Hey all,

It has come time to get the old firewall rubber/foam pad out of there and replaced with something that doesn't have 29 years of funk in it. Also need to clean up some of the HVAC ducting and track down a minor water leak that seems to come and go around the heater core. Not coolant, regular rain/hose water.

1. Has anyone pulled out a dash before that could lend some advice other than take my time and track my parts lol? I have all the trim and upper dash pad pulled and gauge cluster out already. Carpet and center console are also out down to the fiberglass tub. Is the dash and HVAC installed as one unit that comes out together or can I separate it as it goes? I already removed the breadbox...

2. Any detailed spots to look at for this water leak? Already checked the seal around the main HVAC cluster in the engine bay. Had to seal up a section at the top and that minimized it, but i'm still getting a little drip with the hose running in the passenger windshield drain.

As always, appreciate you all and thank you for your time!

 

I pulled the dash out of my 87 a few years ago for the same reasons. The HVAC module is separate from the dash assembly. The wiring harness is the biggest pain because the dash harness runs all the way into both doors. I ended up leaving the entire harness in the car rather than disassemble both doors. (I did remove the harness from the passenger door so I could lay the dash harness off to one side) It is a big job, but doable. The plastic dash "skeleton" is very fragile and prone to cracking out around the mounting points. I've attached a few pics I took during the process. Have fun!

 

This is fantastic man, thank you so much for the pics and info! Seeing the bare dash gives me more context where things are located. Did you absolutely have to remove the steering column?

I agree about it being brittle. The two upper main bolts have cracked plastic around them. Thinking some painted metal washers superglued will shore them up for remount

 

all ears on this thread - this is one of my winter projects.

as for the fractured plastic dash "skeleton," not only the upper main attachment points, but check the center-bottom, where the frame attaches to the transmission hump. mine were cracked on both sides. believe it or not, I had good luck using a thin aluminum, sheet metal patch, and 3M double sided body mounting tape for the repairs. at the upper LH corner, the plastic around the mounting nut was cracked and fractured into several pieces. I was fortunate to retrieve all the pieces, and super-glued everything first, and then added the patch with the double sided tape. it's been at least 15 years now, and the dash still seems to be fairly solid.

whether it's the dash or door panels, or wherever, the plastic used on these cars has become somewhat brittle over the years. to date, I probably have 15-20 such patches on my 85. another repair method that seems to work is a thin sheet metal patch, JB weld, and pop-rivets.

FOOD FOR THOUGHT - here's my original sketch for the patch at the upper-left mounting point. as I recall, the .625 hole for the headlight switch was off about .125" for what ever reason. I had to re-work the hole slightly for installation. somehow I got the .625 diameter hole, locating dimension off, or I didn't allow for something, or ???. it's been several years now, but I remember I got something wrong. so, if anyone is going to fabricate this based on this design, as I said, "food for thought" - double check the dimensions for your application. anyway, you get the idea.

 

I pulled the steering column fairly early in the process because it looked like it may be an issue. It wasn't hard to remove or install, best I can remember!

 

I also used some aluminum sheet to make patches for the mounts. I used a combination of existing fasteners and rivets to install the reinforcements. (I'm an aircraft technician and have the riveting tools and such)

 

I've used this to fix some bezels etc before: http://www.plastex.net/Product_Info.php

Takes a little getting used to how it works but once you figure that out it works well.

Just FYI

 

hi Joe, I noted that you have used a 3M double-sided tape to bond patches/reinforcements over shattered plastic repair subsequent to call me in the plastic parts back together if a person is able to locate them all.

 

VT3 - this is pretty much what I used --



I used super glue just to hold the parts together and did not depend on the glue for any strength in the repair.

 

thnx Joe.

that looks like it is foam? maybe that would be good "gasket" between the windshield frame and the side-windshield weatherstripping retainer as a seal.

 

Rod, I finally got outside and tackled this today. I found the leaks, turns out the blower housing on the engine bay side was leaking at the top where it tucks over the rubber edging on the drip tray. The one on the driver side was coming through the chassis harness firewall passthrough. Easy fixes.
The questions I have now are: the aluminum mounting rib that runs across will not come out. It is being blocked by the lower dashboard mounting bolt on either side. Any tricks to wiggle this out of there? Also, it looks like the heater core plastic housing will need to be unbolted from the engine bay side, is this what you experienced? Found a nice mouse nest in there so I want to pull all the rest of the HVAC and clean it up.

