An age old question in the MKIV Supra world.
This is one of the most common issues new owners face, especially when buying a car that has sat for a while or has high mileage.
If the car blows a distinct puff of blue smoke immediately after starting cold, but the smoke clears up once the engine warms up, the culprit is almost always worn valve stem seals.
What causes this? The factory rubber valve stem seals degrade, harden, and crack over time. When the engine is turned off, oil from the cylinder head slowly seeps past the hardened seals, running down the valve guides and pooling on top of the pistons. On startup, this oil burns off instantly, creating blue smoke.
Newer owners are often terrified they need to remove the cylinder head to fix this, but did you know that the community perfected a method to replace them with the head completely intact on the block?
- The Cylinder Hold: To prevent the valves from falling directly into the engine cylinder when you remove the valve springs, owners either pump compressed air into the spark plug hole or use the rope trick (feeding soft nylon rope into the spark plug hole and turning the engine by hand until the piston rises and compresses the rope against the valves).
- Spring Removal: Using a specialized overhead valve spring compressor tool, the valve keepers, retainers, and springs are removed.
- Seal Replacement: The old, brittle rubber seals are pried off the valve guides, and upgraded Viton rubber seals are pressed on.