STEAM railway volunteers are confident their locomotive could be back on track by the end of the week, after locating the cause of a dangerous steam leak.

Southern Downs Steam Railway fitter John Brady worked hard with volunteers last week to locate the source of the problem, which caused the cancellation of a trip to Wallangarra two weeks ago.

"We located the source of the leak in the bottom of the regulator valve," he said.

"We were able to locate a compatible piece in Ipswich."

It is believed a fault in the casting caused the leak, which had an effect on the ability of train drivers to control the locomotive.

"They're currently working on it at a local workshop," Mr Brady said.

"When it's ready to put in it will be fitted."

The operation to get the repair completed is a one man job, with only one person able to fit in the hole to work on fitting the replacement part.

"If it all works out we're hoping to steam up by the end of the week," Mr Brady said.

However, despite the train's return to the track being imminent, volunteers still have concerns at the lack of back-up in the instance of potential future break downs.

Steam railway treasurer Adam Cole said the group were exploring all avenues to help them find a back-up locomotive.

"We have no guaranteed back-up," he said.

"There's no guarantee there won't be another breakdown."

The group have been meeting with patron Lawrence Springborg to discuss the possibility of locating a back-up diesel locomotive.

Southern Downs Steam Railway are aiming to start their tours with a trip to Clifton later in the month.