March 13, 2026,

Sent VIA Email

Subject: Update to February 25, 2026 Letter Regarding Ballard Fuel Cell External Coolant Leak
Dear Valued Customer,
On February 25, 2026, details were shared concerning an investigation conducted involving coolant leaks
identified on hydrogen fuel cell buses at our Anniston, Alabama production facility.
As was previously shared, during a routine inspection, a New Flyer team member observed liquid beneath a
Ballard hydrogen fuel cell installed on a bus. Ballard subsequently confirmed that the liquid was coolant.
Following this observation, additional inspections at the Anniston facility identified similar instances on a limited
number of buses, typically involving small droplets sometimes collecting below the fuel cell. In these cases,
approximately 250–300 ml of coolant was observed to have escaped from the manifold inlet port, an area subject
to higher inlet-side pressures.
Out of an abundance of caution, New Flyer immediately placed a temporary stop-shipment on all hydrogen fuel
cell–powered buses and initiated a joint investigation with Ballard, our fuel cell supplier. Ballard personnel
continue to be on site in Anniston to support the root cause and corrective action activities.
Working with Ballard, we originally thought and conveyed that a supplier change made in early 2025 to the
manifold-channel gasket was responsible for the leaking conditions. This was based on an observation that the
2026 channel gaskets exhibited better “fitment” properties than the previous 2025 version. Through subsequent
testing and analysis, we have learned that there are 3 primary root causes that can influence how fully the
manifold and gasket seat when bolted together. This reduced seating can create localized areas where sealing
performance is diminished, potentially contributing to the leak condition observed.
The 3 contributing factors include:
•

Returned parts to Ballard exhibited tooling flash on the manifold. This tooling flash is located within the
manifold channel where the gasket seats.

•

Excess volume of webbing on the gasket creates a hydraulic locking condition where the manifold does
not have space for expansion in the corners of the gasket creating a “squeeze out” condition of the
EPDM.

•

The gasket squared profile presents a configuration in which, under certain conditions, the EPDM gasket
volume may approach the limits of the available channel space depending upon assembly conditions.

Red circles indicate areas
of tooling flash on the
manifold

Current manifold gasket
seal profile and hydraulic
locking condition

Through a combination of removing the tooling flash from the manifold and reworking the EPDM gaskets to
remove excess material in the corners of the gasket, we have been successful in eliminating the leak. This has
been verified on over 30 buses.
As a permanent corrective action, Ballard has utilized existing certified tooling to
produce parts with refined profiles that improve channel fit. The updated design
incorporates webbing that supports controlled gasket expansion in the manifold
corners. These parts were produced in silicone based on the tooling already
available for this material. Ballard is also ensuring the manifolds do not have the
tooling flash.

We are confident that eliminating tooling flash, combined with either reworked EPDM gaskets or silicone
gaskets, provides an effective corrective action to prevent leaks and allows buses to be released for shipment.
Both corrective actions involve torquing the manifold bolts to 8Nm, which is the specification. We originally
thought there was merit to increasing the torque from 8Nm to 11Nm but by addressing the root causes, we find
the increased torque is no longer needed.
We are validating the effectiveness of both methods described above by completing a 25-mile road test and
inspecting for leaks using a borescope and then completing a 2nd borescope inspection after 12 hours post road
test.

Customers may have questions on how these findings impact the buses that shipped prior to this discovery. We
reiterate that this condition does not present a safety risk. The coolant seepage occurs externally to the fuel cell,
below electrical connections, and within a protected area of the fuel cell compartment. While the coolant leak
was noticed from visual inspection, the onboard monitoring systems recognize low coolant in the system if a
coolant leak is visually undetected.

Because Ballard cannot state with certainty the long-term durability of this coolant connection joint, Ballard has
elected to proactively upgrade the affected coolant connection on all approximately 170 buses already delivered.
To date, field experience shows a very low observed failure rate (2 of approximately 170 buses), and the
condition is not safety-related as noted above. Available data indicates that any failures occurring after initial
installation would be expected to present much later in the service life. Based on this information, Ballard will
implement a proactive upgrade campaign that is appropriate and precautionary, but not urgent.
This campaign will be carefully planned and scheduled to minimize disruption to customer operations. Ballard is
actively developing logistics and additional service instructions for execution and currently estimates that the
campaign will be completed within approximately one year. Ballard, or New Flyer on Ballard’s behalf, will contact
affected customers with additional details and scheduling information as plans are finalized.
While campaign logistics are being finalized, customers should continue to follow their standard preventive
maintenance practices, including routine inspections for coolant leaks. The below pictures (shaded area
specifically) identify the area where these coolant leaks have been found.

Both New Flyer’s standard 6,000-mile inspection interval and Ballard’s three-month inspection interval include
coolant leak inspection as a normal maintenance item. If a coolant leak is identified during regular inspections,
customers are encouraged to contact their New Flyer representative or Ballard directly so that a repair can be
coordinated in advance of the broader upgrade campaign. If no coolant leak is identified, no further action is
required and bus can be returned to revenue service.
We appreciate the patience demonstrated by customers to allow us the time to confidently identify the root cause and
corrective action measures required. If you have questions or would like additional details specific to your fleet or
delivery schedule, please do not hesitate to contact me or your Customer Program Manager (CPM).
Sincerely,

Sarbjot Sidhu
Margaret Lewis
Senior Vice President, Quality and CI
North American Bus and Coach

Sarbjot Sidhu
SVP and CXO
Ballard Power Systems