Bonnet insulation / sound deadening pad?

[Grizzly]

My 68 S4 certainly had the felt matting on the underside of the bonnet when I first got it. It was soaked in oil and dirt and falling off so if removed it soon after I go the car. I use material like listed below on the bonnet section directly above the exhaust these days which is the only area that gets significantly hot. I glue it on using the high temperature silicone gasket forming material ( the red or copper coloured ones) as this sticks it on well but it is easy to remove if you want to renew the heat shield. I use the same material on the side of the foot well and on the section of firewall behind the exhaust.

http://www.thermotec.com/products/16850 ... rrier.html

cheers
Rohan

I was a bit paranoid about heat round the exhaust area on mine as when i repaired/painted the engine bay the grp in next to the exhaust (side of the foot well) had dried out and burnt away to the degree there was a hole. So now i have a Ceramic coated manifold and ZircoFlex 2 protecting the grp in that area.

Now the bonnet had the Felt still on with a big burn right over the exhaust but the original paint was fairly good on the Bonnet, but more importantly the GRP was good when i removed the original paint which means i'll be defiantly putting some thing back.

[69S4]

If it isn't broken Stuart, why are you planning on "fixing" it ?

Ralph.

Probably because ignorance was bliss (before I read this post) Now that I know the bonnet is living on borrowed time I have an overwhelming psychological need to do something about it.

Actually, underbonnet heat has been a bugbear for some time and before the bonnet was repainted about 8-9 yrs ago you could just see a very slight yellowing of the (original) white paint on the exhaust side. I used to run with wrapped manifold pipes to try and keep the heat levels down but not at present (they rot under the wrapping) so other options would be useful.

[bill308]

It's a good idea to protect the bonnet from heat. Heat accelerates fiberglass creep or distortion and can shorten paint life.

Super insulators have traditionally been made up of a stack of separated, reflective coatings. Absent an Aerogel product, I think Rohan has the right idea. For the bonnet, I'd consider several layers of the material he is recommending.

Bill

[pereirac]

My Sprint never had anything either.. as far as I am aware..It's a tight enough fit so I didn't think there was even room...

[pharriso]

OK... I am yet to be convinced that any Elan came from the factory with insulation on the underside of the Bonnet/Hood!

Can anyone post a picture showing insulation in a road test or Lotus photograph?

Phil aka hood insulation skeptic

[elansprint71]

If it came from the factory, it would be in the parts book. It isn't. If it came in an Elan kit, it would have been there. It wasn't.
If you want to fit some modern reflective heat insulation... it seems to consist of tinfoil and, um, woven fibre-glass matting.
Add more lightness, just fit the tinfoil- you could put holes in it to get the full 26/R effect.

[Grizzly]

Thing is the Fiber mat i removed was exactly the same stuff as the pad between the chassis - Body and i don't mean similar, when i bagged it up i made a note that the colour strands where the same and the rubber coating was the same texture (if i decided to replace it because it was in a bad way)

I can imagine it getting ripped off very quickly as even my cars previous owner said it drove him mad but 100% no doubt about it the factory fitted it. The thing is it was a bit dumb as the felt was quite heavy and the bonnet has reinforcing channels which meant the pad was in an unnatural position so it separated and drooped, so on mine it was hanging down touching the engine and when i opened the bonnet it was only stuck to the Drivers side so flopped about (passenger side was just wedged in position and kept falling down).

Thing is if i didn't know the guy i bought my car from i'd say yes maybe fitted later but i know the Guy was a Flight Test Engineer for BAE for many years and it gave him almost OCD for logging everything in the cars diary that broke or fell off (he even logged Fuel and oil put in it what make and where he bought it), i have a FULL Log of parts he fitted to the car in the time he owned it (no part that fell off was ever thrown away, i have envelopes with random washers he found on the road next to his car he's kept since the 70's). This is why i know my car is/Was Original.

[Grizzly]

My 68 S4 certainly had the felt matting on the underside of the bonnet when I first got it. It was soaked in oil and dirt and falling off so i removed it soon after I got the car.

