Post Number: 3
|Posted on Thursday, 12 January, 2017 - 05:33 pm: |
Thanks for all your comments on the previous thread.
I seem to have a hollow clunking sound from the rear suspension when i go over mostly short sharp bumps. Doesn't happen over every bump, but is quite regular. I have examined the exhaust and mountings with a fine toothed comb, so I think I have discarded that!
Is it possibly shockers? Anyone had an "aha" moment with this problem.
On a separate note, Colortune is magic for setting up the carbs! Front left plug for lhs carb and back left plug for rhs carb - both easily accessible. Also swap the locknutt on you mixture screw for a longer bolt, washer and a spring - makes life so much easier!!
Happy motoring for 2017 to all
Christian S. Hansen
Post Number: 490
|Posted on Thursday, 12 January, 2017 - 07:32 pm: |
My own experience with mystery clunks and thumps coming from rear half of a vehicle that often mimic loose bumpers, brackets, exhaust pipes, brake rods (on pre-war and EPW), etc is to First remove absolutely everything from the car that is not bolted down...spare tire, all boot tools, jacks, anything in your boot, anything in the back seat area, even lose items in dash cubby boxes...then see if the problem goes away. If not, put everything back, but if so, put things back one at a time. I have frequently found it to be something in the boot or tool storage areas. Worth a try as it has worked for me and I have been surprised how often things get loose and shift as driving, making odd sounds!
gordon le feuvre
Post Number: 152
|Posted on Thursday, 12 January, 2017 - 07:43 pm: |
what is your chassis no.? I would bleed height control first. There are two main possibilities apart from main suspension wear/bush failure
1. Shock top mount rubber bush failure where the shock rod comes through body. There were different types of bushes fitted over years. To access these the ram needs to be removed and top shock nut undone. The lower mounting cover then needs to be unbolted from under car and the shock lowered out from below road spring. At this time the shock rod can be tested to see if there is any up/down slack in shock piston rod, indicating the problem is in shock. If no slackness, replace top bush(s)taking care the piston rod is central through body and the bush(s) prevent the shock piston rod from touching the side of the body hole. It is good practice to have assistant hold up shock from below whilst buses are centralised and shock is still extended. this keeps load off top bush and assists with making job easier.
2. The noise can also be caused by the height control restrictors either high or low pressure becoming blocked. The easiest way to test is, only when safe to do so. Stop on slope, select neutral with engine running, allow car to start to roll and move steering wheel backwards/forwards to promote some body roll. The height control will be in fast level mode and the rams can be heard trying to level body. This noise is very different to that of a top shock bush knock. A little practice will "tune the ear"
Hope this helps!
Post Number: 4
|Posted on Thursday, 12 January, 2017 - 10:42 pm: |
Sorry guys - forgot the cardinal rule!
Silver Shadow 1 SRH 17968 owned and loved since new!
Post Number: 2191
|Posted on Friday, 13 January, 2017 - 03:26 am: |
Depending on whether or not the brake and hydraulic system has recently been flushed and refilled, my first reaction is the same as Gordon's.
There's been no recent flush and fill, and this issue has arisen "out of the blue" it's not likely to be height control ram related. In this case Christian's theory and method works, though I'm more conservative and begin unloading piecemeal, starting from the back, until the sound stops. Then I know that I've hit the culprit on the most recent "stuff unloaded" cycle.
However, if there has been a recent flush and fill, and air has somehow been introduced into the height control rams and they have not been bled, this has been known to display itself with sounds precisely as described emanating from the rear of the car: groaning and/or clunking.
While the height control rams are self-bleeding over the long run if the system is activated, unless you have rear seat passengers or load up your trunk it's virtually certain that it will not be activated and that air pocket will remain trapped in the ram until you intentionally bleed it out or force it to self-bleed by a couple of repeated activations of the height control system to do so.
Post Number: 1097
|Posted on Friday, 13 January, 2017 - 05:15 am: |
This may help but there is more on the "brillo mounts]
Robert Noel Reddington
Post Number: 1264
|Posted on Friday, 13 January, 2017 - 07:26 am: |
My car is SRH 17768 1974.
At the very bottom of the trialing arm spring cup is the lower rear shock damper mounting rubbers.
The big nut and half lock are 11/16 AF and the little bolts 4 x 7/16 AF spanner sizes.
Whip this lot off and have a look at the rubbers and the hole in the little cup.
The hole where the damper rod goes through can go oval and the rubbers collapse a bit. A washer can be welded over an oval hole and the rubbers are very similar to lots of other cars.
The little cups bolts are NOT evenly spaced and note drain hole.
also check the roll bar mountings.
To check suspension bushes use a lever and give them some welly.
Dry rubbers should be oiled with DOT type brake fluid which is a use for old fluid. But dont go mad because DOT stuff strips paint.
