Don't forget Diesel was far cheaper to operate, maintain and service. No waterstops, no stopping to cool wheels, Dynamic Braking the biggest advantage, less turnaround time at Terminals, higher speed operation over track sections, same speed operating in reverse(no need to turn loco if hood unit), no additional crews when extra units added, and easy for one man to run the whole train.
I could be here all day listing what can go wrong with a Diesel, but then all loco types breakdown.
Our 1954 English Electric double-ended D
F locos were prone to fuel leaks, crews were later banned from walking through the unit following one fireman getting seriously doused with high pressure fuel spray. Tractionmotor flashovers were the most common fault, especially with the lighter built GM D-19 supplied on the initial orders. Crankcase (over-pressure) explosions from fuel dilution of the lube oil was another early problem on the GM's. Electric loco's have software issues as do the newer types of D.E. control systems. Press F4 for help.
NZR rebuilt the D
A units orders of 1963 and 1965 in the years '78-'82 and those left in service have had one minor shopping since. That's steller service but the G-12 was built with a rugged frame if not robust Traction motors. There was a requirement to reduce to Notch 5 when passing over level crossings prior to the late 70's. The earlier DA's had electro-pneumatic controls that were also prone to contact problems, the Transition switch often was a source of problems. There were several grades of overhaul involved depending on mileage and decay/ electrical problems.
Personally I was only on one D
A breakdown, the Radiator speed increaser drive clutch packed it in. No D
B, D
BR or D
C failures. One D
F (GM, 1979), broke a small pipe on the radiator header tank that fed the low water alarm, so that went back to idle and required a tow once I made the next Station.
No D
X ever let me down, one unit lost the turbo boost clutch when I was starting up the Pukerua Bay Bank, lucky I only had a light train of less than 200 tonnes, but still walked up the hill at 3.72 mph the wind blowing the same speed and enveloped me in a moving cloud of thick exhaust for most of the climb(only time I can say I experienced what it was like to be a steam loco driver).
The D
X had cold idling wear issues with the prime mover mid-80's but that was solved with an automatic power up device linked to radiator coolant temperature. Damned great Traction Motors and Main Alternator on those Beasts.
Most of our 1971-4 D
X fleet is still in service but all have had a full overhaul and provide stellar service. Unlike the new Chinese built MTU powered units purchased over the past 6 years, which are plagued with issues mainly of component quality, durability and design issues.
However I can relate many instances of going out on a relief loco to pull in a breakdown, just what those all were I didn't commit to memory. I haven't included
Stalls either since that was common to all loco's and an Overload, Weather or Driver issue. Our 25KV E
F gave untold issues when introduced in 1988 but that was mainly software issues which were worked out, a number of those locos are still running today unrebuilt.