 

If I remember correctly, there is a piece that unbolts from that mounting bar that makes it easier to get out of the car. I struggled with getting it out until I discovered it. As I recall, it's not obvious, but I think it's the lower center piece that unbolts......

As far as the heater box, I do seem to recall some bolts that had to come out on the engine side of the firewall. I removed the evaporator core housing from the front of the firewall. There may be some hidden bolts underneath it. (It's been a few years, so my recollection may not be accurate.......)

 

[QUOTE=Rod Schneider;1595998862]If I remember correctly, there is a piece that unbolts from that mounting bar that makes it easier to get out of the car. I struggled with getting it out until I discovered it. As I recall, it's not obvious, but I think it's the lower center piece that unbolts......


Got back at it today and realized I could slide the washer type pieces on the lower dash bolts down some and slide the bolts in the frame just enough to get that aluminum support piece out. Got all of the HVAC out, interior and exterior. All that old dash mat is in the trash and DynaMat is going in tomorrow. Thankfully the heater core is in great shape and so are all the AC components. Just need to track down some new double sided sealing tape to use around the edges of the engine bay side HVAC unit

 

Thank you for the pictures! I took my instrument cluster out yesterday, and getting deeper. I needed to see what was next!

 

[QUOTE=JasBass;1596038735]
I know this was years ago, but how did the rest of your project go? I am pretty much doing the exact same thing to my 85. Started with a stereo swap, then an interior refresh, I saw some cracks in the floor I needed to fix so I gutted the car, now I am also swapping in a ZF6 in place of my 700r4.

Curious what you used to replace the dash insulation and how you like it. I definitely want to do it once and do it right. I'll also need to track down some seals or seal material for my HVAC assembly.

As for the question asked a few posts above, the dash will come out with the steering colum installed, but it really sucks. I am shocked I didn't break something. Ended up pulling the colum anyway after the dash was out.

 

[QUOTE=ACMX92;1603433870][QUOTE=JasBass;1596038735]


I know this was years ago, but how did the rest of your project go? I am pretty much doing the exact same thing to my 85. Started with a stereo swap, then an interior refresh, I saw some cracks in the floor I needed to fix so I gutted the car, now I am also swapping in a ZF6 in place of my 700r4.

Curious what you used to replace the dash insulation and how you like it. I definitely want to do it once and do it right. I'll also need to track down some seals or seal material for my HVAC assembly.

As for the question asked a few posts above, the dash will come out with the steering colum installed, but it really sucks. I am shocked I didn't break something. Ended up pulling the colum anyway after the dash was out.



Those pics bring back some memories man! Project ended up going really well. Built it back better than what Chevy did from the factory and sufficiently reduced all of the C4 rattles from the dash.

For the inside firewall I used a generic fit roll of dynamat and cut it to fit where I needed it. I did that on the whole inside tub from the firewall to the trunk. In the places where I could, I found some generic thin mil foil backed cellular foam (eBay I think) and used that from the footwell back under the seats and up the side of the trans tunnel. Laid the new carpet down on top of that. I couldn’t be happier. I live in SC and during some stupid hot summers, my legs were happy and not baking.

When reassembling the HVAC, I some of the thin rubber single sided sticky weather stripping to have everything assembled back a little snug so it didn’t rattle. I used 3m double sided foam tape to join the heater core box to the firewall; same for engine bay side. Everything is super tight and rattle free. Makes for a really enjoyable cruiser that doesn’t sound like an 80s rattle can.

Only thing to consider are seat bolts and not making the padding too thick. I installed Corbeau A4s and had to sit in it and stack weight to compress all of the material down so I could safely secure the nut on the bolt.

It was tedious work, but I’m glad I did it because I can’t say enough how nice it is to have a C4 that does not interior rattle at all!

