When you replace an engine with a crate, remanufactured or long-block engine, most early failures come from the old parts and systems it is connected to, not from the engine itself. This checklist covers what to replace, clean and check so the new engine starts healthy: the cooling system, the oil system, sensors, mounts, the fuel system and the break-in.
Before installation
- Confirm the engine matches your vehicle: engine code, model year and options; see what comes with a long block.
- Find and fix what killed the old engine: overheating, oil starvation, a failed sensor or a cooling fault.
- Transfer or replace parts the new engine does not include.
Replace these
| Part | Why |
|---|---|
| Water pump, thermostat and hoses | Old parts often caused or survived the failure; see bad thermostat symptoms |
| Oil cooler or flush it, and the oil filter | Debris from a failed engine hides in the oil cooler |
| Radiator, or a thorough flush | A clogged radiator overheats a new engine; see bad radiator symptoms |
| Engine and transmission mounts if worn | See engine mount symptoms |
| Crank and cam sensors, knock sensors as needed | Old sensors cause running problems blamed on the new engine |
| Gaskets for everything removed | Intake, exhaust and valve cover gaskets; see valve cover gasket leak |
| Belts and spark plugs | See serpentine belt and spark plugs |
Before first start
- Fill with the specified oil and prime the oil system so the engine has pressure before it fires.
- Fill and bleed the cooling system completely; see how to bleed coolant.
- Check all connections, vacuum lines and the fuel system for leaks.
First start and break-in
Watch oil pressure and temperature closely, check for leaks, and follow the break-in procedure for your engine type; see engine break-in procedure. Change the oil and filter early after break-in.
Common mistakes
- Reusing an oil cooler full of debris from the failed engine
- Starting without priming the oil system
- Leaving air pockets in the cooling system
- Reusing a cracked vacuum hose or a failing sensor
- Skipping the early oil change after break-in
Transmission and drivetrain
An engine swap is a good time to inspect the transmission cooler lines, rear main area, flexplate and torque converter, since they are easy to reach with the engine out. A cracked flexplate or leaking converter seal is far easier to fix now than later.
Keep records
Keep receipts and notes of parts replaced, fluids used and break-in mileage. They help diagnose any later problem and add value when you sell the vehicle.
Related
See how long remanufactured engines last, engine replacement cost and our engines.
More guides: used vs rebuilt engines.
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