| Author | Message | ||
     Benoit Leus Grand Master Username: benoitleus Post Number: 334 Registered: 6-2009 |
Some time ago I replaced the rear roll bar bushes. Since then, the car has developped a mystery problem. When driving at lower speeds there is knocking sound coming from the RH wheel area, when driving over small bumps. It's not a crashing sound from the suspension, but more like something hanging loose, as it sometimes continues to rattle a bit after I've driven over the bump. You can't hear it at higher speeds or bigger potholes. I've checked the roll bar mountings but they seem to be OK. The same goes for the UJ's and driveshaft. When rocking the car by hand I can't hear a thing. I've also checked the handbrake mechanism and there is some play in it, but no more than on the LH side. When turning right(with the weight taken of the rear RH wheel) it's much clearer. I don't believe it's a bearing as I know what that sounds like. I'm all out of ideas and would welcome any suggestions. Benoit | ||
| Larry Kavanagh Prolific User Username: shadow_11 Post Number: 147 Registered: 5-2016 |
If it sounds like a household plumbing knock it could be the low pressure restrictor valve is blocked with crud which would stop return fluid from the height control valves getting back to the reservoir. This causes a rattling or knocking noise in the pipework similar to an air lock in household plumbing. Just a guess. | ||
| David Gore Moderator Username: david_gore Post Number: 2833 Registered: 4-2003 |
Benoit, Possibly a collapsed RHS shock absorber bush/subframe mount/cross member mount/trailing arm mount .... See Chapters H and J in TSD2476. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1792 Registered: 9-2004 |
Maybe the diff torque reaction arm bolts and bushes, I think the arm only fails on early SS1 cars if not updated. | ||
| Martin Taylor Prolific User Username: martin_taylor Post Number: 125 Registered: 7-2013 |
I replaced all the diff housing rubbers to try and find a similar noise, turned out to be the exhaust knocking against the wheel carrier, with the car cold grab the tail pipe and see if you can move it far enough to tap anything, the sound will travel through both the car and pipe | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 335 Registered: 6-2009 |
Thank you everyone for your suggestions. Last year I replaced the rear shocks and springs, so that shouldn't be the problem. Also the rear diff carrier mount bushes were replaced a couple of years ago. Also, it sounds more like a rattling noise than a faulty bush. As for the exhaust, I checked it, but it doesn't seem to knock against anything (it's rarely that easy, isn't it). Larry, your suggestion is definitely worth investigating. It indeed sounds a bit as bad household plumbing. I should check again, but if I remember correctly the car didn't seem to rise or lower the last time I manually operated the height control valves. So I guess I'll start by cleaning the restrictor valve. | ||
| John Kilkenny Prolific User Username: john_kilkenny Post Number: 275 Registered: 6-2005 |
When all else fails check the exhaust boxes for loose baffles. | ||
| Larry Kavanagh Prolific User Username: shadow_11 Post Number: 148 Registered: 5-2016 |
Hi Benoit, Also check that the height control solenoid valve is working properly. If you switch on the ignition and detach one of the wires from the solenoid valve you should hear it click if the electrical side of the solenoid is working. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1794 Registered: 9-2004 |
Have known jack to rattle on bumps, also some boot lids or trunk to rattle on the catches when the lid is not a tight fitting with a bump stop! | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 337 Registered: 6-2009 |
Larry, good advice. I will include the solenoid in my investigations. The work however will have to wait a week or 2 as I also bought another car that I have to collect and make sure passes it's technical control (our MoT) before I can register it. Patrick, I threw everything out of the boot, including the jack, and checked the boot lid and door catches (had to adjust one of them) but it didn't make any difference. | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 233 Registered: 7-2012 |
Try disconnecting height control actuator arm(s) You MUST make certain to secure height control arm in it's normal operating position as it can over centre requiring h/c valve to be stripped. Early cars up to 71/2 suffered with valve noise that was like "cracking" but only heard at low speed. Bit of work, but at least you can eliminate h/c valves} | ||
| Alan Dibley Prolific User Username: alsdibley Post Number: 129 Registered: 10-2009 |
"" Early cars up to 71/2 suffered with valve noise that was like "cracking" but only heard at low speed. "" You can learn something new every day. Thank you, Gordon. Alan D. | ||
| Martyn Grattage Frequent User Username: martyngrattage Post Number: 67 Registered: 11-2017 |
