Lexus LX 4.5 V8 Diesel 1VD-FTV (2017): Cylinder Compression Test

Part numbers are from the manufacturer's original catalogue. Check them against your VIN before ordering.

• Diesel compression tester with a gauge range of at least 40-50 bar
• adapter for the 1VD-FTV glow plug hole
• socket set and ratchet
• extensions
• glow plug sockets
• torque wrench
• compressed air
• clean containers and a marker for labeling fasteners
• battery charger

1. Warm the engine up to operating temperature, shut it off, and let it cool for 20-30 minutes so you don't burn yourself on the exhaust manifolds. Make sure the battery is fully charged: the starter must crank the engine at a steady speed. A weak battery lowers all readings.
2. Remove the decorative engine cover. Both cylinder heads (V8, 4 cylinders each) are accessible from above, but some components (intake pipes, wiring harnesses) get in the way, so remove them as needed. Label the connectors and harnesses with a marker.
3. Thoroughly blow out the glow plug wells with compressed air so that dirt doesn't fall into the cylinders.
4. Disconnect the glow plug connectors (or the common bus bar, depending on the version) and carefully unscrew the glow plugs from all cylinders. Lay them out in cylinder number order. If a glow plug is seized, don't use excessive force: it is fragile, and a broken-off tip will have to be retrieved from the cylinder.
5. Be sure to disable the fuel supply so the diesel doesn't inject while cranking: remove the fuel pump fuse or relay and unplug the injector connectors. If you don't disable the fuel supply, hydrolock and fuel being dumped into the cylinder are possible. Connect a diagnostic scan tool: fault codes for sensors and injectors are unavoidable after disconnecting them, and you will need to clear them afterward.
6. Screw the compression tester adapter into the glow plug hole of cylinder 1, tightening it by hand without cross-threading. The seal must be completely airtight. Make sure the adapter's sealing ring is intact.
7. Crank the engine with the starter (the accelerator pedal isn't needed, since it has no effect on a diesel). Crank until the needle stabilizes, usually 5-8 seconds or 8-10 compression strokes. Record the maximum value, then release the pressure with the gauge's valve.
8. Repeat the measurement on each of the 8 cylinders under identical conditions: the same cranking time and the same battery. Record the results immediately, by cylinder number.
9. Evaluate the result. Reference values for a diesel of this class: in a healthy engine the readings fall in a range of roughly 28-35 bar, and the difference between the "strongest" and the "weakest" cylinder should not exceed 10-15%, otherwise there is wear of the rings, cylinders or valves. Check the exact specification and minimum limit in the manufacturer's service information for the 1VD-FTV.
10. If one cylinder is noticeably lower than the rest, pour 10-15 mL of clean engine oil into it through the glow plug hole and repeat the measurement. If the pressure rises, the rings or the cylinder bore are worn. If it doesn't change, the cause is the valves, the head gasket or a crack. If two adjacent cylinders are low at the same time, a blown head gasket is likely.
11. Reinstall the glow plugs and tighten them with a torque wrench (for glow plugs of this type the typical range is about 8-15 N·m (6-11 lb-ft); verify the exact value in the service information), then reconnect the connectors. Reinstall the fuel pump fuse or relay, reconnect the injector connectors, and refit the removed pipes and the cover.
12. Connect the scan tool, clear the fault codes, start the engine and let it idle, then check for fuel leaks and other leaks.

• Do not perform the test with the fuel supply active, and do not crank the engine with the glow plugs removed without disconnecting the injectors: this risks hydrolock and engine damage. Under no circumstances screw adapters from gasoline compression testers into the glow plug hole: the thread and length do not match. If you have no experience with Common Rail diesels, or if the measurements showed serious differences between cylinders, take the vehicle to a specialist repair shop: the decision to repair the cylinder head or the piston/cylinder assembly on this engine should only be made after a full diagnosis.