Mandatory Service Bulletin: Inspection and/or replacement of expansion tank assy. for ROTAX® 912, 914, 912 i, 915 i and 916 i (Series) Aircraft Engines

This is a reiteration of what was previously stated, as there still seems to be some confusion regarding the welds and the part number (P/N) visible on the side of the expansion tank. (We will address Jason Fish's post at the bottom of the statement below.)

Expansion tanks with a sticker labeled P/N 622051 OR 622050, located on the side of the tank, may correspond to Rotax P/N 922 666 or 922 668, which are affected by this Service Bulletin (SB). Please note that the sticker number alone cannot be relied upon to accurately identify the correct part number for the affected coolant expansion tanks. If your engine serial number (S/N) is listed in the SB document (certified or non-certified), you must inspect the expansion tank and replace it if necessary. (See attached photos for reference.)

Identifying Weld Quality:

We understand that many individuals may find it challenging to distinguish between a good and proper weld versus a bad one.

Good Weld: Consistent and uniform around the entire connection port.

Bad Weld: Inconsistent or missing sections around the connection port.

At this time, we do not have additional photos to illustrate what a bad weld looks like beyond those included in the SB. However, we have edited the photo provided in the SB to better highlight the characteristics of a bad weld. (See attached photos.)

 Clarification About Tack Welds:

Some have raised concerns regarding the weld blob at the top of the port. Please note that this is a tack weld and is considered normal. The primary concern should be any missing welds around the edges of the port hole. In the attached photo, the dark spots around the circumference of the port indicate missing welds, which are considered unacceptable.

Jason Fish,

To address your concerns:

We agree that photo #5 looks odd, but it does appear to be welded all the way around (as do all the other photos). The choice is ultimately yours, but if this were our coolant expansion tank, we wouldn’t worry about this one (solely based on the photos you provided)

That said, when in doubt, swap it out!

I've attached a number of photos of the inside of my expansion tank.  My engine was brand new in the factory crate when I received it in 2023.  Serial number is 9144585.  Expansion tank has label with part # 622050.  There are some areas that look more like dark caulking instead of weld beads.  Comments?  Thanks!

Hi Michael

You need to inspect the ports from the side rather than straight on to determine if any welds are missing. It is not possible to provide an opinion based solely on the photos you posted.

That said, if you have any concerns, our advice is to replace it under warranty.

I will try to get some better pictures from the sides of the ports.

I sent a picture to Lockwood and they requested i send them the tank that i had removed for inspection. They found several inadequate welds in that tank which was from a 2023 912ULS and filed a warranty claim for me. Awaiting results.

Alan