Signs of a Bad Connecting Rod

Signs of a Bad Connecting Rod

December 27, 2021

In an internal combustion engine, a connecting rod is the link between a piston and the crankshaft, and it is an essential engine component. Connecting rods undergo an extreme tensile force as the pistons move back and forth. Even though they’re built to last for years, they can eventually bend or even break.

A bad connecting rod is a significant problem for an engine because it can no longer perform intake, exhaust, compression or power strokes. Continue reading to learn a few of the signs that a rod is damaged:

  • Knocking noise: A knocking sound is one of the more common signs of a failing connecting rod, which is why it’s referred to as rod knock. This knocking tends to get louder as you speed up, but it may go away once oil starts to circulate and lubricate the failing connecting rod. Instead of ignoring the loud sound, bring your car to a mechanic for an inspection.
  • Low compression: Compression refers to a piston’s ability to take in air and fuel and compress them. A lack of compression in one or more of the pistons often leads to misfires or underperformance while driving. Getting a compression test is the best way to see if you have low compression, which a professional can perform rather quickly.
  • Low oil or oil pressure: Engines tend to lose a whole lot of oil very quickly when a connecting rod fails. This issue can even lead to a drop in oil pressure, meaning the oil isn’t circulating through the engine. Low oil or low oil pressure will cause your dashboard lights to illuminate, so be sure to bring your car into a professional ASAP if that happens.
  • Visibly bent or damaged rod: The easiest way for a mechanic to tell whether the symptoms above are due to a bad connecting rod is to check under the hood. We emphasize the word mechanic here, because inspecting the rods requires disassembling the engine, which is something only a trained professional should do.

Causes of a bad connecting rod

Connecting rods can bend or break for a variety of reasons. Here are a few of the most common causes of failure:

  • Flooded engine: An engine that’s filled with fluids instead of just air is known as hydrolocked. When this occurs, connecting rods can bend or break when you start up your vehicle. A hydrolocked engine needs to be drained before you can continue to drive.
  • Over-revving the engine: The harder you rev your engine, the more force gets exerted on the connecting rods. If you make a habit of over-revving, rods are bound to break. Thankfully, newer engine technology prevents over-revving, but it can still occur if you drive an older vehicle.
  • Engine modification: If you upgrade your engine to make your car go faster, be warned! Most stock connecting rods aren’t built to handle heavy modifications and can fail if the upgraded pistons put too much pressure on them.

Let us diagnose your issue

If you think you’re experiencing a connecting rod issue, come on down to Auto Truck Service Inc. We have a full-service machine shop and can replace any failing connecting rods.

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