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By: Toby Peterson
As our DeLoreans get older, we are starting to see some different forms of wear and tear on them. One area that is becoming a concern is the security of the door strut lower mount ball stud. At DMC Northwest, we have seen several cars that had visible damage in this area, and we have completed a repair for this condition on one car.
The door strut lower mount ball stud (lower mount) is fastened to the fiberglass underbody with a steel plate that is embedded in the underbody. The lower mount is screwed into an outer plate with a weld nut which is then bolted to this inner plate. The door struts exert about 270 pounds of force on the lower mounts at all times. Because of the extremely high stresses put on the lower mount by the door strut, the fiberglass can fail, allowing the plate to become detached from the underbody. When the lower mount fails, the door strut is usually damaged, and the door will not be held open until repairs are done to restore the strength of the structure.
When the failed lower mount is removed at the start of the repair, the resulting hole in the fiberglass underbody must be repaired. You can see the broken fragment of fiberglass in Figure 2. Figure 3 shows the hole left in the underbody. Note the foam inside.
The repair for this damage involves removing the rear stainless steel quarter panel, roof "tee" panel, upper rear infill panel, weatherstripping, and the inner door seal. The door must be propped open with a tool during the repair. Figure 4 shows a fiberglass pad that is built up to provide a flat base for the final steel plate repair. The steel repair plate that will provide support for the lower mount is shown in Figure 5. The plate is made from .100 inch thick stainless steel, and is shaped to nest as shown in the photo. The final step in the repair is to bolt the plate into place using steel rivnuts in the fiberglass, and countersunk bolts through the plate.
After the repair plate is attached to the fiberglass pad with adhesive and countersunk bolts, the rest of the parts are put back in place. The resulting repair is stronger than the original, and will last indefinitely. If done correctly, the entire repair is invisible with all the other pieces in place.
Many people think that this type of damage was caused by the use of door struts that were made with an incorrect length. These incorrect door struts were made around 2002, and were widely sold by several vendors. While this may be true in some cases, the car that is shown being repaired has had the same door struts since 1997. In this case, the damage occurred due to thousands of cycles of door opening and closing and participation in many parades with the doors open while driving. This practice causes a great deal of extra stress on the door struts.
This repair is complex and costly, so it would be a great idea to keep an eye on the lower mounts to see if this damage is starting to happen. You should avoid driving your DeLorean with the doors open over rough roads or at speeds greater than walking speed. If you have any questions regarding the topic of this article, please contact Toby Peterson at DMC Northwest for further information.
