"We aware that we are having technical problems in Iraq and we expected this, it is impossible that it would be otherwise," Defense Minister Nikolai Svinarov told a press conference.
"Everybody knows how old this equipment is," he added.
US forces on Tuesday handed control of the central Iraqi city of Karbala, 80 kilometres (50 miles) south of Baghdad, to 250 Bulgarian troops who form part of an international force under Polish command.
Bulgaria chief of staff Nikola Kolev said the problem was that the vehicles did not run on diesel, but had gasoline-powered engines that stalled easily in Iraq's searing temperatures.
"We will find spare parts to ensure that the equipment at our disposal works as well as it can," he said. The army had called in the help of experts at Sofia's technical university "to tell us what we could do."
Kolev said the Bulgarian military was also looking to replace the tracks on their caterpillar vehicles because they were not built for street patrol and could damage the roads in Karbala.
Bulgaria has deployed 470 troops in Iraq since mid-August to help rebuild the country.