1989 C4 Functional Restoration

[SirReal63]

The car had an intermittent ABS light since day 1. It may have been a steady light but I had connected and disconnected the battery so many times the first month I can't really say. I expected to have a bad relay but as so many other things were going on with he car I had it way down on the list of things to check. I had removed the little black box behind the center console when I blew the interior out. I had no idea what it was for, I just pushed it off to the side. While inspecting the wiring in the burn zone I pulled the black box out and inspected it, the two leading to it had been taped up and were loose. While unplugging it I felt something sticking me, and after getting it out, discovered what was poking me. The ABS Lateral Accelerometer Anti Lock Brake Sensor had been burned badly.



The taped up wires were crispy fried under the tape.



I cut back to good wire, new wire added, heat shrink tubing added and taped back up.



This burning wire appears to pre-date the fire so it makes me wonder if this was the actual ignition source? Of course, there is no way to know but considering the proximity of the burned spot on the ABS Lateral Accelerometer Anti Lock Brake Sensor and where the fire appears to have started it is a possibility. The connector is good and now the wiring is good so I ordered one from Mirrock. I am going to have to peel back the factory tape on all of this wiring and inspect everything really well and correct any issues I find.

 

[SirReal63]

I finished up the sound deadening, it took almost 4 rolls of Frost King and some other foam/foil product I had left over after doing the old F350. I covered virtually every surface with sound deadener/insulation. Most of the original jute and carpet mass loading is still in excellent condition and will be used again. Tapping on the flat panels gives a nice dull thud now instead of a drum beat. This may be one of the quietest C4 convertibles when I am done. I have run 6 channels of RCA to the rear for amplifier leads and speaker wires from the rear to the front.

Time to correct another burn zone issue, the plastic carpet runner from the console that was ripped out when the car was burning. I had most of the pieces that were torn out but not all of them, first we need to join the two pieces back together. I plastic welded the seam to physically join the two pieces back, adding plastic where needed until they held together firmly.




This worked but did not address the one missing piece, I needed or wanted to recreate that missing piece. If I were going back with carpet I could probably leave this piece out and no one would ever know. I do not plan on going back over this area with carpet so I need to fabricate the missing piece to make it look right. I started by heating and flattening out the bumpy surface where it was heat damaged, this worked out fairly well, with a heat gun and blocks of wood I was able to soften and form the pieces to most of their original shape, not perfectly but close enough.

The first step was to create some semi-flexible fiberglass strips and panels. These will be used to form missing pieces and repair screw holes as well as reinforcing broken mounting tabs on the dash. It is basically one layer of chop or biaxial soaked in epoxy resin and cured on a silicone mat for easy removal.



With these pieces I could make my repairs, forming the missing piece that curves around the tranny tunnel. I bonded it in with West System 5 minute epoxy in two stages so I could shape it without having to hold it in place for 24 hours. My old body could not stay in one place that long. Once it was in place and roughly the right shape I glassed over the plastic weld to add strength and rigidity and give the repair a fighting chance of bending where it needs to without breaking. I used the smaller tabs to go over the mounting holes that were broken out and reinforce others.









Now to fill in the rest of the missing piece that was formed and epoxied earlier. It took 4 pieces of .75 oz chopstrand to equal the thickness of the rest of the plastic and that gave me exactly the right thickness. In order to match the profile of the existing pieces I laid a cut up zip lock baggies over the epoxy/glass and clamped it into place to give me the line that matched the original contour. I did not expect this to work, but it did, and much better than I expected.






I have one more layer of glass to add to cover the whole repair. As it is, it fits back onto the car and contours are correct.

I really wish I had some fast cure epoxy resin, it is really borderline too cold to be working with what I have, it takes about 12 hours to set up enough to not just run off but it is what it is and I will use what I have as it is a few years old and needs to be used up.

 

[SirReal63]

The (mostly) finished product...

The front...



The back...

 

[SirReal63]

I tidied up a lot of loose ends this week in preparation for getting the interior back in.

My ABS Lateral Acceleration sensor arrived from Mirrock in perfect condition. The more I look at this and where the burn marks are it is becoming more apparent that this is what caused the fire/smoldering mess.



I finished the tunnel side pieces and added some 1/8" medium density foam to them to smooth out the bumps and get them ready for covering.



