Turbo underbonnet heat insulation

[Lowtimer]

Evening, all.

Who else is running a Turbo with no under-bonnet heat insulation, and have you found any disadvantages, such as paint bubbling or softening or discolouration?

Clarks site says that late cars came ex works with no insulating pads fitted. Mine doesn't have any but it is open to question whether this has let to any trouble. At some point my existing bonnet has been heavily dented and consequently has a lot of deep filler in it which has sunk, and the paint isn't very good. But whether the poor paintwork and sinking of the filler are heat-related I can't say.

I am about to change the bonnet for a much better one which hasn't had a cannon-ball dropped on it, and which will shortly be well painted, and would welcome facts and informed opinion on whether there is any case for getting some insulating pads.

 

[jonnyporsche]

Mine doesn't have insulation, there is a bit of blooming near the offside edge of the bonnet but I can't say its due to the heat as it was there when I bought the car, there isn't any bubbling though.

 

[Riverside]

Mine doesn't have any, tbh I thought it was sound insulation. My old 2.7 (same age) had it & was much quieter in-car.

 

[Suffolk944]

Mines without too and with no noticeable effect (other than the rain steaming it off it at times !). My early turbo did have it but was so brittle and flakey I seriously considered trying to get rid.

 

[rav]

I own Jon's old car and as he says the insulation is very brittle.
I will try and remove over this winter but have heard that the glue used is a nightmare to remove.

 

[zcacogp]

If the bonnet has a poor quality filler repair, it is quite likely that the paint is poor as well.

This is more likely to be the cause of the discolouration than excessive heat.


Oli.

 

[scam75]

As Oli says, probably repair quality related. My late car has no insulation and no issues although the rain does fizzle on it if you are at a standstill in a downpour!

Stuart

 

[Trevor68]

I removed mine a few months ago as clumps had started dropping onto the engine and melting [:'(] Clearly 25 years was enough for the foam to glue relationship. The bonnet does get hot as I was paranoid about this for the same reasons as you and check after most journeys. Whether or not this is hotter than when the insulation was in place is hard to say as I didn't have the paranoia so didn't check. Certainly no ill-effects so far though, paint is still looking good.

In case anyone else is thinking of removing, I used the hoover (whilst the wifey was out) to great effect although a lot of the glue remains as does some foam in those hard to reach engine nooks and crannies.

 

[Diver944]

No insulation here either.

The poor paint and filler work will not be as a result of the heat under the bonnet

 

[robwright]

None on mine either. Have often wondered whether applying some would have any noticeable noise reduction effect. I am more keen to reinstate the underlay to the boot carpet. On a trip to Leeds I noticed the car was considerably quieter when the boot was packed full of bags. Amazing how much work that carpet insulation does.

 

[Frenchy]

Early cars had it but not later cars, i do not know what year it stopped being fitted, my 86 has it but not the 88, both bonnets are good paintwise and both cars are tuned = more heat.
I had some after market sound insulation pads which i recently sold on e bay, it looked so much better than the original, i am always cleaning it out of the engine bay whenever i lift the bonnet.
I do not see the advantage of it as well as Porsche who seemed to have stopped fitting it from factory.
Bet it is a complete PITA to remove along with the glue []

 

[George Elliott]

It was a cost and a fire hazard (it was actually sound deadening as Riverside suggests)

The material was soft, and the surface was profiled in a special way, for acoustic reasons.

BMW's of the era also had the material fitted, (non-turbo engines) so you could not hear the tappets after 20,000 miles[].

It also reduced the tinny noise when closing the bonnet, that mattered once upon a time.

George
944t

 

[Lowtimer]

Right then, no insulation going on the replacement bonnet. Thanks all.

 

[George Elliott]

Simon,
would you consider wrapping the turbo and D/P, or better again the manifold and crossover pipe too?

I have not done this, but I reckon the under bonnet temperature would benefit, especially in hot weather and slow traffic. I think it would be difficult to do a tidy job of it, but ceramic coating, see turbo dynamics / zircotec, may be the job.

Whatever, if you blister the bonnet, you are trying too hard!

good luck

George

944t

 

[Lowtimer]

No, I am not planning on wrapping anything.

For the record I haven't blistered the bonnet on the car as it stands. But since I am changing the existing dodgy bonnet for a nice one as part of the body restoration / respray I thought I should get chapter and verse on the insulation.

Once it was stripped, the current bonnet turned out to have a massive amount of filler in it; in the middle, about a foot forward from the windscreen. About the size of my hand and about half an inch deep. From underneath you can't see it because of the double-skinning. Looks like someone has dropped an anvil on it, or some such disaster. Very odd, and no wonder it has sagged a bit, which it would probably have done anyway, though that horrible mass of filler has surely not benefited from being regularly cooked.

Having heard from people here I have no concerns about the nice new one (thank you Elliot Newman) suffering from the under-bonnet heat, since it has the advantage of being made out of steel rather than filler.

Meanwhile the car is making progress. All the major metalwork is done and with luck it might be in primer by the end of next week.