Preventing/repairing dash cracks

So I got the "new" dash for the 900s today, it's in very good condition overall but there are a few very small cracks just starting to form. Is there a good way to repair these or at least prevent them from spreading? Are there any good products to put on the dash to protect it? I've heard a lot of negative things about ArmorAll so I'm very reluctant to use it. Why are these dashboards so prone to cracking in the first place?

Reply to
James Sweet
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If you drill a hole slightly larger (only very small drill bit) than the closed tip of the crack at the very end of the crack (so effectively a pin hole) it should stop it spreading as you have given a small ammount of area for the plastic to flex rather than crack. Of course if there are lots of small cracks it, you dash may look like swiss cheese anyway.

Reply to
MeatballTurbo

This product is very popular with professional detailers for their own cars. There used to be a guy who was an auto interior/exterior product chemist who hung around some forums I frequented and he preferred this product AFAIR. Regardless of what the labels and promo's say for any product it's the chemical contents (UV blockers, etc) that count.

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Reply to
Bob

Sorry, but these products just don't (_can't_) work. For a couple of reasons:

[a] To absorb any significant proportion of the incoming UV you need a much thicker layer than that. [b] There's hardly any incoming UV anyway! The vehicle's glass does a very good job of absorbing 90% of it. Most of the damage is caused by heat and some is caused by visible light.

Plastics degrade - the only thing you can do to delay this is to keep them in a temperature controlled dark room.

For the OP - your best solution is to drill small holes as Meatball said. You can then fill the holes/cracks with polyurethane sealant. If you do this carefully, they are a lot less visible.

Reply to
Grunff

Grunff:

I don't know that I accept your hypothesis on the thickness. Sunscreen for people is not applied in a "thick" layer yet it quite obviously does the job for people. UV protection _can_ be had in thin layers of goo.

As to glass absorbing UV - I've researched this in-depth by talking with a professional engineer. Unless the glass is specifically designed for UV deflection and/or absorption, a significant portion (most) of the UV passes right through. There are several components of UV and the nasty ones don't get removed passing through auto glass.

Reply to
Bob

The thickness of the layer is key - while you would easily tolerate a

200um layer on your skin, if you had a layer of anything more than say 20um on your smooth dash it would look like it was covered in grease.

In addition, sunscreens work by absorbing UV and decomposing in the process, which is why you need to reapply every few hours. It's this decomposition that provides enough UV absorption. Unless the product is meant to be reapplied to the dash every few hours, it can't work in the same way.

It's actually very much the other way round. Deep blue light is ~400nm. Beyond that you're into near UV. Near UV does pass through glass with reasonably low absorption. The cutoff point for ordinary silica glass is around 350-320nm. Anything shorter than that is completely absorbed.

These shorter wavelengths contain a lot more energy than the longer wavelengths, and are therefore a lot more damaging to both skin and plastic. They are the ones that matter.

Reply to
Grunff

I'd have to dig out my notes to see if I concur with that. :-)

Reply to
Bob

Oh joy, ok I didn't mean to start a big argument here, I just wanted to know how to preserve the existing condition of the dash.

Reply to
James Sweet

I heard of a method of "repairing" the cracks. You get a matching color silicone caulk and fill the cracks. You put a textured duct tape over the caulk, so when the caulk dries, it will have some texture. The caulk will not stick to the adhesive on the tape. Then you go buy a fabric or carpet cover for the dash and put it over the mess :-)

Reply to
ma_twain

We don't argue in this group. We discuss, learn, and enjoy ourselves. It's one of the few civilized groups on the usenet. (Don't let that out - the trolls will be by to visit if you do :-).

Reply to
Bob

That link doens't work. 8-)

I agree with you though that it's the properties of the product which count, not the labelling or marketting. That's why it is important to stick with something once you know it works, because you've hit on the right properties for the task.

Craig.

-- Guru Will Sellit! ** 'sunrk' on Ebay ** | Get Back on Track at the Sun Shack Craig Dewick - aka the one4sun! |

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+------------------------------------- SRK's Ebay Shop is now available at
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Reply to
The One4Sun - GWS

He he - my C900 has a carpet cover made specifically to cover the top of the dash which is extremely cracked. I can't be bothered to try and replace the whole dash structure at present, and the carpet dulls some of the engine noise coming through the firewall before it gets to where my head is. 8-)

I see a lot of 'dash pad' and 'dash pad cover' listings on Ebay from time to time, and don't quite know what the difference is unless a 'dash pad cover' is the same as the piece of carpet over the top of the dash in my car...

One side issue I'm having at the moment is that I removed the four long bolts to remove the instruments from the dash and now that I've put everything back into place, I can only get one of the four bolts to mate with the fixed captive nuts in the dash structure. This isn't a huge issue but it means the whole instrument and control assembly is secured with one bolt (the extreme RHS one - I'm in Australia remember so the car is RHS drive). It creates more vibration when driving, but I put up with it. At least when I next need to work on the instrumentation I only have to remove one bolt instead of 4. 8-)

Craig.

-- Guru Will Sellit! ** 'sunrk' on Ebay ** | Get Back on Track at the Sun Shack Craig Dewick - aka the one4sun! |

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or
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Main info website at
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+------------------------------------- SRK's Ebay Shop is now available at
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Reply to
The One4Sun - GWS

Those screws are a real pain, the idea is that there's plastic tubes that they route up through, but on the car I worked on those were broken. What I ended up doing was removing the radio and bracket, and the headlight switch and I found I could reach around with my finger to guide the screws through the upper loop and into the threaded hole in the bottom of the dash. It takes some dexterity but it can be done. Also some of the screws are different lengths, gotta put the right one in the right hole.

Reply to
James Sweet

They're *all* different lengths. Theyr'e markes with grooves at the end (1,2,3 or 4) to indicate the correct order.

Reply to
Grunff

Just tried it and it worked for me....

Reply to
Bob

Worked for me too, next time make sure there is at least one space between '>' and 'http://.....'

------ MH

Reply to
MH

Then how does one account for feeling warm next to a window on a sunny day?

And why oes one never get a tan indoors?

I understand that the UV is almost entirely absorbed and the IR goes blythley through in both directions and can be a consideable heatlosswith unshshaded windows inon dull winter days and at night.

Malcolm

Reply to
Malcolm William Mason

That's pretty much exactly what the guy who you replied to said.

Reply to
James Sweet

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