Knocking on Xantia not picked up on MOT

LeeDJC · Post by **LeeDJC** » 01 Jul 2006, 22:14

My xantia just flew through it's MOT (see other thread), but there is still a knocking when going over bumps. Sounds a little like the drop links (just recently replaced), but louder and a bit heavier. I can't feel it through the pedals or steering wheel. Also it sounds the same whether the n/s or o/s wheel hits a bump

I assumed that it would be picked up in the MOT, so hadn't got it checked out yet, but no mention was made of it.

Would it be (clutching at straws now) anything to do with strut tops or bearings? I'm just about to replace these and killing two birds with one stone would be great!

Cheers,
Lee

Post by **Peter.N.** » 01 Jul 2006, 22:49

I have a similar noise on my XM, its in the front n/s suspension, sounds just like a drop link but I have replaced it twice! (forgotton I had allready replaced it, senior moment!). I cant find any play in anything so will be interested in the MOT results!.

Mandrake · Post by **Mandrake** » 01 Jul 2006, 23:36

One source of "phantom knocking" in the suspension is if there is air being pumped into the hydraulic system.

If you're 100% sure all the balljoints, bushes etc are ok, and it clonks on broken surfaces, that could be what it is...

All the bushes and balljoints on my Xantia are fine (replaced the only droplink which had any wear) and I have an intermitantly varying air leak on the pump, and some days it knocks and clonks over broken surfaces like the droplinks are stuffed, and other days its perfectly quiet!!

(Obviously a true mechanical problem causing clonking would not come and go at random, and when it is clonking its usually all 4 wheels which clonk over the bumps, or at least both front wheels, rather than just one individual wheel)

Regards,
Simon

LeeDJC · Post by **LeeDJC** » 01 Jul 2006, 23:43

Mandrake wrote:One source of "phantom knocking" in the suspension is if there is air being pumped into the hydraulic system.

If you're 100% sure all the balljoints, bushes etc are ok, and it clonks on broken surfaces, that could be what it is...

All the bushes and balljoints on my Xantia are fine (replaced the only droplink which had any wear) and I have an intermitantly varying air leak on the pump, and some days it knocks and clonks over broken surfaces like the droplinks are stuffed, and other days its perfectly quiet!!

(Obviously a true mechanical problem causing clonking would not come and go at random, and when it is clonking its usually all 4 wheels which clonk over the bumps, or at least both front wheels, rather than just one individual wheel)

Regards,
Simon

I've been under the car and checked everything that I can, but can't find anything loose.

It only happens from the front of the car, but whichever wheel hits the potholes/drain covers etc the sound still seems to originate from the same place and also sounds the same.

It doesn 't seem to make any difference as to how harsh the bump is, the sound still seems pretty much the same.

Also, now you come to mention it, it's pretty much always there, but it does seem to come and go a bit.

I'm going drain and put some hydraflush in the system when I do the strut tops and also bleed the brakes, so if that doesn't fix it, it's back to the drawing board!!

Homer · Post by **Homer** » 02 Jul 2006, 08:40

It's not the handbrake cables is it?

LeeDJC · Post by **LeeDJC** » 02 Jul 2006, 09:04

Homer wrote:It's not the handbrake cables is it?

Do you mean by not being clipped in properly?

jeremy · Post by **jeremy** » 02 Jul 2006, 09:53

Have a good look at the inner wishbone bushes on the front suspension - just found one on my Bx has gone and think its the knock I've been looking for for ages. - thought it would fail the MOT on them 2 years ago! and had new ones in the back of the car.

AndersDK · Post by **AndersDK** » 02 Jul 2006, 12:33

There is one single test I always do to find dodgy components in the front suspension - never failed :
Grap the top of the tyre both hands (gloves are OK

) - then rock the complete car sidewards as violent you can. Its important to sort of "catching the wave" such you get the largest possible excursions.
Some practice - and you can immediately diagnose swivel joints, wheel bearings, droplinks, ARB bushings and control arm bushings.

