Front end ‘thunk’. I can’t find it…

[Stuart Tierney]

Hello All,

Looking for some ideas of where to look for a front suspension noise in the little car we have.

It’s not in the bushings or ball joints, they’re all new. It’s not in the steering, everything is tight, freshly greased and boots are either new or in great condition. It’s not in the sway bar, which is tight and no slop. It’s not in the strut tops as they’re tight and the bearings are smooth and all is fine. The left side has no wiggle or wobble at all, but the right has the slightest side to side wiggle when I wiggle it. But the noise isn’t from there.

And I can’t find where the heck this noise is coming from, and it’s bugging the carp out of me.

Symptoms are that when the front end is unloaded, it tends to set up for a bit of a ‘thump’ that sounds all the world like a bad ball joint. The left side bad ball joint made the same noise, until I replaced it, reducing front end thunks by 50% or so. Under load (compression) no noise at all, save the usual ‘old car’ noises which are really quite minimal.

Everything under the dash is as tight as it should be, save the brake ‘axle’ which has a little looseness to it. I don’t think that’s heavy enough to give this sort of thunk though and would tend to do so under all bumps.

Has anyone here had a really strange source for a front end thunk that wasn’t one of the usual suspects? It’s possible that the front shocks are where it’s at, but if they were worn, I’d expect they’d be giving more trouble than this and would be noisy under compression, not extension.

I’ve kind of run out of things to check, which is why I’m looking for an alternative source of this noise. There’s just nothing about that’s loose enough and heavy enough to cause this thunk, and after having the front end in pieces several times now looking for it and replacing bushings, I’d think I would have found the problem by now. Coming more from the left (passenger) side than the right I think, and yes, that was the worse ball joint as it should have been.

It’s the last problem that needs fixing on this little car and if I can get rid of it, I’d be very happy. But as it is, it’s not going to fall apart or break down, and as of today, it doesn’t even leak that drop of oil every now and then. It’s RWD, so there’s only a basic strut suspension and not much else there. Enough space to hide a body, but no bodies to be found in there either.

Thanks for any suggestions, but I admit I don’t expect much. It’s a strange one.

Stu.

Topic

[Rob]

is it a whinding noise or a groling noise or a knocking noise… things to check cv axle, tie rod inner and outer, ball joint, wheel bearings, brakes sometimes they will sqeek or wobble if something like the caliper is stuck…
wheel bearing will make a wining noise, cv will make a knocking noise when you turn the tire or the wheel, ball joint knocking noise, tie rod’s knocking noise
how to check to see which one it is… wheel bearing and cv will make noise when you spin the tire… ball joint grap tire and shake up and down, tie rods shake left and right… say bar and way bar links … grab them and shake them…. that is some basic test wo conform it you will have to take that part apart but will give you a good idea what to look for

[Mike]

A small car with RWD? What are you driving, a ’70 Beetle?

[Stuart Tierney]

Mitsubishi i. Google it. Smaller than a beetle, more egg shaped than bug shaped. A FWD drivetrain under the rear floor, and 660cc with all the tech Mitsubishi in 2006 could throw at it.

Not bearings, not brakes (fixed), not ball joints (new!) as they’re all checked and all in good shape. Even the sway bar linkages (fixed length rose jointed rods) are in good shape. No CV joints in the front, and the ones in the rear are in excellent shape as I’ve had both in my hands in the past month when I replaced the transmission, in the back of the car.

It’s a weird one. I might replace the bearings because I can, they don’t cost much and it’ll take that possibility completely out of the equation. They’re not at all noisy, and have no play in them but $20 a side, no big cost to change and I have the gear to do it.

It’s a weird one. Not one of the usual suspects and a stock answer isn’t going to work because everything that can usually cause these noises has been thoroughly checked or replaced. Just wondering if there was something else in the there that could be causing a heavy thunk under extension only (not under compression at all, that thunk was lower strut ball joints and banished) like something is loose but held tight when there’s weight on the front end.

I though it was strut top rubbers/bearings, but with the wheels off the ground, no looseness and taking the spring tension off them showed no play and everything looks to be in good enough shape.

Stu.

[Author]

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