Faulty shock?

I would check, or have checked, all the joints in the steering and suspension geometry. Ditto any Silentblocs, or whatever they call them nowadays.

Good luck.

Thanks Davey / Tim, all good points and whilst I can / will check for some, the others may well be checked during the MOT that is due soon.

The question still stands that short of a damper / strut being broken, loose or leaking, how do we test them for spec / functionality?

Cheers, T i m

The classic way was to push down on a corner and watch the rebound.

If you push down in the middle of the bonnet, the least effective shock will allow that side to rebound more quickly that the other.

Any competent garage should be able top check joints for slackness. Ball-joints, trackrod ends, etc. They should be able to relieve the weight on them, and then check for play.

speed humps can be used as well, you soon notice if one side bounds into the air more than the other

Sure, but what about the effectiveness of a damper?

If a non-structural damper breaks (a eye or bolt comes off the lower end of a rear damper for example) the whole un sprung mass would then be un damped and then free to oscillate and also not resist rebound of said mass and that of the vehicle.

If a structural damper breaks or wears badly (MacPherson strut) you would probably know about it (broken) or find it easily (clonks and rattles) but what if it's de pressurising or slowly leaking fluid?

My point / question is there could be a point where it would seem ok (structurally) but be slowly losing efficiency to a point where someone like me might sense it but many others wouldn't (present company accepted of course). ;-)

Maybe it's efficiency goes off when hot so would only be measurable once hot etc? [1]

Cheers, T i m

[1] And they do get hot as Jacky Ickx can attest, even with very high spec Bilsteins (where an exploding one blew a wheel arch off!). Oh, and damper fluid is also inflammable ... ;-(

Again, can't really help you other than to observe that like so many car components, damper durability seems to have improved a lot over the years. That last car that our family owned that had a damper that actually failed to function was a Renault 4.

There have been a couple of replacements due to leaking in the intervening years but not lost significant function. To lose function without significantly leaking oil first must be rare these days I imagine.

Tim

It will certainly show the difference between a good damper and a clapped out one. Given both on the same axle won't fail at the same time.

And are they the only two modes though (for a bog std road car I mean)? ;-) [1]

Highly unlikely, agreed. ;-) [2]

So, as long as there hasn't been a significant loss of damper fluid and the damper is still good mechanically then they generally either work or don't ... it couldn't *degrade* functionally to a point that the loss of function could creep in over time (the fluid 'worn out' for example)?

Cheers, T i m

[1] I am still to replace the 'stock' 1300 Mk2 Escort Saloon dampers in the front of the kitcar with stock 1300 Mk2 Saloon dampers over the 'uprated' offerings that are in there now ready for the 2L Pinto 'upgrade' (that isn't to be). [2] Daughter had a rear road spring fail on (what became) her Corsa when in Scotland and it (singular) was replaced by the local garage.

The other one failed when she was back home with it a week later. ;-)

(if you try that on most cars today the bonnet will probably fold onto the top of the plastic cover that hides the engine!)

FWIW, I don't think the / a damper has gone (as in failed completely), I was just asking if one could typically weaken to a point where it was no longer to manage the more subtle / extreme circumstances (like a particular road surface or speed (or an out_of_balance wheel) that hits the resonant frequency of the unsprung mass etc)?

Cheers, T i m

[snipped]

Firstly, to eliminate a minor tyre balance or wheel damage problem, swap the fronts to the rears.

Chris

A bump /hole on the outside of a bend should be the most obvious - cornering force drops off as well.

I take my previous car to national tyre and other bits centre to confirm which damper was wrong, and they could not tell by bouncing. When I drove the car over the bumpy car park it was obvious. Rear dampers definitely do still wear out, but I've never had a problem with front struts.

I have, and quite recently, damping still ok, not leaking, but the strut had worn such that it wobbled in the middle, that gave some odd juddering effects. I ruled out every other bit before deciding to strip the spring off the shock, then it was very obvious. On the car I reckon that you would need to clamp to the shock in such a way that you could try to twist it front to back, something like a heavier version of a crutch tool for turning a water tap buried under ground.

