Ram’s 5.9-liter Cummins diesel engine has proven to be a solid power source for medium-duty 2500 and 3500 trucks. The first 12-valve 5.9 debuted in 1989 from the Ram and Cummins collaboration. With fixed geometry turbocharger, it was a strong but simple design. Then, in mid-1998, the new 5.9-litre 24-valve design was introduced, which was to last until 2002. Both developed two problems that could be catastrophic in many cases and required an entirely new replacement engine.
These two songs even have names, ’53 block’ and ‘killer dowel pen’. Name any of these terms and 5.9 12v and 24v enthusiasts will know exactly what you are talking about. So what are these two 5.9 problems, when can they happen and what can be done to fix them?
Cummins 5.9 liter “53 block”
“53 block” refers to Cummins 24-valve diesel engines with the identification “53” molded into the blocks. The casting number can be found on the passenger side of the block. These castings came from TUPY in Brazil. They are notorious for their thin water jacket walls that crack over time. The causes can be overheating, pulling heavy loads and not allowing engines to warm up after a cold start.
It should be noted that some 12-valve 5.9-liter Ram Cummins engines also had 53 block castings. So far there don’t seem to be any cracked water jacket issues with these engines. Ram estimates over 100,000 ISB 53 block 24-valve engines have been produced.
Once the cracks progress, coolant can begin to leak. If the cracks go undetected, they can eventually lead to shell wall degradation, causing coolant to travel through the engine. Coolant-contaminating oil can lead to catastrophic failure due to burnt cam bearings and/or faulty crankshaft main bearings. Block castings with “54” or higher casting numbers are preferred over previous blocks.
How To Repair Cummins 5.9 Liter 53 Block Cracks?
The recommended solution is to use Lock N Stitch. It is not recommended to weld the cracks as this hardens the surrounding metal, which can cause more serious cracks. Trucks with automatic transmissions can be harder to see where cracks are most common because the transmission heat exchanger gets in the way.
If you have a truck with this casting, do not make any changes to the engine, warm the engine after a cold start and try to avoid over-throttling under load. And keep an eye out for coolant leaks in the lower part of the block, especially under the freeze plugs.
Cummins 5.9 liter “killer dowel pin”
During the assembly of both the 12v and 24v 5.9-litre Cummins, a small metal plug is used to align the front gear housing. You’ll find it to the left of the injection pump sprocket just above the camshaft sprocket. If that pin, or should we say, if that “killer dowel pin” comes loose, it can come loose and fall past the front cover.
If that happens, it could have catastrophic consequences. Most cases of this involve the 5.9 with 12 valves, although this is known to happen with both versions. The 1994 to 1998 engines with a Bosch P1700 injection pump are thought to create different harmonics than previous engines with the VE44 rotary injection pumps. Those harmonics cause the 12v dowel pins to loosen over time.
What happens if Cummins’ dowel pin comes loose?
If a dowel pin falls out, it will be knocked around in the housing. The first two possible defects are cracked camshafts and/or cracked housing. It can also fall down between the cam gears and the injection pump.
This is the worst case because it causes valves to contact the pistons, causing the engine to stall. And the catastrophic damage cannot be repaired. The best case scenario if the locating pin comes loose is that it will slide down the housing and into the oil pan, where it can live happily ever after.
To prevent the dowel pin from falling is a simple solution. Diesel Hub recommends an inexpensive metal lip kit that nestles between the block tires and fastens into a bolt next to the plug. This will keep the plug in place forever. You will need to remove the front cover which means removing some components which can be time consuming. However, the alternatives make it more than worth the effort to secure that dowel pin. It is also recommended to use RTV silicone instead of a replacement gasket when reinstalling the front cover.
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