I did clean the carpet with OxyClean and laundry detergent in my carpet shampoo machine. I had been concerned about getting the padding wet as it would take a long time to properly dry, so I removed it carefully with a plastic scraper and it worked beautifully.



All clean, dry and padding glued back in place and finally installed. I used very little soap but it took many gallons of hot water to extract it, my guess is this carpet had been cleaned with that crappy carpet cleaner in a can. My laundry detergent and Oxy is low sudsing so that is the only reason I can see for the amount of soap that came out. The install was really pretty easy when you consider the KilMat and foil/foam added thickness. There are still some rough spots, thin spots and burn spots but it is clean and otherwise in good condition for the age.



I started working on the dash mounting tabs, specifically the one on the driver side that is always broken. Mine was more than broken, it was destroyed and the area where the light switch mounts brittle and cracked.

When I made these earlier...



... it was not only to repair the console side pieces but for dash repair. I found many of the broken pieces on top of the knee bolster so I mixed up thickened 5 minute epoxy and managed to get them back in place and bonded. The epoxy also fills in the missing pieces, and there were a lot of missing pieces. I did not need to be perfect here as this is just step one.



I lightly sanded and cleaned the area where i could reach and cut 3 pieces of the fiberglass strips to the approximate shape and thickened epoxied one in the rear and two in the front with enough extra to fill in the voids as well as replace the missing material on the top where the bolt attaches. I clamped them in place from both the front and back to ensure everything got filled and remained flat and the proper shape for alignment.



This repair is super strong, semi-flexible and should last a long time. I have used this method before, on both my old Firebird and E38.

I will let this continue to cure today and begin shaping, painting and drilling it next week while looking for any other hidden areas than need repair.

 

[SirReal63]

The finished repair of the broken dash mounting tab.





I pulled the knee bolster to check the wiring under there and found it surprisingly clean for the age. A little dusty and several pieces of dash plastic debris but no droppings.



I am surprised by one thing more than any other, I have not found a single mouse dropping or chewed wire. Obviously I have found plenty of crispy wires but no evidence of mice. This car has lived from New Orleans, East Texas from Houston to Madisonville, Canyon Lake, Leander and now my place. Most of it's life it has lived rural where mice are typically an issue. This may change when I get into the engine bay more but from what I have seen in the engine bay, Bubba has been an issue, not mice. We do have a large population of mice here and typically trap a mouse a day somewhere on the property but mostly up near the animal feeding areas. I will have to be extra diligent to keep any food items out of the car.

 

[SirReal63]

It has been a busy week but not a lot to show in pics. I managed to pick up a nasty cold so that put a damper on work.

I did more dash crack repairs, this is the lower console where it attaches to the tunnel, both sides of this were cracked and no longer attached.
The passenger side was not only cracked but also melted from the burn area. This one was a little harder as I had to flatten and straighten the piece that was also cracked and pulled apart. It took longer to make the piece fit back into place enough to bind thhan the actual bonding did.









The driver side was only broken in two, I glassed around both sides of the "L" shape to give it back the proper strength.



The whole dash is now solid and I think/hope I got the major pieces done for the dash structure, there are cracked and missing pieces of the trim that I probably won't do anything about at this time.

 

[SirReal63]

I also worked on the carpet some more. The rear was actually good for color but the front was sun-faded badly. I ordered 3 cans of the "correct" SEM Cognac dye/paint from Mid America and tried to bring it back to the original color. Since this is really a paint the color of the substrate effects the color of the dried paint, the front carpet pieces were several different shades and the first can was a waste as the different shades all came out a different color and not the color of the rear carpet.

I decided to paint all of the front carpet white with the Duplicolor product so all of the substrate would come out close to the same color. It took 3 cans of white to get them all about the same color. Now when I applied the SEM Cognac it all came out close enough though still not exact. Fortunately most of the carpet up front is covered with seats and shaded enough that it isn't very obvious that they are a slightly different shade. I am saddened that I wasted the first can of SEM, that third can would have really helped even it out but I am calling it a win either way.

The faded carpet I began with...



Finished product installed...

















I am not disappointed in the SEM product, it is a little pricey but getting a close color match was worth the added expense.

 

[SirReal63]

It has been a busy past few weeks, not a lot to show in pics but I have also been doing things other than working on the car. I need to get the interior done before lifting the car and working on the mechanical things.

