Conrod engine problem - CRACKED / BROKEN

The most common con-rod breakage is the result of a failed big-end bolt. Big-end bolts fail due to over tensioning or stretch.(some manufacturers recommend replacement of big-end bolts when overhauling the engine)

Another cause is the big-end nut was left loose on assembly. Close inspection can determine if this was the cause. The normal evidence when this is the cause is one big-end nut has come off the big-end bolt without any real damage to the threads and the other bolt is broken or severely bent.

Fatigue can cause the con-rod to fail. Excessive loads and or revs can stretch and break the con rod. This usually breaks midway at the weakest point. Tests can be carried out to determine the cause.

Rods can be damaged and may fail due to overheating and distortion of the rod eye when fitting press fit pistons to rods. This procedure is best carried out by an engine reconditioner as the correct tools and procedures are required to ensure no damage occurs and alignment is checked and corrected as needed.

Disclaimer Agreement

: Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2001 UMR Engines www.engineproblem.com.au

Conrod engine problem - BENT

Bent con-rods are often missed when engine rebuilds are carried out due to the con- rod alignment not being checked as the correct equipment was not available. Con-rods bend most commonly due to hydraulic action caused by the induction of water. (Blown head gasket or driving through water above the air intake.) Severely bent con-rods should be replaced not re-aligned.

Foreign object forced between the piston crown and cylinder head is also a more obvious cause. (Broken ring, valve, valve seat or carburettor /air cleaner parts)

Minor bend can occur due to severe operating conditions. This will be evident by the unusual diagonal wear pattern on the big end bearings. Visual inspection is important at time of strip down to record which rod requires attention. Engine reconditioners can rectify minor bend damage by re-alignment.

Disclaimer Agreement

: Every care has been taken in writing this information and procedures, but no responsibility can be excepted for errors, omissions or misuse of this information and procedures. The information available on this site is for your instruction only and cannot be copied for sale, © copyright 2001 UMR Engines www.engineproblem.com.au