Citroen goes bang !!

[johnway]

Hello,
Just spoken with my Dad (BX) about a problem he is having. Every now and then there is a load bang from under his car - everything has been checked and no problems found. I remember that my own BX had the same problem which was permanently cured by some kind female T-boning it at a road junction!! I had previously removed and greased the large rear arm bolts without success. My 2002 C5 estate has also developed this strange banging underneath but has just sailed thru the MOT again. The noise either sounds like a loud crack or as if the exhaust is hitting the floor pan. I have heard of other cases but no successes - any ideas people?
Regards,
John.

[DickieG]

Does it occur when you lift off or apply the drive, if so it may be due to a broken engine mount.

[elma]

Something about this on the c2 rings a bell.
I think I read about it in citroneon and its something to do with little ballast weights under the car.
I'll dig it out if I have the magazine here, it may be in north wales though.

[elma]

found it, july 2007 citroenian p 71
look under rear of car
u will see on each side in line with the suspension, mounted to the subframe cylinderical weights mounted on rubber bushes.
Don't know if your cars have these, but worth a look.

The other thing I would look at is the drop links, these bang awfully when they are knackered but its nearly impossible to feel movement in them by rocking the wheel.

I've been all over a xantia looking for a banging noise (I do mean all over, at first I thought it was the exhaust, then the engine, then the lower ball joint, then the gear linkage) which eventually dissapeared when I replaced the 6 month old droplink.

Does the noise seem to come from between the front seats sometimes and sometimes from one of the wheels? If so its almost definetly a droplink.

[johnway]

Hi Guys,
Thanks for the replies. Definitely not engine mounts causing the din. Noise is most frequent when going over bumps so I favour the drop-link suggestion. I have just remembered that my Xantia also developed this annoying crack/bang on occaision. The only Citroens we have owned that have not suffered strange underneath banging noises were AX's. Hmmnn......must be hydro suspension related then? All my problem related cars have over 100,000 miles - Dad's has not done nearly as many miles, but is the oldest. He's off to bang heads with his local Citroen Service Manager tomorrow - poor chap.
Regards,
John.

[elma]

must be hydro suspension related then?

You're dead right, because they go up and down and have a rather long droplink it gets a lot of stress. Also no one I know of make one very well cos its just a crappy droplink, although delphi ones may be ok their balljoints and trackrod ends are the best I've found.

Also you can't feel the play because of the forces exerted on the droplink by the car. I only ever felt it once when the lower balljoint on a droplink had gone. I had the car on intermediate height, the steering turned to the other side and the weight of the car on a jack but the wheel still on the floor.
No point tring to feel it though I've had a lot of knackered droplinks and only ever felt movement in one of them.

Come to think of it I actually need to replace my n/s one. My car knocks as well.

Small word of advice, they come in 10 and 12mm thread diameter.
Measure yours first. I naively just bought a pair and they turned out to be 12mm. They didn't fit my car. Thats why I have one knocking I couldn't get hold of two before I had to travel back to uni. Don't go thinking its ok to put a 10 mm one into a 12mm hole either it really won't last very long.

Have you done them before? Theres definetly a knack. My first one was terribly frustrating.

[RichardW]

"Have you done them before? Theres definetly a knack."

Yep - don't try and undo them with a spanner, just wade in with the angle grinder and cut them off - you will struggle for ages trying to get them undone, then resort to the grinder anyway

[johnway]

Hi again Guys,
Thanks for your assistance - much appreciated. No, I have never attempted to change one of these drop-links (although I do have the right tool to do the job i.e. an angle grinder). I'll let Dad go thru the motions with his BX first as he would get Citroens to do it - well he is over 80!! If the job proves to be a success I will have a think about tackling my C5. I'll keep you posted if you are interested.
Regards,
John.

[johnway]

Hi again Guys,
The penny has just dropped!! I did have the drop-links changed on my Xantia which cured front-end knocking BUT not rear end knocking. Why I didn't remember this earlier is a mystery (maybe my age?) Anyway, the crack/banging noise from the rear end of Dad's BX does sometimes seem to come from under the front seats as well as the back of the car, whereas the noise on my C5 always comes from the back end. I think the mystery is still with us!!
Regards,
John.

[mooseshaver]

Might not be any help, but sometimes my C5 scrapes its mudflaps on the road becuase the back end hasn't come up. Ocasionaly its a bit lazy.

[elma]

Drop link can sound like the back.
I thought mine was an exhaust once.
Try putting your foot against the top of the back tyres and rocking as hard as you can.
Never happened to me, but I've walked away from a few cars as this made a definate donk. That would be a sign of worn out rear arm bearings, probably too the stage of new rear arms needed. Doubt you have this as tyre wear would be noticible (but on the inside maybe you haven't noticed)

I only angle grind the top of the drop links as a flames dodgy up there, the lower one i blow torch til its quite hot and it unscrews easily.
Some people use nut splitters as well, but I've never owned one.

[johnway]

Hi again,
Thanks but we can rule out mud flaps - it's a bang not a scrape, besides Dad's car hasn't got mud flaps and my C5 is always at the right height!! Tyre wear not evident during complete under car inspection at garage - I will be going to see his BX tomorrow so shall have a go at Elma's rocking suggestion. I remember speaking with a former C5 owner a year or so ago who bought one from new - he said that his car sounded like someone was hitting it with a hammer under the car within the 1st year - Citroen changed this and changed that under warranty but to no avail, so he sold it!! This must be a common problem -surely?
Regards,
John.

[slim123]

Cracking and banging at the back !!!!!!!

Sounds like rear suspension arm bearings to me.

A common fault found on CX, BX, XM, Xantia and now the C5

Check the rear arms and especialy the rear tyres for wearing on the inside of the treads, you wont allways find any play when they are wearing, but as they get worse the wheel will tend to lean in at the top and out at the bottem.

Regards
Slim.

[ncoll]

I've got the same problem with my 2.2 estate. Cant hear it with the windows closed, makes noise the when going over speed bumps (back end of car only) and if I lay it heavily into corners. had the rear wheels of and de-pressurised system and checked rear arms for play even wedged a 4x2 under the arm and across a brick and belted the 4x2 with a sledge hammer but could not re-produce the noise. It passed the Mot this week, so I give until I find a fix or something falls off!

[jeremy]

Banging from the back on a BX sounds like rear arm bearings - but also worth checking the exhaust - are all the mounts still attached to the bodywork - especially the one right at the back? - also the spare wheel and its cradle.

Manifold/frontpipe joint can sieze - causing strange untraceable noises. Rear subframe mounts are not usually a cause of problems but are worth checking as is the rear subframe just in case someone has jacked the car by the bar under the strut and distorted it.