Question 1

Sill (Rocker Panel) Corrosion

Accepted Answer

The sills become soft, bubbly, or perforated. The body may flex excessively when jacked up or driven over bumps. Doors may not shut properly as the body distorts. The MGA's sills are box-section steel that traps moisture from road spray, condensation, and water ingress through the body seams. Rust starts inside and works outward, by the time it's visible on the surface, the internal structure is compromised. Blocked drain holes accelerate the problem. Cut out the corroded section and weld in a repair panel (or a complete replacement sill). The sills are structural, so the repair must be done properly, pop-riveted patches and filler are not acceptable. Repair panels are available from Moss Motors, SC Parts, and other suppliers. Cost: $500-$1,500 per side for supply and professional fitting.

Question 2

Floor Pan Corrosion

Accepted Answer

Soft or perforated metal in the floor pans, visible from underneath. Water may pool in the footwells. The floor may flex under foot pressure. Water enters through deteriorated body seals, leaking weather equipment, and condensation. The flat floor pans offer no drainage, so water sits and rusts through the steel. Cut out corroded sections and weld in repair panels. Complete floor pan assemblies are available. Cost: $300-$600 per side for panels, plus fitting.

Question 3

Front Crossmember Corrosion

Accepted Answer

Visible rust, scaling, or perforation of the front crossmember (visible from underneath the front of the car). Road spray, mud, and trapped moisture attack the crossmember. It's a hidden area that's easy to overlook during casual inspections. If surface rust only, clean, treat with rust converter, and protect. If structurally compromised, the crossmember must be replaced, this is a major job requiring the front end to be disassembled. Cost: $1,000-$3,000 for replacement.

Question 4

Rear Spring Hanger Corrosion

Accepted Answer

The rear spring mounting points show rust, cracking, or distortion. The rear of the car may sit unevenly or make clunking noises. Road spray attacks the spring hanger brackets and the surrounding bodywork. The stress of the spring loading concentrates corrosion damage. Weld in new spring hanger brackets and reinforce the surrounding body metal. Cost: $500-$1,500 per side.

Question 5

Oil Leaks

Accepted Answer

Oil weeps from the rocker cover gasket, timing cover, rear main seal, and sump gasket. A layer of oil covers the engine and transmission. Cork and rubber gaskets deteriorate over decades. The B-series rear main seal is a scroll-type design (early engines) or a lip seal (later engines), both leak eventually. The rocker cover uses a cork gasket that compresses and loses its seal with repeated removal. Replace all gaskets systematically. Use modern gasket materials where possible. The rear main seal requires the engine or gearbox to be removed. A complete engine reseal: $300-$600 in parts, $500-$1,000 in labour if paying a workshop.

Question 6

Carburettor Wear (SU H4)

Accepted Answer

Rough idle, poor fuel economy, hesitation on acceleration, black smoke from the exhaust. The engine may run rich or lean depending on which component has worn. The SU H4 carburettors use a throttle shaft that rotates in the carburettor body. Over decades, the shaft wears the bore oval, allowing unmetered air to enter. The jet and needle also wear, affecting mixture control. The dashpot piston and suction chamber can wear, affecting the carburettor's response to throttle changes. Rebuild the carburettors with new jets, needles, gaskets, and throttle shaft bushes. Throttle shaft rebushing requires removing the carbs and having the work done by a specialist, the bodies need reaming and new bushes pressing in. Cost: $80-$150 per carb for basic rebuild kits; $150-$300 per carb for complete rebuild including shaft rebushing.

Question 7

Head Gasket Failure

Accepted Answer

Coolant loss without visible external leak. White smoke from the exhaust. Milky emulsion under the oil filler cap. Overheating. Bubbles in the header tank. The B-series engine uses a cast-iron block and aluminium head, different thermal expansion rates stress the head gasket. Overheating events are the primary cause of failure. Low coolant level, a stuck thermostat, or a failing water pump can all trigger overheating. Remove the head, inspect and resurface if warped, replace the gasket. Check the head for cracks (particularly between valve seats). Cost: $800-$1,500 at a workshop.

