DIY gasket?

Submitted: Wednesday, Dec 14, 2016 at 13:34
ThreadID: 133936 Views:2216 Replies:4 FollowUps:7
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I've got to improve the sealing of an airbox and I'm wondering about making my own gasket.

Seem to recall some time ago someone writing about their effort with a door seal, where they improved decaying pinchweld by smearing vaseline on the mating face, putting a bead of silicone on the top of the rubber and closing the door.

Transferable idea?
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Reply By: Frank P (NSW) - Wednesday, Dec 14, 2016 at 14:02

Wednesday, Dec 14, 2016 at 14:02
I was thinking similar. A bead of Silastic around the perimeter on one half of the box, coat the mating surface of the other half with a smear of vaseline and assemble.

If you could partially pull the two parts together until the Silastic cures, so that the bead ends up a little bit thick, that might be good. Then when you fully assemble it with clips, screws or whatever, the bead would compress to give a repeatable good seal on future occasions.

Or cut the nozzle so that you form an O ring of small cross-section all the way around. Wait for it to cure then assemble with clips, screws etc.
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Reply By: Allan B (Member, SunCoast) - Wednesday, Dec 14, 2016 at 17:48

Wednesday, Dec 14, 2016 at 17:48
Hi Sigmund,

I did promote the technique of using silicon for a gasket a while back.
The method I have used a number of times on industrial electrical enclosures was to lightly oil or grease one surface, apply the silicon to the other surface, then press the two components together to evenly distribute the silicon. Only tighten the screws fully after the silicon has cured. Has worked each time. If need be, to avoid dust sticking, any remaining lubricant can be removed after the silicon has cured.

I have not tried the method on decaying pinchweld. Seems to me that applying silicon to anything that is decaying may be temporary at best.
A bond to rubber with any adhesive is greatly improved if the rubber surface is thoroughly cleaned with acetone first.
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Reply By: Hoyks - Wednesday, Dec 14, 2016 at 17:54

Wednesday, Dec 14, 2016 at 17:54
We do it all the time to provide a seal between panels on aircraft.

Basically it is clean side one that you want the sealant to stick to and clean and also lubricate the side two you don't want it to stick to.

Apply sealant to the side one, assemble and allow to cure.

The problem with your application is that most commercial sealants air cure, so will take forever to harden,

and

air boxes generally have spring loaded clips or a wing nut so that they provide some tension against the seal when closed to keep the water out.

Not insurmountable though. You may be able to get some polysulphide or polyurethane sealant that is a 2 part product, so it chemically cures rather than dries, or just use the single part product and stick it in the corner of the shed for a few days.

The clips though, you could either put the sealant on and only 1/2-3/4 tension them down, or put some spacers in where the seal goes to set the spacing and then repair the small sections when you are done. I'd go with the 1/2-3/4 tension option myself, then put it somewhere where nothing will get dropped on it.

Even with lube, separating the 2 parts can be fun. Even poor adhesion over a large area can make it a struggle.

Once it is all cured, trim the seal to provide a neat appearance and then dust it with talc. The talc takes any residual tackiness away.

Good luck.
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Follow Up By: Allan B (Member, SunCoast) - Wednesday, Dec 14, 2016 at 18:26

Wednesday, Dec 14, 2016 at 18:26
.
Hoyks makes a good point about separation. Early problems I had with this method was ineffective grease coverage and over-application of silicon. Too much silicon in some areas required extra assembly pressure to form it resulting in the grease being wiped off and adhesion to both faces. Use only sufficient silicon, apply it as evenly as possible and press together only sufficiently to just form the gasket.

One disastrous event early in the advent of silicon sealant was an an asquaintance who sealed the distributor cap of his rally car with silicon. He had to smash the cap to get it off.
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Follow Up By: Sigmund - Wednesday, Dec 14, 2016 at 19:28

Wednesday, Dec 14, 2016 at 19:28
Thanks gentlemen.

It's not a filter housing but the box that joins that to the throttle body. It has a rep for leaking around the horizontal join (5' of it) which is screwed together. The stock gasket isn't up to the job.

It doesn't in normal maintenance get opened but needs to be openable.

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Reply By: Batt's - Thursday, Dec 15, 2016 at 12:19

Thursday, Dec 15, 2016 at 12:19
What vehicle is it your having problems with an older 4wd or recent model. Is the factory seal worn maybe done up to tight warping the lid and creating a gap.
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Follow Up By: Sigmund - Thursday, Dec 15, 2016 at 12:57

Thursday, Dec 15, 2016 at 12:57
It's a European-made dirt bike Batt, a 650 single.

A bit of sloppy design as well sub-par materials - not uncommon in Euro bikes as far as air filtration goes. They don't seem to appreciate how pesky the dust can be in the southern hemisphere.
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Follow Up By: Sigmund - Sunday, Dec 18, 2016 at 12:24

Sunday, Dec 18, 2016 at 12:24
Well in the event Plan B worked. Silicone was Plan C.

Plan A was to get a length of unusual size neoprene foam from the US but shipping to Aus was beyond the supplier. B was to get some generic sticky back of the same from Clark Rubber and cut 4mm width from it; 10' with a razor blade. My mate, who was doing his bike too, had a steady hand and did it with a rule and razor blade.

The fit's very good.

Due to the poor seal and a rubbish filter the inside of the airbox was dusty and the throttle body and butterfly were coated in dust. It only has 5 K on the clock. Hope there's not too much wear.
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Follow Up By: D-MaxerWA - Monday, Dec 19, 2016 at 22:52

Monday, Dec 19, 2016 at 22:52
When I had an old Triumph Trident, I used some blue gasket in a tube. Not sure of the name of it now, but apparently, Rolls Royce used it for their gaskets.

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Follow Up By: Sigmund - Tuesday, Dec 20, 2016 at 05:11

Tuesday, Dec 20, 2016 at 05:11
Gasket Goo maybe.

I had a BSA. Used a lot of it.
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Follow Up By: D-MaxerWA - Wednesday, Dec 21, 2016 at 00:15

Wednesday, Dec 21, 2016 at 00:15
You may well be right there Sigmund, if it was blue. Those old English bikes, you either payed for a good sealant to stop the leaks, or you paid more for oil.

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