Noise from the rear end!!

[Owlsman]

Hello guys 'n gals - I've been plagued for ages with a noise coming from the rear......er, settle down at the back and the rest of you, just behave and stop making your own jokes up.

Seriously though, on my 4 door saloon, I can't seem to identify a clonking sound definitely coming from behind me, virtually every time I have to go over a sleeping policeman (and he's getting pretty fed up of it too ).The arched/domed ones that go from kerb to kerb are not too bad but the ones that look like a pyramid with the top cut off are the worst. There are also road surfaces near me where there are extended indentations in the road where the tarmac has sunk and began to break up and they can cause it.

The obvious cause was one of the many spares and tools carried in the boot rattling about but I've even taken everything out, including the spare wheel and the raised boot floor boards, and it still does it. For long enough after that, I was convinced it was the exhaust knocking against the bodywork as it arches over the rear axle, although there is no evidence whatsoever of any regular metal to metal contact. I've eliminated that however as, for as start, everything exhaust-wise is rock solid and I went for a very short run round the block with a folded towel jammed between the exhaust pipe and the bodywork so that the pipe could not move and even it it did there could be no chance of any metal to metal contact. Any ideas how to sneak the towel back into the bathroom with a plausible explanation why it is covered in oil and grease, would be appreciated.

This afternoon in between showers, I think I might be getting somewhere at last. I had been ruling out the rear bump stops, particularly as they were both replaced recently and of course any contact is between rubber and metal. The rear springs were also replaced about 5 years ago, as part of the deal when I bought the car. To see if the stops were reaching the bodywork, I fixed a small piece of card with a glob of grease to the top of each rubber and then put a bit more grease onto the bodywork, directly above the card. After maiming a few more slumbering constables (and hearing the usual clunk on most occasions) I returned home and looked underneath the car. Both pieces of card had transferred from the bump stops to the bodywork, so clearly the stops had been doing their job and had come into contact with body.

This leaves me with 2 questions:-
1) In a perfectly set up saloon with all new and correct suspension components, would it be quite common for the bump stops to engage with the bodywork when going over uneven road surfaces or speed inhibitors? (I confess to going over them rather quicker that I would normally.....purely for the purposes of the test - but by no means flying over them)
2) Whether bump stop engagement is usual or not, what sort of sound does it actually make? I still think the sound generated in my car is more of a 'clunk' than a 'thud'. A dull thud is what I would expect from a block of rubber hitting the underside of the bodywork.

Maybe I am expecting too much from 60 year old cart spring suspension....particularly on today's roads!! Any thoughts or suggestions what else it could possibly be would be much appreciated please. Thanks in advance.

Cheers,
Alan

[Chief]

just behave and stop making your own jokes up.

always someone spoiling our fun

I take it you checked the rear seat base/back are properly in place/tightened?

Also, maybe first try lifting and looking under the rear seat base in case there's something in there (it's a great storage space ).

I'm also presuming your petrol tank is secure

[svenedin]

My leaf springs had become very tired and worn out. They had last been replaced around 30 years ago when one actually snapped (this is quite alarming by the way but then I was driving way too fast as teenagers often do). My tired old springs were absolutely hopeless when going over speed bumps. It was very obvious that the car body was hitting the rubber bump stops with a jarring whack even if I was driving very slowly (5mph). Tired springs are usually quite obvious because they no longer hold an arch and have gone flat. This can be seen most easily by looking at the angle of the rear spring shackle plate. With good springs the shackle plate is perpendicular to the body but as the spring goes flat the shackle plate starts to point backwards (because the effective length of spring gets longer).

There are many reports of disappointed owners who have bought leaf springs from the major suppliers only to find that the springs have gone flat in not much more than a year so sadly this could be the case for your springs fitted 5 years ago. I was aware of this so I ordered springs from Jones Springs. These are much more expensive and made to order but they are vastly superior and I would expect them to last 30 years as the previous springs did.