Question 8

Timing Chain Stretch

Accepted Answer

A rattling noise from the front of the engine at idle. Valve timing wanders, reducing power and efficiency. The single-row timing chain stretches with mileage. The tensioner compensates for some wear, but eventually the chain exceeds the tensioner's range. Replace the timing chain, tensioner, and sprockets. The timing cover must be removed. Cost: $200-$400 in parts.

Question 9

Piston and Bore Damage

Accepted Answer

High oil consumption, blue smoke from the exhaust, loss of compression. In severe cases, complete piston failure. The Twin Cam engine's high compression ratio (9.9:1) and tendency to pre-ignite on poor-quality fuel causes piston crown erosion and bore scoring. Early engines were particularly prone, the combination of high compression, inadequate fuel quality, and owner ignorance about fuel octane requirements destroyed many engines. Rebore and fit new pistons (lower compression pistons are available for improved reliability). A complete Twin Cam engine rebuild is a specialist job. Cost: $5,000-$10,000.

Question 10

Oil Consumption

Accepted Answer

The Twin Cam consumes oil at a rate that seems alarming to anyone accustomed to modern engines. Topping up between services is normal. The DOHC head's valve stem seals and the engine's breathing characteristics lead to oil consumption. Some is inherent to the design; excessive consumption indicates worn valve guides or piston rings. If consumption exceeds 1 litre per 1,500 km, investigate valve stem seals and piston ring condition. Valve guide replacement and ring replacement require engine disassembly. Cost: $3,000-$8,000 depending on extent.

Question 11

Dynamo Undercharging

Accepted Answer

The charge warning light stays on or flickers. Battery goes flat. Headlights dim at idle. Worn brushes, a dirty commutator, or a failed voltage regulator. The dynamo's output is limited, approximately 22 amps, and marginal for cars with upgraded lighting or accessories. Rebuild the dynamo ($200-$400) or convert to an alternator in a dynamo-style housing ($400-$600). The alternator conversion is the better long-term solution.

Question 12

Wiring Degradation

Accepted Answer

Intermittent electrical faults. Lights flicker. Gauges read erratically. Fuses blow without apparent cause. Original wiring insulation becomes brittle and cracks, exposing bare copper that shorts to ground. Earth connections corrode. Bullet connectors lose contact. Replace the entire wiring harness. Complete reproduction harnesses cost $300-$500 and are a weekend installation job. Cost: $300-$500 for the harness.

Question 13

Wheel Bearing Wear

Accepted Answer

A rumbling or grinding noise from a wheel, increasing with speed. Play detectable when rocking the wheel at 12 and 6 o'clock with the car jacked up. The front wheel bearings are tapered roller bearings that wear with mileage. Lack of regular greasing accelerates the process. Water ingress past failed seals causes corrosion of the bearing surfaces. Replace the bearings. This is a straightforward job that requires removing the hub. Cost: $100-$200 per side for parts.

Question 14

Leaf Spring Sag

Accepted Answer

The rear of the car sits lower than normal. The ride becomes harsh. The car bottoms out over bumps. The rear leaf springs lose their camber over sixty-plus years. Individual leaves can also break, reducing the spring's load-carrying capacity. Re-temper and re-camber the springs, or fit new replacement springs. Cost: $300-$600 per pair.

Question 15

Kingpin Wear

Accepted Answer

Vague steering, front-end wander, uneven tyre wear. The MGA's front suspension uses kingpins (on early cars) or ball joints that wear with mileage and lack of greasing. Replace kingpin bushes or ball joints as applicable. Kingpin kits: $150-$300 per side.

Question 16

Radiator Inefficiency

Accepted Answer

Overheating in traffic or on hot days. Temperature gauge climbs above normal. The original radiator's capacity is marginal for Australian conditions. Core tubes block with scale and corrosion over time, reducing cooling efficiency. The original thermostat may be stuck or incorrect. Flush the radiator and cooling system. If the radiator is severely blocked, have it re-cored with a higher-efficiency core. Check and replace the thermostat. An electric fan behind the radiator is a common upgrade. Cost: $200-$600 depending on what's needed.

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