At seventy minutes under load, it dropped hard.
Isaiah shut the machine down before doing anything else.
He removed the pump housing on the concrete floor while Patrice watched from the doorway.
The cause was small enough to fit on his fingertip.
A seal.
It had swollen along one edge and begun shedding material into the fluid passage. The pump itself was not destroyed. The seal had simply changed enough under heat and time to restrict flow.
Isaiah recognized the housing.
He also recognized the donor serial number on his build sheet.
Later production year.
Same external part number.
Different internal seal compound.
Otis’s ledger had a note Isaiah had read and misunderstood.
“Late pump takes late fluid. Don’t mix generations because casting number lies.”
Isaiah sat back on his heels.
He had interpreted “generation” as pump design.
Otis had meant seal chemistry and fluid specification.
Patrice stepped closer.
“So?”
Isaiah held up the seal.
“This passed every bench test I ran.”
“That’s not what I asked.”
“No, ma’am.”
He took a breath.
“I used a pump from a later production run. Same outside number, but the seal compound is different. It works until heat and sustained load expose the mismatch.”
“Your mistake?”
“Yes.”
Patrice crossed her arms.
“What now?”
“I replace the tractor within two days. No charge. I take this one home and rebuild the hydraulic system correctly.”
“And my lost crew time?”
Isaiah had not planned for that question because he had not yet learned that business failures damaged more than hardware.
“I can credit your next service invoice.”
“Assuming there is one.”
“That’s fair.”
Patrice looked at him for a long time.
“You know what most small rebuilders do when something like this happens?”
“No, ma’am.”
“They tell me my operator abused it. Or my fluid was wrong. Or a used tractor is a used tractor and I got what I paid for.”
Isaiah said nothing.
“You did not do that.”
“It was my build.”
“It was.”
She nodded once.
“Bring the replacement.”
Isaiah did.
Then he went home and stopped every pending sale.
Stopping sales felt worse than making them.