Other things to consider are the rubber bushes in the spring eyes, especially the front ones; the drop links and their bushes and most obviously the condition of the lever acting dampers. When I replaced my springs I found that everything else needed replacing at the same time. Give the back of the car a good push down at each corner and let go. How quickly does it stop moving and how hard is it for you to get it to bounce? It should be damped very quickly and be really reluctant to bounce. Does doing this recreate your noise?

In terms of what to expect from a 60 year old car with "cart springs", with the suspension in good condition it should cope with sleeping policemen without any drama at all but you do have to slow down more than you would have to in a modern car. When going over sleeping policemen at a sedate (but not ridiculously slow) pace the body should not hit the bump stops.

Stephen

Have a look at the angle of your rear shackle plates

IMG_9182.jpeg (2.87 MiB) Viewed 2394 times

[Chief]

There are many reports of disappointed owners who have bought leaf springs from the major suppliers only to find that the springs have gone flat in not much more than a year so sadly this could be the case for your springs fitted 5 years ago. I was aware of this so I ordered springs from Jones Springs. These are much more expensive and made to order but they are vastly superior and I would expect them to last 30 years as the previous springs did.

If you don't mind my asking, how expensive were they? I know I really should (when I can afford it) get the rear springs done on mine and it is dissapointing to read your post that some people have found their new ones go flat in a year. Mine are flat, but they're also now into their 61st year.

[svenedin]

There are many reports of disappointed owners who have bought leaf springs from the major suppliers only to find that the springs have gone flat in not much more than a year so sadly this could be the case for your springs fitted 5 years ago. I was aware of this so I ordered springs from Jones Springs. These are much more expensive and made to order but they are vastly superior and I would expect them to last 30 years as the previous springs did.

If you don't mind my asking, how expensive were they? I know I really should (when I can afford it) get the rear springs done on mine and it is dissapointing to read your post that some people have found their new ones go flat in a year. Mine are flat, but they're also now into their 61st year.

Jones Springs were £130 +VAT each for 5-leaf springs last year. They are extremely busy and you will have to wait a few weeks as the springs are made to order.

Stephen

[Bill_qaz]

Have you removed the door cards and checked nothing loose in the rear doors.

[Pete Bags]

I had a similar knocking/banging noise when I went over sleeping policemen, bumps etc, and in the end it was the rear axle hitting the exhaust pipe. When stationary, there was a gap between the axle and the exhaust pipe, but as the springs compress over a bump, the axle moves up, and that was causing the banging sound. When I shortened the strap holding the exhaust above the axle, the banging stopped.

[svenedin]

I had a similar knocking/banging noise when I went over sleeping policemen, bumps etc, and in the end it was the rear axle hitting the exhaust pipe. When stationary, there was a gap between the axle and the exhaust pipe, but as the springs compress over a bump, the axle moves up, and that was causing the banging sound. When I shortened the strap holding the exhaust above the axle, the banging stopped.

That is definitely worth checking. When I fitted a new exhaust I had to do quite a lot of adjusting to stop the exhaust hitting in one place or another. Common places for the exhaust to hit are: as it passes through the bulkhead; where it bends to go over the rear axle; the petrol tank.

Stephen

[Owlsman]

Many thanks, gentlemen for your helpful thoughts and suggestions. Apologies for my slightly tardy response but I had my Covid 'booster' on Tuesday and apart from my upper arm feeling as though it had been kicked by a horse, I was generally feeling a bit rubbish, until today.

Before I go on to suggest where I think the problem may now lie, let me put to bed, from your ideas, what it deffo is not. Everything within the passenger compartment is secure and rattle/noise free and there's nothing loose, such as the petrol tank. After wrapping the exhaust in a towel and effectively jamming against the bodywork, I've eliminated that one too. Try as I might, I can't replicate the clunk whilst the car is stationary and the suspension at each corner is by no means 'wallowy'. When depressed, each wing returns immediately to its static position.

From what you have suggested, Stephen, I'm increasingly drawn to an issue with the leaf springs. I hadn't really considered them, as they were fitted just over 5 years ago! As, hopefully, you can see from the photos of the rear shackle plates, mine are definitely no longer vertical.

