A clonk, a groan and a bit of a lean...

1396midget

1396midget

Well-Known Member
Hello all! this might be a bit of a long one so bear with me... :)

Successful weekend of P6-ery rebiulding my master cylinder, it was properly nasty in there and the brake fluid was a suspicious black colour. Brakes are no longer totally stuck on.

Anyways, had it over dad's pit poking at all the suspension bits (working out this independent-y rear suspension malarky) and noticed that there's a groany graunchy noise from the de-dion tube. This happens under small movements, e.g while shutting the boot or damepr testing. I can feel it vibrating through the tube when it's doing it, it's unnoticeable when driving. It had no oil in it, so I filled it up and it went away for a bit but has come back. The oil's not leaked out either. Is it a thing that can be stripped and fixed (did a search for taking it apart, doens't look that challenging) ?

It also has a clonk on rebound, like when coming off a speedbump. Definately from the back and does both sides the same. The springs and shockers look brand new (and were new, according to reciepts, 17K miles ago), is it just a question of getting under there and checking the bushes again? they're all there, some more rubbery looking than others I'll admit, but they don't look dead. Might this and the groany tube be related?

And lastly, it has an appreciable lean to the driver's side, all by itself. Looking through the forum it seems that there's a rubber thing in the front spring holding area that can collapse - might it be this and how easy is it to check?

or are all three things related?

I am continually impressed by the engineering and design gone into this car. Super strong double thickness cleverness where the master cylinder goes - It's not what I'm used to at all, it's so well made, not a parts bin special :)

Thanks a lot for any help, it's much appreciated. 8)

Rob (still very pleased with his P6)
 
Mine made exactly the same groan so I replaced the DeDion tube with a better spare - then discovered that the noise was actually caused by the lower bushes on the rear dampers. So that's where I'd suggest you check first.
 
Hello Rob,

You could check the shock mountings and verify that they nuts are tightened appropriately. Being loose will certainly introduce a clonk which would otherwise not be present. With the front suspension, there are ball ends which are fitted with a rubber cap for want of a better word that reside between the top link and the spring cup. If you use a bright light and look into the spring cup, you will be able to confirm one way or the other as to whether the rubber has parted company.

Ron.
 
When I got pae it had clonking front suspension and a lean... Turned out to be the drivers side sfront spring was broken in two....
 
thanks chaps.

Tightened damper end nuts a bit they were tight but not loose, but still could take a bit more tightening. Did the top ones as well as the bottom ones. Bottom ones were slightly challenging as it's too damn windy to jack it up, the doors won't even stay open...

front springs are in one piece (phew) and there's a rubber cap evident on both sides.

the graunchy noise is still there perhaps slightly reduced, haven't checked the clonk over speedbumps yet. It says in my book that you can put shims in the back to level it up, but I'd rather know the cause first...

Unless of course the PO has had shims in both sides then taken them out of one side. It was a caravan mobile so may have had shims fitted.

hmmmm
 
Ride height is entirely governed by springs so you might want to raise the car at the back and take all pressure off and measure all springs when compressed and when not. Maybe the po has replaced 1 rear spring or something of that nature.

Rich
 
Hi Rob

First off, stripping the de dion tube is not a difficult task. You should also be able to get new internal bearings, actually more like nylon sleeves, quite easily. I agree it shouldn't groan, so that would be a job to add to the list. You'll find the diagrams of the internals on Ian's Rover-Classics site in the reference section.

But before you go there, have a read of the problem I had with mine. Lucky was registered August '70 so may not be a huge distance from yours in build date. So the possibility of a build fault with the O/S/R spring seat my exist. Rear springs are easy to change - fronts are not. The levelling technique I used is very easy once you've got your head round waht you are doing. So my advice would be to tackle the de dion tube and have the rear springs out at the same tmie to check for free length side to side and do the levelling. If the springs were to be different lengths and the levelling off, then you'd be certain you needed to change the fronts as well. If not then you'd be able to leave the front well alone!

http://www.classicroverforum.com/viewtopic.php?f=6&t=6730&p=43570&hilit=lucky#p43570

Chris
 
cheers chris, I'll give that a go at the weekend! The clonk is still there at the moment, interestingly it only does it on 'one wheel' speedbumps (those cushion-y ones), but not on the normal ones. Makes me think it's a tube thing...

it doesn't detract form the driving at all, and the handling is still fine, there's a curly slip road thing with a lump in it (perfect for suspension testing!) near us and it goes round there fine without feeling unlocated or clonking. Guess I'll leave it till I've got more time, or till it gets bad enough to tell for sure what's wrong. I'll still try that alignment check thing though.

thanks all!
 
