About I-CAR - Current Events/News: e-newsletters: Advantage Online: February 26, 2009

Figure 1 - Notice how the upper rails angle toward each other, locking in the upper tie bar.

Figure 2 - This photo shows some welds removed from the upper rail and tie bar assembly.

Figure 3 - Two slot-shape silicon-bronze weld joints are located on top of each end of the upper rails.

Figure 4 - The cut location for the upper rail is located 50 mm rearward from the end of the rail.

Figure 5 - First, the top portion of the rail is bent upward. The rail is then bent outward.

Figure 6 - The upper rail is bent back to the original shape, overlapping the end of the tie bar.

CHEVROLET HHR UPPER TIE BAR
REPLACEMENT PROCEDURE

The procedure for replacing the upper tie bar on the Chevrolet HHR has been updated. The most significant aspect of this change is the instructions for cutting and repositioning a front upper rail to allow the replacement upper tie bar to fit between the upper rails when installing. Before this update, further disassembly had to be done to allow enough room for the installation of the new part. The updated procedure also identifies four silicon-bronze welds located on the upper rails that require replacement. At this time, the updated information is only on the GM pay site: www.acdelcotds.com and not the free site:
www.goodwrench.com/gmgoodwrenchjsp/gmspo

The upper tie bar replacement procedure required updating because both front upper rails pitch inward, toward the center of the vehicle, and sleeve over the upper tie bar ends. The ends of the upper tie bar pitch outward, conforming to the angle of the rails (see Figure 1). This design of the front structure results in the space between the front upper rails being shorter than the length of the upper tie bar. A replacement upper tie bar will not fit between the two rails during installation without further disassembly.

Another vehicle that has a similar front structure design, and also requires a unique procedure for replacing the front upper tie bar, is the 2005 and newer Chevrolet Cobalt. For this vehicle, two partial upper rail sections are included in a replacement upper tie bar kit. The entire procedure is covered in the March 17, 2008 Advantage Online article, Chevrolet Cobalt Upper Tie Bar Kit Available.

The updated procedure for the HHR tie bar recommends cutting and repositioning the end of an upper rail to allow a replacement upper tie bar to fit between the two rails. The following is a brief overview to highlight certain aspects of the updated procedure. It does not include every step, such as measuring vehicle dimensions, preparing the replacement part, or applying corrosion protection.

To begin, all of the welds connecting the damaged upper tie bar assembly to the vehicle are removed (see Figure 2). This includes removing two slot-shaped silicon-bronze welds located on the topside of each upper rail (see Figure 3).

Since the damaged upper tie bar is going to be replaced, it can be cut to allow for removal. Before the replacement upper tie bar can be installed, one of the upper rails has to be cut and repositioned to allow for installation of the new part. This is done by scribing a cut line, on the top side of the upper rail, 50 mm rearward from the front end of the rail (see Figure 4). After making the cut, the top portion of the rail is bent upward and outward (see Figure 5). The replacement tie bar is then fit between the two rails.

After the replacement upper tie bar has been properly positioned on the vehicle, it is clamped into place, and the bent portion of the upper rail is returned to the original shape (see Figure 6). The cut on the upper rail to the tie bar is welded using a GMA (MIG) butt joint. Prior to welding, the E-coat is removed and weld-through primer is applied to the top of the replacement upper tie bar. This is done before installation to ensure proper corrosion protection.

The four silicon-bronze slot welds that were removed from the top of the upper rails can be replaced with MIG brazing. According to the General Motors Steel Reparability Matrix, MIG brazing is allowed on mild steel, using 8 mm X 16 mm slotted holes. The upper tie bar and the upper rails are made from mild steel and the slotted holes were previously made on the parts when grinding out the original welds. To access the General Motors Steel Reparability Matrix, go to the GM Collision Technical Repair Information www.goodwrench.com/gmgoodwrenchjsp/gmspo web site, click on Tech Info located in the upper left portion of the screen, and choose the Steel Reparability Matrix from the list of
pdf files.

MIG brazing is a type of welding process that uses less heat than conventional welding methods, which can reduce the heat-affect zone and help preserve corrosion protection. MIG brazing is explained in the I-CAR MIG Brazing (BRZ01) online training program. To review this program, please go to
www.i-caronlinetraining.com.

General Motors has updated the procedure for replacing an upper tie bar on the Chevrolet HHR. The updated procedure recommends cutting and repositioning one of the upper rails to reduce the amount of disassembly that would otherwise be required when installing a new part. The procedure also calls out four slotted silicon-bronze welds, which can be replaced with MIG brazing.

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advantage@i-car.com.

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