Jaguar MK10/420G
Published: 29th Jun 2011 - 0 Comments - Be the first, contribute now!
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It is a myth that Jaguars suffer from poor cooling. If everything is in top order, then all should be well. However, an uprated radiator is a wise step.
Engine
All versions use twin-overhead camshaft, in-line six-cylinder in two capacities 3.8: 3781cc, 220bhp 4.2: 4235cc: 245bhp
Valve clearances
Inlet 0.004in; exhaust, 0.006in. (cold); the gaps are measured using feeler gauges placed between the back of each cam and the appropriate tappet. Adjustment is by selective shims. It is advisable to check the clearances every 12,000 miles; re-setting the gaps is a major head -off operation; not for the faint-hearted!
Ignition
Firing order: 1-5-3-6-2-4 (No. 1 cylinder at REAR). Spark plugs: Champion N5 or equivalent (L7 for 7:1 low compression ratio engines). Later 3.4/3.8 litre units, Champion UN12Y or equivalent. 4.2, Champion N5 or equivalent (later specification, N11Y; consult Jaguar specialist for correct type). Gap 0.025in. Check/clean every 6000 miles or annually (whichever comes first); renew regardless every 12,000 miles. Contact points: Gap 0.014in. to 0.016in. corresponding with dwell angle reading of 35 +/- 2 degrees. In each case, check/clean points every 3000 miles or annually (whichever comes first); renew regardless every 6000 miles. Distributor cap, rotor arm and high tension leads: Every 3000 miles, clean and check condition, ensuring that all connections are sound. Distributor - mechanical aspects: Every 3000 miles, remove rotor arm and apply a few drops of engine oil to moving contact pivot, distributor shaft/cam bearing and mechanical advance mechanism (via holes in distributor’s baseplate). SPARINGLY apply grease to distributor’s cam. Timing – examples (static; refer to timing marks on crankshaft pulley damper and timing case): 3.8-litre: 7:1 compression ratio, 0 degrees (TDC) 8:1 compression ratio, 7 degrees before top dead centre (BTDC) 9:1 compression ratio, 5 degrees before top dead centre (BTDC) 4.2-litre: 8.1: compression ratio, 9 degrees BTDC; 9:1 compression ratio, 10 degrees BTDC (mark on crankshaft damper).
Fuel system
Every 3000 miles or annually (whichever comes first), examine all fuel system pipework and check/top up S.U. carburettor dashpots with SAE 20 oil. After valve clearances and all ignition settings have been checked/set, and with engine fully warmed up, re-adjust carburettor mixture/ idle speed settings (use proprietary do-it-yourself equipment for synchronising carburettors, and proceed in conjunction with workshop manual). Aim for a tickover speed of approximately 500-650 rpm. Clean/lightly re-oil gauze air filter elements every 5000 to 6000 miles; renew paper types every 10,000 to 12,000 miles (or sooner if visibly dirty). If an oil bath type air cleaner is fitted, remove top cover, lift out gauze filter and clean in paraffin, then allow to dry. Empty out oil/sludge from filter housing, wipe dry then re-fill with fresh engine oil to level indicated by arrow on side of housing; re-fit gauze filter and housing lid. Clean fuel filters approximately every 10,000 miles or annually, whichever comes first (include tank filter, accessible after removing drain plug - do this only when fuel level is very low!).
Lubrication
Engine oil: For maximum engine life, ideally change oil and filter at least every 3000 miles or annually (whichever comes first). Ensure that oil filter assembly components are correctly installed on re-assembly (consult workshop manual for sequence). Use premium quality, SAE15W50, 20W50 or 20W60 oil. Please dispose of old oil in environmentally friendly manner - local councils provide waste oil collection points. Drain/refill capacity, approx: 13 pints (7.38 litres) Manual gearbox oil: Check oil level at least every 3000 miles or annually (whichever comes first); investigate need for frequent topping-up. Early cars with synchromesh on second, third and top gears, use engine oil. Later cars with all-synchromesh gearboxes, use SAE90 EP gear oil. Every 12,000 miles (approx.) drain old oil after a long run, and re-fill with fresh lubricant. If overdrive is fitted, overdrive unit’s oil supply is shared with gearbox; to drain, remove plugs in both gearbox and overdrive unit. Every 12,000 miles remove/clean gauze within unit (accessible when drain plug is removed). Capacity: 2.5 pints (1.42 litres), or 4 pints (2.27 litres) if overdrive is fitted. Automatic transmission fluid: Check fluid level at least every 1000 miles/ monthly (whichever comes first). Be scrupulously clean when checking fluid level and when topping-up. Torque converter must be full of fluid when checking level: First, with handbrake firmly applied, engage ‘P’ and run engine. Apply footbrake and engage ‘L’; run engine at 800 rpm for approximately three minutes, then return to the footbrake, and with engine still at tickover, withdraw dipstick, wipe clean, then re-dip and withdraw again to check level. Top up with automatic transmission fluid if required (DO NOT overfill); difference between ‘high’ and ‘low’ marks on dipstick equates to approximately 1 pint (0.57 litres). Change transmission fluid approximately every 12,000 miles; capacity 15 pints (8.52 litres). Final drive oil: Check oil level at least every 3000 miles or annually (whichever comes first); investigate need for frequent topping-up. Use SAE90 EP hypoid oil. Renew axle oil every 12,000 miles (approx.); drain old oil after a long run (so that it flows more easily), and re-fill with fresh lubricant. Capacity 2.75 pints (1.56 litres). Steering/front suspension: Every 1000 miles, re-lubricate all greasepoints using multi-purpose, lithium-based grease. There are nipples on: Upper and lower swivels (assuming original types are fitted), steering rod ball joints, and steering idler unit (cars with non power-assisted steering). Front and rear wheel bearings: Every 5000 miles, re-lubricate bearings with grease specifically stated as being suitable for wheel bearing use; grease nipples are provided. Steering: Cars without power-assisted steering: Check oil level in steering box approximately every 3000 miles/annually (whichever comes first). Note: Filler plug has hexagon head; don’t confuse with externally threaded rocker shaft adjuster screw. If necessary, top up with SAE140 EP oil. Car with power-assisted steering: Check fluid level in reservoir every 3000 miles or annually (whichever comes first); use automatic transmission fluid to top up to the mark as necessary. Renew filter in reservoir every 24,000 miles. Other aspects: Ever y 3000 miles, re-lubricate handbrake operating linkage.
