Clunk under hard cornering - Bushes?

[Roadrunner]

Under hard cornering or more specifically on hard switchbacks (on the track) I hear one solid metallic clunk from under the car. Most of the times from the rear, sometimes the front.
Its most apparent on the shift of weight between T3 and T4 at Wakefield Park (when the weight shifts from the front right side to the rear left for T4).
From my searching, most find the culprit is slipping alignment bolts. But after my last alignment I marked all the bolts, checked after a session and none have moved.

At the last hill climb day, Verne suggested my rear bushings looked shot, as after I did a burn out the car still wobbled a bit. (he was queued behind me).

They are all the original 150,000k old bushes so probably do need replacing, but I don't want to go through the exercise of replacing ALL of them and have the clunk still happen on race day.

My train of thought is if the bushes deformed etc under load, and the clunk is the bushes moving/compressing etc, then the alignment bolt would move with it and the white marker lines wouldn't line up?

Is there a way of checking bushes? And are there other bushes other than the control arms that I should check?
Do the lower control arm bushes wear more/receive more stress than the top or should I just lump it and do all of them top and bottom, front and rears.
Not a cheap experience but willing to get things sorted.

[manga_blue]

Exhaust pipe swinging into something is a likely problem. It can move a fair way under cornering. Look for any marks on the pipe and nearby chassis/suspension areas for signs of touchng or rubbing.

[ManiacLachy]

Exhaust pipe swinging into something is a likely problem. It can move a fair way under cornering. Look for any marks on the pipe and nearby chassis/suspension areas for signs of touchng or rubbing.

Good thinking. I had a noise I swore was a suspension thunk, it was the exhaust! Mine had a small crack in it allowing for some extra movement, just the crack opening and closing made a decent noise.

[Tony]

Basically spanner check everything under the car.

Make sure all the underbody bracing is tight and also check bolts that hold the suspension sub-frames to the body.

While you're under there, it would be wise to check sway bars and end links.

[The American]

I had been hearing something under mine which I thought may have been alignment bolts. A very solid sounding thunk mid corner.

I have not heard it again since a fresh wheel alignment was done. I too had checked and could not see evidence of movement in the alignment bolt positions.

[Luke]

Mine in the exact same part at Wakefield was the exhaust banging. New poly hangers and bugger all movement in it now.
I also had a clunk under hard track braking up front. That was caused by the front lower control arm bushes. They were not badly worn-out just a small tear in each where the hole is in the arm housing. The noise cause was that they came 1/3rd of the way out in the arms allowing metal on metal contact. Replaced them anyway as I already bought new bushes and it would have required much the same amount of work to correct or replace.
I changed all the rears at the same time and they looked new. I would say the front lowers are the ones that take a beating from what I saw. This was at 83500kms.
I also get clunking from the rear pads. Can't do much about it as you cannot purchase new spring clips for nb8b rear brakes.

[Roadrunner]

Thanks for the tips everyone. Glad to hear you had the same thing in the same place with an SE too Luke. I'll definately check out the exhaust hangers. Where did you pick up the poly hangers from?

I'll also check the metal around the control arm bushes. One would assume if mine were worn and causing metal to metal contact there would be scratches/wear on the metal faces between control arm and sub frame?

[Luke]

I got the poly hangers from Flyin Miata as I finally bit the bullet and ordered the one way oil valve (check valve) for the catch can at the same time and it costed nothing extra to ship them.
There was a downside to the poly hangers, I didn't know my muffler baffles rattled a little until they went in.

There were no visible marks on my front suspension bolts or mountings without pulling the arms out. The biggest cue was that the bushings had a huge gap at the front and the rear of them was butted hard against the mounting point. There was also a bit of rubber oozing out the holes in the bottom of the housing. I gather they are drain holes??? That's where the small tear was located after inspecting them upon removal.
I also changed all 8 alignment bolts, nuts and washers at the same time.

