The Cummins “53” Block was used in Cummins 24 valve ISB diesel engines from 1998.5-2002. Manufactured by Brazilian company, TUPY.

The “53” block casting has thin water jacket walls that are susceptible to cracking. With coolant cavitation, corrosion, coolant pressure in the block, frequent or heavy towing they may crack, causing a loss of coolant. Failing to let an engine properly warm after a cold start, and engine overheating can contribute to the development and propagation of cracks in the water jackets of these blocks. 

Cracks commonly develop on the passenger side of the 53″ blocks, right below the freeze plugs. Automatic transmission owners may have difficulty viewing cracks because they often occur directly beneath the automatic transmission heat exchanger.

Cummins “53” Block Identification

Cummins “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 near the front of the engine.

To determine if a particular engine has a “53” block, on the passenger side of the engine, you should see a large wiring harness mounted to the block. Directly below oil filter mounting assembly, and directly in front of the front turbo drain port in the block, just above where the oil pan meets the block, if present there will be a “53” cast in the block. The numbers will be about 1 inch tall.  

Cummins Diesel “53” Block Repair

Temporary “53” block fixes include block stitching and welding. These temporary fixes can hold you over until you can find a replacement engine. 

The real problem with these temporary fixes is the wall thickness in that area of the block. That’s why drilling out the ends of the crack, V-notching the wound, and welding don’t necessarily permanently fix the problem. The block could re-crack.