Blown engine: how to decide whether to repair, replace or sell the car
By Unique Cash For Cars · Published · 9 min read
Sometimes it is worth fixing. Often it is not. A blown engine is the most expensive single fault most cars will ever have, but whether to fix it depends on three things more than on the size of the bill: what actually failed, whether someone else should be paying, and what the car is worth once it is running again compared with what it is worth now.
Get those three answers before you commit to anything. Paying for a replacement engine first can put more into a car than it will ever return. Selling first can hand away a claim against the dealer or the workshop that caused the failure.
This guide is general information, not legal or mechanical advice. Consumer-law remedies, modification rules and Queensland sale requirements change. Check the ACCC's current guidance on cars and vehicles, TMR's vehicle modification rules and its safety-certificate rules for your circumstances.
Which situation are you in?
- You bought the car from a dealer recently, or a workshop worked on the engine shortly before it failed: stop and read the consumer-guarantee section before you authorise any repair.
- The engine is damaged because the car went through water or was in a collision: it may be an insurance claim, not a repair decision. Call the insurer before anything is dismantled.
- The car is otherwise sound and you want to keep it for years: get two written quotes and compare them with the car's repaired value.
- The engine is one of several problems: rust, a worn gearbox, tired suspension or an expired registration all push the answer towards selling.
- The car has already been sitting at a workshop or tow yard: ask what storage it is costing you each day, then decide quickly.
What "blown" actually means
Blown engine is a catch-all phrase for very different failures, and the difference matters to the quote. Before you compare prices, get the diagnosis in writing:
- Head gasket failure. Often follows overheating. Signs include white exhaust smoke, coolant disappearing, milky oil or bubbles in the radiator. The engine block may be fine, and the repair is usually a cylinder head job rather than a new engine.
- Seized engine. The engine will not turn over at all, typically after running without oil or badly overheating. That usually means a replacement engine or a full rebuild.
- Internal mechanical failure. A heavy knock followed by the engine stopping, sometimes with a hole in the block, points to a failed connecting rod or bearing. That is rarely repairable in place.
- Hydrolock. Water drawn through the air intake, usually after driving through floodwater, can bend internal components. Engine damage from water ingestion is part of a flood insurance question, and a flooded car can also be written off; our guide to statutory and repairable write-offs explains what each classification allows.
A compression or leak-down test, and a check for combustion gases in the coolant, separate a head gasket from a dead engine. That is a small cost against a decision worth thousands. Do not keep driving an engine that is overheating or knocking to see whether it clears up. It turns a head repair into a replacement engine.
Check who else might pay first
The consumer guarantees in the Australian Consumer Law apply separately from any warranty, and they cover both the car and the work done on it. According to the ACCC, a car bought from a dealer must be of acceptable quality, and a major failure can entitle you to choose a refund or a replacement. The dealer has to deal with the problem itself rather than sending you to the manufacturer.
The same guarantees require repairs and services to be carried out with due care and skill. If a workshop replaced a timing belt, a water pump or the coolant shortly before the engine failed, ask them in writing whether their work caused it. Keep the failed parts and the diagnosis report.
Two limits apply. The Queensland Government notes that the guarantees do not cover one-off private sales, so a car bought from another owner through a classified ad is unlikely to qualify. And a claim is far weaker once the car has been sold or the engine replaced by someone else, so raise it before you do either.
Insurance is a separate question. Policies differ on mechanical breakdown, wear and tear, and damage caused by an insured event such as a flood or a collision. Read the product disclosure statement or ask the insurer directly how they treat an engine failure like yours.
Your repair options, compared
When nobody else is paying, there are usually four ways to get the car running again:
- Repair the existing engine. For a head gasket or a cooling-system failure, the head is removed, checked and machined if needed. It is usually the cheapest path, provided the block and bottom end are undamaged.
- Rebuild it. An engine reconditioner strips the engine, machines what can be saved and replaces bearings, rings, seals and worn parts. Quality depends heavily on who does it.
- Fit a used engine. A second-hand engine from a dismantler or an imported low-kilometre engine is often the quickest path for a common model. Its history is usually unknown, so the warranty offered on it matters more than the kilometres claimed.
- Fit a new or factory-reconditioned engine. Usually the most expensive and the most certain, if one is still available for the model.
Whichever quote you get, ask what caused the failure and whether the quote fixes that cause. A replacement engine fitted to a car with a failing radiator, water pump or cooling fan can overheat in exactly the same way. Ask, too, whether the quote includes a new timing belt or chain, gaskets, fluids and a flush of the cooling system, and what warranty covers the parts and the labour, in writing.
If the replacement is not the same type as the original, check the modification rules first. TMR classes a like-for-like engine replacement as a basic modification, which does not need approval or certification as long as the car still meets the applicable vehicle standards. An engine upgrade is a complex modification that must be done under a Queensland modification code and certified by an approved person. A cheaper or more powerful engine that does not fit that description can cost more than it saves.
Is a blown engine worth fixing?
Compare the written quote with two figures: what the car would be worth running, and what it is worth as it sits now. Leave out what you paid for the car or have already spent on it. That money is gone whichever way you decide.
The repair is easier to justify when:
- the car is otherwise in good condition and is not due for other major work
- you intend to keep driving it for several years
- the repairer puts a meaningful written warranty on the engine and the labour
- a comparable replacement car would cost clearly more than the repair
It is harder to justify when the quote is a large share of the car's running value, the gearbox or body also needs work, the registration has lapsed and a safety certificate would be needed before it could go back on the road, or no one will warranty the work.
A car with a failed engine still has value. It depends on the make, model and year, the condition of the body and interior, whether the car is complete, and how much demand there is for its parts. The gearbox, wheels, panels, glass, lights, interior and catalytic converter are often unaffected by an engine failure. Our guide to what a scrap car is worth explains what a buyer is actually paying for.
Selling a car with a blown engine in Queensland
The registration status decides the paperwork, not the fault. A registered car sold privately generally needs a current safety certificate before it changes hands, and a car that cannot be driven to an inspection station is hard to get one for. The two common alternatives are:
- Cancel the registration and sell it unregistered. An unregistered vehicle can be sold without a safety certificate. Our checklist for cancelling Queensland registration covers the plates and any refund of unused registration.
- Trade it to a licensed motor dealer. A trade to a licensed dealer does not need a safety certificate. Confirm the licence belongs to the business actually buying the car; our roadworthy guide explains why that check matters.
Do not strip the car before you sell it. Each part removed comes off the offer, and a complete car is usually easier to sell than a shell and a pile of parts. Be plain about the fault on the sale receipt, for example "engine seized, sold as is, not driveable", with the date, the VIN, the price and both signatures.
Moving a car that will not run
A car with a seized or failed engine can usually still roll in neutral, which makes it easier to winch onto a tow truck. Tell whoever collects it that the engine is dead, whether the steering is locked or the handbrake is stuck on, and exactly where the car is.
Where the car sits changes what is needed. A car that failed on the M1 and was towed to a holding yard needs the yard's release process and its storage charges confirmed before anyone arrives. A car at a workshop in Molendinar or Burleigh Heads after you declined a quote may be adding storage fees too, so ask the workshop. A car at the back of a sloping driveway in Mudgeeraba or a narrow lane in Labrador needs the access described in advance, so the right truck and equipment come the first time.
Do not try to drive the car to a buyer or an inspection, even a short distance. Beyond the damage, an engine that seizes in traffic leaves you stopped in a live lane.