I've also shown - as best as possible - the base of the springs where they attach to the rear axle. To the expert eyes out there, does everything look as it should? The other pic shows one of the bump stops - does the top of this look about right distance-wise from where it's obviously hitting the bodywork?

I assume that if the leaf springs have flattened out then the chance of the bump stops hitting the bodywork increases substantially. But would that not make more of a thud rather than a clunk, which is what I seem to have? If the springs are indeed ready for early retirement and their associated fittings, could that somehow create a clunk? What's the difference between a 'clunk' and a 'clonk', by the way?........and please don't anyone say, a vowel.

[svenedin]

I think your leaf springs have become tired even though they are not very old. I attach a picture of the rear shackle plate with very tired old springs and with a new spring. I also have a picture of the bump stop but the angle isn't terribly useful in showing how far the bump stop is from the bodywork. It sounds like your lever acting dampers are working fine and also everything else looks normal. I can see the rubber spring pads in place. It is not just about how the car is sitting at rest but whether or not the spring is actually resisting the movement when the car goes over a bump. If it is weak there will be little resistance.

If you do decide to replace the springs it would be an idea to consider whether you might want to use polyurethane rather than rubber spring pads and bushes. I did and I am very pleased with the result. It is quite a big job to replace both springs. I think it took me about 10 hours to do both sides but I did have a lot of rusty fasteners to fight. Your nuts and bolts look in good condition and will probably undo without causing undue fuss. Nonetheless it is a good idea to drench them in PlusGas several days before trying to undo them and ideally giving them a drench several days in a row.

Very tired leaf spring

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New Spring

IMG_9182.jpeg (2.69 MiB) Viewed 2260 times

Bump stop

IMG_0045.jpeg (3.12 MiB) Viewed 2260 times

[ManyMinors]

Without hearing it, it is very difficult to make useful suggestions but could the noise simply be the rear bump stops hitting the bodywork too hard and too frequently? My saloon suffered from this after I replaced the rear bump stops. The new ones looked OK but the material was very hard and this combined with fairly worn old springs meant regular contact. I simply sawed the top off the bump stops to make a quick "cure" but have since purchased new springs. I too used Jones Springs. Expensive but hopefully worthwhile in the end

[Allen70]

When we bought our 62 Moggy 2 Door around 2 or 3 years ago, while driving around, the wife and myself kept on getting a knock type bump every time we went over speed bumps and potholes. Had a look underneath, and then noticed all the work that the privios owner had done inc new Spring hangers on the chassie.So the old flat lined springs were hitting the spring hangers,Out with the Angle grinder and thinned out the shape of the new spring hanging metal making a bigger gap which works about 75% of the time so in the winter it looks like the need to replace rear springs is near.

[Owlsman]

AN UPDATE........AND A RESULT.

No longer any strange noises from the rear end - and my Moggy is nice and quiet too.

I think it was merely coincidence but the very first time I had 3 passengers aboard, the exhaust strap that supports the tailpipe, decided to break. For the last couple of miles home, there was a clunk-cum-knock every time I went over a cigarette paper. Less than 48 hours later, ESM delivered what I needed.

When I came to fit the new strap, with the rear part of the exhaust waving about, I saw for the first time where the pipe had been making contact. It was on that section that loops over the rear axle but not the top part. It was the inside of the rear section as it scraped against the top bolts of the damper as the suspension moved up and down, when the car was in motion. I refitted the tailpipe strap but inclined the top part as far to the left as possible i.e. towards the petrol tank. This of course took the exhaust pipe with it and away from the damper.

A quick spin round the block, to find as many slumbering members of the constabulary as I could.......and no undue noises from the rear at all. Whoo Hoo.

Notwithstanding the pictures and info kindly provided from Stephen, I'm now not sure if the rear springs do actually need replacing. Whilst at the National, I looked underneath a few saloons (incl. one that has had £1,000s spent on it) and not one had, what I would describe as, perpendicular rear spring hangars. For the moment I'll shelve that decision.....whilst I bask in the sound of silence from the rear.

Such a simple fix to something that had really been bugging me.

Thanks all, for your input.

Alan