Fun With Dashboards

[Strife]

I bought a dash cap for my 380SL project car, and I dug out/cut the cracks in the dash, and filled them in (mostly) with plumber's epoxy. Filling them in and cutting out the curled up edges is recommended. Anyway, although I intended to use the cap, I thought I'd try a little experiment. I had some Mar-Hyde 2-part flexible bumper filler around (about 10 years old and unused). I found a vinyl fabric with grain very similar to the dash; I coated the cracked areas with it and as it was drying, I pressed down with the vinyl fabric with the grain facing into the material. Even though the pattern was reversed (grain "out" instead of "in"), after spraying with (cheap) vinyl dye semi-gloss, my repairs came out darned good on the typical "temperature gauge to window" crack. Unfortunately, in my case, I also had a big crack behind the instrument cluster, and it's extremely difficult to work back there; I couldn't do a very good job because of lack of room for my hands. With the window out, or with the dash itself out, things might have been different.

I've been trying out this flexible bumper filler and it does "give"; I can flex it for weeks after putting it on a piece of cardboard.

Bottom line, for a small, accessible crack, I think with a little practice, this technique can work.

Now, for some planning on how I'll brace the dashcap in order to install it...on a test install, I it seems like it can look pretty good with a good installation. Unfortunately, the next 65 degree + day might be in March...

[Roncallo]

It will actually look pretty good even if you dont glue it in and let it just lay there. But it will also rattle without glue.

If you dont want to take the dash out, I would just follow the directions and put the 6 dime sized dabs of glue they give you and try it out. Many people have said this work fine. But the beauty is you can always do it some otherway again if it fails. You wont be ruining anything.

Then if that doent work you can try something else, or if later on down the road you have to do some AC diaphram work, you can try the John Roncallo vacume bag trick.

John Roncallo

[Strife]

Well, I got the garage up to sufficient temperature today and I did it; it went on really well and conformed darned near perfectly-I can't find that it is sticking up anywhere beyond the thickness of the silicone itself. A few things I learned:

1. IF you don't think it fits right on a test fit, read 2-8.
2. Tucking the L/R sides in between the pillar parts and dash is very important.
3. You have to start out with a "flat" dash, with no upward cracks; my previous attempt worked well for this.
4. Removing the temp gauge and gauge cluster is CRUCIAL to a good fit.
5. Roughing up the plastic and dash as per the instructions-important.
6. Removing the temp gauge gives access to feeling where the "hole" for the interior temp sensor goes; I put a dab of paint on my finger and located it perfectly.
7. I cut some pieces of wood, and by loosening and tightening the steering wheel made a "clamp" for this area. I also used some 36" outdoor railing turnings, braced between the headrest posts and dash to clamp that way. Turning the seat knob forward gives this pressure.
8. Stuff every item of "junk" t-shirts you can in between the window and the dash/cap, and inbetween the instrument cowl and window.

[al76slc]

Strife

Which brand dashcap did you use?

Thanks
Al

[Roncallo]

Originally Posted by al76slc

Strife

Which brand dashcap did you use?

Thanks
Al

I thought Coverlay was the only one. Are there others?

John Roncallo

[Roncallo]

Originally Posted by Strife

Well, I got the garage up to sufficient temperature today and I did it; it went on really well and conformed darned near perfectly-I can't find that it is sticking up anywhere beyond the thickness of the silicone itself. A few things I learned:

1. IF you don't think it fits right on a test fit, read 2-8.
2. Tucking the L/R sides in between the pillar parts and dash is very important.
3. You have to start out with a "flat" dash, with no upward cracks; my previous attempt worked well for this.
4. Removing the temp gauge and gauge cluster is CRUCIAL to a good fit.
5. Roughing up the plastic and dash as per the instructions-important.
6. Removing the temp gauge gives access to feeling where the "hole" for the interior temp sensor goes; I put a dab of paint on my finger and located it perfectly.
7. I cut some pieces of wood, and by loosening and tightening the steering wheel made a "clamp" for this area. I also used some 36" outdoor railing turnings, braced between the headrest posts and dash to clamp that way. Turning the seat knob forward gives this pressure.
8. Stuff every item of "junk" t-shirts you can in between the window and the dash/cap, and inbetween the instrument cowl and window.

