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MG B Gt Problems & Known Issues

The most common MG B Gt problems ranked by severity — what to watch for, what it costs to fix, and what happens if you ignore it.

Generations

MkI — MG B GT Mark I
1965–1974
B-Series 1.8
MkII — MG B GT Mark II
1974–1980
B-Series 1.8

Top issues to watch for

The most serious MG B Gt problems ranked by severity. We track 5 known issues — here are the ones you need to know about first.

Dangerous
Structural corrosion compromising vehicle rigidity
MkI, MkII1965–19800k–150k miles
The MG B GT uses a monocoque steel construction without a separate chassis, making structural corrosion particularly serious. The most critical areas are the A-posts, door frames, sills, and rear suspension mounting points where corrosion can compromise the structural integrity of the entire vehicle. This is a documented characteristic of 1960s-1970s British steel construction with minimal rust protection. MOT data shows this model fails structural rigidity tests at 34 times the fleet average, with failures becoming more frequent over the monitoring period.
What happens if ignoredStructural corrosion can lead to catastrophic failure of the vehicle's load-bearing structure, particularly in an accident. The car becomes unsafe to drive and may fail its MOT. Repair costs vary enormously depending on extent but can exceed the vehicle's value, with full restoration involving cutting out and replacing entire sections.
Independent garage
£500–£8,000
Specialist
£800–£12,000
Parts only
£200–£3,000
Major
Excessive emissions failing MOT limits
MkI, MkII1965–198040k–120k miles
Cars built before emissions regulations struggle to meet modern MOT emissions standards, particularly carbon monoxide and hydrocarbon limits. The MG B GT uses twin SU carburettors and a basic ignition system without catalytic converters or oxygen sensors. MOT data shows this model fails emissions tests at 264 times the fleet average, with the worst failures occurring between 60,000-80,000 miles. The failure rate has been worsening over the monitoring period as these cars age further.
What happens if ignoredThe car will fail its annual MOT test and cannot be legally driven on public roads. Carburettor overhaul and ignition system attention typically resolve most emissions issues. Total cost including labour ranges from £200-800 depending on the extent of work required.
Independent garage
£150–£400
Specialist
£200–£600
Parts only
£50–£200
Major
Suspension bush and joint wear
MkI, MkII1965–198020k–100k miles
The MG B GT uses rubber bushes throughout its suspension system that deteriorate with age regardless of mileage. After 40-50 years, original rubber bushes become hard, crack, and allow excessive play in the suspension geometry. MOT data shows this model fails for excessive suspension wear at 127 times the fleet average. The problem affects trunnions, A-arm bushes, and anti-roll bar mountings, and is getting worse as the remaining car population ages.
What happens if ignoredWorn suspension bushes affect handling, steering precision, and tyre wear. The car will eventually fail its MOT test. Driving with severely worn bushes is unsafe as it compromises vehicle control. A full suspension bush replacement typically costs £300-800 depending on extent.
Independent garage
£200–£600
Specialist
£300–£800
Parts only
£100–£300
Major
Wheel bearing wear and failure
MkI, MkII1965–198030k–120k miles
Wire wheel MG B GTs use knock-on wheel hubs with taper roller bearings that require regular adjustment and maintenance. The bearings are exposed to road dirt and moisture through the splined wheel mounting system. MOT data shows this model fails for wheel bearing problems at 28 times the fleet average for excessive play, with additional failures for rough bearings. Neglected bearings can seize or collapse completely.
What happens if ignoredFailed wheel bearings can cause wheel wobble, steering vibration, and in extreme cases wheel detachment. The car will fail its MOT and is unsafe to drive with severely worn bearings. Bearing replacement typically costs £100-300 per corner including labour.
Independent garage
£80–£200
Specialist
£100–£250
Parts only
£30–£80

1 more known issues tracked

Including wear items, electrical niggles, and generation-specific problems. Check a specific car to see which issues apply to its age and mileage.

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MOT failure hotspots

Based on DVSA MOT test data. These are the items where the MG B Gt fails at a significantly higher rate than the average car.

Emissions failure
Exhaust & Emissions · 40-60k miles
MOT failure rate: 307x the fleet average
Sample: 674 tests
Transmission joint, belt or chain worn
Bodywork · 0-20k miles
MOT failure rate: 139x the fleet average
Sample: 1,290 tests
Coil springs broken
Suspension · 40-60k miles
MOT failure rate: 128x the fleet average
Sample: 631 tests
Steering rack wear
Steering · 20-40k miles
MOT failure rate: 78x the fleet average
Sample: 945 tests
Stop lamps all missing or inoperative
Lights & Electrics · 20-40k miles
MOT failure rate: 59x the fleet average
Sample: 639 tests
ABS fault
Suspension · 0-20k miles
MOT failure rate: 50x the fleet average
Sample: 1,451 tests

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Related

MG B Gt reliability FAQs

What are the most common problems with the MG B Gt?

The MG B Gt has 5 known issues across 3 severity levels. The most serious are: Structural corrosion compromising vehicle rigidity.

Is the MG B Gt reliable?

The MG B Gt has 1 dangerous and 3 major known issues. Most can be avoided with a thorough pre-purchase check and full service history.

How much does it cost to fix MG B Gt problems?

Repair costs range widely. The most significant issue (Structural corrosion compromising vehicle rigidity) costs £500–£8,000 at an independent garage. Minor issues can be under £200. Always get a full inspection before buying.

Which MG B Gt generation is most reliable?

The MkI (1965–1974) has the fewest dangerous issues (1). However, condition and service history matter more than generation — a well-maintained earlier car can be more reliable than a neglected newer one.