Daughters Connect still give a clear 'clonk' from the nsf (that I have mentioned here before) when going over speed humps and the like that I think may have been attributed to some sort of wear in the shock (top piston bush)?

I love those 'found ya' moments. ;-)

Her van MOT is coming up soon so it will be interesting to see if whatever it is is deemed worthy of attention. Same with the Meriva (MOT soon) but in it's case the issue (this resonance somewhere) doesn't seem to show itself (in a way that I can feel from inside the car at least), outside some fairly specific and (possibly) not easy to demonstrate circumstances.[1]

I'd like to have someone traveling beside my car and observing the wheels but again, not an easy thing to arrange.

Just OOI, could a CV joint(s) that 'click' on heavy lock also be slack enough in a straight line to allow the drive shaft to wobble?

Cheers, T i m

[1] We had the same thing when after over an hour on two different long / high speed [2] trips we had 1st a pronounced shuddering that after stopping, went away for the rest of the trip and on the second a very loud and high pitched scream / whistle. Both potentially cased by an issue with a brake disk or pad and I've since changed all of them and the problem has not returned. [2] A reasonably constant 70 mph on the odd clear day on the M25+ ;-)

Whilst I could do that fairly easily, I generally like to keep the same tyre in the some role to minimise wear (but would be happy to do it as a test) but wondered that if it came to it if a straight balance check would be 'better' than any of the other options?

eg. Is a professionally balanced wheel (where you can also easily check for wheel / tyre runout and tyre damage the like) guaranteed to be good for all speeds up to say 80 mph?

I mean, if there is a weight missing somewhere ... that's likely to show up pretty quickly on a balancing machine, similarly if they have gone out of balance slightly since the tyres were first fitted, but that wouldn't also test for a wonky wheel trim (and you do seem them on cars going round eccentrically).

I was hoping to wait till we need to go out on the motorway again to re-check the scenario and see if it also happens from cold etc (rather than after an hour or so when I first noticed it).

If it does seem time (>heat) related then I guess it could be a slightly seizing brake caliper just catching the disk at the same point and causing the issue?

Cheers, T i m

A shit make car came in once with a wobble after it got hot, that was a brake problem, but bizarrely the caliper was not seized, discs and pads cured.

[...]

It would eliminate any possibility of a wheel or tyre deficiency causing the problem, in the cheapest way.

Chris

True (and the option not ruled out etc) ... but if I swap the wheels round and the issue remains (as I'm not *sure* it is on the front) what has that proved?

My thought was is if I'm going to the trouble of pulling two wheels off on each side (two jacks and in the road etc) and then find it doesn't make any difference, I'll still need to get the wheel balance checked to be able to rule them out?

Whilst I'd prefer not to waste money , I'd happily pay my local tyre fitter to jack the car up, remove the wheels, put them on their machine, check / re-balance and re-fit them for me than just doing the swap myself to find that I'm still none the wiser, especially as it may not be that easy to replicate the situation in the first place. ;-(

Cheers, T i m

When I changed the disks and pads recently I noted the pistons were all fairly stiff but the car rolls pretty easily (even with a gentle push or on the slightest gradient) when all the brakes are released so ... ?

However, that could change after it's been running at 70mph for an hour?

This happened on the old Sierra Estate. After we had done about 5 miles up a dual carriageway I started to feel a 'judder' and then slowly became worse to a point where I could feel something dragging. A quick feel round found the osf wheel fairly hot and a even hotter disk and caliper. Leaving it to cool for a few minutes allowed us to carry on to the family members house we were going to.

We left the car with them and carried on with some of them in their car (we were going to take two cars etc) and called the AA to come and sort it (and with fairly clear instructions what the fault was and how it would manifest itself).

We got back to theirs that night to find an AA ticket on it saying NFF ... however a couple of miles later on our way home proved it was still there. ;-(

We limped back to the families house and the AA re-called and this time they turned up with a recovery lorry ... and as they were loading the car on the lorry sidelights failed.

He was 'just' a driver so I got under the dash and rewired the switch to bypass the melted sidelight position so we could all get home. ;-)

The thing was, just on the point before it started to heat seize it was 'shuddering quite a bit ... similar in fact to one of the two independent instances on the Meriva a while back.

Cheers, T i m