Appendix “E” & "K" Replacing seat upholstery

I am not a professional automotive upholstery installation technician so use my procedure and guidance in the document at your own risk. This is a job for an advanced DIY worker who is not inclined to rush and enjoys doing a little research on the installation. It also requires good hand and arm strength. If you have never done this before plan to spend an entire day from start to finish.

These instructions are for installing new coverings for the hard-back sports seats. The soft-back seat is done in a more conventional manner of slipping the seat back covering over the frame. The seat bottom is done similarly to the hard-back seat as described in this document below. I do not have experience with the soft back seat but the procedure is well covered in videos for other cars on YouTube. 

Also, read this document from beginning to end before proceeding with the procedures contained herein. Contact the publisher here or your seat cover manufacturer with any questions you may have before proceeding: Contact Page.

Seat Cover Ordering & Prep:

• Read through this entire document before using it;
• Order two seat cover sets even though your passenger seat may look good. After you recover the driver seat you will know why;
• If your seat bolster foam seems misshapen new foam can be
  
  ordered from the dealer or the original foam can be reworked by adding some additional foam purchased from a sewing supply store;

• When you order the seat covers request that the maker install the hem wires and rods into the seat covers for you; 
• The hem wire is a thin steel wire reinforcement sewn into the hem edges of the leather cover as reinforcement. It is captured along with the leather hem by frame hooks to hold the leather in place and under tension along the bottom edges of the seat;  
• The seat rods are thicker steel rods sewn into the center section facia of the seat and are used to pull it down and tension the bolsters and center section of the seat bottom to the seat frame;.

•  Also, ask them to provide the hog rings as finding these fasteners at a local store can be difficult;
• YouTube.com  is a great place to start learning the basic steps of mounting automotive seat upholstery;
• Some have used tie-wraps to tie down the seat bottom rods, however, my experience is that tie-wraps become brittle with age and fail;
• A special hog ring plier is unnecessary a regular slip joint pliers work better;

  

  Hog Rings and Pliers

  
  
• At times partially closing a hog ring before placing it makes it a lot easier to position;
• Purchase or borrow a leather belt punch plier as in the picture later in this document to cut clean tie-down holes in the leather as you go;
• Before removing the seat from the car raise the seat height adjustments to their highest position to make access to the seat mounting cap screws and the seat frame’s upholstery mounting hooks easier;
• As you remove the original seat covers observe how they are attached as a reference;
• The entire process involves tying down seams securely using rods and stretching under tension the components of the seat cover. If your covers when installed did not involve tensioning, the cover appears to have a less than form-fitting appearance, or the seams do not lay properly something was not done properly with the installation or less often the cover is not dimensionally correct. Contact the maker of your cover for guidance on this issue before doing any non-reversible part of the installation such as cutting holes for the seat controls.
• I used no adhesives.

Hard-back seat: Mounting Seat Back Outer Horseshoe cover:

• Punch a series of holes in a similar distribution to the original cover along the inner rim bead of the new seatback horseshoe cover;
• With the foam removed, attach the horseshoe’s inner rim bead to the hard back's mounting hoop using hog rings;
• Insert the seatback horseshoe foam;
• Starting at the center top pull the seat leather over the foam, fold the edge bead back into a cuff,  and force-fit it into the mounting lip on the hard seat back;
• If needed use a one-inch non-marring plastic chisel-shaped scraper from Harbor Freight., not a plastic paint spatula to assist in forcing the bead fully into the mounting lip.
• Use care not to cut the leather while forcing it in.
• This is the hardest part of the entire installation  job;
• Tuck the horseshoe's leather bottom shirttails into the bottom of the seatback;

Covering Seat Back Center Cushion:

• Recover the seat back center cushion.
• I used a large curved needle and black waxed thread to sew the cover back flaps to the foam..
• This is not a precision process as one or two thread loops for each leather holdback tab is probably enough. Using a curved needle purchased at a sewing store makes this a lot easier
• A few years later I went back and completely covered the rear-facing side of the center cushion foam with Velcro-compatible upholstery fabric. Not sure it matters much as the back of the cushions is not visible

