Top 5 Common Problems with L67 Supercharged Holden Engines (And How to Fix Them)
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Top 5 Common Problems with L67 Supercharged Holden Engines (And How to Fix Them)
The L67 3.8L Supercharged V6 engine was a game changer for Holden performance fans, especially in models like the VT–VY Commodore, WH Caprice, and VY Crewman. But like any boosted motor, it comes with its quirks. If you own one, you’ve probably dealt with at least one of these five common issues.
1. Intake Manifold Gasket Leaks
This is by far the most common and most annoying problem. The factory plastic lower intake manifold (LIM) gaskets are notorious for warping, cracking, and leaking coolant or oil into the valley. This can lead to rough idle, misfires, or even full engine failure if not caught early.
Fix: Upgrade to a steel valley gasket kit designed for the L67. It handles boost, heat, and vibration far better than OEM.
→ View our steel valley gasket kit for L67 here
Need one specific to your model?
2. Boost Loss from Cracked Hoses or LIM Seals
If your L67 sounds fine but doesn’t pull like it used to, it might be leaking boost. Common failure points include vacuum hoses, throttle body gaskets, and — again — the LIM seals. Even a small leak will kill power and torque.
Fix: Inspect all vacuum lines, bypass valve operation, and manifold gaskets. Replace brittle rubber with silicone and consider a LIM reseal.
3. Overheating Due to Coolant Crossover Failures
Over time, the coolant passages near the valley area can warp or clog due to gasket breakdown or poor flow design. This causes overheating — especially under load or in traffic.
Fix: A new valley gasket set with proper coolant channel sealing can resolve this. Also flush and replace coolant regularly with quality additives.
4. Knock Sensor Failures in High-Boost Builds
Planning to pulley down or run more boost? The factory knock sensors often throw false codes or become unreliable. This can cause your PCM to pull timing and kill performance.
Fix: Use high-quality sensors and consider relocating them with a custom tune if you're building a high-power L67 setup.
5. Oil Leaks Around the Valley and Rocker Covers
The combination of old gaskets, boost pressure, and engine heat can lead to oil sweating out around the rocker covers and pooling in the valley.
Fix: Replace both your rocker cover and LIM gaskets with modern, heat-resistant versions — ideally steel-based like ours.
Final Thoughts: Fix It Right, Fix It Once
The L67 is a killer engine when looked after properly. Whether you're chasing power or just want reliability, the right gaskets and maintenance are everything. Start by fixing the root cause of most of these issues — the manifold sealing.
→ Shop our L67 manifold gasket kit now
Want model-specific fitment info?