Crack detection
Engine crack testing in Sydney is often the first job in a rebuild. A crack can hide in a head, a block or a crankshaft. If it is missed, the machining and new parts can be wasted. Testing early tells you whether a part is worth saving.
Read the full crack detection guide
What is crack testing?
Crack testing is a type of non-destructive testing. It checks a part for flaws without harming it. The tester compares what they find with the part's specifications and records the result. The right test depends on what the part is made of.
Magnetic particle testing
The part is magnetised. Fine iron particles are then put on the surface. Where there is a crack, the magnetic field leaks out and the particles gather along it. This shows up cracks at the surface and some that sit a little below it.
It only works on iron and steel. That suits cast iron heads and blocks, crankshafts, camshafts and conrods. It cannot be used on aluminium.
Dye penetrant testing
A thin dye is sprayed on and soaks into any surface crack. Then a developer is applied. It draws the dye back out, and the crack shows as a coloured line. Some dyes glow under ultraviolet light.
This works on aluminium and other non-porous metals. It only finds cracks that are open to the surface.
Pressure testing
This test is for the water passages in heads and blocks. The passages are sealed with plates. Air pressure is pumped in. The part then goes into a tank of water, or is sprayed with soapy water. Bubbles show where air escapes.
Pressure testing does not find cracks that do not reach a water passage. It is often used together with another test.
When do you need it?
- Before a rebuild. It is better to find a crack before money is spent on machining.
- After overheating. A head or block that has run hot should be checked.
- Coolant loss with no outside leak. A crack into a water passage is one possible cause.
- Before reusing a crankshaft or conrods, especially in a performance engine.
How we do it at Reco
Crack detection is one of our services at the Auburn machine shop.
What it costs
The price depends on the part and the test it needs.
Questions
Which crack test is used on an aluminium head?
Dye penetrant or a pressure test. Magnetic particle testing does not work on aluminium. It only works on iron and steel parts.
Is a pressure test enough on its own?
Not always. A pressure test only finds cracks that let air escape from a water passage. A surface crack that does not reach a passage will not show. That is why a second test is often used.
Can a cracked head or block be repaired?
Sometimes, but not always.
Related services
- Cylinder head reconditioning
- Crankshaft grinding
- Engine reconditioning
- All engine servicing and reconditioning
More answers are on our FAQs page.
Who it is for
- Before a rebuild. It is better to find a crack before money is spent on machining.
- After overheating. A head or block that has run hot should be checked.
- Coolant loss with no outside leak. A crack into a water passage is one possible cause.
- Before reusing a crankshaft or conrods, especially in a performance engine.
Price guide
The price depends on the part and the test it needs.
Crack detection FAQs
Which crack test is used on an aluminium head?
Dye penetrant or a pressure test. Magnetic particle testing does not work on aluminium. It only works on iron and steel parts.
Is a pressure test enough on its own?
Not always. A pressure test only finds cracks that let air escape from a water passage. A surface crack that does not reach a passage will not show. That is why a second test is often used.
Can a cracked head or block be repaired?
Sometimes, but not always.
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