Let's start with the center console lid. This was really showing it's age and use. There were a few cracks, the rubber under the cover was deteriorating in places and the cover was loose. First I had to glue the cover back after cleaning up the foam and then repair the cracked pieces.











I recovered this in leather that was saved from a 20+ year old sofa/loveseat that served our family well. The leather from this was still in excellent condition but the frame of the sofa started to fall apart, I cut up the sofa but we decided to save the leather for various crafts. Prior to recovering I added a 1/4" piece of high density closed cell foam to help with cushioning.

Beginning the long process of making it fit, I do not do upholstery work but I do know leather has a stretchy direction and a not so stretchy direction.







All finished and put back together. This was way more work than I had intended but I also got to learn a little so it was a week well spent and I could do it inside.





The console lid light had been improperly repaired at some point and no longer worked, this is why.





I used this same leather to replace the carpet on the console that was burned and horribly faded.

Attached to the plastic side pieces and left long so I could fit it correctly. I could have used the carpet as a template but I was concerned it had shrunk so I left it long. I will need to add some foam between the tunnel and the leather to smooth it out.











Trimmed and test fit with the seat covers on. I am waiting on the foam for the tunnel to come in and then we can finish this part up.





The armrest covers will covered in this same leather to tie it all in, but that will have to wait until I re-do the doors as they are in bad Bubba shape.

 

[SirReal63]

It has been a busy few weeks, not a lot of work on the car but still progress.

I had a plan for the stereo head unit replacement, a cheap Android unit on top and a half din EQ on the bottom. I gathered up my supplies and dug in. The primary reason for the change from the old JVC CD player was I wanted a backup camera. With the top down it is easy to see where you backing to but with the top up it is difficult. Though I always head check while backing I have grown fond of having the camera as a silent assistant. In addition I also wanted a GPS, the ability to play files from USB, phone connectivity and more tone controls than just Bass and Treble. It is difficult to pack all of that into a 1.5 din slot but I gave it a shot.

The head unit, https://www.amazon.com/dp/B0CP3D46NH?ref=ppx_yo2ov_dt_b_product_details&th=1 just a basic Android single din unit with an almost 1.5 din screen. I had hoped to have the EQ under it but that meant the screen would have to go over the dash trim and there would be no way to adequately secure it, and it meant if you wanted to take the dash trim off you would have to take the head unit out first. That wasn't very clean and it wasn't going to work. Not a problem, I can work around it. I had many issues while doing this install, the factory radio wiring was showing it's age and a couple of the leads broke out of the connector, I had to de-pin, clean out and solder those wires back to the connector and get them pushed back in.

The only issue with the head unit is the Blue ANT lead is electrically dead, I swapped out units with Amazon and the replacement was the same. The mfg/seller was not really helpful at all, as in they have no real knowledge of the units they sell. I did get a $30 refund for my trouble of diagnosing their head unit for them, so there is that. I mounted a small switch next to the cigarette lighter port to control the antennae and the amp. It is small and unobtrusive and gives the ability to not have the amp and antennae on except when I want them on.



I ran the GPS antennae through the dash and it will come up where the defrost vent is and be secured with Velcro. The microphone went through the dash, up the A pillar and is clipped to the visor. The visor will get replaced at some point in the future, low priority currently.



The EQ, https://www.amazon.com/dp/B09B45X7C3?psc=1&ref=ppx_yo2ov_dt_b_product_details not a bad little unit, the fitment issues with the head unit turned out to be a blessing, the led lights on this EQ are exceedingly bright and blue of course. I have a strong dislike for blue LED as it does more to blind you than is needed, red is a better choice to preserve night vision but these are a fixed blue. The solution was to add it next to the amp which made everything cleaner.



I had a lot of fun with the back up camera, mostly the wire routing. I knew how I wanted the wiring to go but it didn't want to go that way. I am glad I chose the path I did as it exposed other issues I did not know about. I ran the wire along with the rear electrical/bulb wiring and found the connector a disaster, corroded badly with broken wires. It took a lot of deciphering and help from others to get all of this corrected but in doing so I now have a much better connector and found the spare tire light where it had been pushed up into the frame and now it works as it is supposed to.



