2017-2020 Toyota 86 Right Cylinder Head: Auto-Only Fitment and FA20 Engine Flaws

Key Compatibility Warning: Automatic Transmission ONLY

The reason for this specific fitment is due to differences in the engine's auxiliary systems. The cylinder head for the automatic model is machined to accommodate a vacuum pump that is not present on manual transmission cars. Additionally, there are internal oil passages specific to the automatic transmission version's valvetrain. Attempting to install a manual transmission head on an automatic vehicle (or vice-versa) will result in incompatible connections and likely engine failure. Always verify the part number and the transmission type of the donor vehicle before purchasing.

Symptoms of a Failing Cylinder Head

Cylinder head failure often presents symptoms similar to a blown head gasket, as one problem can quickly lead to the other. Be aware of the following signs:

• Engine Overheating: This is the most common and critical symptom. A cracked head or failed gasket can allow coolant to leak out or combustion gases to enter the cooling system, reducing its efficiency and causing the engine temperature to spike.
• White Smoke from Exhaust: Thick, sweet-smelling white smoke from the tailpipe indicates that coolant is leaking into the combustion chambers and being burned off as steam.
• Milky or Frothy Engine Oil: If you check the oil dipstick or oil filler cap and find a milky, mayonnaise-like sludge, it's a classic sign that coolant is mixing with your engine oil. This contaminated oil cannot lubricate properly and can quickly destroy the engine.
• Unexplained Coolant Loss: Constantly needing to top off the coolant reservoir with no visible external leaks is a strong indicator of an internal leak through a cracked head or bad gasket.
• Poor Engine Performance: A loss of compression from a damaged head can cause a rough idle, engine misfires (which may trigger codes like P0300-P0304), hesitation, and a noticeable loss of power.
• Bubbling in Radiator: With the engine cool, removing the radiator cap and starting the engine may reveal bubbles in the coolant. This is caused by high-pressure exhaust gas being forced into the cooling system.

Known Issues for 2017-2020 Toyota 86 / Subaru BRZ

The FA20 engine is generally robust, but it has well-documented weaknesses that can lead to cylinder head damage or failure. Understanding these is crucial when diagnosing problems or buying a used part.

Issue 1: Rocker Arm Ejection (The "Fatal Flaw")

The FA20 engine's valvetrain design does not use retaining clips on the valve rocker arms (also called followers). During certain events, like a slight valve float at high RPM, a misfire, or if a valve momentarily sticks, a rocker arm can become dislodged from its pivot. Because this is a boxer engine, the rockers are oriented sideways, and gravity can cause the dislodged part to fall. It may land harmlessly in a cavity, or it could be struck by the spinning camshaft, getting violently ejected through the thin valve cover. This can cause a massive oil leak directly onto the hot exhaust manifold, creating a significant fire risk. If the rocker falls, the corresponding valve may also drop into the cylinder, causing catastrophic piston and engine damage.

Issue 2: RTV Sealant Clogging Oil Passages

A class-action lawsuit has been filed concerning the excessive use of RTV (Room Temperature Vulcanizing) sealant on the oil pan and timing cover from the factory. Over time, pieces of this sealant can break off and get sucked into the oil pickup tube in the oil pan, potentially clogging it. This restricts oil flow to the entire engine, a condition known as oil starvation. The camshafts and their journals inside the cylinder head are highly dependent on a steady supply of clean oil. Oil starvation can quickly cause scoring and heat damage (visible as blueing) to these precise surfaces, ruining the cylinder head.

Buying a Used Engine Cylinder Head: Inspection Guide

A used OEM cylinder head is often a cost-effective and reliable alternative to expensive new parts, provided you inspect it carefully. Given the known issues with the FA20 engine, a thorough inspection is mandatory.

1. Verify the Part Number: First and foremost, confirm you are buying the correct part for an automatic transmission: SU003-00111 or 11039AC390. Do not trust a seller who says it "should fit."
2. Check for Warpage: This is the most critical check. Overheating is a primary cause of head failure. Place a precision straightedge across the mating surface of the head in an 'X' pattern and from end to end. Try to slide a feeler gauge under the straightedge. If you can fit a gauge thicker than 0.05mm (0.002 inches) underneath, the head is warped and will need to be resurfaced by a machine shop. If it's severely warped, it may be unusable.
3. Inspect Camshaft Journals: Remove the cam cradles and inspect the journals (the smooth surfaces where the camshafts spin). Look for deep scratches, scoring, or any blue/purple discoloration. Any of these are signs of severe oil starvation. A head with scored cam journals is junk—do not buy it.
4. Look for Cracks: Visually inspect the entire head for cracks. Pay close attention to the area between the valve seats and the spark plug hole, as this is a common weak point on many engines, though less so on the FA20. A machine shop can pressure test the head to find hidden cracks.
5. Check the Valvetrain: Ensure all rocker arms and pivots are present and in their correct positions. Check the tips of the valves and the cam lobes for any signs of unusual wear or damage.

Cost Comparison for Cylinder Head Replacement

Replacing a cylinder head is a labor-intensive job. Prices can vary significantly based on location and the extent of any related damage found during the repair.

Note: These costs do not include related parts that are almost always replaced during this job, such as the head gasket set, new head bolts (which are torque-to-yield and cannot be reused), timing components, coolant, and oil.

Frequently Asked Questions (FAQ)