MGB GT

1965-1980 / Coupe / United Kingdom

All MGB GT problems All workshop problems

Minor Engine

Overheating

Symptoms

Temperature gauge climbs into the red, particularly in traffic or on hot days. Coolant loss through the overflow.

Cause

The MGB's cooling system is marginal for Australian conditions. The original radiator loses efficiency with age. The thermostat sticks. The water pump impeller corrodes. The electric fan (rubber bumper cars) or mechanical fan (chrome bumper cars) may not move enough air at low speeds.

Fix

1 Replace the radiator with an aluminium upgrade ($300--500). New thermostat ($15--30), new water pump ($60--100), and ensure the fan system works properly. A supplementary electric fan is a sensible upgrade for chrome bumper cars. Check the coolant expansion tank (later cars) is functioning correctly -
2 the system relies on drawing coolant back from the tank as it cools, and a faulty pressure cap or cracked tank breaks this cycle. Total cooling system refresh: $300--700

Cost mentioned in fix

$300$15$60

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Other known issues

Critical Engine

Bottom End Bearing Wear

Low oil pressure at idle when warm (below 15 psi). A deep rumbling or knocking sound from the lower engine, particularly at idle and on acceleration. This is the main and big-end bearings wearing out.

Critical Engine

Oil Leaks

Oil residue on the engine, drips on the ground, burning smell from oil on the exhaust manifold.

Critical Engine

Cylinder Head Cracking

Coolant consumption with no visible external leak. Milky residue on the oil filler cap. White smoke from the exhaust. Overheating.

Common Engine

Exhaust Manifold Studs and Cracking

Exhaust manifold studs corrode and snap when you try to remove them. The manifold itself can crack between the ports, causing a ticking exhaust leak that's louder when cold.

Minor Body and Structure

Sill Corrosion (Inner and Outer)

The outer sill skin bubbles, softens, and eventually perforates. In advanced cases, the outer sill crumbles when prodded. The inner sill -- the structural member -- rots from inside the box section and loses its load-bearing capacity.

Critical Body and Structure

Floor Pan Corrosion

Soft or perforated floor pans, particularly in the footwells and under the seats. Wet carpet is a telltale sign. In severe cases, you can see the road through the floor.

All MGB GT problems