The groan you mentioned I also have in my car, I had put it down to the fact that when compressing the rear suspension at standstill the de dion tube will not be able to expand and contract due to the tyres/track being in one fixed position as the wheels are not rotating. Let's say the car was moving the track would be able increase and decrease without the load on the de dion tube. I'm still not sure reading this back if I've made sense here, I realise the link rods will only allow a slight increase/decrease in track but the resistance in lateral movement from the stationary tyres I would imagine could cause this to be the case.
 
restojon said:
The groan you mentioned I also have in my car, I had put it down to the fact that when compressing the rear suspension at standstill the de dion tube will not be able to expand and contract due to the tyres/track being in one fixed position as the wheels are not rotating.
Click to expand...


Regardless of whether the car is moving or not, the de dion must expand and contract as the suspension is moved up and down, it's not even under any extra load as it's the driveshafts pushing and pulling the hubs in and out that are doing all the work. If the wheels were rigidly fixed in place then you wouldn't be able to move the suspension at all. Chances are that if it groans at idle, it's doing it as you drive but you can't hear it because it's drowned out by road noise etc.
 
Bear with me here, I'm trying to explain my theory but doing a fairly bad job of it for the minute. I'd like to expand on this further though so tell me what you think.
When the suspension is compressing the driveshafts at the hub end will travel through an arc which in turn expands the de dion tube itself and on the return will contract the tube again. If the hub cannot travel through this arc as the tyre is in a fixed contact position with the ground could this then load the tube or associated components in such a way that this groan could occur? In my limited knowledge of this the job of the de dion system is to keep the roadwheel in an upright position through the travel of the suspension on either side and in my estimation, the arc through which the wheel travels would necessitate a small change in track which could not be achieved at standstill test, however this is not considering how much of this track increase/decrease is taken up by the sliding joint in the halfshafts.
Can you see the cut of my jib? :D
 
restojon said:
If the hub cannot travel through this arc as the tyre is in a fixed contact position with the ground could this then load the tube or associated components in such a way that this groan could occur?
Click to expand...

As far as I can see if the hub can't travel through the arc, the car won't move up and down. In other words, if the tube siezes, then the suspension goes solid. Regardless of whether the car is moving or not, if the suspension goes up and down, the de dion goes in and out, and there's no extra load on it just because the wheels are on the ground. All the load goes through the driveshafts.

restojon said:
however this is not considering how much of this track increase/decrease is taken up by the sliding joint in the halfshafts.
Click to expand...

There are no sliding joints in the halfshafts, the sliding joint is in the de dion.
 
I see exactly what you mean, and now having gone back over the arrangement of the stabilising rods and the suspension arms themselves my theory doesn't quite work in it's entirety, if the bushes at either end of the radius arm or stabilising rod were to give out though could that cause the elbows to twist slightly therefore causing the de dion tube to be loaded at a funny angle?
Hope you don't mind discussing this, I find the de dion a fascinating thing.
 
There are no sliding joints in the halfshafts, the sliding joint is in the de dion.
Click to expand...
I have sliding joints on my halfshafts, :?: Sounds like a PO may have been playing around then. Never thought that wasn't standard no wonder I've had trouble finding U/J's for a P6 to fit my one.
 
restojon said:
if the bushes at either end of the radius arm or stabilising rod were to give out though could that cause the elbows to twist slightly therefore causing the de dion tube to be loaded at a funny angle?
Click to expand...

If the bushes on the rear of the trailing link where it joins the elbow were shot, then you could see how that as the driveshafts tried to push the hub outwards with the wheel on the ground, the elbow might take up that wear by twisting outwards at the top, and if both sides did that then the de dion wouldn't be operating in a straight line, and so could conceivably be noisy because of it.
 
restojon said:
I have sliding joints on my halfshafts, :?: .
Click to expand...

If you're looking at a loose halfshaft, it has splines on the outer end, but they're not a sliding joint, they are there to transmit the drive from the halfshaft to the hub. If you had sliding joints in the halfshafts, and a sliding joint in the de dion, then every time you went round a corner the body would move outwards leaving the wheels behind.....
 
There's what looks like a screwed collar which I presumed was part of a sliding joint about 2/3rds of the way up the halfshaft. I'm unable to get under the car at the minute to have a look as I've slipped two discs in my neck, otherwise I would've posted a pic or two.
*EDIT* Maybe they're a pattern replacement item?
 
restojon said:
There's what looks like a screwed collar which I presumed was part of a sliding joint about 2/3rds of the way up the halfshaft.
Click to expand...


Errrrrr.......That sounds more like the propshaft......
 
definitely halfshafts, just to clarify it it's the shafts that come off either side of the diff travelling out to the hubs and de dion elbows. We're definitely on the same page here :D . They may be some sort of pattern replacement or maybe a multiple application shaft which when fitted with other components/flanges in a recon place can fit other vehicles?
 
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