Return to Website

Citroen Specials Club

This Forum page is provided for members of the Citroen Specials Club to ask for, or respond to offers of, advice or assistance and to offer hints and tips with building and maintaining a Citroen Special (kit or one off special) or similar vehicle. Would members please include their membership number and/or e-mail address so they can be identified. Guests are welcome to place messages but must give a valid e-mail address. Feel free to disguise the address by, for instance, replacing "@" with "*", to avoid spam robots copying it.

Anonymous messages and messages not in keeping with the aims of the forum will be removed.

Note: If there is a closed padlock on the message then no more replies can be added.

If there is the word 'Sticky' then it means the message is important.

 

The Search facility is now active.

Citroen Specials Club
This Forum is Locked
Author
Comment
metalic cracking sound

Hi. I have a problem with a loud metalic cracking sound, its not regular but is evident in second gear when floored,and at between 40 & 50 in top, or under load, I don't think it is in the engine, I have recently changed the gaskets on the manifold and this seems to have made the problem worse! When the manifold was leaking it wasn't too bad. I'm now down to thinking its the exhaust or a gearbox problem,any help would be apreciated, many thanks.

Membership No. not a member yet

Re: metalic cracking sound

Gearboxes generally hammer or knock under load in my experience. I had this happen last spring and had a rebuild by Rick Pembro(gearboxguru). Ken Hanna also does good re-builds. I can recommend both.
Cracking sounds are a new one on me, high-pitch knocking would suggest little end or piston wear. Can't work out how the exhaust manifold gaskets could make it worse but perhaps I'm showing my ignorance here. Difficult to tell without hearing it......

Membership No. 1759

Re: metalic cracking sound

Wonder if it's the engine pinking/detonating and the sound was masked by that leaky manifold?
If it disappears when you back off the throttle, it's almost certain to be your problem.

For a 2CV engine, the rpm where pinking would be most severe would be around 3,750, which is peak torque.

The most common cause is that the ignition timing has too much advance, followed by the mixture being too weak.
Spark plugs with too high a heat range can cause pre-ignition, which is similar to detonation but not the same.
( For A series engines with the cowling removed, I always use NGK B8HS plugs, the original recommendation of B6HS is too hot. )

If this is your problem, it should be addressed as soon as possible, otherwise you're risking partial or complete engine seizure, with melted pistons a possibility in extreme cases.

The ignition timing should be set dynamically, using a strobe to check the maximum ignition advance.
The 'pin in hole' setting only sets the timing at idle and does not guarantee that it's correct when on the road.

http://www.flickr.com/photos/30132857@N06/3732492655/sizes/o/in/photostream/

http://www.flickr.com/photos/30132857@N06/5196126650/sizes/l/in/photostream/


Ken


Ken Lee
Hi. I have a problem with a loud metalic cracking sound, its not regular but is evident in second gear when floored,and at between 40 & 50 in top, or under load, I don't think it is in the engine, I have recently changed the gaskets on the manifold and this seems to have made the problem worse! When the manifold was leaking it wasn't too bad. I'm now down to thinking its the exhaust or a gearbox problem,any help would be apreciated, many thanks.

Membership No. 724

Re: metalic cracking sound

Found the audio version... ;o)

http://www.youtube.com/watch?v=GGJZ6kKzLus

Membership No. 724

Re: metalic cracking sound

Many thanks for your replys to my question, I will invstigate futher. hopefully it will be the timing and not the gearbx as was sugested, once again many thanks..

Membership No. not a member yet