To get the ride height to work open boot and sit on rear bumper and let the hydraulic pick the car up a few times. If there is lots of air then load boot with water in drums and allow hydraulics to pick car then open the nipples so any air pushed into the rams will go down the pink tagged bleed pipes.
Safety---- because the car will be moving up and down so will the suspension meaning that bleeding the rams on the deck is dangerous so use a pit or 4 post lift. One can imagine the car settling down on a person underneath.
Because of the above my ram bleed nipple are screwed directly into the rams and bled from inside the boot.
Post Number: 53
|Posted on Friday, 13 January, 2017 - 09:05 am: |
I know this sounds weird, but my 1975 Shadow LRD20648 also had clunking sounds from the rear end when going over bumps. Drove me crazy for months. It turned out that the front top shock bushings were bad and the sound somehow was manifested toward the rear of the car. Just something you may want to check out.
Also, I'm not sure if this was addressed in other replies but you may want to check the rubber bushings that are part of the rear differential carrier assembly. Mine were bad and seemed to contribute to the clunking sound.
Post Number: 2194
|Posted on Friday, 13 January, 2017 - 10:55 am: |
RNR/Bob_UK wrote: Safety---- because the car will be moving up and down so will the suspension meaning that bleeding the rams on the deck is dangerous so use a pit or 4 post lift. One can imagine the car settling down on a person underneath.
I've never had trouble bleeding the rams reaching my arm in from the side. The lowest the car ever gets is very well above what could pin one's arm in place.
Another option is to back the car up on ramps, in which case "full down" is still very well elevated above the mechanic beneath adjusting the arms on the HCV and turning the bleed screws. It's amazing how much higher the car is above your head using ramps when there's no need to remove the tires than it is using jack stands (which one wouldn't use in this instance, but I've had to work beneath the car when that's what it's been elevated with. I got a good bunch of graded exposure to work on my claustrophobia!)
Post Number: 166
|Posted on Saturday, 14 January, 2017 - 06:45 am: |
Claustrophobia . . . you and me both, brother. Bad stuff.
John, who during a program detailing inventions for letting the world know someone was buried alive turned it off
Robert Noel Reddington
Post Number: 1265
|Posted on Saturday, 14 January, 2017 - 07:48 am: |
good point Brian
Post Number: 1555
|Posted on Saturday, 14 January, 2017 - 07:55 am: |
I'm not claustrophobic per se, but I do have a problem when putting my head under the car when it's jacked up. I always use 4 stands, the lifting jack and sometimes even push a wheel under the car. Massive overkill I know, but I do get phobic when under a car. I think it's to do with risk/consequence i.e. very low risk of the car falling but very very high consequence if it does. Mechanics work all day under vehicle lifts without a second thought about this. I wish I could get rid of this irrational fear.
Post Number: 61
|Posted on Saturday, 14 January, 2017 - 09:31 am: |
I replaced many bushes on the diff carrier and suspension mounts only to later find it was the exhaust, these cars are beautifully made and the rear suspension (with the exception of the diff carrier) is overkill check the boot floor for torn metal around the diff mounts, if it has not been reinforced make sure you do it, these don't warn you by clunking, they drop on the road!, with a cold car on stands or ramps, grab the exhaust and move it as much as you can, if you can ge it to touch the body anywhere it needs moving, there may be evidence of where it has knocked on the heat sheilds etc (look for shiny marks), engine mounts can be very soft and the whole system dances around quite a bit, it also grows a lot title when hot.
Post Number: 31
|Posted on Saturday, 14 January, 2017 - 10:03 am: |
@ Geoff, Caution is wise, I too like to be sure that the car is well supported and that there are extra safety measures in place just in case an axle stand or jack moves and still I'm somewhat apprehensive crawling underneath. I draw an analogy where I know a number of people who have had boating accidents and two of them sadly drowned, they were all excellent swimmers and had little fear near the water.
Post Number: 901
|Posted on Saturday, 14 January, 2017 - 10:14 am: |
Don't ever get complacent with safety.
You are right to be scared or cautious of cars when all 4 wheels are not on the ground.
I started my apprenticeship 38 years ago as a mechanic, and I have seen some horrific accidents, from people thinking they are safe.
Never take short cuts, and never not use stands.
In the blink of an eye, your life and the ones you love will be changed for ever.
Pride yourself on safety.
People used to look funny at me when I used ear plugs/muffs and safety glasses every time I did my lawns and edges.
I still do. My eyes and ears are still ok.
My car had a knock when starting or stopping it with the key, and I traced it to the exhaust pipe that runs through the hole not much bigger than the pipe itself on the left hand side.
Funny thing is, it would only do it on starting and stopping the engine.
I put a large bar on the engine, and could flex it quite dramatically from left to right, but that pipe NEVER touched in that area!!
Just when starting and stopping the engine.
