Knocking noise Mazda Axela

stevo2, May 3, 3:48am
Mrs Stevo has an 04 Axela 2300cc auto done bout 120,000km.
It has just developed a knocking noise somewhere up front. At first I thought it was the plastic tray underneath the engine flapping when driving but its not.
The noise is a knocking noise deeper than a CV clicking and is speed dependent.
It starts at about 50kph and gets louder when you take your foot off the gas. It will disappear completely as soon as you touch the brake. It will only happen when steering straight ahead.
If I throw it into neutral, the knocking continues and if I change gear the noise doesn't alter.
As the car gains speed the knocking gets faster and slows down as the car slows (but it gets noisier when slowing). So its definitely not the engine.
She took it to our mechanic on Friday but he couldn't find the problem.
Any ideas?
Cheers Stevo
franc123, May 3, 3:56am
Not being accompanied by vibration of any sort? It sounds very much like an inner CV joint issue, when its being steered the relationship between the inner and outer parts of the joint are changing ever so slightly due to the slight length change occurring in the halfshaft and unworn sections are being presented to each other stopping the noise temporarily. It would also pay to check the brakes and wheel bearings properly too, it may be a case of getting axle stands under the control arms so the weight of the car is on them and spinning it up and having a good listen to it.
stevo2, May 3, 4:00am
No vibration through the pedals or wheel. Interesting that its stops as soon as the brakes are touched
mugenb20b, May 3, 4:40am
Do the drive shafts have vibration dampers? If so, sometimes they come loose and knock about.
bigfatmat1, May 3, 5:38am
Sway bar bushes are a common failure
esprit, May 3, 6:07am
Lower arms are useless on these. Usually the balljoints and inner bushes die on them at about this age, causing the issues you describe.
poppy62, May 3, 9:51am
Sounds like an Inner CV rumble to me. Braking loads up the drive (in reverse so to speak) in that the shaft from the box to the inner cv has any play taken up, as the outer shaft shifts the direction of force. Does that make sense! I'm sure most women would agree with me and they're never wrong.
stevo2, May 3, 7:03pm
Jacked it up yesterday and the wheel bearings and brakes are fine.
Went out for dinner last night 20km away and the noise got a lot louder.
Sounds very much like a retread letting go as they did in the old days (the tyres are fine).
Will put it back up on the ramps again and have another look today. :(
stevo2, May 3, 8:59pm
I've just put it up on ramps and can see no issues with it. All CV boots look good, nothing loose, no oil or gease, no shiney metal. There does seem to be a bit of play when trans is in "Park" and front wheel is spun but I dont know how much play is allowed.
On drivers side, An axle comes from the Trans/Diff for about 300mm then after a bearing goes through the CV down towards the outer CV. I have a feeling the issue is in this area?
I guess I better find a different mechanic as the one I used on Friday couldn't find the problem
NZTools, May 4, 7:54am
Run it on axle stands and use a long screwdriver as a stethoscope to check that support bearing bolted to the engine block. It will be as noisy as.
gmphil, May 4, 8:53am
if the intermediate bearing has gone u should be able to feel it .put it back on stands grab shaft in try move up in down checkin for bearing play
stevo2, May 4, 8:55am
So thats the bearing on the main shaft just before it hits the inner cv?
inkapuka, May 4, 9:13am
Check all the engine mounts common prob
str81, May 4, 9:46am
Check the boot for refugees?
gmphil, May 4, 9:50am
yes the housing is bolted to the block !
dingo011, Feb 13, 12:48am
we bought a ex Avis Mazda 3 which was 12 months old and 20,000. Had the same problem when changing using tiptronic. After 6 trips back to Mazda they finally found a large stone trapped in between the block and engine mount.