Note : its not a test for Mr peabody - you got to exhaustive put in your Umphh and weight in this test

Warning : do not raise your body too sudden after this test

LeeDJC · Post by **LeeDJC** » 02 Jul 2006, 13:10

Is this with the suspension on high, with the car on the ground, or with it up on stands?

vanny · Post by **vanny** » 02 Jul 2006, 16:39

Have you had a look at your engien mounts?

I had an annoying knock/crack that only seemed to occur when going over speed bumps and pot holes, got to be a sticking drop link then! Wrong, changed that for a complete new unit and nothing changed. Had already done the bottom ball joint, and checked everything was free and so on, still nothing!

Left it a good 5000 miles mostly towing and it didnt seem to get much worse. Having now changed the bottom engine mount, its cured, silent as a mouse

My next suspicion was going to be the bottom arm bushes, hence why i put of the job for 5000 miles but now it seems just fine and dandy!

AndersDK · Post by **AndersDK** » 02 Jul 2006, 17:51

LeeDJC wrote:Is this with the suspension on high, with the car on the ground, or with it up on stands?

Car in normal height & weight on wheels - i.e. engine idle.
Its one of those standard test you can do immediately - as a DIY'er out there looking on a possible new bargain.
Note : works on the rear as well.

LeeDJC · Post by **LeeDJC** » 02 Jul 2006, 19:12

AndersDK wrote:
LeeDJC wrote:Is this with the suspension on high, with the car on the ground, or with it up on stands?
Car in normal height & weight on wheels - i.e. engine idle.
Its one of those standard test you can do immediately - as a DIY'er out there looking on a possible new bargain.
Note : works on the rear as well.

OK, done that. TBH I was slightly sceptical, but it worked!! Now, just to identify that knock!

Basically it happens when the car gets to the bottom of the "bounce". It's a quick double knock. This is happening when pulling on the top of the wheel. You get the knock on both sides, slightly louder on the left hand side than the right.

Any ideas anyone?

deian · Post by **deian** » 02 Jul 2006, 19:19

i have those symptoms too... and vanny, i am gonna change my bottom engine mount too (as u already know from my thread), maybe it will help, if that sorts my clonks out i will leave the spheres, i may change all 4 spheres after the mount.

AndersDK · Post by **AndersDK** » 02 Jul 2006, 19:46

LeeDJC wrote:
AndersDK wrote:
LeeDJC wrote:Is this with the suspension on high, with the car on the ground, or with it up on stands?
Car in normal height & weight on wheels - i.e. engine idle.
Its one of those standard test you can do immediately - as a DIY'er out there looking on a possible new bargain.
Note : works on the rear as well.
OK, done that. TBH I was slightly sceptical, but it worked!! Now, just to identify that knock!

Basically it happens when the car gets to the bottom of the "bounce". It's a quick double knock. This is happening when pulling on the top of the wheel. You get the knock on both sides, slightly louder on the left hand side than the right.

Any ideas anyone?

You didn't quite get my point then - as you only did half the job until now

You're supposed to persuade those indicating knocks/noises - by grapping on the lower control arm - the ARB - the driveaxle - etc. etc. one hand while rocking with the other hand.
Its dead easy

You just have to practice a bit

LeeDJC · Post by **LeeDJC** » 02 Jul 2006, 19:48

AndersDK wrote:
LeeDJC wrote:
AndersDK wrote:Car in normal height & weight on wheels - i.e. engine idle.
Its one of those standard test you can do immediately - as a DIY'er out there looking on a possible new bargain.
Note : works on the rear as well.
OK, done that. TBH I was slightly sceptical, but it worked!! Now, just to identify that knock!

Basically it happens when the car gets to the bottom of the "bounce". It's a quick double knock. This is happening when pulling on the top of the wheel. You get the knock on both sides, slightly louder on the left hand side than the right.

Any ideas anyone?
You didn't quite get my point then - as you only did half the job until now
You're supposed to persuade those indicating knocks/noises - by grapping on the lower control arm - the ARB - the driveaxle - etc. etc. one hand while rocking with the other hand.
Its dead easy You just have to practice a bit

Aaaaahh. Got you. Sounds stupid not doing it now!! Will go out and try in a mo!