Cummins Counterbore Repairs
Cummins NT and to a lesser extent, N14 engines often suffer from cracking in the liner counterbore areas.
This problem is most frequently evidenced by water leaks that appear to be coming from the head gasket itself. In other circumstances there are no symptoms at all and the cracks are not detected until the liners are removed from the cylinder block during overhaul or other major intervention.
This coolant loss problem typically gets worse over time and is even seasonally inconsistent (worse in winter) but rarely does it result in a catastrophic engine failure. Therefore, counterbore repairs are most often carried out at the time of engine overhaul.
Some workshops, particularly if they don't have specific Cummins NT experience, have been caught out with coolant loss from the head gasket area after the cylinder heads (only) have been removed and refitted to a customer's engine. Sometimes that initial work may have been carried out with the uninformed intention of specifically rectifying the coolants leaks which were already evident. It's a trap for young players - and for some older ones too.
When troubleshooting coolant leaks from the cylinder head area in Nt/N14 engines Torquepower's Service Department uses a Cummins approved fixture that assimilates heads being fitted but allows visible access to the liner to block sealing area. The engine block is pressurized and leaks can be determined while the engine is partially disassembled. This special fixture is used everytime that NT heads are removed and coolant loss is reported or is evident.
If leaks are identified, the customer has the option of going ahead and fixing the problem once and for all - or of having the engine reassembled as-is and assuming the risk of future coolant leaks.By far the majority of our customers opt for the repair.
This involves removing the liners and crack testing the counterbore areas. Cummins engineering has determined that certain cracks are acceptable while others are not. Torquepower uses this manufacturer promulgated criteria in its assesments and subsequent recommendations to the customer.
Where cracking is not acceptable, a number of options still remain. Either oversized flanged liners can be used or inserts can be fitted to the upper counterbore area to bring the liner seat area back to standard specifications.
Both cases involve in-frame machining of the cylinder block and Torquepower is properly equipped to carry out this work.
There are some cases where the top of the block surface is worn to the point where accurate machining is not possible because the tool needs to reference a square upper deck surface. In those less common situations, the engine will have to come out of the truck and the block will go to an engineering shop for top deck re-facing. Alternatively, we will substitute another prepared block from our stock.
Without properly addressing your counterbores at the time of the
initial repair, you are setting yourself up for re-work and unnecessary
other costs.
So, give us a call if you have any concerns with NT/N14 coolant losss from the cylinder head area.