Seat Bottom:

I found a neat trick to make mounting the seat bottom cushion easier and more reliable. Using hog rings to tie down the bottom cushion rods seemed to me to be very difficult because positioning the rods and closing the ring at the same time seemed to be an impossible procedure. For this reason, I made up some twist-ties out of coat hanger wire that allows one to pull the rods tight from the underside of the seat with pliers and then twist them closed over the seat springs tying down the rods, see the picture below. In retrospect making the twist-ties out of thinner machine wire would have made them easier to use and would have resulted in a neater installation.

Once the seat was completed I taped over the twist ties under the seat bottom to cover their sharp points; see the picture above;

• Insert position and tie down the three seat bottom cushion rods using the homemade wire twist ties discussed above. I used 4 tie-down points on each side rod and three across the one center rod. When complete clip down and tape over the twisted tie ends under the seat as they can be sharp.
• During the process, you will poke the twist tie through the fabric hem enclosing the wire rod, thread it around the rod, and push it down through the seat bottom;
• You may need to pull the twist tie out and reposition it on occasion so it will line up with and can be twisted over a seat spring on the underside of the seat;
• Use care not to slide the left and right side rods between the seat center and the side bolsters so far forward that they will protrude beyond the front of the seat foam;
• Make one of the tie-down points very near the back end of the left and right rods so they hold the leather seam well into its gutter between the center section and the bolster all the way to near the rear of the seat;
• If you make your own rods, be sure to roll over the ends into a loop so they do not perforate the seat cover over time.

• Pull the leather over the front of the seat, punch holes in the seat cover hem and hook over the frame hooks;
• I found in some positions bending the hooks out a little made it easier to align the mounting holes in the leather’s hem. Once hooked I bent the tips of the hooks back under the seat slightly. If you do this minimize the bending so you do not inadvertently snap one of the hooks off  of the seat frame;
• In this and future steps where the bottom hem is tied down by a hook make sure the reinforcing wire threaded through the hem is captured by the hook along with the leather covering over it.

• Adjust the position of the seat bottom pulling it tight from the back;
• Pull the rear left and right side leather tails back and fold over their top edges slipping them into the metal cuff near the back of each side of the seat bottom frame;
• Tie the rear left and right side leather tails back by twisting the seat bottom hem wire ends together behind the seat;
• If needed to hold the tails flat punch an additional hole in the top corner of the L/R tie-back tails and tie them together with a length of thin wire.
• Hog ring the seat bottom back cover flap, over the tie back tails, to the seat frame using an inserted hem rod;
• Pull the left and right sides of the seat bottom cushion over the bolsters into the final position and hook them over the frame hooks using the leather punch to make mounting holes in the hem;
• Pull and tug the leather as you go to get it to lay flat;
• After you are completely satisfied with the leather positioning, leather tension, and all the leather is completely tied down in its final position cut the holes for the electric switches and the seatback release lever and install the switch and the lever. Cut minimally as you go as you can trim the hole as you fit the switch. Less is more here.

Adding Heated Seats:

Adding heated seats is very easy since the heating grid can be cut to fit, peeling the adhesive backing off the grid and sticking it flat under the leather covers.

It can be powered by the OE seat plug connection pins, Pin-1 for ground, and Pin-2 for hot, under the seat. The plug attached to the seat is designed to be pried open and the pins within are designed to be soldered to. I mounted the round rocker high-off-low heat setting switch through the skirt cover on the front of the seat; see the picture at the top of this document. The entire addition is, in this way, a self-contained part of the seat with no extra external wiring attached. For more details on adding heat to hard-back sports seats in your 993 see:
Appendix "J" adding heat to hardback 993.html

Carpet repairs:

If, with the seats out, you plan to replace any of the glued-down carpet sections a little-known trick is to use a hand clothes steamer to easily release the adhesive. A lot easier than using solvents or brute force. Let the moisture dry

Hand Steamer

 out before reapplying any new carpet sections.

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