5.9L Cummins #53 Block Castings
5.9L Cummins ISB #53 Block History, Identification, & Repair Info
#53 Block History
Between 1999 and 2001, Cummins 24v ISB engine blocks with casting #53 were manufactured by a Brazilian company named, TUPY. The #53 block casting has thin water jacket walls that are susceptible to cracking. Cracking usually occurs when towing heavily, not letting the engine properly warm after a cold start, or a combination of the 2. The cracks can grow several inches in length, at which point owners will experience coolant loss and overheating if the problem goes unnoticed long enough. The problem affects approximately 100,000 24v engine blocks. Many "53" block castings have been identified on 12v Cummins blocks, but the 12v blocks do not experience cracking like the 24v blocks do. 1998/1999 trucks are the most likely to have a #53 block and experience cracking.
#53 Block Identification
#53 blocks can be identified by a "53" casting number located on the side of the block. The casting number is commonly seen on the passenger side, below the injection pump, although some #53 blocks have the casting number located on the driver side. If your block does not have a 2 digit casting number, it is likely a less common Mexican made (produced by Teskid) Cummins ISB. These blocks are highly desirable due to a stronger casting. Cummins identified the problems with the block casting, and as a result #54 and higher casting number blocks feature increased thickness in the problem areas and an overall stronger block.
#53 Block Repairs
The recommended repair method for #53 blocks that experience cracking is Lock N Stitch. #53 block owners report excellent success using the Lock N Stitch repair method, and do not experience additional cracking. Welding is not advised because it would harden the cast iron and likely cause cracks to spread, or cause more severe cracks.
Cracks commonly develop on the passenger side of the engine, right below the freeze plugs. Automatic transmission owners may have difficulty viewing cracks because they often occur directly beneath the automatic transmission heat exchanger.
What do I do if I own a #53 Block?
If you have identified your 24v engine to be a #53 block casting, become familiar with the region in which cracks typically form. Properly warm your engine after a cold start, especially if you will be towing. Avoid heavy throttle input under load and aftermarket performance parts if you hope to avoid block cracking.
Cummins #53 Block Images
"53" Block Casting Numbers
Typical crack resulting from thin casting in this region.
Smaller crack, cleaned & prepped for repair.