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911 (Classic Air-Cooled)

1964-1989 / Coupe / Targa / Cabriolet / Germany

All 911 (Classic Air-Cooled) problems All workshop issues
Common Engine

Thermal Reactor Exhaust Damage (1975-1977)

Symptoms

Exhaust valve recession, burnt valves, cracked exhaust studs. The thermal reactor runs extremely hot to burn unburned hydrocarbons.

Cause

The thermal reactor system was Porsche's solution to US emissions regulations before catalytic converters became standard. It operates at much higher temperatures than a conventional exhaust, stressing the exhaust valves and the cylinder head studs.

Fix

Replace the thermal reactor with a conventional exhaust manifold and catalytic converter (or, for track-only cars, a header).

Replace burnt valves and cracked studs.

Cost: $1,500-$3,000 for exhaust conversion, $2,000-$4,000 for valve work.

Cost mentioned in fix
Cost: $1,500-$3,000 for exhaust$2,000-$4,000 for valve

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Other known issues

Minor Engine

Cam Chain Tensioner Failure (3.2 Carrera)

The cam chain tensioner fails, allowing the duplex timing chain to go slack. The chain skips teeth on the sprockets, the camshaft timing shifts, and the valves collide with the pistons. The result is catastrophic, bent valves, damaged pistons, and potentially a cracked cylinder head.
Common Engine

Valve Guide Wear

Blue smoke from the exhaust on start-up (oil pooled on valve heads drains into the combustion chamber) and on the overrun (oil drawn past the guides by manifold vacuum). Increased oil consumption.
Critical Engine

Oil Leaks, The Usual Suspects

Oil residue on every surface of the engine. Active dripping in the garage.
Critical Engine

2.7-Litre CIS Engine, Nikasil Cylinder Scoring

Increased oil consumption, loss of compression, rough running, and blue exhaust smoke. The engine gradually loses power and efficiency.
Common Transmission

915 Gearbox, Second Gear Synchro Wear

Second gear crunches or grinds on downshifts, especially when cold. The synchro cannot match shaft speeds before gear engagement. Over time, it worsens and eventually grinds on upshifts as well.
Common Transmission

915 Gearbox, Shift Linkage Slop

Vague, imprecise shifting. Difficulty finding gears, especially third and fourth.
View all 13 911 (Classic Air-Cooled) problems