Sounds like something that will work just fine. One of my areas of concern has always been arround the temperature sensor. If you dont get it down flat in this area the sensor will not have enough length to engage into the hose adapter underneath. Ive never used the silicone meathod so I dont have any experiance with it but the directions given to me with my coverlay dash asked for only about 6 dime sized dabs of silicone arround the parimeter and nothing near the temp sensor.

My understanding of the directions is that they want to allow for local expansion so they dont want glue the full area of the dash. If I were to do this job without removing the dash, I would probably do it according to the directions but add a good maybe 4" circle of contact cement arround the temp sensor hole and clamp it down with a nut and bolt with some large padded fender washers through the hole.

I'm hoping that with the 2 methods I'v used, of full area contact cement using lots of clamps or a vacume bag with the dash removed, that heat transfer will take place over the entire surface of the dash cover through to the original dash and both will expand and contract uniformally.

The first car I did was with contact cement and lots of clamps. That was done about 1 year ago and is holding up fine except in one area behind the right side windshield defroster. I attribut the failure in that area to be due to 2 reasons.

1) The cover was on the car when I bought it and already deformed and curled up in that area.

2) I had used brush on contact cement and had difficulty getting the cement fully coverd over the whole dash area before the first areas of application dried out. This could be corrected by spray on contact cement or the use of the Pliobond #20 contact cement which can be brushed on and fully allowed to dry, then reactivated with a spray bottle of acetone. I used that meathod on my second dash.

The second dash I did has yet to see a single summer thermal cycle so its sucess is still to be determined. But I used the Pliobond #20 and acetone meathod for this dash but with a vacume bag technice. So far it seams to be working OK. I think the vacume bag is over kill and the clamps would work just fine, but the application of the glue and the fact that I started with a new coverlay will make this work.

If I were to remove a dash and do this again, I would probably use the Pliobond and acetone and vacume bag only because its easy. But I would also investigate the possibility of putting several pop rivits with backup washers along the windshield edge, if I could do it in an area where it would not show. This might be along the edge where that cloth strip is (the one that turnes white over time and looks ugly). Hopefuly I could catch the rivit heads under a replacement cloth strip (something that wont turn white).

Keep us posted on the success of this installation

John Roncallo

[Strife]

I used one from Accu-Form, Called a DASH-CAP (probably a trademark thing). I think ONCE PROPERLY INSTALLED, the conformity of the part was excellent; too bad the leather grain is coarser than the original.

On the CC hole, making it bigger (once installed) was nasty - I used a cable-operated Dremel-like tool from above and a tiny router bit to do this. But I didn't really install the CC sensor properly because the foam tube was shot to hell. This will have to wait.

[Roncallo]

Originally Posted by Strife

I used one from Accu-Form, Called a DASH-CAP (probably a trademark thing). I think ONCE PROPERLY INSTALLED, the conformity of the part was excellent; too bad the leather grain is coarser than the original.

On the CC hole, making it bigger (once installed) was nasty - I used a cable-operated Dremel-like tool from above and a tiny router bit to do this. But I didn't really install the CC sensor properly because the foam tube was shot to hell. This will have to wait.

The foam tube is about $40.00. I dont know what it is there for. On both my cars they were also shot. On one of them someone just put a piece of heater hose in place of the foam. I have no idea whats wrong with that but I figured MB put the foam in for a reason, so I replaced it on both cars. Its easy enough to install.

John Roncallo

[Walrus]

Originally Posted by Roncallo

The foam tube is about $40.00. I dont know what it is there for.
John Roncallo

John,
If I understand correctly, you are unsure of the reason for the tube? Perhaps you mean "...why foam...", but I'll continue for the sake of a greater audience. It is a duct for air to be drawn across the in-car temperature sensor. One end is attached to a hard line that is open to the fan compartment, and the other is attached to the sensor. As the fan runs, a bit of cabin air is drawn across the "aspirator" as it is called. This allows the sensor (a thyristor*) to sample the in-car temperature and adjust air temp and fan speed accordingly. I believe foam is used to insulate the "tube" from the under dash temp and more accurately sample the actual in-car air temp. On a convertible, this is academic as there is no way the sensor is going to read in-car temp; however, with the roof up, perhaps it does have a chance. Seems to me the air sampled will be influenced by the def output, so I fashioned a little hood to shield the temp sensor grill. Seems to work nicely.