Sums it up nicely...........

http://s248.photobucket.com/albums/gg17 ... 1263-1.jpg

http://s248.photobucket.com/albums/gg17 ... 101270.jpg

I know these are earlier and have the bigger rad that said mine was very similar but it stopped at the foam for the rad. When mine was pushed up into position properly from afar it looked like the back of the bonnet had been stone chipped but when you get close up you notice the Grp reinforcing bars look almost flat.

[RichC]

I'm resurrecting this posting as I've removed the aged black coated underlay -type mat for my respray ...
I thought I'd find some nice classy stuff to put on instead but haven't found anything yet so opted to spend less than ?12 inc pp for this .....
http://www.ebay.co.uk/itm/1-2mx1mx5mm-A ... Swv9hW3qKm

I expect it might not last very long...................
anyone got a better solution??
cherrs
RichC

[Grizzly]

Bit of an update, i fitted a Dynamat Hoodliner http://dynamateurope.com/product/hoodliner/ was expensive (?50) but i lost allot of that cost through work

First thing i noticed was the Bonnet after a run was cold to the touch (before around the Exhaust area it was uncomfortably warm especially if i had been caught in traffic) a bit of a knock on effect that some may not like is the engine noise is quite dramatically reduced too.

I would have preferred some thing black but the self adhesive backing sticks well as long as the inside of your bonnet is clean etc. I did think it may droop as the liner is quite thick but the inside of my Bonnet is quite smooth and i've had no issues upto now.

[1owner69Elan]

I hadn't read this topic the first time around but will just add a further note:

My 1969 S4 SE DHC (Federal) never had a bonnet liner. I picked the car up myself at the factory in the UK and have had it for the last 47 years here in California. No previous ownership to conjecture about.

The only thing affixed to my bonnet (hood) is a foam strip running along where the top of the radiator is. The foam is still there, although in poor shape where the radiator cap hits it.

I also have the original paint on the hood (bonnet) and there is no apparent yellowing (cirrus white car) due to exhaust manifold heat nor really any other blistering or apparent heat damage. And I am not in a cooler climate (California) to help under bonnet temperatures.

So, a bonnet liner might not be a bad thing to add - but it wasn't there originally, at least on my car. I also note no mention of it in the original parts catalog (though the foam strip above is also not noted). Nor is there mention of it in Brian Buckland's book (that I could find).

I also think that a liner, fitted to my non-flat S4 hood with the so-called "power bulge", might be difficult to fit. Also, clearance with the over the cam cover throttle cable (LHD car) might may have clearance problems with a liner.

So, in my case, I probably won't be adding a liner.

[Grizzly]

I'm not saying every one rush out and buy one, if you feel it's not needed then don't fit one. Both my +2 and S4/Sprint 100% defiantly did have a felt pad (exactly the same as the felt that goes on the Trans tunnel between the chassis and Body) but i can see why every one pulled it off as mine was sagging badly with bits everywhere.

TBH i'm more surprised you have a Original paint Elan in California, all the paint on mine was cracking and falling off and it sat in a nice cool dry garage since 1984 you must really look after it.



I had a chat with our GPR suppliers this morning and they seemed to think it's more the rapid temp change that causes a problem in old GRP, the sun can warp large fresh panels but if its cold on one side and hot on the other it will start to de-laminate, seems the air (and moisture in that air) trapped in bubbles around the Matting expands at a different rate to the grp/resin so the idea is to keep the ambient and under bonnet temps as close as possible. (or so i'm told)

[rcombs]

Thought I would put my 2 cents in. My 67 SE was purchased from the original owner and it doesn't appear to have ever had a pad. The bottom of the hood "bonnet" is black and shows no sign of old glued or padding. But as has been stated, every one of these cars is probably a little different. I can see where it would help with heat though.

Rick

[saildrive2001]

69 S4 I have had from new, no padding.

[Grizzly]

Should know by now then Lotus do odd things.

I know the pad isn't in the Service parts list but then neither is the Trans Tunnel Felt pad or the chassis Pad over the diff.

I get many didn't have the Felt pad but some did.