Hi Benoit, Unfortunately I haven't actually been able to even drive my RR yet I am mid vacuum hose renewal and figuring out exactly what should be there. and hopefully driving her soon..!! Ha ha..!! You are in exactly the same position as me - I had exactly this problem get worse and worse on my old 1984 Mercedes 280CE - it was the upper control arms and bushes in the end - it failed Rego because of it 3 weeks ago. Various advice from various mechanics over the years about it was she is old and to start changing any bushes would be a start but they weren't sure what it was. It actually resulted in tracking issue and bald tyres an on the inside. Are you able to check these at all - worth checking if its easy enough. Good luck with it. Martyn | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 234 Registered: 7-2012 |
To clarify my earlier comments, R-R moved the location of the rear height control valves at 11970 (1971) The reason was because it had been found through experience that the rear of the car would settle before the valves would react to this. The consequence of moving valves was to put increased load onto the bushes of the valve, that would manifest itself as a low speed crack, crack, crack noise emanating from somewhere under rear seat/floorpan. The fix was to replace bushes with ones of different material. The short term/early fix was to strip valve and put double saw cut across bushes to aid extra lubrication. Also, don't forget lubrication of height control arm ball joints. Just another thing to look at/eliminate. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1797 Registered: 9-2004 |
Nothing as simple as a loose hub cap! | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 340 Registered: 6-2009 |
I had my son lightly push the RH rear corner of the car, while I lay under it to try and identify the knocking sound. It seemed to come from everywhere and nowhere, so I took a long screwdriver to use as a stethoscope. After a very long search I think I finally found the source. It seems to come from the area around bottom of the shock absorber and the shock absorber bracket (cup). I nipped up the bolt at the bottom of the shock which compressed the bush but didn't eliminate the knocking sound. The shock and bushes are less than a year old so I hope they haven't failed yet. When holding the shock itself I cannot feel the knock. I will dismantle the damper bracket and see if I can find the problem. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 2019 Registered: 6-2006 |
Hi. You could try listening to the rams in the boot as well. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 341 Registered: 6-2009 |
Paul, I already did that, but the sound really seems to come from the bottom of the shock assembly. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 343 Registered: 6-2009 |
The mystery continues. I removed the RH rear shock absorber bracket so that the shock is totally decompressed. This didn't stop the knocking sound. Without the resistance of the shock the sound will now occur at the slightest upwards/downwards movement (a few mm's is enough). The harder I push, the louder the sound (up until a certain point). I disconnected the height control valve and pressurised the hydraulic system. Could it still be a fault within the hydraulic system (low pressure restrictor valve) or should the engine be running and the system pressurised for that ? What bothers me, is that the sound started after I replaced the rear stabiliser bar bushes. It could be pure coincidence of course, as I checked that the bar doesn't touch anything and the mountings are correctly installed. I might remove the stabiliser bar as a next step to see if that changes anything. | ||
| Larry Kavanagh Prolific User Username: shadow_11 Post Number: 150 Registered: 5-2016 |
You would hear a knocking from the restrictor valve only if the engine is running. From what you have described I would rule out the low pressure restrictor valve and the height control valve and anything to do with the hydraulic system except perhaps a stiff height control ram. I think I would try reconnecting the height control valve and bleeding the RH rear ram and see if that makes any difference. Maybe if you remove the stabiliser bar bushes and smear a little silicon rubber grease on them it might cure thee problem. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 2020 Registered: 6-2006 |
Are all the points where the handbrake cable touches anything well greased? Are the trailing are check straps well greased? Are the anti-roll bar drop links tight and in good order? Is there rust or a stone or dirt inside the rear spring cups and the spring is chaffing on the cup or itself? Good luck. . . I hate mystery noises!! | ||
| richard george yeaman Grand Master Username: richyrich Post Number: 941 Registered: 4-2012 |
I think you are right to remove the stabiliser bar and see if that changes anything, as that is where the mystery started. Richard. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 344 Registered: 6-2009 |
After spending several hours under the car, still with the RH rear shock disconnected at the bottom to make rocking the suspension easier, I still couldn’t localize the sound. However, I was more and more convinced it was something hitting the floorpan. For reasons unknown I decided to jack up the RH rear wheel (with disconnected shock) and rocked the suspension. No sound ! I lowered it again and still no sound ! I guess while changing the stabilizer bar bushes something in the suspension/ differential assembly moved, causing the knocking. And by jacking the rear wheel it moved back in place. Now I only have to reconnect the shock absorber and hope the sound doesn’t come back. | ||
