Can Broken Or Bent Conrods Be Repaired?

An automotive machinist should never try to repair a broken or bent conrod. When conrods bend or break in any way, they will most likely require replacement. Eagleharm Engineering will never attempt to repair a broken or bent conrod. This article looks at why we shouldn’t attempt to repair broken conrods, why conrods get bent or broken, and the types of conrod repairs that are possible in certain situations.

Why you shouldn’t repair broken conrods

When a conrod breaks, it can end up being the most catastrophic thing to happen to an engine. Connecting rods are vital engine components, and any conrod repairs that aren’t done precisely and by seasoned conrod repair or refurbishing specialists run the risk of completely wrecking the engine. In most cases, the risk of repairing a broken or bent conrod far outweighs the potential benefits of doing so. Again, in most cases, it’s better to replace than to repair when it comes to conrods.

Why conrods get bent or broken

Conrod failure, or “throwing a rod,” can happen for a number of reasons, including:

  • Pre-ignition
    This refers to abnormal combustion of the air/fuel mixture inside an engine’s combustion chambers. Carbon buildup, low-octane fuel and too advanced ignition timings are three common reasons for pre-ignition. This can cause massive amounts of pressure in the cylinders, often more than what the engine is capable of handling, and can lead to connecting rods becoming bent or broken.
  • Flooded engine
    Liquid is much less compressible than air. When an engine is flooded, or hydrolocked (filled with fluid instead of air), pistons and conrods have to work harder at compression when you go to start the engine. You might have to de-flood the engine entirely before attempting to start it if you want to avoid potentially putting your conrods under so much pressure that they bend or break.
  • Over revving
    Another common cause of bent or broken conrods is over revving. This can easily occur when, for example, you shift gears to one that is too low for the speed you’re travelling. The engine’s pistons have to rotate faster than they should, and this can lead to conrods bending or worse engine damage. Luckily, modern engines are able to cut fuel supply when an engine redlines.

Our conrod repair steps

  1. Conrod alignment
    We first check conrods for alignment and ’roundness’. This assesses whether they can be machined. Broken or bent conrods are discarded and must be replaced.
  2. Replace smallend bushes
    Each conrod’s smallend bush is removed and a new semi-finished bush is fitted.
  3. Machine smallend bushes
    The new smallend bushes are then machined to manufacturer’s specification. This ensures the correct piston pin clearance.
  4. Machine bigend housing
    The ‘bigend’ housing of each conrod is machined to within 0.05mm of the finished size. Then it is honed to the manufacturer’s recommended specification.

Engine repairs and refurbishment in Durban

Eagleharm Engineering provides professional automotive machinist services in Durban and surrounding areas. Our engine repairs and refurbishments are trusted by countless of our clients who keep bringing their engine components to us for expert attention. Explore our engine reconditioning services, get to know us better on our About Us page, or contact us directly with any questions, concerns or engine reconditioning requirements you may have.