Under bonnet foam liner deterioration. Again..

Started by carl888, 13 January 2014, 11:47 PM


I replaced the underbonnet foam liner on the W116 280 SE in 2008 with the genuine article.  Fast forward to 2014 and it's already falling apart after just 6 years and 11,000 kms.  Contrast that to the W126 280 SE that I did at the same time however that's done 55,000 kms over the same period, and I cannot detect any deterioration so far.

The W126 version is different though, it's a foam backing with what looks like a woven cotton outer layer with a reflective aluminium foil section above the exhaust manifold.  The W116 version is plain square blocked solid foam and somehow the foam cells look bigger than the W126.

Question, this seems like a short lifespan for the W116 liner, does anyone have a similar story?   And....has anyone bought a replacement of late, and does it look like a W126 version nowadays?  I have enclosed pictures of both for reference.  W126 first two images.  Thanks for any information.


I decided to get rid of mine all together. Sorry I can't answer your question exactly how to fix it but I would try to retrofit some padding from a benz that you know holds up well.


Hey Carl, I just bought one for the 123, it's a Febi and exactly the same as your 126 lining in the pic here. My original lining on the 450 se is different again, it's a thicker woven material, sort of like a doormat but not that dense.


Bought a replacement recently from MB for the 450 and it is foam exactly like your photo. The original was the same and falling apart. The 126 looks the best bet and shouldn't it fit?
1974 450SE silver green/bamboo velour/green vinyl roof


The current replacement items are crap, most of them are manufactured in china and I find that rubber products from there have a distinctive smell about them are second rate and do not last. I prefer to use original bits off "parts" cars wherever possible.
116   1978 450SEL 6.9 #  4848
116   1979 450SEL  6.9 # 5884
116   1979 450SEL  6.9 # 6225  SOLD
116   1978 450SEL  6.9 # 5128  SOLD
116   1979 450SEL  6.9 # 5884  SOLD
116   1974 450SEL  DJet

TJ 450

That type of foam is very unlikely to last more than 10 years at best... especially if subjected to high temperatures. It also looks like you've had engine components touching it, and that would not have helped.

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500


Shame they don't last, but they always were fragile!  Totally useless if you intend keeping your engine clean with a pressure wash.  And I guess NOS is just that; OLD.  Unless recently manufactured, it's been sitting on a shelf for years and likely brittle before it was even fitted.  So I say get rid of the damn thing and just repaint the bonnet!  It's only for noise anyway...
1979 6.9 #5541 (Red Bull)
1978 6.9 #4248 (Skye)
1979 6.9 #3686 (Moby Dick)
1978 6.9 #1776 (Dora)
1977 450SEL #7010 white -P
1975 450SEL #8414 gold -P

Squiggle Dog

I've heard that another purpose of the hood pad is to protect the hood from the engine heat, keeping the paint from peeling off. This may be a myth, though, especially on the W116s that came with aluminum hoods, which I imagine wouldn't get as hot.
Stop paying for animal cruelty and slaughter. Go vegan! [url="https://challenge22.com/"]https://challenge22.com/[/url]

1967 W110 Universal Wagon, Euro, Turbo Diesel, Tail Fins, 4 Speed Manual Column Shift, A/C
1980 W116 300SD Turbo Diesel, DB479 Walnut Brown, Sunroof, Heated Seats, 350,000+


Hi Carl

My original bonnet (hood) liner had a type of material backing finish.  As far as I know it was the original (don't know if the V8's were different to the 6's), as it was shaped to fit the under side of the bonnet.  However at some time in the distant past, oil sprayed onto this surface, and despite cleaning it numerous times with detergent, it still wept oil over the entire contents of the often cleaned engine bay. >:(   Naturally it had to go...

The new liner is the same as the one you have, and thought the oil bath situation is now remedied, and despite using two aerosol cans of 3M contact adhesive, the liner is saggy. :'(   Naturally it has to go...

So when I have the bonnet replaced (or repaired) and re-painted due to a rust issue developing on the leading edge, I may consider cutting out some paper templates to fit between the strengthening struts, and apply something like dynamat.  But being a stickler for originality, I suppose in the end I will go with the MB product, use a larger quantity of glue, and replace the said if it becomes oil soaked or deteriorates.

I know the R107's have a different liner that comes in a roll and appears similar to my original material backed number.  Perhaps one could cobble together a new liner from these...Good luck fixing the problem and let us know how it pans out.

Keep 116ing :) 

1979 450SE "Mrs White"
2022 Touareg-R 3.0TSi Hybrid


Carl, ive noticed this too. my 6.9s  liner ha a bit missing too despite limited use and only time.
1979 116 6.9 #6436
2018 213 e63
2011 212 e63
2011 463 g55
2007 211 e500 wagen
1995 124 e320 cabriolet
1983 460 300gd
1981 123 280te


Thanks for all the replies.

After further investigation I think Robertd is on the money.  The reason, the hood pad on the W123 lasted 27 years and 596,000 kms.  Additionally, the hood pad on the above mentioned 280 SE appeared to be the original.  Same with my two W126s.  Finally, all the new rubber firewall grommets that I bought at the same time as the new hood pad...........................................are cracked.  So is it true that the replacement parts are inferior in quality to the originals? 

The tear in mine pictured above was not the result of something rubbing against it, that's the area above the manifold, there is nothing there on a M110.

So it appears the replacement is in fact identical with the one I have (Complete with the small circular cut out for the header tank on the V8 models)

I'm also detailed orientated with that car, so I will replace it with an original.  Some pics BTW of me replacing the old one, just 6 years ago....


Hi Carl

After much searching through my computer I finally found an image of the original hood liner.  You will see the oil stain that kept on contaminating the clean engine bay.  It is quite different to the current ones.  Perhaps the insulation pad for cooler climates is a different spec?


Old oil soaked hood liner - note the different finish of the material

1979 450SE "Mrs White"
2022 Touareg-R 3.0TSi Hybrid

TJ 450

It makes sense that the foam would start to deteriorate first above the exhaust manifolds. Also, if you purchased from Mercedes Benz directly, the part has probably been on the shelf for a while anyway... enough that aging of the foam had probably already commenced.

There are any number of other possible factors here that would lead to this condition.

I would doubt that manufacturing quality would have anything to do with this... it is simply the type of material used, and its primary purpose would be to offer acoustic attenuation from the engine bay, not reflecting heat.

1976 450SEL 6.9 1432
1969 300SEL 6.3 1394
2003 ML500


Update on the hood foam.  It just fell apart after 16,000 kms, turned to dust.  I had to order it from Germany the first time, so I can't believe it had been sitting for 20 years before dispatch.  Wonder if the Selleys adhesive I used is to blame?  Anyway, going to send a sample back to MB as all the other rubber parts I bought at the same time have turned to shit.  Including all the firewall grommets, gee that was fun to replace, not.  They now just look like they did when I bought the car in 2007.  Rubbish spare parts!

Here we go again..............


Use 3M Super Trim Adhesive, that stuff is simply amazing. Use half the can on the hood, and half on the surface you are sticking onto the hood.
Wait a few minutes until it is nice and tacky, then stick that sucker down and never look back.
1977 450 SEL 6.9 - Astralsilber