| Larry Kavanagh Prolific User Username: shadow_11 Post Number: 153 Registered: 5-2016 |
Check that the brake pipe to the calliper isn't too close to the rear spring and rubbing when the spring moves. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 345 Registered: 6-2009 |
Larry, that's a good suggestion so I checked it only to find everything is OK. When I reconnected the bottom of the RH shock the knocking sound came back. I know it's not the shock itself, so probably the rear moved slightly again causing it to knock on the floorpan. I read somewhere that when installing new rubber bushes you should always do it with the load of the car on the wheels. So I dismantled the rear stabilizer brackets that hold the rubber bushes in place, drove the car around the block to settle the suspension and reinstalled the brackets with the wheels on the ground. Unfortunately, no success. So back to square one I guess. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 349 Registered: 6-2009 |
As the sound drove me mad, I tried again : , loosened the stabilizer bar mounts, disconnected the RH rear shock bottom mount, jacked up the suspension (compressing the spring) and tightened the mounts again, lowered the suspension and reconnected the shock. Result : the knocking sound is gone ! .... untill, on the test drive, I floored the throttle from standstill and back it was. It is now only when I really put the pedal to the metal, which I rarely do. I still guess something in the rear suspension has moved and touches the floorpan, I just have to find out what it is. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 1837 Registered: 9-2004 |
Diff carrier cross member mounts worth a check! | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 350 Registered: 6-2009 |
Patrick, I replaced them about 5 years ago but you are right that I should be investigating them. It is well known that the quality of rubber parts can be poor, so I will certainly take a look at them. | ||
| richard george yeaman Grand Master Username: richyrich Post Number: 956 Registered: 4-2012 |
Benoit, I have read all the above suggestions and the clues seem to be that the hole in the shock absorber hole is worn as well as the rubber bushings etc, I had this trouble with my own car years ago cure is to weld a heavy waster to the bottom cup to eliminate the free play. Richard. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 351 Registered: 6-2009 |
Richard, that’s a good suggestion indeed and when I replaced my rear springs and shocks last summer I had to make that exact repair. I’m still convinced something moved when I replaced the stabilizer bar bushes.   | ||
| richard george yeaman Grand Master Username: richyrich Post Number: 957 Registered: 4-2012 |
Hi Brenoit mine weren't as bad as yours bet they created bit of a noise. Richard. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 354 Registered: 6-2009 |
It’s getting worse. I jacked up the front of the car so I could change the oil filter. When I then drove the car, the knocking sound was back with a vengeance. But now I also have a major cluncking noise coming from the LH rear when accelerating hard. Under normal acceleration everything seems fine. When I replaced the roll bar mounts I also took the roll bar out to repaint it. For this I had to disconnect the diff torque arm mount and now have the impression that the rear diff assembly is not properly alligned anymore. Is there a way to properly align the whole rear ? | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 240 Registered: 7-2012 |
Benoit, if one assumes that the diff carrier has not torn away (or started to) from the bolts that hold it to the boot floor, the torque arm is bolted to the side of diff, that being bolted to diff carrier, this should all line up with torque arm front mounting on the beam which holds both trailing arms in place. This beam is located by 2 x vertical mounts at each end (pan scrubbers) 2 x horizontal mounts inboard of height control valves ( 2 x pan scrubbers) AND the 2 long torque arm tubes that run forward along the inner sills. The prop shaft also runs through this beam. Do the mountings (any) look collapsed, is there clearance between beam and vertical face of body shell ( where main battery cable and hydraulic pipes run) This clearance is never great, but should be able to slide fingers across forward vertical face of beam. Is there any evidence of prop having rubbed beam, where it goes through hole. Given what I said in opening statement, if all ok with diff carrier/torque arm, it does point to movement of beam, and if so why. Easiest to change are torque tube rubbers. How worn is every thing. Is there any evidence of either drive shaft contacting anything. It all helps with diagnosis. The 4 x pan scrubbers, which will ALWAYS look compressed because of load they carry can be changed in place (one side at time), but it is not an easy task, even with proper workshop facilities. Does one side of beam mounts look worse that other side, is one side of beam in different position, horizontally/vertically to body shell angles where beam lives? Changed a set on 73 Corniche last year, without removing beam. Need to read manual very carefully, but I am jumping the gun. As I have said long way round, if diff carrier/torque arm good, look forward. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 355 Registered: 6-2009 |