[forcedfive]

Hi Roadrunner,
I believe I mentioned to you that your rear end had around 10 - 20mm of movement when we were at the hill climb. I noticed this when you were doing your burnouts. I am pretty sure the cluck would be coming from the rear upright hitting the upper outer wishbone. Check the upper outer bush in the upright and the upright will likely show signs of rubbing / hitting on the wishbone. I did mine the day before the hill climb as my car was doing the same thing for some time in the same spot amongst others on the track. I did all 14 bushes in the rear and they were all pretty flogged out after 18 years. Had the fronts also but they looked OK so will do those later. It is a bit of a task pressing them out and in but it will definitely sure up the rear end and hold its alignment far better when under load.

If it is the exhaust you are lucky.
Cheers

[Luke]

Hi Roadrunner,
I believe I mentioned to you that your rear end had around 10 - 20mm of movement when we were at the hill climb. I noticed this when you were doing your burnouts. I am pretty sure the cluck would be coming from the rear upright hitting the upper outer wishbone. Check the upper outer bush in the upright and the upright will likely show signs of rubbing / hitting on the wishbone. I did mine the day before the hill climb as my car was doing the same thing for some time in the same spot amongst others on the track. I did all 14 bushes in the rear and they were all pretty flogged out after 18 years. Had the fronts also but they looked OK so will do those later. It is a bit of a task pressing them out and in but it will definitely sure up the rear end and hold its alignment far better when under load.

If it is the exhaust you are lucky.
Cheers

There is only one bush you need a press for in the rear. The upper outer one. I didn't even bother changing my one in the end as the rears all came out good so it was not worth the time or hassle pressing it out. Then again I only have 84000k's.
The rest can be done far easier with a threaded rod, some nuts and washers. YouTube is your friend. It only works when you have 2 holes lined up, ie all NA/NB's bushes line up in all the arms bar the single one on the upper outer.

[Roadrunner]

Hi forcefive, yeah you chatted with Lindsay about it at the hill climb.
I jumped under the car to poke and prod but only looked at the lower control arm and didn't even think about the upright, as I had it in my head that it was the alignment bolts and/or bushes moving.
I'll stick my head back under there tonight while its still on the trailer and check out the upper.

I'll also see how far I can swing the exhaust across to see if its that hitting something.

[Roadrunner]

So climbed under the trailer to suss it all out.
As far as I can tell, the exhaust isn't hitting anything. I pushed it/swung it both sides pretty hard with my foot and the tip touched the bumper cutout and nothing else. My clunk is definitely metallic so that's not it.

I checked the rear upper wishbone bushes. There's no obvious metal to metal touching marks, but the driver side bushes look like they are trying to escape.

Passenger Side:


Drivers Side:


The wishbone looks like its moved forward on the bushes. I couldn't see any contact wear but its pretty tight in there.
Does this look like the culprit or is this normal?

All other bushes as far as I can tell from the outside looking in, look perfectly normal.

[Luke]

On your right pic, that is what happened on my front lower wishbones, just mine was far more extreme than that and was seriously limiting my caster adjustment.
The mounting point of the arm may be coming into contact with the sub frame mounting point where the bush is pushed in. You won't be able to see it until you remove the arm, and even then it doesn't really help as the bushing has been rubbing there for many years to begin with so there will be marks regardless.

And wow, my bushings in that location were perfect. I'm surprised those are the ones that have dislodged as that arm does not really have that much load on it.
No wonder they were seeing movement in the rear of your car at the hill climb.

Did you have a look at the front lowers while you were at it as they are the ones that should take the most load out of all of them.

[Roadrunner]

Yep looks like I'll be replacing the uppers in the not to distant future.

The fronts looked perfectly fine to me.

Am I right in thinking that removing just the rear upper wishbone and replacing the bushes wont effect the wheel alignment?

[Luke]

It will affect the alignment because the old ones are not sitting in the right place to begin with.
Also, I found that arm the easiest to get out, but the hardest to get back in. Both sides just didn't want to fit in so easily afterwards. Hammers and jacks do wonders.