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bonnet shake ?

Not Anumber - 21/5/12 at 03:37 PM

Whats the cure for bonnet shake ? I decided to repair and use the thicker of the 2 fibreglass bonnets which if anything is now about 20% heavier and more rigid than before. Even secured (tightly) with 6 catches the bonnet shakes and wobbles visibly when the car is being driven. The bonnet has plastic edge strips on the front and back edges but has plenty (too much) movement at the top where it meets the scuttle. Would a rubber strip help here ?

James - 21/5/12 at 03:54 PM

quote:
Originally posted by Not Anumber
Whats the cure for bonnet shake ? I decided to repair and use the thicker of the 2 fibreglass bonnets which if anything is now about 20% heavier and more rigid than before. Even secured (tightly) with 6 catches the bonnet shakes and wobbles visibly when the car is being driven. The bonnet has plastic edge strips on the front and back edges but has plenty (too much) movement at the top where it meets the scuttle. Would a rubber strip help here ?

If it's the same as my ali bonnet where it would jump up and down in the middle at the scuttle then it's caused by air pressurising the engine bay. Not healthy as it means your hot air isn't getting out.

I proved this was the problem with mine by temporarily removing the firewall panel so the engine air blew out through the cockpit.

The permanent fix is holes in the bonnet or side panels to let the air out!

Cheers,
James

Not Anumber - 21/5/12 at 04:48 PM

I hadnt thought of that and was just assuming vibration. There is a hole in the bonnet round the air filter but nothing on the other side. The side panels stop short of the wishbones and there is no panelling under the nose or engine compartment so there must be a lot of air getting in that can't find a way out. It doesnt immediately appear to be heat related in that it does it as soon as i start driving, before the car has had a chance to warm up.
Should i look at panelling under the nose and front of the engine bay too or just some holes in the bonnet to let it out ?

bobinspain - 21/5/12 at 05:34 PM

Mine's a standard factory car with bonnet scoop. No extra holes.
No problems with bonnet shake, even though there was some 'play.'
Took the play out of the equation with draught excluder in matching colour.
Snug as a bug now and virtually undetectable.

austin man - 21/5/12 at 08:23 PM

I have a rubber / foam strip on the front and rear of mine and also fitted vented side panels no shake

renetom - 22/5/12 at 07:58 AM

Hi
We put 4 X 70mm round grilles on each side
See our photo archive.

40inches - 22/5/12 at 08:18 AM

Closed cell foam strips and vents on side panels, and back of bonnet on mine.

Vents

blakep82 - 22/5/12 at 09:51 AM

if its just vibration, you could fibreglass some paper rope on the inside of the bonnet, sort of up and over. gives strengthening ridges to help stop it flexing.
if its air pressure causing it to flap, then that might break the bonnet quicker, so releasing the air is the way as said above

Not Anumber - 24/5/12 at 10:36 AM

Thanks for the advice. A length of thin rubber strip stuck to the edge of the scuttle solved it immediately. Solid as a rock now and it improved the tension on the bonnet clips at the same time.