Engine
What to Do With a Seized Engine
An engine that will not turn over feels like the end of the car. Often it is not. Three quite different conditions produce the same symptom, and one of them is an inexpensive repair.
What this guide covers
Stop Cranking First
Before anything else: stop trying to start it.
If there is liquid in a cylinder, every crank attempt is trying to compress something that will not compress. That is what bends connecting rods.
An engine that might have been saved by draining a cylinder becomes a rebuild after a few more attempts on the key.
Which of the Three Do You Have?
It clicks once, or clicks rapidly, and does not turn
This is the good outcome and the most common one.
A rapid clicking is almost always a flat or failing battery. A single heavy click with no movement is usually the starter motor or its solenoid.
Both are ordinary repairs. Before assuming the worst, have the battery and charging system tested, and check whether the engine turns by hand.
It turns a little and stops hard, or will not turn at all
If the starter is clearly trying and the engine will not rotate, something mechanical is stopping it.
That is either hydrolock or seizure, and the difference matters enormously.
The engine turns freely by hand but will not start
Then it is not seized at all. That is a fuel, spark or timing problem and a different investigation entirely.
Hydrolock: Liquid Where Air Should Be
Cylinders compress air. They cannot compress liquid.
If water, coolant or fuel has entered a cylinder, the piston physically cannot complete its stroke and the engine locks solid.
How it happens here
Driving through standing water after heavy rain is the classic cause, with water drawn in through the air intake.
Coolant entering through a failed head gasket is the other route, and that one fills a cylinder slowly while the car is parked.
What can be done
If it is caught before repeated cranking, the plugs come out, the cylinders are cleared, the oil is changed and the engine is inspected properly.
Some engines survive that. Whether yours did depends on how many times it was cranked, which is why the first instruction on this page is to stop.
If you have driven through deep water and the engine has stopped, do not restart it. Have it recovered. That single decision is often the difference between an inspection and an engine.
Seizure: The Serious One
A seized engine has components welded or worn together to the point where they cannot move.
It is almost always the end result of running without adequate oil pressure, and the two causes are a serious oil leak that was not noticed, or an oil level that was never checked.
Severe overheating produces the same outcome by a different route.
What it usually means
A genuinely seized engine is a rebuild or a replacement rather than a repair.
The honest question at that point is the value of the car against the cost of the engine, and that is a conversation worth having with numbers rather than assumptions.
Exotic Auto Services will tell you plainly when an engine is not worth rebuilding. See car engine repair.
How It Is Diagnosed
- Test the battery and starter first, because that is the cheap outcome and it is common.
- Try to turn the engine by hand at the crankshaft pulley. This alone separates electrical from mechanical.
- Remove the spark plugs. If the engine then turns, there was liquid in a cylinder and you have hydrolock.
- Inspect the plugs and cylinders for water, coolant or fuel, which tells you where it came from.
- Check oil level and condition, because oil starvation and coolant contamination both show here.
- Compression or leak-down test if the engine turns, to assess what damage was done.
That sequence takes a fraction of what a wrong assumption costs.
Preventing the Ones That Are Preventable
- Check the oil level monthly. Most seizures are the end of a story that started with a slow leak.
- Never drive through standing water deep enough to reach the air intake.
- Treat the oil pressure warning as an immediate stop. It is the warning that prevents this entire article.
- Investigate coolant loss rather than topping up, because a head gasket can fill a cylinder while parked.
- Do not ignore overheating. Severe overheating and seizure are the same story at different stages.
Frequently Asked Questions
How do I know if my engine is seized or just will not start?
Try turning the engine by hand at the crankshaft pulley. If it rotates, the engine is not seized and you have a fuel, spark or starting fault. If it will not move, remove the spark plugs and try again: if it then turns freely, there was liquid in a cylinder and you have a hydrolock rather than a seizure.
Can a seized engine be repaired?
A genuinely seized engine, one that has run without oil pressure until components welded together, is a rebuild or a replacement rather than a repair. The realistic question is the value of the car against the cost of the engine, and that deserves a straight answer with numbers rather than an assumption either way.
My car stopped after driving through water. What should I do?
Do not restart it. Water in a cylinder cannot be compressed, so every crank attempt risks bending a connecting rod. Have the car recovered. If it is caught before repeated cranking, clearing the cylinders and changing the oil sometimes saves the engine entirely.
Is a clicking noise when I turn the key a seized engine?
Almost never. Rapid clicking is usually a flat or failing battery, and a single heavy click with no movement is usually the starter motor or solenoid. Both are ordinary repairs, and they are far more common than seizure, so they are worth testing before anyone assumes the worst.
What causes an engine to seize?
Loss of oil pressure, in the great majority of cases. That is usually a leak nobody noticed or a level nobody checked, until the bearings ran dry. Severe overheating reaches the same result by a different route. Both are preventable by checking the oil monthly and treating the red oil pressure warning as an immediate stop.