I have been swapping out to LED lighting whenever I open up a new area of the car.



I cannot test the back up camera as I have no back up lights, if you remember. I got the car as high as I safely can with 4-6 ton jack stands and went about working on the back up light switch. I took a cheap harbor Freight offset 7/8" boxed end wrench and ground it until I could get it on the reverse switch and remove it. I got it out and sure enough it was bad so I ordered a replacement from Zip and decided to drain and fill the transmission. I ordered some Castrol 10W60 and then figured since I was right there I would see if I could figure out why the speedo didn't work.

I removed the VSS and gave it a spin with a variable speed drill and it showed varying AC voltage. It works or at least sends a signal, so I went to inspecting the plastic gears and both are in perfect condition. While checking the small gear on the tranny shaft I noticed it would spin freely and move laterally, this of course wasn't right. No retaining clip on the shaft so that explains why the speedo doesn't work. I think/home I have found a replacement from transmissioncenter.net at least I hope it is right or can be modified to work. It has a different part number than ZF shows but I believe they are the same part. https://transmissioncenter.net/shop/th350-700r4-516″-speedometer-drive-gear-clip-6261781/ I hope someone lets me know if it is wrong and has a source for the right part because I could not find an original ZF part. (Edit, this is the wrong part for a Black Tag ZF, this was the correct one. https://www.classictransmissionsolutions.com/th400-speedo-drive-gear-clip/ )

This coming week I get to remove the C Beam, the driveshaft and tailhousing to try and get the gear attached back to the tranny. I am going to go ahead and replace the driveshaft u-joints while I am there.

 

[SirReal63]

I did not have a speedo or reverse lights. It took a little while to get the cross brace off, the exhaust off and to diagnose the issue. It turns out the issue with the speedo was the drive gear clip had broken and while doing so mangled up the drive gear. The driven gear on the VSS was perfect and the VSS functions with an AC signal being generated. I do not know if it is the correct pulses per minute but I have a spare VSS if the original still has issues. I removed the driveshaft, C-Beam and tail housing to remove the drive gear. Thanks to @IHBD for the guidance on replacement parts and Classic Transmission Solutions I was able to source the correct gear, tail housing bushing and seal. It was an education, and a good wrenching experience.

Old gear, just enough damage to warrant replacing.



New bushing, seal and drive gear.



While waiting on parts I replaced the reverse light switch. This was a pain to get to, not enough room to get any of the wrenches or sockets in that I have. I ended up taking a 7/8 offset wrench from a cheap Tractor Supply set I had and ground it to fit into the small space and removed the clutch slave for more access. The wrench set was one of those $5.99 deals in the bins by the front door, I had zero guilt in grinding on wrench as it is the poorest quality you can imagine. I had to grind not only the head to a smaller diameter but also the handle to get enough purchase on the hex part of the switch to turn it. Now it functions perfectly to remove that dang switch.



Switch replaced, for now.



The irritating part of this reverse light is it still does not operate when you put it into reverse. The old switch tested bad and the new one tested good. The factory wiring is good as I can jump across the terminals and the backup lights come on but they do not connected to the switch. I suspect something in the tranny is amiss but I will deal with that at a later date, getting the speedo to function was the main goal.

The wheel well to hood seal was worn and torn on the driver side only. I know these are inexpensive but I had time to kill while waiting on tranny parts so I took the 3M weathersrip adhesive and glued the tears back together. I really didn't expect this to work but to my surprise it did. I will replace these at a later date as they are not a priority and now they won't be flapping in breeze until they get replaced. For the time being the repair is as strong as the rubber, which was still very pliable.



The crossbrace had 34years of damage from speed bumps and other obstacles. Since I had it out I straightened it and gave it a nice flat black paintjob. A variety of adjustable wrenches from large to small made easy work of this once it was clean, it was really dirty too.













Time to button up the removed pieces, fill the tranny and see if the speedo works. I won't pull the tranny out and apart just for reverse lights, it is easy enough to wire them to a switch if I cannot find the issue elsewhere. As this is a functional restoration and I have pratically zero experience in tearing a manual tranny apart if it has something wrong internally that prevents the reverse switch from operating it does not make sense to pull it apart for just that as the transmission otherwise operates correctly. Parts availability being what it is for the ZF-S6-40 I won't make a bad situation worse.