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What To Check When Checking Out A Used Engine?

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Finding out your car needs a new engine can be a painful experience, especially in the financial sense. That's what makes used engines from used auto parts mechanics such an attractive buy for many car owners. However, there are plenty of pitfalls to be avoided when it comes to purchasing a used engine from a salvage yard or even a trusted rebuilder.

The following offers plenty of important tips that'll help you find the best used engine available and avoid some the more common traps that could prove painfully expensive.

It's the Simple Things That Count

Sometimes the most costly mistakes are those that could have been prevented with just a simple action. Performing these simple steps will help you find out more about your engine of choice as you shop around:

  • High-mileage warrior or low-mileage creampuff? Checking how many miles the engine has clocked is a prudent step, as high-mileage engines are bound to have suffered greater wear and tear. This is relatively easy to do when the engine is still in a car whose odometer can be read. If the engine is already out, chances are you'll only have the salvage yard's word to go by.
  • Eyeball the engine for a moment. Preferably, you should have a reference image and schematic of the exact engine intended for your vehicle. This would help you spot any details that appear out of place, such as a missing or damaged component.
  • Turn it over by hand. To make sure the engine's not locked up due to rust or mechanical failure, you'll want to turn its crankshaft. You can do this by attaching a wrench or ratchet with the appropriate socket onto the crankshaft pulley nut and turning the nut clockwise.
  • Take a look at the oil dipstick. Just looking at the condition of the oil can tell a lot about an engine. Look out for metal flakes, sludge or signs of coolant mixing in the oil (such as a milk chocolate-like appearance and/or consistency to the oil.

Looking for signs of collision damage on the donor vehicle is another useful trick, but only if the salvage yard hasn't already pulled the engine from the car.

Digging Deeper

Checking a used engine's condition isn't just skin deep. For starters, you could perform a leak down test to gauge the engine's compression capabilities. This test essentially records the amount of air that's capable of leaking past the piston rings. For this, you'll need a pressure gauge and a source of compressed air. Since no engine is capable of a perfect seal, you can expect a 10 to 12-percent loss of air pressure for an engine in good condition. A 20-percent loss (or more) is a clear sign of major problems.

Remember the bit about the oil saying volumes about the engine's current state? You can dig deeper by sending the oil off to a laboratory for a professional analysis. A typical analysis checks for a variety of items, ranging from the concentration of aluminum, iron and other metals to the "total base number" of useful additives left in the oil sample.

You can also pull the oil pan and check the contents within. In addition to checking for metal shavings within the pan itself, you should also make sure the crankshaft bearings and caps haven't taken on a blackish "burnt" appearance. That usually means the engine has suffered some form of overheating at some point in its life. Don't hesitate to remove the valve cover and inspect the camshafts or pushrods for signs of wear, damage or oil sludging.

With the above advice at hand, finding a good used engine for your vehicle should be simpler and less fraught with unpleasant surprises.