Edit: The correct device type is a thermistor, not thyristor as indicated here.

[Strife]

I think the part that sticks up is a thermistor - which progably goes down in resistance as the temperature goes up (most resistors do, but this type is designed to do this a lot and in a predicatable way). Thermistors can be tricky to work with, because the wires themselves that connect to it conduct heat, and maybe the foam tube tries to control this.

Here is a picture of my bracing system, which may be useful, because this worked very well. Note the wood between the steering wheel and cowl - the wheel was clamped down after installing the wood; the seats were pushed forward with the seat knobs after installation. Much of my raggy, car-working clothing was stuffed in between the dash and window. Plastic garbage bags were underneath them in case of silicone leakage (there wasn't any).

[Walrus]

Originally Posted by Strife

I think the part that sticks up is a thermistor...

Strife, you are absolutely correct... In my evening stupor, I typed the name of the wrong device. Thanks for correcting...

Rory

[Roncallo]

Originally Posted by Walrus

John,
If I understand correctly, you are unsure of the reason for the tube? Perhaps you mean "...why foam...",

Edit: The correct device type is a thermistor, not thyristor as indicated here.

I understand the reason for the thermistor and tube and even why they might want to insulate the tube. What I dont understand is why would anyone in there right mind make this tube out of a rubber tube glued to an 8" pice of foam tube and glued again to another rubber tube the same size as the first tube. Why not just sleave the tube in that area with foam or for that mater the whole length of the tube. Im not sure if the foam is closed cell air tight. Maybe its not and maybe they wanted air under the dash to filter in through the foam???. Attached are pictures of the tube showing the disintegrated one and the replacement. From these you can get an idea of how it is constructed. You can see that the foam tube only glues to the last inch of each end of the rubber tubes.

John Roncallo

[Roncallo]

Originally Posted by Strife

I think the part that sticks up is a thermistor - which progably goes down in resistance as the temperature goes up (most resistors do, but this type is designed to do this a lot and in a predicatable way). Thermistors can be tricky to work with, because the wires themselves that connect to it conduct heat, and maybe the foam tube tries to control this.

Here is a picture of my bracing system, which may be useful, because this worked very well. Note the wood between the steering wheel and cowl - the wheel was clamped down after installing the wood; the seats were pushed forward with the seat knobs after installation. Much of my raggy, car-working clothing was stuffed in between the dash and window. Plastic garbage bags were underneath them in case of silicone leakage (there wasn't any).

This looks about as good as it can be done without removing the dash. How much silicone did you dash cover instructions say to apply. How much did you apply.

John Roncallo

[Strife]

Originally Posted by Roncallo

This looks about as good as it can be done without removing the dash. How much silicone did you dash cover instructions say to apply. How much did you apply.

John Roncallo

The instructions were to squeeze out a pencil-diameter bead 1" from all edges and all holes (vents, gauges). I may have used maybe a 3/16" bead but I'm glad I did, because I used every bit of the silicone supplied and just barely finished.

[Strife]

Originally Posted by Roncallo

I understand the reason for the thermistor and tube and even why they might want to insulate the tube. What I dont understand is why would anyone in there right mind make this tube out of a rubber tube glued to an 8" pice of foam tube and glued again to another rubber tube the same size as the first tube. Why not just sleave the tube in that area with foam or for that mater the whole length of the tube. Im not sure if the foam is closed cell air tight. Maybe its not and maybe they wanted air under the dash to filter in through the foam???. Attached are pictures of the tube showing the disintegrated one and the replacement. From these you can get an idea of how it is constructed. You can see that the foam tube only glues to the last inch of each end of the rubber tubes.

John Roncallo

The only thing that I can think of is that it gets hotter than heck inside the dash (particularly above the radio if you have a modern, 25 watts per 4channel radio without an external amp) and they were trying to keep heat away from the thermistor and the wires leading to it (which can, and do, conduct heat in and of themselves). Solid rubber will conduct and retain heat better than the foam will. You could probably get the same effect with insulating tubing or even tape that's on sale in the winter months in the North at places like Lowes, etc if originality is not important. This is likely what I'll do - $40 for a piece of foam is a bit over the top for me.

I've had one side of my stereo shut down in warm, sunny weather going full -tilt on the highway with the stereo blasting - they almost all have thermal protection in the amps.