405 TD 'clonk'

Hi Folks,

I recently aquired a '94 405 TD estate, and barring a few minor problems it
seems to be o.k. - it's remarkably rattle and smoke free for a 140k mile
car (I suspect much of the mileage was done on the motorway)

One of the minor problems is a 'clonk' noise when lifting off the
accelerator. I assume that this is a dodgy engine mount or similar,
allowing the engine to move slightly, but anyone with ideas about common
culprits, or sensible ways to diagnose exactly what it might be will win my
eternal gratitude and half a mars bar I found in my desk drawer this
morning.

Cheers,
Albert

 

mmmmmm Mars bar
My first port of call would be the engine mounts, as you say. The top one
normally has far too much play in it IME, and the bottom one can become a
bit too 'squidgy' as it gets old and not really do much. Not sure of the
exact arrangement of the front suspension on a 405, but on a 205 there are 4
bolts (2 each side) that hold the front subframe to the actual underbody
that can come loose/fall out and cause clonking - worth checking that. One
more thing is to check that the turbo isnt banging on the heat shield on the
bulkhead, again this was a 205 problem i had, i'd imagine its quick unlikely
in a 405 due to the extra space, but you never know (although this may
actually be due to worn engine mounts).

Hope that helps

Carl

 

in "Carl Gibbs"

Oh ah.... Hadn't thought about the turbo hitting the heat shield -
presumably if that's happening, then it's going to be stressing the
exhaust quite a bit - bad thing, I reckon.

Cheers Carl - I'll send the Mars bar by PayPal.

Albert

 

In my old 205 it used to clonk when i reversed for that reason. Then i blew
up the engine and put a new one in with a slightly bigger turbo and it just
rested against the sheild. A few precise adjustments with a lump hammer
soon had that sorted! I'd imagine it would stress the heat sheild more,
that would definately give way before the exhuast!

Wooo hoo

 

Hope the mars bar is still up for grabs. Another thing to check is the
bushings in the wishbone as when these are worn excessively they can
make the noise you are talking about. Check if the car has had a
recent service including the replacement of these bushings if not
another way of checking is jacking up the car at the front and check
if there is any play when you push and pull the front wheel out and in
if there is excessive movement then theres your problem.

 

in hig_gti

Carl's got the first half of the mars-bar, so I reckon you're in luck for
the second half I can either paypal it to you or attach it to an
email....

Thanks for the suggestion - when I had the wheels off recently, I did try
to find play in the bushes in the wishbone, the ball-joint and the drop-
links. As far as I could tell, all were apparently clonk-free.
When these bits went on my 205 I could usually feel play, except the bottom
balljoint - I needed to use a crowbar to see movement in that, but there
are none of the other symptoms of bottom ball joint wear, so I don't think
that's it. Hmmm.

Cheers,
Albert

 

Aw well worht a try. Well keep us informed on whats happening wouldn’t
mind finding out whats wrong with it sounds like a real mystery

 

Hi,

I had exactly the same thing on my 94 405 GTX TD estate - and it turned
out that the pivot bolt had fallen out of the alternator, allowing it to nod
forward and touch the radiator. How it didn't damage the plastic radiator
header is beyond me - total luck, I think - fitting a new bolt solved the
problem, and also stopped the engine from looking as though it had broken a
mounting and moved forward onto the radiator all in one piece.

I'll pass on the Mars Bar, nice offer tho.

Philip