Gordon, thank you for all this information. This will be really usefull in trying to identify the cause of the problem. I’m away for a few days now but will definitely check it all early next week. | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 241 Registered: 7-2012 |
Benoit, On page H34 of section "H"- sub frames of Shadow workshop manual there are figures for beam alignment check relating to position relative to front suspension sub frame. | ||
| Patrick Francis Prolific User Username: jackpot Post Number: 230 Registered: 11-2016 |
Hi Benoit Have you tried one of these. It is a stethoscope with 6 clip on microphones that you can switch between whilst driving. May help to pinpoint the sound ? https://www.directsupplyukltd.co.uk/steelman-electronic-stethoscope-ste06606/p347 Good luck in your quest. | ||
| Patrick Francis Prolific User Username: jackpot Post Number: 231 Registered: 11-2016 |
It really is an excellent piece of kit. Can be used for isolating failing injectors, noises within the engine, etc It is volume controlled and therefore as sensitive as you need. | ||
| Benoit Leus Grand Master Username: benoitleus Post Number: 360 Registered: 6-2009 |
Over the last 250 miles the noise coming from the rear supsension was even more present than before. As suggested on this forum I checked all the subframe mountings and suspension bushes. They're obviously not brand new, but there is definitely life left in them. I also checked the dimensions and distances of the rear suspension/subframe and they're all OK. I disconnected the driveshafts to rule them out as the source of the noise. I also rechecked the exhaust, spare wheel carrier, etc ... I then again disconnected the RH rear shock at the bottom : there was still a knocking sound, but not as loud as before. I then also disconnected the LH rear shock : no knocking noise whatsoever ! Reconnecting the RH rear shock produced the knocking sound. It seems both shocks (Introcar items bought last summer) have developed this knocking sound, especially the RH one (the LH one is much more quite). I'll contact them and see what they say. | ||
| Omar M. Shams Grand Master Username: omar Post Number: 1508 Registered: 4-2009 |
Oh dear Benoit. Looks like you have bought substandard shock absorbers. What if Introcar have a batch of defective shockers and even the replacement shocks are bad? Beware of that when the new ones arrive. | ||
| Patrick Francis Prolific User Username: jackpot Post Number: 232 Registered: 11-2016 |
Hi Benoit Just a shot in the dark, but I had a similar problem which was the top connection of the shock absorbers - two washers sandwiching two little rubber doughnut washers. You might be able to tell by moving the shocker up and down by hand, but not always. The whole thing has to be quite straight, true and tight, else it can knock. Good luck! | ||
| John Rowney Experienced User Username: johnrowney Post Number: 41 Registered: 2-2015 |
Hi Benoit Hopefully you have fixed the problem, but just in case you haven't, I have the following which may be of interest. I had an awful knocking noise on my 1978 Corniche DRH32489 for almost a year. I have tried lots of things discussed in this forum but to no avail. My knocking was a particularly unusual noise since it only occurred for the first 15 minutes or so from cold - then the noise disappeared. I completely sorted it out yesterday after much hard work - it was the driveshaft knocking on the lower cover plate. Removing the plate is a pain since lots of the bolts are difficult to access, and dropping the handbrake cables is part of the awkward problem. The point of knocking was evident due to wear on the cover plate and missing paint from the drive shaft. The cover plate (with several curved and straight sections) has a couple of dished areas so that there is clearance between the plate and the driveshaft. I had a couple of attempts at panel beating to extend and magnify the dished area where the contact point was evident. The result was that the clearance between the driveshaft and the cover plate was increased and the job was successful. No noise at any time! I had been given this tip by a Gold Coast RR and B mechanic, Colin Brown, who recalled something similar occurring years ago with a client's car and panel beating the cover plate did the trick. Maybe a Shadow, unlike a Corniche, doesn't have a cover plate for the driveshaft - but I thought I would post this just in case. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 2098 Registered: 6-2006 |
Hi John, have you got any photos? Can't picture the part you mean. Edit. Forget that. Prop shaft.  | ||
| John Rowney Experienced User Username: johnrowney Post Number: 42 Registered: 2-2015 |
I have confirmed that the cover for the Corniche drive or prop shaft is only found on some Corniche dropheads. It is not installed on Shadows or fixed head Corniche vehicles. This cover was apparently added to help increase the rigidity of the body of the drophead. Another addition was the installation of a large "X" steel member to also improve rigidity. So, sorry, my suggestion re noise is of no use to anyone except for owners of Corniche dropheads. |
