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W116 Bonnet Soundproofing Pad Refinement.

Started by kertbache, 24 February 2021, 02:40 PM

kertbache

[/i]The attached images show a removable soundproofing panel that I've installed on my W116, because I have never liked the idea of gluing the sound proofing pad directly to the metal. The base is made of Correx, and it cut precisely so that it springs in to position. It's then held securely by just three stainless steel clips after the pad is glued into position. The clips lock into the bonnet frame. This refinement allows that panel to be replaced in coming years without all the problems of scraping off the old pad, and it also allows me to remove the panel and keep underside of the bonnet in good condition.

AceWolff

~Ace

kertbache

#2
Quote from: AceWolff on 24 February 2021, 11:05 PM
I appreciate this. How can I get one?

Thank you ! ...  I've made this myself. You can buy the Correx sheet and the shaped soundproofing pad online from Ebay.

ptashek

Have you tested it long-term or on longer journeys?

Why ask is because Correx is made from Polypropylene which has a heat deflection temperature of just 100*C, and will get soft not much above it. It's normally extruded at around 200*C. Given the size of the panel, and the vicinity to exhaust manifolds which can easily reach 350*C on the outside surfaces I'd be worried of the whole thing collapsing under its own weight while driving.
1993 "Pearl Blue" W124 280TE
1988 "Arctic White" W124 200T
1979 "Icon Gold" W116 450SE

kertbache

#4
Quote from: ptashek on 25 February 2021, 12:05 PM
Have you tested it long-term or on longer journeys?

Why ask is because Correx is made from Polypropylene which has a heat deflection temperature of just 100*C, and will get soft not much above it. It's normally extruded at around 200*C. Given the size of the panel, and the vicinity to exhaust manifolds which can easily reach 350*C on the outside surfaces I'd be worried of the whole thing collapsing under its own weight while driving.


I installed the panel just before the lock down in the UK last year, so there's not been much chance of many long runs. The foam pad is the standard replacement which would normally be glued into the same position, so I can't see that material being a problem. The Correx panel is heat resistant, but not fire proof obviously. The panel is sprung securely into position, aside from the retaining clips, so I can't see it sagging at all. I have also fitted stainless steel heat deflectors to my manifolds, as attached. I can't imagine the temperature on the underside of the bonnet ever reaching a point where there would be a problem other than an engine fire that would cause the same damage as the standard glued fitting. I will obviously check on it further over a period. But when you think about the amount of heat deflected from the spark plug leads. and how long they survive. I can't see the panel getting anywhere near as hot as some would imagine.

adamb

It seems like a great solution to me. On a related not it would be interesting to record the temperature under the bonnet during a run. I would imagine that temperature build up is highest during summer slow city driving - something that my car has done a lot over its 40+ year lifespan. I have a temperature sensor on my multimeter so may try that out later in the year.

kertbache

Quote from: adamb on 25 February 2021, 04:24 PM
It seems like a great solution to me. On a related not it would be interesting to record the temperature under the bonnet during a run. I would imagine that temperature build up is highest during summer slow city driving - something that my car has done a lot over its 40+ year lifespan. I have a temperature sensor on my multimeter so may try that out later in the year.


That's a good idea !