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My wifes manual car had a stange knocking/flapping noise at the front during initial takeoff at low revs, and when coasting down in high gear to vey low revs, say <25mph in top. Something was vibrating in sympathy with the engine when the revs/load at low speed reached a critical resonance point! :?
I initially thought of engine mountings going :shock: or something else loose in the engine compartment however I got her to pull away a few times while I stood next to the car, and found it was the bonnet/hood vibrating.
In the engine compartment when the bonnet/hood is closed it makes contact with the body at about four points at the front, and has rubber bump stops, two on the bonnet and two on the chassis which are supposed to cushion it. Mine were all in situ but examining the metal area's opposite to the bump stops showed worn paint, bare metal and obvious signs things had been shaking. The rubber also probably hardens with age making it less flexible.
Now you could adjust the bonnet release mechanism to take up any slack in the system and make it a tighter fit, but the bonnet release is a bit fiddly, and quite difficult to position without a lot of experimenting to get a better fit (I tried it so you don't have too
). You do not want it too tight or you need excessive force to close the bonnet, and might dent it Pushing down on the bonnet when shut did not reveal much slack anyway in my case.
So I used some self adhesive door seal insulation cut into 4 small 1" square pieces and stuck to the chassis/bonnet opposite the rubber stops. This is only 5mm thick and very soft, it took up any slack resolving the problem at once with only a very slight increase in bonnet shutting force reqd.
Easy.
Peter
I initially thought of engine mountings going :shock: or something else loose in the engine compartment however I got her to pull away a few times while I stood next to the car, and found it was the bonnet/hood vibrating.
In the engine compartment when the bonnet/hood is closed it makes contact with the body at about four points at the front, and has rubber bump stops, two on the bonnet and two on the chassis which are supposed to cushion it. Mine were all in situ but examining the metal area's opposite to the bump stops showed worn paint, bare metal and obvious signs things had been shaking. The rubber also probably hardens with age making it less flexible.
Now you could adjust the bonnet release mechanism to take up any slack in the system and make it a tighter fit, but the bonnet release is a bit fiddly, and quite difficult to position without a lot of experimenting to get a better fit (I tried it so you don't have too
). You do not want it too tight or you need excessive force to close the bonnet, and might dent it Pushing down on the bonnet when shut did not reveal much slack anyway in my case.So I used some self adhesive door seal insulation cut into 4 small 1" square pieces and stuck to the chassis/bonnet opposite the rubber stops. This is only 5mm thick and very soft, it took up any slack resolving the problem at once with only a very slight increase in bonnet shutting force reqd.
Easy.
Peter
