What Is a Seized Engine and How to Fix It


Oct 16th, 2019

What Is a Seized Engine and How to Fix It

Seized engine moments are perhaps one of the lowest points for a driver. It's very annoying when a vehicle’s ignition cranks, the fuel tank is full, and the spark plugs are new, yet the car cannot start. This behaviour is typical with seized engines. 

Engines are said to be seized or locked when mechanical failures lock down the crankshaft from rotating on the bearings in response to piston movement. The locking of internal components, such as the piston getting stuck to the cylinder walls, piston rod bearings malfunctioning, and crankshaft breaking, are some of the primary causes of crankshaft lock down

Seized engines are a nightmare as it usually means replacing costly parts or worse the replacing the engine entirely. 

Causes of seized engines

An engine can jam due to several reasons that include:

  1. Inadequate engine lubrication - the starvation of lubricant causes moving engine parts to start grinding, and friction builds up. The friction emits heat that causes engine parts to expand. The expansion reduces the clearance between the moving part and may eventually constrict the movement when the pieces start grinding. The excessive heat may also melt and amalgamate or weld the parts together, locking down the engine. Continued grinding also causes the parts to wear out and eventually malfunctions and gets stuck. For example, the piston head and the cylinder sleeves may wear out, eventually causing the piston to stall.
  2. Rust - when a vehicle is unused for long, rusting of the engine parts may occur. When sensitive parts such as piston sleeves or the piston and crankshaft bearings rust, their movement is restrained, and the engine seizes.
  3. Bending of the engine parts - with usage, some of the vehicle parts may bow to pressure. When parts such as the piston rod or the crankshaft crook out of alignment, they may cause jamming and lock the crankshaft.
  4. Damaged piston or crankshaft bearings - the bearings play a significant role in facilitating smooth movement of the piston and the crankshaft. When the bearings are damaged, this movement is cramped and may lock down even the entire system, seizing the engine.
  5. Broken crankshaft - although rare, crankshafts at times develop cracks and eventually break. The broken crankshafts jam the pistons against the piston sleeve, stalling the whole engine.
  6. Excessive heating in the engine - heat may not necessarily come from friction due to lubricant starvation. Sometimes lack of coolant, continuously overworking the engine beyond its designed capacity, poor carburettor jetting or poor ignition timing may cause excessive heating. This excessive heating causes the oil to overheat, lowering its lubrication properties and eventually leading to metal-to-metal wear that seizes the engine.
  7. Accumulation of water in the engine - water may accidentally find its way into the engine. Since water is not compressible like gasoline and does not ignite readily, it causes the engine to seize up.

Symptoms of a Seized Engine

Seized engine symptoms appear in two stages: when the engine is on the edge of seizing up and when it eventually seizes.

Early Warning Signs

  • A faint knocking or tapping when the engine is running – this sound is produced by the piston rod hitting the crankshaft at the initial stages of the problem. With time, the sound grows into a loud knocking referred to as the 'dead-knock.'
  • The check engine or check oil dashboard-warning light also appears as a warning sign            
  • Strange noises when the engine is idling like there is air leaking at every stroke
  • Unending grinding sound when you start the engine
  • Excessive consumption of engine oil and always low on engine oil when you check
  • A smell of overheated oil
  • Abnormal violent shaking of the engine commonly experienced from a bent crankshaft
  • The engine starts performing poorly – a typical symptom when there are leaks past the piston seals

Signs of a seized engine

  • Broken piston rod piercing through the engine block
  • A loud breaking sound commonly experienced when the crankshaft breaks and immediately the engine stops running
  • The engine fails to kick off, even on a full tank with a fully-charged battery and new spark-plugs, while all the other battery-power operated accessories are fully functional. This typically happens when the piston jams inside the cylinder.
  • Finally, the dreaded verdict from the mechanic saying: It's dead sir/madam.

Fixing a Seized Engine

  1. Do not wait for your engine to seize up or start showing signs before you take action. Always check and maintain the required engine oil level and the coolant among other essential engine fluids. Make sure to service your vehicle on time and never miss servicing schedules.
  2. If you notice an issue or abnormality with your car, make an appointment to have the vehicle checked the soonest possible time.
  3. If you're lucky and the damage is not significant, your vehicle will kick back into life immediately once you top up the engine oil. So check your engine oil, top it up, and test if the engine will start. It may also be essential to check the cause of your engine oil level going low. You may probably be having an oil leak that requires fixing.
  4. Unfortunately for most vehicles, once they start stalling, the damage is usually already severe and requires changing of the affected engine parts. Check which affected parts need replacing: it may be the worn-out cylinder sleeves, piston rings, the piston head, the piston rod, the bearings, or the crankshaft. Replace the part with quality spare parts and if possible with Original Equipment Manufacturer - OEM parts.
  5. If the damage is extensive, especially one affecting the engine block, you may have no other option but to replace the whole engine.

Take good care of your vehicle, and it will serve you right. Do not wait until your car is on its knees for you to tend to it. By all means, prevent an engine seize up. Follow the manufacturer's recommendation on servicing and replace worn-out parts with high-quality manufacturer-recommended parts. For vehicle servicing and spare parts in Australia and New Zealand, Carpart.com.au is your one-stop-shop. We link you to the best car service providers in Australia and the best car part sellers in the country.