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MG MGB Technical - Contact adhesive for underbonnet felt insulation

I've just bought an aerosol can of 'Quality Heat Insulation Contact Adhesive' from Moss, to glue some new felt insulation to the underside of the bonnet (hood). The instructions on the can read:

For porous materials such as fabric, cardboard or paper, coat one surface only. Bonds should be made while the adhesive is wet and tacky.

For non-porous materials such as metal, etc., coat both surfaces. Allow 30 to 60 seconds before bonding.

As I will be fixing a porous material (felt) to non-porous (painted steel) I'm not sure which procedure to follow to achieve the best result.
Brian Shaw

Funny you should ask. I hadn't driven my car in months and
last weekend when I raised the bonnet I found the engine was
blanketed by the bonnet insulation.

I had used the exact same stuff as you under my own bonnet.

Spraying on only one surface doesn't cut it for long as my
insulation fell off within days.

Spraying it on both surfaces lasts longer - but it, too, is not
lasting. Be very generous with spraying the stuff on. It'll hold
for maybe a season, or two, before the edges start to peel.
I've been using the rest of the spray for quick touch-ups.

I've heard of folks using construction adhesive with better
success (: Liquid Nails) and I may go with this after I exhaust
what's left on my spray adhesive.
Daniel Wong

I have had excellant results using Weldwood Contact Cement, don't know if it is sold in the UK.mine has been in for 12 years with no problems. Also used it for all the carpet and insulation in the cockpit.
John H

In the past I have used a non flammable contact adhesive for bonding the felt, It came in a tin not an aerosol can,t remember where it came from I,m afraid.

C Bintcliffe

There should be some archives on this. I believe some people have used 3M Heavy Duty or High Temp spray adhesive with success. I definitely spray both surfaces.
Robert McCoy

Well, that was timley. I was about to use the yellow snotty 3M weatherstrip adhesive, but I think I'll go get some Weldwood Contact Cement instead.

C R Huff

Used contact cement on mine. Still had a little failure at the edges, but easy to put contact cemtent in there and fix it.

I used Dunlop 'Thixofix' in the mid 90s and the insulation is still stuck OK. It's quite a good impact adhesive because it allows you to reposition slightly if you get it wrong the first time.
R. Algie

Brian - because at least one surface is porous follow the instructions for that. The others would be used if both surfaces were non-porous.

I used spray-on adhesive (can't remember the name) to fix my sill and rear arch carpet and the under-bonnet, that was 18 years ago and it's all still there. I did have a small gap between the insulation and the bonnet stiffners, and the insulation wasn't particularly thick, and was able to use some old bathroom tile edging plastic to wedge under the stiffners to keep the insulation press up against the bonnet while it dried. Others have saod their insulation either overlaps the stiffeners, or is much thicker, and weren't able to do that.
Paul Hunt

I used evostick very successfully with no sign of it failing after many years. Have recently tried a spray on contact trim adhesive on an MGC and that failed quite quickly. I restuck it using evostick and its still ok. To stop it fraying at the edges, buy the material of a roll rather than pre cut and cut it slightly oversize, then you can tuck the edges under the bonnet frame which will help hold it in place.
P J Morgan

My experience of the spray on adhesive availabe now is that is useless. I have used in the past 15/20 years ago like Paul and it worked. Not now though, the stuff has changed so the insulation just falls off after a short while.

Evostik have introduced a silicone based adhesive ( in a tube like the stuff for showers and baths edges) suitable for high temperature applications. Got some for 5.95 from my local Builders Merchant - works very well. Cannot remember the actual product name as I have given the tube to friend for the same job. Will try tomorrow to find the trade name.
G R Wilder

I think the problem with many of these spray can adhesives is that it is thinned down so much so as to be able to spray it, loosing much of its power.
Trevor Harvey

That's a good point about the age of the adhesive, I think a lot of modern glues, garden chemicals and cleaning chemicals etc are nowhere near as effective as they used to be, presumably this is due to environmental considerations??
R. Algie

At long last the Evo-stik product I used sucessfully.

It is called STICKS LIKE all weather adhesive, described as water resistant and heat resistant. It descibes its bond as unaffected by temperatures as high as 100C or -40C.

Available from builders merchants at about 5.95 - usual no connections or ties to Evo-stik.
G R Wilder

I did mine with evo-stick contact adhesive too but had to take the bonnet off to do it on the floor (carpeted). I applied a beed of it to the steel and pressed the felt on. Its been on 6 months and shows no sign of comming off.
Paul Hollingworth

When I replaced my under-bonnet insullation, I used some 3-M spray adhesive. I then put sections of old carpeting over the engine in sequences that would put the hoods weight on the edges. Closed the hood overnight. It's been there a couple of years now.
Dan Robinson

This thread was discussed between 21/11/2008 and 28/11/2008

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