Unrelated engine trouble caused two 38-Geary buses to catch fire within a week of one another earlier this month, according to Muni, which added that it has taken steps to ensure the same thing does not happen to its other 60-foot articulated buses.
Both fires broke out in the rear engine compartments of the buses, which are prevalent on the heavily used 38-Geary line. No passengers or operators were injured in either incident. Articulated buses contain a pivoting joint in the middle to assist with turning.
The first bus caught fire Aug. 2 near the 48th Avenue terminus on Geary Boulevard in the Richmond district when the biodiesel-powered vehicle's exhaust treatment device — used to meet state-mandated emissions controls — overheated when the fuel injectors failed, according to a preliminary Muni investigation.
Firefighters arrived within minutes and doused the flames, but the bus was left with more than $500,000 in damage, according to a Fire Department estimate.
An electrical problem caused the second fire Aug. 8, when a short-circuit — which began with a faulty power-feed terminal — caused an oil supply line to fail on a bus that was traveling on Geary Boulevard near 28th Avenue, according to Muni's initial review. The Fire Department has not finished that investigation.
Both buses were 13 years old, according to Muni spokesman Paul Rose, who said the transit agency has revamped maintenance rules on its bus fleet by increasing how often the engines are serviced, stopping the use of in-house cleaned air filters on the exhaust treatment devices and increasing the frequency of safety checks.
There are about 200 of the 60-foot buses in Muni's fleet of roughly 800 buses, Rose said.