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Buying a replacement car engine – what do you need to know?

  Monday, 10 July 2017

Engines are the heart of any vehicle.  If you’ve got an engine problem, you’ve got a car problem.

Despite their importance, though, engines can be purchased second-hand like almost any car parts.  However, there are many things you’ll need to consider when purchasing a replacement second-hand engine for your vehicle.

Which type of engine do you need to get?

Understandably, car engines aren’t completely interchangeable.  This doesn’t mean that there isn’t some crossover: two slightly different models released by the same company within a five-year period might well be able to use the same engine.

(Time periods in particular are important, as modern engines are more feature-equipped and – as a result - far more complicated).

Long or short block?

One of the main considerations is whether or not the engine is a long or short block.  These two variations can actually be found on what is otherwise the same engine, so it’s an important point.

The difference between the two is on which engine components are included:

A long block engine includes the full works when it comes to parts: cylinder heads, camshafts, valves, valve springs and an intact head gasket.  As such, long block engines can normally be installed quickly and easily, and will make a suitable replacement for any engine that’s been written off.

A short block engine, on the other hand, is designed for cases where the full engine doesn’t need replacing; just parts of it.  A short block engine is usually much cheaper as a result.

A note on replacing parts: it’s worth checking (and double-checking) to ensure that it’s not a single part of the engine causing the problems.  The following individual bits are all capable of causing wear and tear:

  • Engine valves.  These work together, one responsible for taking in the air and fuel mixture and the other responsible for expelling exhaust.
  • Piston.  This is a piece of cylindrical metal that moves upwards and downwards within the cylinder.
  • Piston rings.  These seal off the area between the cylinder’s inner edge and the outer edge of the piston and prevent the leakage of fuel and air into the sump during the compression and combustion phases.
  • Connecting rod.  This allows the crankshaft to be connected to the piston; both ends may rotate to allow for full movement of both pistons.
  • Crankshaft.  Changes upward and downward strokes of pistons into a circular pattern, allowing the pistons to perform their function.
  • Oil sump.  Otherwise known as the oil pan, this surrounds the crankshaft.

Remember that every single one of these parts need to be working perfectly for the engine to function.  Check the individual parts before you replace the whole thing.

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Check out the exterior housing

It is important to inspect the engine’s shell to make sure there is not too much wear and tear.  If you’re going for the second hand approach – which is cheaper – there will be some, but if there’s too much it can be a warning sign.

You should also check for any cracks and make sure that all of the nuts and bolts are securely fastened.

Look out for the tell-tale signs

We’ve mentioned the individual parts above, but it’s worth noting that some of them will display ‘tell-tale’ signs that an engine is suffering from long-term wear.  Keep an eye out for any of the following:

  • Check for rust, discoloured oil and oil foam on the oil dipstick.  This can be a signal that either water or coolant has entered the oil chamber.
  • Check the rockers located on the underside of the oil cap for contaminants.
  • Check any spark plugs to make sure they’re clean, and that there’s no rust build-up on the thermostat housing
  • The motor should spin freely when the crank pulley is spun at the same time

But what if I can’t carry out my own inspection?

If you’re unable to test out the engine, then ask the seller if they’re able to provide a full service history of the engine.  Also ask if any of the individual parts have been replaced, and check how many miles the engine has already done.

Needless to say, it’s also important to ask if the engine’s ever suffered from any known issues.

Is it salvaged or rebuilt?

There are two main kinds of used engines available: salvaged and rebuilt.

  • Salvaged engines have been taken from a car that’s either been in an accident or is too old to use.  In some cases, salvaged engines can be in great condition: they might have only been on the road for a few years and are often very easy to evaluate.
  • Rebuilt engines can be tougher to get a handle on and it’s recommended that if you get one – and some of them can be very good – you buy one from a credible source.  Some rebuilt engines from private sellers are less than stellar.

Be thorough

This is our last tip and possibly the most important.  Be VERY thorough when purchasing a replacement engine.  Along with the brakes, the engine represents the most important part of running a safe vehicle.

If you’re at all unsure, consult your local specialist, or give ASM Auto Recycling a call today on 01844 268 940.  We’ll be happy to help.

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