Post Number: 2195
|Posted on Saturday, 14 January, 2017 - 10:41 am: |
It's interesting, but since my father was Safety Supervisor for decades for our local United States Postal Service Processing Center I learned early on the importance of safety practices.
At the same time, I also learned that there is such a thing as "an overabundance" of caution that can be a safety issue in and of itself. This isn't meant as a "call out," but Geoff's example strikes me as just that.
When I first started working beneath SRH33576 I was almost as inclined to overkill as Geoff describes himself as being. I would have stacks of hard maple blocks placed in front of the jack stands in case they fail. Since I work in my driveway I always placed (and still do) plywood platforms beneath the jack stands so that the feet cannot dig in to the pavement and destabilize the car (which I observed happening at one point before I ever got under the car on a hot day after the car had been on the jack stands since the day before.)
Whenever possible, I put the car up on jack stands the day before I intend to work on it to let everything "settle." I will sometimes place a second set of backup jack stands just in front of the primaries, with their own sill blocks, that I theorize would be able to withstand a sudden "shock" loading were one of the primaries to fail. Thank heaven that theory has never been tested and, God willing, it never will.
I never keep the actual floor jack in place anymore as it generally makes working far more difficult than it need be.
I've never become cavalier, far from it, but have developed a comfort level after having done the "up and down" routine so many times on both ends of the car.
I really prefer ramps to jack stands and am less "skittish" about them even though they're plastic, of all things. The set I have is load rated for 12,000 lbs for the pair.
I don't think I've ever had all four wheels off the ground except when I'm using a hydraulic lift. When the car's on the lift I have a much higher comfort level moving around beneath it, often on my mobile work stool.
Omar M. Shams
Post Number: 995
|Posted on Saturday, 14 January, 2017 - 03:20 pm: |
great points about safety.
Geoff - Dont stop the way you do things - being cautiuos is not a bad thing. As Pat says - complacency can make people more comfortable than they should be.
My worst fear is seeing a car that has subframes on a 2 post lift. There have been many an accident of jaguars lifted on a 2 post jack only for the rear subframe to fall down completely under its own weight due to poor mountings. Consequently the process of that happening disturbs the balance of the car and then the car also falling. You dont want to be in any of that type of scenario.
I am like Geoff - I am scared of cars. Maybe because i saw lots of cars falling off jacks when i was younger.
Post Number: 1558
|Posted on Saturday, 14 January, 2017 - 05:54 pm: |
Hey Guys - thanks for your comments.
I've just checked out garage lift failures on youtube. Seems that most fails were due to incorrect positioning of the lifting arms and overloading.
Post Number: 5
|Posted on Saturday, 14 January, 2017 - 06:45 pm: |
I personally have seen a big trolley jack fail before I managed to get axle stands in place. Also on my 2 post lift, the very big bronze bushing (the nut on the long lifting screw) that actually supports that side of the lift, cracked and failed. The car crashed sideways against that post but stayed airborne now hooked on the other arms. No one was hurt but untold damage to car!
2 x reality check!!!!
Have you seen how surveyors pass these lifts? They put a weight just above the registered limit, and watch it go up and down. If it doesnt fail, it passes !!!
Post Number: 210
|Posted on Saturday, 14 January, 2017 - 08:07 pm: |
I'm with you on this one Geoff.
Post Number: 170
|Posted on Sunday, 15 January, 2017 - 12:06 pm: |
I've just installed a 2-post lift and will be appropriately cautious whilst using it, I assure you. However, my understanding of the device is the locking posts prevent it from falling. That said, the caution about the sub-carrier falling off completely is eye opening. Are our cars prone to this type of failure?
Christian S. Hansen
Post Number: 492
|Posted on Sunday, 15 January, 2017 - 12:31 pm: |
John...Service manual specifically cautions against elevating the chassis without supporting the rear suspension assembly.
Post Number: 6
|Posted on Monday, 16 January, 2017 - 08:18 am: |
Gordon, thanks for your suggestions. I couldn't find a safe slope, so it may help you to know that I managed to get the self levelling rams to create their clunking sound by putting the car in "park"(also fast levelling), and rocking her from side to side. Once you get a rhythm, it is surprising how much you can get her to rock!
That is not the clunking that I hear, but thanks for helping me tick one culprit off my list!
richard george yeaman
Post Number: 685
|Posted on Monday, 16 January, 2017 - 08:39 am: |
I would go with Roberts diagnosis rear damper bushes and oval shaped hole and loose nut, that was the fix I used on SRH19529.
Post Number: 15
|Posted on Tuesday, 31 January, 2017 - 08:25 am: |
Thank you all. It was damper bushes top and bottom - the rest OK
Robert Noel Reddington
Post Number: 1269
|Posted on Wednesday, 01 February, 2017 - 02:09 am: |
nice and cheap then, good O