aaddpp

The car I bough has a near perfect dash with the exception of a tiny crack (about 1-2 mm) starting on the right angle corner just above the glove box door.

First I want to check what is the best way to keep the dash material hydrated to prevent further cracking, and second I wanted to know if there is a way repair a minor crack like this to eliminate all together.

Thanks,
Dave

pcar928fan

Yea, take good care of that...don't let is spread!

I wish I could help you but honestly I have no idea of the best way to keep that from getting worse. I would think an epoxy or some sort of actual dash repair kit might work. I had some sort of filler used on my pod on my '81... didn't last. Looks better than it did, but not good 6 or so years down the road now. It was done at a leather/upholstery shop too!

928 at last

There are threads I've read here in the last couple of years with some intersting options for dash crack repairs and finishing. A search should pull some up for you. IIRC, one involved using fibreglass reinforced bondo and touching up the finished repair area with interior paint.

Nicole

One thing that will definitely help is to keep the dash out of the sun. I'm convinced that sun exposure and the temperature changes that go along with it are the major factor in making these crack in the first place.

tveltman

That is definitely true nicole. The dash cracks because the vinyl stays supple only so long as there are sufficient plasticizers in the matrix. When the dash heats up, these plasticizers vaporize out of the matrix and then end up on your windshield (that's why you have dirty fog on the inside after a while, even in a non-smoking car). Best solution is stay out of the sun, though you may find some products that purport to reintroduce plasticizer into an old dash to preserve it. It may work, it mainly depends on how viscous the product is compared to the pore size of the vinyl. Plasticizers are also the cause of the famous "new car" smell.

DanielD

tveltman, can you recommend one? My dash needs help!

Mike Simard

My dash cracked back in the day on my 85 when it was only 4 years old.
It was outside during a really cold night and in the morning there was a full length crack right in the middle! It was all the way from the windshield down to the HVAC.

BTW, thanks for that great post!

tveltman

Honestly, my dash needs way more help than yours does, and I have not decided on an appropriate course of action yet. I looked into plasticizers briefly, and the standard one for vinyl dashes (though there are several, and many could be used) is DEHP, alternatively known as BEHP or di(2-ethylhexyl)phthalate. It is used primarily because it is cheap. I don't know what armor-all contains, but look for anything ending in phthalate, or alternatively check out the wiki article on http://en.wikipedia.org/wiki/Phthalates
for more pthalates. Based on the wiki, I'd say you could go with DIDP, DIHP, or DINP, as they should have similar chemical properties.

tveltman

Plasticizer loss reduces the vinyl's ability to deform, and so heat cycling will definitely result in cracking. I think the chief problem with repair is the difficulty of finding something that has a similar coefficient of expansion to fill the cracks. I was actually thinking that the black "tar" used on step flashing for roofing applications might be a suitable substitute, although I don't know if anyone has tried it. It seems like it should heat cycle very well, and it is also somewhat pliant, and thus may be willing to stretch or compress if it's expansion is not quite identical to the original vinyl. I'll poke around on the forum and see what products others have used.

G Man

My dash and pod were both crack free when I picked up the car in FL. FIrst winter here in NV I ended up with cracks on both. Below freezing temps did me in.

Mike Simard

When I was experimenting with materials to seal drop-in cylinders I tried some asphalt sealant spec'ed for military runways with jet traffic. The stuff has properties that must make it good for something interesting. It's a 2 part mix and was something like hundreds of dollars for a quart or so IIRC. I still have it here if you ever want to experiment and would gladly send some.

928 Is My Favorite Time of Day

Has anyone ever tried black GE silicone sealer on a black dash? I'm sure at the very least, it will stay pliable. I've tried the two part bumper repair epoxy. It is sandable when cured but shrinks quite a bit requiring several coats. I did not like the result. YMMV.

tveltman

It looks like the armor all MSDS says that it's just suspended silicone. That won't really help you, you'll have to look for something else in order to restore the dash. Sigma-aldrich (which you can't purchase from unless you have a TaxID number, though this chemical probably isnt any sort of drug precursor, so that's likely all you need) sells what appears to be straight dioctylphthalate (same compound) for 69 bucks for 2 liters. That's a crapload of the stuff. It's dangerous to infants, children, and pregnant women, though if you wear rubber gloves (like the thick ones for kitchen cleaning, etc), you will probably be fine, especially since you wouldn't be bathing in it or drinking it (hopefully). You may be able to find a source for the stuff, and you certainly don't need to purchase 2L of it if you decide to try it. My advice would be to try it in an inconspicuous location first. I don't think it would dissolve the vinyl (since it shipped with the vinyl originally, and also vinyl is pretty inert), but discoloration might occur or something. There may be other products out there, but the plasticizer is what does the job. You might want to wait until it warms up so that you can apply the stuff, then leave your windows down and your car in the sun. That should allow the fumes to escape so that you won't gas yourself, and then you might even end up with a new-car smell!

tveltman

Mike do you know what the stuff is called? I may be able to find out more about its specific properties if you give me a name or formula or something to go on. Thanks!

Mike Simard

Here it is:
https://www.epoxy.com/techdata/917.pdf

It's probably too serious to be inside the car.

There is something else that might be of interest:
http://www.resintech.co.uk/downloads/tds/RT125.pdf

It's a flexible epoxy that I use when building wiring harnesses that use the best materials and are works of art, the kind with 20-50 dollar boots.
That stuff could be applied using a 'mixer snout' into a small bead.