good to know pulled this up on google may help
What is the "53" block?
The "53" comes from a casting number on the side of the block and is used to identify the problem blocks. Supposedly it affects about 100,000 blocks, but not only in Dodge Rams. Here is information regarding the castings from a thread on TDR:
Copied from:
2001 cracked block - TDR Roundtable
1. Brazilian Blocks are cast by a company named "TUPY" and are marked such. They are identified with cast evolution numbers. #53's are TUPY's. #54 and later evolutions were improved to correct the block issues that the 53's had.
2. Mexican Blocks were made by "Teksid" these blocks to my knowledge never had a problem with cracking, as they are heavier duty by trait, but they did follow the evolutions and got thicker. These blocks do not have the 2 digit "cast number" embossed on the side, instead a series of numbers that are unidentifiable to me. The Mexican blocks were rumored to even be harder to machine do to a harder cast overall, basically better quality in my opinion.
Brazilian Tupys always seem to outnumber Mexican blocks during the ISB's production probably about 8 to 1. So basically if there is a pattern number its Brazilian, if there is a series of small numbers its Mexican.
By the way the Mexican equivalent of a 56 pattern was the Heaviest ISB block of all. This means if you have a 2002 without a #56 on it and instead it has a series of numbers that are smaller and hard to identify, you got the the big boy!!!
Why the Worry?
Simply, the worry is that the block will crack. These blocks have thinner water jacket walls than other blocks so with coolant cavitation, corrosion, coolant pressure in the block, and torque, they may crack, spilling your coolant. I know from experience that it will not blow up the engine, but you will see that temp gauge rise more often than you'd like.
How Do I Find out?
If you want to see if your engine block could be one of these dreaded "53" blocks, crawl under the front, left side, and look up at the block on the front, directly under the injector pump (by the PS pump). You should see a large wiring harness mounted to the block. Directly below this, just above where the oil pan meets the block you will look for a "53" cast in the block. The numbers will be about 1 inch tall. See picture below:
Read more:
is cummins or dodge doing anything about the 53 ... - JustAnswer