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Casting Repair Products > Crack Repair Tools & Supplies > Kits For Specific Repairs > Order # LC59RB3K  
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Order # LC59RB3K, 5.9 Cummins #53 Crack Repair and Reinforcement Kits

The Cummins 5.9 diesel engine block with the number 53 cast on the side is a typical situation where the block cracks under be normal operating conditions. Some believed the problem to be found only in high horse power versions or those with standard transmissions or those that were used to pull heavy loads. We now know that this is not the case. We have repaired and sold repair products to many who have not used their trucks in these conditions. In fact many owners who have used their engines in high load conditions have not experienced a failure.

To understand a common cracking phenomenon we look for operational commonalities that can provide clues. Because we have repaired a large number of these, we have had the opportunity to discuss driving habits and operational potentials that could be capable of causing these cracks to develop.

What we have concluded is interesting. First we have found no sign of a casting flaw. What we did find is the area that cracks is thinner than the surrounding cast iron to the extent that it is the thinnest part of the entire side of the block. The thin area was caused by a slight vertical core shift. This is a very common problem with casting complicated parts like cylinder blocks and heads. It only became an issue in this case because of the shape of the outside wall of the block. Just below the core plugs (freeze plugs) the side of the block turns under and then goes straight again. The area that turns under is close to a 45 degree angle. If the core shifts upward this area gets thicker and if it shifts downward the area gets thinner but everything else stays the same.

The next issue that contributes to the problem is the reduced coolant flow around the lower third of the cylinder walls. This is due to reduced passageways in comparison to the upper two thirds of the cylinders.

Engine coolant provides two important functions. It removes heat produced by combustion and it transfers heat to areas of the engine that are not close to the combustion chambers (like the outside walls of the water jacket).

When the engine is first started all of the heat is centered in the combustion chambers, exhaust ports and exhaust manifold. The coolant does a stellar job of removing heat from the inside surface of the water jacket which is the opposite side of the combustion chamber and in turn transfers the heat to other parts of the engine. Once the engine reaches a uniform operating temperature the heat is transferred through the coolant into the radiator and then to the air passing through the radiator.

The problem for the 5.9 #53 Cummins engine blocks occurs during the warm up period and not during high load periods. Heat causes thermal expansion. Thermal expansion can develop enough pressure to cause cracks in cast iron. We see it frequently. If the cylinder walls get hot faster than the lower section of the outside wall of the water jacket, strain will occur because all of these parts are connected together at some point. The passenger side of the block has less mass and is therefore not as strong as the driver’s side of the block.

It takes all of these factors to create the right conditions for the cracks to form plus a non-controllable variable of the driving habits of the driver. If the driver normally waits for the engine to fully warm up after starting on cold days before driving away, the lower part of the outside wall will have a chance to warm up and expand (thereby eliminating the strain on the thinner section where the cracks form).

Using the block heater on regular basis can prevent the strain from developing. Once the engine is properly warmed up the load doesn’t seem to make a difference unless a crack has already started to form. Once the crack starts it becomes a focal point for strain and the growth rate accelerates.

Once the crack has developed and starts to leak it can be repaired by stitching. In the beginning, many repairs were performed before we understood the cause of the cracks and developed the reinforcement bracket system. Several engines later developed new cracks extending beyond the repair. The repairs did not fail but new cracks emerged. We then saw a few of the early stitching only repairs fail after a lot of miles and time on them. (This is to be expected as long as the original cause is not addressed)

This led us to spend the effort to really understand the cause of these cracks that occur under normal operating conditions. I had an opportunity to review this issue with Cummins Remanufacturing on a visit to develop some special tools for them. It was very interesting that they were not aware of an issue here in the states with the blocks with the #53 cast on them. It appears that only a very small number of these blocks actually develop cracks and the number is so small that they thought they were freeze cracks and just scrapped the cores. I took the opportunity to measure the area with a micrometer I modified to reach into the area through a core plug hole and discovered the ones with cracks were much thinner than those that had not cracked. This validated my core shift theory.

This led us to develop the bracket reinforcement system that can be attached to the side of the block to add additional strength to the area where the cracks form. The system includes three brackets that are installed into the three core plug (freeze plug) holes above the crack. The bottom end of the brackets are mounted to the heavy horizontal rib on the block below the crack. These brackets make the side of the block strong enough to prevent future cracks. We have seen cases where there are small cracks that probably started on the inside that had not yet propagated through to the outside. We have not yet seen any cases where a crack has formed after the brackets has been installed but need to caution you that it could occur. If it does, the brackets can be easily removed, the new crack stitched and sealed, and then the bracket can be reinstalled. This would require disassembling the turbo and exhaust manifold from the engine again.

The reinforcing bracket requires drilling and tapping two 5/16” holes into the block near the motor mount directly below the center core plug hole. The upper part of the bracket installs into the core plug hole after removing the plug. This causes the bracket to span the thinner section of the block thereby adding strength to the area.

The bracket is held in place by two self-locking clamping tabs that rotate into place behind the inside wall of the block when the socket head cap screws are tightened. The part of the bracket that sits inside the core plug hole seals with an O-ring.

Tightening of the lower bolts creates the clamping load that adds strength across the thinner area of the block.

All items including three brackets, drill bit, tap, cutting fluid and thread locker comes in the kit.