2003 RX300 clonking from front.

Haylands · July 2, 2022

I've had the RX for around three months now and it has always had a knock coming from the front, it sounds just like loose pads or worn calliper carrier pins, every time you touch the brakes it goes "clonk" the only problem was that it went "clonk" every time you pulled away as well so sort of rules out pad or calliper movement...

So... get it on an MOT ramp and start the investigation... The air suspension has been changed to coils, struts look fine, upper bearings fine, no broken springs... get a 3ft pry bar and test every bush and joint, newish ARB links, all new bottom arms and bushes, nothing shows any sign of wear, callipers fine, pads secure.... Both sides tried by me and my mate who is the MOT man... no play or movement in anything....

So, move onto the rear as some noises just travel... all the rear replaceable suspension components have been replaced, all new and shiny, bolted up to a clean and shiny repainted rear subframe...

It seems like the previous owner has been chasing the issue and replaced everything they could...

So, start to eliminate items, slacken all suspension links and drop the car on it's wheels to retighten in the correct orientation... Still "clonks"

Remove the ARB links, still "clonks"

Clamp off individual front calliper flexes... still "clonks" (test done inside, not on the road..)

Mate went to have his lunch while I carried on looking around to see if I could spot something...

I noticed this...

Not a brilliant picture but what you can see is rust dust around the bottom of the strut to hub mount, you can wipe it away with your finger and more importantly it was only on the nearside which is where the noise seemed to come from... This is a tell tale to movement within the joint.

These are supposed to be at 210nm which is very tight... they turned about 4 flats to get them tight enough, funnily enough the other side was worse and took 6 flats to get them tight... We had put pressure on the joint before with the pry bar and it "looked" tight...

Test drive revealed no noise at all so this was the issue...

Just thought I would leave this on here as more folks will be doing the conversion away from air and more Rx's may have this issue, If you DIY it then you need the proper tool to make sure these bolts are tight enough...

I then had a very pleasant drive home...

Herbie · July 2, 2022

Excellent detective work Pete, great post. Glad it's now sorted for you.

Illogan · July 2, 2022

What a useful article (post).

Wonderful stuff, Pete.

Barry14UK · July 3, 2022

Good to add to a list of things to check.

patrick264 · July 21, 2022

Hi I get this clonk every time I brake it's coming from the right side kind of under the drivers footwell. Are you indicating that this issue you were having was loose bolts? Thanks Patrick

Haylands · July 21, 2022

Do you get the same noise when you accelerate from standstill, if you do then it "could" be the same issue, loose strut bolts.

It could, of course, be a lot of other things, if it just does it when braking it could be worn calliper carriers or even the brake pads moving within the calliper...