Continuous knocking from left side of car. Advice appreciated

[MarkB1983]

Hi all,

Apologies for my diagnosis being slightly vague but I have an issue with my GS450h with 105k which has an incessant knocking noise coming from the front left side of the car. My first thought was exhaust bracket, as the rattling sounds like metal on metal however the exhaust is fine, with no movement. My next guess would be something suspension related however it has recently passed an MOT with no advisories. It had been suggested to me by a local garage that it could be something on the top suspension mount causing the noise, as it sounds like it is coming from that area, however another garage said it might be the differential, however neither garage were willing to investigate further, saying it would be main dealer. Has anyone had a similar experience of noise and what it could be? 

[AmbroseJohn]

I have a knocking noise too. The car has been serviced by Lexus twice since I've owned it and they can find no fault, in fact they don't even recognise there's a problem. The car has also been MOTd twice at my local garage with no problems.

 

I thought it may be a warped disc, so I changed the discs and pads all round. I've changed the wheels and tyres too but the knock persists. I also got weeping shock absorbers and the engine rattles like an old diesel.

My old 5 series BMW went on for 14 years and 150k miles, without any real problems, so whilst I love the Lexus, I feel my next car will be another BMW.

[Upex]

Mark, is the knock steady in pace, how quick, speed related variance, only knocks below or over certain speed, still knocks when stationary, knocking at all drive angles, ie straight ahead, turning one way or the other, only over bumps, going forward and back, does it get worse or better with greater steering angles, does it stay, go, get worse or better when braking and or sterring angle?

Need some more to go on before can start guessing really.

Have touched for anything lose underneath and around engine and suspension, ie are strut mounts tight, suspension joints showing any play, bushes ok etc.

John, I think all cars can be as bad as each other. I have issues with the Lexus, don't get me wrong, but nothing compared to the wife's x5 that's same age, less miles. We got the car, was brilliant for 6 weeks, then issues. Spent 1500 on it, without any labour as done it all myself and still not fixed. Ive nearly given up as all the next things are mega books. Two local garages, a Bmw indie and bmw main, despite taking hundreds off me, haven't a clue. Bmw dealer told me to buy another car in the end, it's too old for us to fix, as we can't diagnose anything without the right sensors say of the last 4 or 5 years, after that the tech has moved on and we can't help much. It also needs suspension strut, at 130k and other bits and bobs, 

My Lexus, needs a strut and exhaust after 148k, I'd take this Lexus over the x5, but the next person issues might be the total opposite. In the end, it's down to that individual car, individual component, conditions, etc etc etc I think. You pays your money and takes your chances. Still I'd rather have the older better cars for less money than a new cheap plastic one, which still suffers failures, just have a warranty. 

[MarkB1983]

4 minutes ago, Upex said:

Mark, is the knock steady in pace, how quick, speed related variance, only knocks below or over certain speed, still knocks when stationary, knocking at all drive angles, ie straight ahead, turning one way or the other, only over bumps, going forward and back, does it get worse or better with greater steering angles, does it stay, go, get worse or better when braking and or sterring angle?

Hi Rob. Thanks for the reply. Knocking is only present when moving, at slow and fast speeds, little variation in noise, however knocking is quicker when going over a bump, sounds like a quicker vibration. No difference when steering either direction.

Nothing obvious visually looking at usual suspects. Rocking the left side of car when stationary causes slight knocking, like checking for shock wear.

 

[Upex]

If it's knocking stationary, then it has to be suspension or metal object contact, so I'd be checking that corner for every bush, joint, mounting point and metallic part that could be touching. Calipers, stone guard, suspension strut etc.

When bouncing car stationary, is it a knock or grinding noise?

Get a pry bar on everything and check for slack, and also check if still does it under braking and in reverse to.

[MarkB1983]

Hi Rob,

I did, but for some reason it sent it in the quote I copied from you;

"Hi Rob. Thanks for the reply. Knocking is only present when moving, at slow and fast speeds, little variation in noise, however knocking is quicker when going over a bump, sounds like a quicker vibration. No difference when steering either direction.

Nothing obvious visually looking at usual suspects. Rocking the left side of car when stationary causes slight knocking, like checking for shock wear."

[Upex]

Saw and edited but we crossed posts lol.

[MarkB1983]

The noise is still very much there and having gone over bushes to the best of my ability I can't seem to find the issue. 

I've always described the noise as a knocking, which is exactly what it sounds like on the move, however while investigating with the car stopped, it is almost like a deep squeak/friction type noise, very tricky to describe. When I rock the car on the spot I can feel where the noise is coming from, and it's coming from the black thing on top of the suspension mount, which I'm guessing is something to do with the sports suspension? I want to take this off to investigate but I want to be sure of what it is first. 

As always, help is appreciated. 

Mark

[Britprius]

If the noise is coming from there the chances are the nut on top of the shock absorber is loose. 

Remove the 3 top cover nuts, and lift off the cover. Underneath you will find the actuator motor. Quarter turn this and lift off "like removing the bayonet style light bulb". Then tighten the centre nut to 21ft/lbs then reassemble in the reverse order. 

If this does not cure the problem it is almost certain the shock absorber needs replacing. The part will cost upwards of £265 there is no aftermarket replacement available.

John.