 

[QUOTE=JasBass;1603434015][QUOTE=ACMX92;1603433870]Awesome, that is really good to hear. I feel like I am going way overboard on a car I bought for $4k but I know it will be worth it in the end.
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I thought about going with dynamat on the firewall and some cheap peel'n'seal roofers flashing for the rest of the floor as that has worked well for me on other cars. Maybe I'll splurge and use dynamat for the whole thing. I also have some foil backed precut insulation to put down so I don't want to make things too thick and have difficulty installing the carpet.

I pretty much figured there was no real kit to seal the HVAC so that sounds like a good way to go.

How do you like the A4s? I hear they are one of the few seats that fit well in C4s. I love the look, just not sure I am ready to give up having a power seat. I'd also like to see if Corbeau does custom stiching or colors.

 

[QUOTE=ACMX92;1603435436][QUOTE=JasBass;1603434015]Dynamat has definitely gone up in price lately, there isn't anything wrong with generic ebay or amazon sound deadner. And the whole thing about overboard on a C4, these are good cars that are fun and produce a lot of fun on a smaller budget. For me, the slice of 80s makes it worth all of the headaches. That digital dash with all of the info right there at your fingertips rivals some modern expensive digital dashes.

The A4s I have been 50/50 on honestly. My seats were trash so I had no choice and had to replace them. They fit perfect when you buy the right seat sliders for them. They are reasonably comfortable and definitely hold you in nice and snug, but that comes at the expense of long drive comfort. When I moved down to SC from NC, the 5 hour drive down 95 was about as much as I wanted to do in a single day. I wasn't hurting or terribly beat up, 5 hours in any sport seat is tough. A small lumbar pillow would help and maybe getting around to fixing the cruise control...lol. They give the car a nice look and update the interior a touch. I did a breadbox delete and I think it really took the interior to something that is 80s retro and not 80s tacky. No regrets overall

 

Your water leak could be from rain getting past the hood seal where it's bolt to the firewall and running into the HVAC/Heater core box and getting into the car. Could also be from the seam that runs along the firewall down inside the wiper well area. It could also be coming from the corners of the cowl under the windshield.

My dash was cracked on the left side where that large nut going into it is. And so the left dash would like to bounce around and shake. I ended up using some zipties to hold the dash to that nut area and it's been rock solid ever since.

I'll give a tip on cracked plastic. Like the A pillar and B pillar trim which likes to get cracks at the screw hole areas. But I wipe the backside with rubbing alcohol, though you don't want any of that getting on the face of the plastic as it will stain it. Then I use sand paper to sand off the outer layer of plastic around the crack and/or screw holes. (I don't know if that is needed). I then wipe it again with the alcohol. And then I use some black ABS cement from the hardware store and I brush on a thick layer around the crack and screw holes making sure not to get it down into the screw holes. And that stuff dries to the touch in 10 minutes, and I let it sit for a couple of days to cure. And it's pretty much rock hard after that but kind of flexible which means it doesn't recrack like say if you were to use an epoxy that cures rock hard. This stabilizes to the crack to keep it from flexing say when you tighen down a screw.

My A-pillar piece on the side had a crack that ran almost all the way through it from side to side. It was real flimsy until I spread a thick layer of ABS cement on the backside. Now it feels rock solid, and it doesn't flex and the crack doesn't open up when I tighten screws down.

Many years ago my center console lid door was really saggy if you pressed on it as the internal honeycomb plastic was all cracked. I got a can of ABS cement and poured it all over the inside plastic honeycomb piece. Let it set for several days, and it was hard as a board for probably a decade before it finally went. Obviously you have to remove the plastic piece that has the RPO sticker sheet.

 

[QUOTE=ACMX92;1603433870]Man, I had to fix a bunch of cracks on the floor board, and I had to bang out dents on the metal floorboard that was under the seats. There were even some holes in the fiberglass where a chunk I guess broke off. I'm guessing the shop the PO used decided to jack the car up via the floorboards. It was a nightmare researching how to fix it, and then actually having to fix it. I laid glass on the inside and outside. I think sprayed the outside with some rubberized undercoating stuff. My car had already been sprayed with that stuff anyways at some point in the past like maybe at the GM dealer when it was first bought.

What speaker are you using in your door? I modified mine for a larger speaker. Though I cut those flaps off on the door as I wanted to be able to remove the speaker from the front instead of having to go around where the inner metal skin part is of the door.