UNDER BONNET INSULATION

B

Barry Cox

New Member
Hi folks - just had the car resprayed and am well chuffed with it. The guy even sprayed the underneath of the bonnet - so hence this question. Does the under bonnet insulation serve any purpose other than sound deadening? It's just that without the insulation the car isn't noticably noisier and I don't want to put that manky insulation back in and spoil the under bonnet looks unless it serves another important service - ie stopping the bonnet melting??!!
Any ideas gratefully received.
Cheers, Barry :D
 
Hi Barry,

Not to many replies on this one! Personally I t may have two or three benefits, as you say sound deadening, heat protection and possibly vibration? have not really thought about it seriously until now!

George
 
In the absence of any other replies on this...: I'd personally be a bit nervous about engine heat damaging the bonnet paint. But, I've no experience to support or refute, and against this, many "normal" cars of the period seemed to manage perfectly well without insulation. If you chose to replace the insulation there is a second problem of what with? If you can find a standard Rover pad in good condition (which I rather doubt) then no problem. But I have tried using the self adhesive type with a foil face from Woolies and am considerably undewhelmed.

Any other offers?

Chris
 
Many turbo diesels don't have underbonnet felt and they must generate some heat.
Have a feel of the bonnet after the car's been standing after a good run and see if it is hot enough to concern you
Was it sprayed in 2 pack ? Is the underbonnet satin black or body colour ?
 
I have a friend with an MGC fitted with an alloy bonnet.
He repainted the bonnet one weekend and 4 days later we went off on a 300 mile road trip. Half way round there was a big star crack in the middle of the section that he painted due to the heat from the engine.
Moral of the story: use insulation. :p
 
Thanks for your thoughts folks - J.C.s story has got me worried now!! As Dave suggests I'll keep an eye (or hand?) on bonnet temperature. The bonnet is painted with 2 pack and and is satin black underneath. Chris' idea of a suitable adhesive foil insulator could be the way to go - nice and light compared to the old insulation / metal supports and a tad more attractive. My metal supports were so badly corroded that I don't think they have much life left in them anyway.
Thanks again
Barry
 
I took the underbonnet pad off my SD1 for a while and the bonnet used to steam in the wet, so I guess it does get quite hot. I put it back on when a friend of mine said you can worsen pedestrian injuries in a collision because, in an impact a pedestrian's head hitting the bonnet will cause it to deform until it is stopped by the (very hard) top of the engine but the insulation pad would normally absorb some of this impact. I'd imagine that, because it has an alloy bonnet and not much clearance to the top of the engine, this is a particular concern in a P6.
 
Considering the big hard chrome bumper and quite sharp bonnet leading edge, I suspect a lack of under bonnet insulation would be the least of their worries ! :D
 
If its 2K then perhapse you will be alright?
My friend with the CGT was using Celly.

Either way, I would be inclined to leave the bonnet off for a month whilst it cures with a cheap n cheerful bonnet in place so you can still use the car?
 
Don't forget roofs and bonnets get very hot in the summer sun without the paint cracking
May only be a problem if you have loads of layers of old paint/filler under the new paint
2 pack is quite flexihble - it is used on plastic panels albeit with additives
 
All car bonnets get hot after being driven. That is why cats like to sit on them in cold weather. (And leave lots of feetmarks.)
 
the under bonnet 'felt' is both sound deadening and heat resisting. it ought to deflect some heat. will aluminium bonnet we can get paint cracks due to expansion and contraction rates under some circumstances. so best to use NEW heat- shield / sound proofing. the paint under bonnet is black and satin ( non glossy) though most P6 owners tend to repaint as high gloss. even club members who show cars. I stand to be corrected on last point but was assured by man who knows a thing or three about these cars that factory finish under bonnet was dull black not glossy.
 
And the winner of "Revive the oldest thread" award today goes to...........:)

Personally I took my under bonnet felt out and painted it. It weighs almost nothing btw

Richard
 
Was the paint under the bonnet always black? I ask because I've just been rummaging for my best bonnet for a respray and found that one is body colour on both sides and looks like original paint (almond!). It's from a 2200, leading me to wonder if later cars were all like this?
 
can't say if always black but one would assume so for p6. probably part of basic coat /under coat as cheaper than colour painting when going through factory but seems at odds there as the dip paint was in light grey.( as far as I am aware) looking under my cars rear seat and in boot under and behind any covering entire car is a sort of grey. we see modern Ford cars for example having no gloss paint under hoods to save money ( who looks under bonnet when buying new?) therefore one may assume that the black satin engine bay finish was applied as a final coat. ( funny but see lot of show cars at NEC etc that all have high GLOSS black paint hmm) As to under bonnet heat shield/felt this is probably an option for most cars , as again adds costs to cars on a production line so would be fitted where needed only. as P6 at time was deemed an 'executive type car' then both nose reduction .anti vibration and heat reflection ( V8 can give a lot of under bonnet heat) would make sense to use as standard fit. bear in mind aluminium is a fast heat absorber and will apply same heat to paint possibly not good idea to have hot steaming bonnets in rain etc.
I had a Ford v6 mark 4 once no under felt or shielding but we added this ourselves to reduce noise. as we also added extra in car and boot! come to think of it boot insulation on my P6 is rubbish. bit of hardboard and rubber like sides that clip to bodywork. maybe its time I updated that area too. money pit= a P6 ...cannpt comment on rover P4 as outlined by rover100ich . or rover P5? maybe others can add some nuggets of knowledge here.
 
Hi classicalgreen,
I have had both the outside and underside of my bonnet sprayed with 2-pack paint (underside mat black). To date I have not had any issues with the paint and the engine is a 4 litre used as a daily commuter.
That said, I introduced an OEM bonnet scoop and large hole in the bonnet to help remove excess heat from under the bonnet (particularly when idling in traffic jams). With a decent paint job, I would expect your paint work to be ok (the bonnet should not distort enough to be an issue either).
Simon
 

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my 2 bobs worth,
if under bonnet insulation was fitted as standard , it was with a definite purpose that the manufacture intended, rover knew there stuff and did nothing without a purpose.
If your car had it as standard from new then it still needs it now, if you can find a suitable material and replacement.
Go for gold..
Peter
 
I reckon sound insulation was surely Rover's main aim, creating that smooth executive experience
Could the design also have been an attempt to insulate the carbs from extreme cold weather?
A properly executed 2pack paint job should have no problem dealing with engine heat, afterall many engines get painted this way and the finish remains unblemished for years, even right next to headers etc.
Jim
 
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