Technical Knocking with weight in the back

[Archie Croft]

Hi, I have a 55 plate 4x4 - Phoebe. You may have seen her at Fiats and Friends, identifiable by her shonky wipers which I'm pleased to say are now back to their rightful resting position.

I have an ongoing knocking issue and have come here for ideas, if anyone has experienced something similar:

There is a distinctive knocking sound which gets worse when taking corners and particularly when there is weight in the back.

She has been in to several garages and it's nothing obvious - bearings seem fine, not seeming to be a suspension bush issue. It was recently thoroughly checked over and it also doesn't appear to be a seals or gaiters issue which was my best bet.

I'd like to know if you've had anything similar or could maybe suggest a few more troubleshooting ideas that I can throw at a mechanic!?

She's done about 6000 miles on the knocking and nothing catastrophic has happened, yet.

Thanks in advance for any insights!

 

[koalar]

Before you go any further test the viscose coupling

I don't think it will be the problem, fingers crossed



But if it's seized solid, is not an easy repair and most parts fitted latter will not last long


Let's get this simple test out if the way first so we can move forwards

Is it a regular knocking sound, at a set frequency

 

[Archie Croft]

Before you go any further test the viscose coupling

I don't think it will be the problem, fingers crossed



But if it's seized solid, is not an easy repair and most parts fitted latter will not last long


Let's get this simple test out if the way first so we can move forwards

Is it a regular knocking sound, at a set frequency

Ah interesting, thanks. I will mention this, as most of the obvious moving parts have been ruled out.

Yes, a regular sound. I thought at first it was a bearing because of the rhythm. It increases in frequency when cornering and gets louder with weight in the back.

Definitely a knock rather than a rattle I'd say.

 

[koalar]

Is it turning on particularly direction or both

 

[Archie Croft]

Is it turning on particularly direction or both

Turning right - particularly noticeable on roundabouts.

 

[portland_bill]

I've not got experience of the 4x4, but on my 1.2 the exhaust was knocking on the suspension.
The exhaust mounting rubbers have a nylon band around them, so that the exhaust is not lost when the rubber deteriorates. This can mask the deteriorated rubber when checking, but will still allow greater movement, allowing it to hit stuff.
Grovel underneath, and wriggle the exhust while checking the mountings very carefully. Remove each mounting to check. See if the exhaust shows any witness marks from hitting stuff.

On the 2wd, the rear shocks tend to knock a little. They were specially designed with 11mm eyes on 10mm bolts, pure genius.

 

[koalar]

Regularly frequency noise

Only in one direction

Worse when loaded

Sounds typical of a wheel bearing

Which normally alters frequency with road speed

Not the only cause but that's what I would check if the viscose coupling passes

 

[Archie Croft]

Thanks both for your help - I'll look closer at the bearing and exhaust mounting solutions and see if I can get a fix.

When listening it does just sound like something has a little give or play in it.

I've got my fingers crossed it's a simple and cheap fix. And now the wipers have stopped deciding 'home' is in the middle of the windscreen she's in otherwise pretty sound shape.

 

[koalar]

Take a few seconds of video on your phone and post it

It's hard to describe a sound

I can't see it being the brakes, as it's effected by weight but being a 4x4 it will have disc brakes

While it's making the noise, just lightly press on the brake, does the sound alter

 

[portland_bill]

I've got my fingers crossed it's a simple and cheap fix. And now the wipers have stopped deciding 'home' is in the middle of the windscreen she's in otherwise pretty sound shape.

Check the chamber below the windscreen where the wipers are. It can fill with water if the drain tubes are blocked with rotting leaves. That can get into the wiper motor, and also into the car. There are two black drain tubes, need squeezing to clear.

 

[Archie Croft]

Check the chamber below the windscreen where the wipers are. It can fill with water if the drain tubes are blocked with rotting leaves. That can get into the wiper motor, and also into the car. There are two black drain tubes, need squeezing to clear.

Yes, thanks! I got all sorts out gunk out of there!

I think the adjustment the mechanic did was fairly simple. The motor worked perfectly and the intermittent timing etc., she just panicked going around a tight bend once and from then on out decided 'home' was in front of my eyes.

 

[Archie Croft]

Take a few seconds of video on your phone and post it

It's hard to describe a sound

I can't see it being the brakes, as it's effected by weight but being a 4x4 it will have disc brakes

While it's making the noise, just lightly press on the brake, does the sound alter

Great suggestion thanks. I'll be back with my car next week so I'll see if I can pick up the sound on video.

 

[DaveMcT]

I have had an annoying knock from the LH front usually (but not always) when taking right turns. I pushed and pulled at the suspension joints on the floor and on axle stands but found nothing. I removed the LH front strut thinking it was the top spring seat. Reseated the spring and fitted a replacement top mount and bearing. No change.

Then it failed MOT - the bottom ball joint pin was moving in the steering hub clamp. Obviously an immediate fail. The drivers side had a cautionary note of some wear on the ball joint but not excessive. It passed fine last year and has not done many miles since. But whatever.

I got it home and spent an hour trying to replicate the issue. Eventually I found a suitable lever (pry bar) that would lift the hub and found the pin was clearly not being clamped. It's really awkward with the job near the floor. The clamp bolt was very tight and the clamping slot was not dirty. The pin could not fall out but was clearly not being gripped.

I made a shim from 0.7mm brass and moulded it around a 15mm OD socket. Some heat allowed me to flange one end of the shim so it would not damage the ball joint rubber boot. This was awkward to fit but I got it in opposite to the clamp slot. It worked and the "pin" stopped moving. Once properly retained, it showed the LHS ball joint was slightly more worn than the RHS so I have replaced both bottom arms. The shim is working fine. No more noises on small traffic islands or over corrugated surfaces.

So now what? Replace the hub/knuckle only to find the same problem? A brand new one will cost silly money.

 

[koalar]

Knuckle to ball joints clearance it's a tight fit

You normally have to tap them in even on cars with high milage

The fact you can fit a 0.7mm shim in is ridiculous, to be able to get a 0.7mm shim in half way round it must be approximately 1mm over size

I'd fix it properly, and replace which ever part is under or over sized

As to why it's happened, we don't have enough information, my guess is someone in the past has used an air chisel to open the gap, causing not to clamp properly when refitting and constantly banging has elongated the hole

Could just as easily be a fake suspension arm with the wrong diameter joint