406oc.co.uk

The wife's car has in the past month had a new crankshaft pulley, alternator, aux belt, top engine mount (with new torque damper), bottom engine mount, and complete exhaust from flexi-hose back. All the important rubber bits, and bits destroyed by knackered rubber bits. Yet there's still a nasty increase in vibration under torque, especially at idle revs.

We've just been out to have a look at it before buying a new gearbox mount tomorrow, and ran through some tests - handbrake on, let clutch out until it moves... and it looks solid! No visible vibration at all, just a slight rotation under torque as expected. What?

So I shut the bonnet, and hear a new vibrating noise. Put my hand on it towards the n/s and it stops With the wife driving back onto our drive, I put my hand on the bonnet and it all gets a load quieter!

So there you go! When investigating engine vibration, check the bonnet ain't causing it!!!

Just saved ourselves £40 for a new mount I'll "fix" it tomorrow with some blu-tac, duct tape or sugru

Yes, I had the same issue - though even with the bonnet no longer shaking the rest of the car to pieces, I still have an annoying steering wheel rattle

mjb wrote:
So I shut the bonnet, and hear a new vibrating noise. Put my hand on it towards the n/s and it stops With the wife driving back onto our drive, I put my hand on the bonnet and it all gets a load quieter!

So there you go! When investigating engine vibration, check the bonnet ain't causing it!!!

Just saved ourselves £40 for a new mount I'll "fix" it tomorrow with some blu-tac, duct tape or sugru

You know there are rubber bonnet adjusters on the front panel to make the bonnet fit tighter and eliminate vibrations, don't you?

They are about an inch or less in diameter with slots, you turn the rubber so the slots move the rubber closer to the bonnet.

jasper5 wrote:You know there are rubber bonnet adjusters on the front panel to make the bonnet fit tighter and eliminate vibrations, don't you?

They are about an inch or less in diameter with slots, you turn the rubber so the slots move the rubber closer to the bonnet.

I do now... I'll have a look at that when I get home - cheers

Be well worth a try, all cars have them, like a rubber stopper with a coarse thread to it.

jasper5 wrote:[You know there are rubber bonnet adjusters on the front panel to make the bonnet fit tighter and eliminate vibrations, don't you?

They are about an inch or less in diameter with slots, you turn the rubber so the slots move the rubber closer to the bonnet.

On the 406 - D9 saloon/estate at least, the rubber feet are on the body, just behind the lights. You use mole grips to un-stick the rubber bit, then pull it off. Underneath is a Torx T30 screw with a 10mm nut to lock it. Generously apply WD40, adjust to taste, tighten up the locking nut, then push the rubber back on.

To test the fit, I smeared a bit of engine oil over the top of the rubbers then shut the bonnet as carefully as I could. Upon re-opening, the oil was nicely transferred to the bonnet, so I'm happy

mjb wrote:

jasper5 wrote:[You know there are rubber bonnet adjusters on the front panel to make the bonnet fit tighter and eliminate vibrations, don't you?

They are about an inch or less in diameter with slots, you turn the rubber so the slots move the rubber closer to the bonnet.

On the 406 - D9 saloon/estate at least, the rubber feet are on the body, just behind the lights. You use mole grips to un-stick the rubber bit, then pull it off. Underneath is a Torx T30 screw with a 10mm nut to lock it. Generously apply WD40, adjust to taste, tighten up the locking nut, then push the rubber back on.

To test the fit, I smeared a bit of engine oil over the top of the rubbers then shut the bonnet as carefully as I could. Upon re-opening, the oil was nicely transferred to the bonnet, so I'm happy

Ah, right, yours has that type, most have the rubber only that screws up or down in the slot.

An alternative is to move the bonnet locking catch down a bit to tighten down the bonnet.