step by step

Every engine has its quirks, keep your unit's workshop manual open throughout, but this sequence holds across the classic range.

1.       Preparation. Disconnect the battery, drain the coolant, and label and photograph everything before disturbing it.

2.       Strip the top end. Remove the air intake and turbo pipework, exhaust downpipe, manifolds and rocker cover.

3.       Deal with the valvetrain. The 2.25, 2.5, Tdi and V8 engines are pushrod designs: lift off the rocker shaft and withdraw the pushrods, keeping them in fitted order. The overhead cam TD5 and TDCi need the camshaft drive released and re timed, follow the manual's locking procedure exactly.

4.       Release the head. Slacken the bolts in the reverse of the tightening sequence, in stages, with the engine cold.

5.       Lift it clear. Four cylinder cast iron heads are heavy, get help, and never lever between the faces.

6.       Inspect and clean. Work through the bench checks above, verify the block face is flat, and keep debris out of the bores and oilways.

7.       Fit the new gasket. Never reuse the old one. On the 200Tdi and 300Tdi, measure piston protrusion and select the matching one, two or three hole gasket.

8.       Fit new head bolts. Tdi, TD5 and TDCi bolts are stretch bolts, torqued to yield, and must never be reused. Tighten in the specified sequence and stages, finishing with the angle figure from the manual.

9.       Rebuild and adjust. Refit the valvetrain, set the valve clearances where adjustable, and reassemble with fresh gaskets, a top end gasket set covers most of it.

10.   Refill and check. Refill and bleed the cooling system, run the engine to temperature and check for leaks. Above all, fix whatever caused the failure, a new head bolted to an overheating engine will follow the old one.

Which cylinder head fits your Land Rover?

Turner Engineering remanufactures cylinder heads across the full classic range:

•         Series 2a and III, and early 90/110: 2.25 petrol and 2.25 diesel heads, plus the later 2.5 petrol and 2.5 naturally aspirated and turbo diesel. All petrol heads are built to run on unleaded fuel and LPG.

•         Defender, Discovery 1 and Range Rover Classic: 200Tdi (RTC6896) and 300Tdi (LDF500180) heads, bare, fully built, or gasflowed to performance specification.

•         Defender and Discovery 2 TD5: new AMC heads in early (LDF500160) and late (LDF500170) versions to suit your engine.

•         V8 models: heads for the 3.5, 3.9 and 4.2 and the 4.0 and 4.6 Rover V8, including gasflowed performance options.

•         Puma era Defenders: Ford 2.4 Duratorq (LR004428) and 2.2 TDCi (LR037049) heads.

Unsure which head your engine takes? Call the team on +44 (0)1342 834713 with your engine number.

Why choose a remanufactured head from Turner Engineering?

Turner Engineering has specialised exclusively in Land Rover engines since 1979 and is the only UK remanufacturer dedicated to the marque. Every head is remanufactured in house on specialist machinery, supplied built up and ready to fit, warrantied for 12 months with unlimited mileage, and delivered worldwide. Whether your 300Tdi has cracked between the valves or your TD5 is pressurising its coolant, browse the full range of remanufactured Land Rover cylinder heads, or talk to the team about the right head for your engine.

Frequently asked questions

What are the signs of a cracked Land Rover cylinder head?

Unexplained coolant loss, persistent white exhaust smoke, a pressurised or bubbling expansion tank, overheating and 'mayonnaise' under the oil filler cap. A combustion leak test and a compression test will confirm the diagnosis.

Can a Land Rover cylinder head be skimmed instead of replaced?

Yes, if it is crack free and within minimum thickness limits. On Tdi engines the gasket thickness must then be re selected by measuring piston protrusion. Previously skimmed heads, or heads cracked between the valve seats, are usually better replaced.

Do I need new head bolts when refitting a cylinder head?

On the 200Tdi, 300Tdi, TD5 and TDCi engines, yes, the bolts stretch to yield and are strictly single use. On older engines check the manual, but new bolts are cheap insurance on any rebuild.

How long does cylinder head replacement take?

A competent DIYer can remove and refit a head on the pushrod engines over a weekend; the overhead cam TD5 and TDCi take longer because of the timing procedure. Fitting a ready built remanufactured head keeps the vehicle off the road only for the removal and refit itself.