Cooling system
At all times, use quality anti-freeze mixture containing corrosion inhibitors. Every 3000 miles/annually, inspect radiator, all hoses and water pump/fan. At least every three years, drain system and reverse-flush prior to re-filling system with fresh anti-freeze solution (observe dilution recommendations of anti-freeze manufacturer – printed on container). Capacity, including heater assembly: 22 pints (12.50 litres) but may differ.
Brakes
At least every 3000 miles or annually (whichever comes first), carry out following operations: Examine front and rear brake pads and discs, also separate handbrake pads. Inspect also brake pipes/flexible hoses and master cylinder. Renew any ailing components immediately. AVOID INHALING DUST FROM BRAKE LININGS AS THEY MAY CONTAIN ASBESTOS. Assess handbrake operation and re-adjust cable length if necessary (consult manufacturer’s literature for full details). DON’T over-tighten cable or brakes will bind. Check tightness of caliper securing bolts; ensure locking wire is fitted and secure. Inspect brake fluid and check level; overhaul system if fluid is cloudy. Every 6000 miles/annually (whichever comes first), clean brake servo filter; rinse in methylated spirits, allow to dry, lubricate in clean brake fluid and then re-fit. At least every 24,000 miles/two years (whichever comes first, change brake fluid regardless. Note: The inboard-mounted rear brakes are notoriously difficult to reach. If the rear axle/suspension assembly is ever removed from the car, it is a good idea to fully service the brakes, and replace leaking oil seals, at the same time. Check especially for seized rear caliper pistons (more likely on cars which are used infrequently), also for oil contamination on the discs/pads.
General
Every 3000 miles, or annually Check front hub bearing condition/free play Examine ball joint gaiters for splits. Examine fan belt and re-tension if necessary (¾ in. deflection at centre of longest belt run). Check/re-adjust power steering drive belt (where power-assisted steering is fitted); move pump on mountings to re-tension belt. DON’T over-tighten belt. Scrutinise clutch operating system hydraulics for deterioration/leaks. Check cleanliness/security of all electrical connections; inspect wiring for damage. Assess condition/security of all running gear components and suspension mounting bushes.Inspect underbody for damage and rectify. Check propeller shaft joints for wear/damage. Inspect exhaust system. Lubricate (with engine oil): Handbrake lever, cable compensator on rear axle, windscreen wiper arms, petrol filler flap hinge, brake and clutch pedal pivots, hinges and catches. Don’t forget the seat runners either!
Best Mods
- Electronic ignition is worthwhile. Luminition has been a popular upgrade for a few years and does away with the points for maintenance free motoring. Prices start at £150.
- It is a myth that Jaguars suffer from poor cooling. If everything is in top order, then all should be well. However, an uprated radiator is a wise step. Not only is the cooling enhanced, but with the engine driven fan removed, a few bhp can be gained. Prices start around £375.
- Polyurethane bushes have become popular; they’re easy to fit, long lasting and more efficient on the famous IRS set up. In some instances though, they can effect the ride, which on a comfy MK10 you might not want to spoil. Prices start at £22.50 for a top wishbone kit. Adjustable dampers from Gaz/Spax/Koni offer great improvements. Prices start at around £46 a pop.
- Want more ccs? 4.2 is the most sensible pick plus can be taken to around 4.5-litres but even in stock guise tunes well; XJ6 S3 head and camshafts are a good swap too. Fuel injection from same car best but even on carburettors it’s fine. Jag did fit V12 E-type engines in test mules during evaluation of that engine – now there’s a thought!
Top Tips
- It pays to check the ride height annually. The front springs are known to settle, leading to worsening ride and an even heavier steering. If really bad it can ground the sump on sleeping policemen. Uneven tyre wear with excessive inner scrub is a clue.
- Still at the front, the front suspension bushes wear quickly and apart from wandering can display itself as a knock over bumps.
- The IRS suspension is the same as employed on the E-type and its myriad of bushes deteriorate and ruin the car’s poise. But the front suspension is just as susceptible and let go in the same way and are often overlooked.
- Over-silent tappets indicate that the valve clearances have closed up and need re-shimming ( a job that requires a micrometer). If the timing chains are worn (there is decent adjustment to be fair) then consider this too, although the bottom one requires dropping the sump – which is akin to a major overhaul and a two day job for most folk.
- However there are ways to change just the top chain (which wears most) without removing the head. It’s an old mechanic’s dodge: Break the chain on top of one of the sprockets and attach the new one to it. Wind off the old chain with new and so long as you keep it tight…
- The disc rear brakes are peculiar to the Mk10 being inboard mounted and these can seize, especially the handbrake which – being a Jag – is rarely that effective anyway!
- Also irregular are odd wheel and tyre size (205 x 14) that are becoming hard to source (watch for van tyres fitted instead: okay for the car’s weight but unsuitable for high speed cruising). Early XJ6 (15 inch) can be substituted and are fine although the car rides a tad higher.
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