| Author | Message | ||
     David Lacey Experienced User Username: dlacey Post Number: 15 Registered: 11-2010 |
All, Just returned from a 10 day trip to Thailand in SRH4452, managed to squeeze 13mpg out of the fully loaded barge. During the trip it developed a creaking noise which is something to do with the left rear suspension hydraulics. Car appears to be levelling fine, just noisy. So, I decide to bleed the rear rams with car on the ground, ignition on, in neutral with drivers door open. The right side bleed screw emits a nice stream of clear fluid. The Left side is different...open the bleed screw & nothing comes out... if i reach under and push up the height control valve drop link (just taking up the little slop in the mechanism) then clear fluid emits from the bleed screw...but only while i push up. So, whats going on with that ram? I thought with the weight on the suspension it would depressurise & retract as i opened the bleed screw... its behaving like its mechanically seized. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1105 Registered: 6-2006 |
David, the fluid is coming from the accumulator, not from the ram. The ram is probably already retracted. Dirty Restricter valves often cause noises. | ||
| David Gore Moderator Username: david_gore Post Number: 1327 Registered: 4-2003 |
David, About a decade ago, Castrol changed the formulation of RR363 and this resulted in previous dignified cars developing all sorts of internal noises from the self-levelling system. Creaks,groans and a tapping noise best described as "Maxwell's Silver Hammer" by one afflicted owner became a problem. The formulation was changed again after a relatively short time and the problem disappeared. This is covered in some detail elsewhere in this forum. It is possible your car and this "limited edition" fluid may have become acquainted. As far as the failure to bleed goes, you need to load the rear of the car to activate the load sensing valve before attempting to bleed the system. Getting an assistant to sit on the boot sill is usually sufficient to activate the valve. If you disconnect the actuating arm from the trailing arm and carefully move it up and down manually, that side of the car should move accordingly [be careful not to move the arm too far; about half an inch [13mm] should be the maximum]. | ||
| David Lacey Experienced User Username: dlacey Post Number: 16 Registered: 11-2010 |
Paul & David, Thanks for your inputs. I believe the rams aren't fully retracted as i have in the past lowered the car when i disconnect & pull down the actuating arm [ = sagged rear springs]. I need to look closer at that left side...can I still lower it on the actuating arm? I still think it's odd that I can't get fluid from that bleeder...there should be significant static pressure in the partially extended ram... | ||
| Omar M. Shams Grand Master Username: omar Post Number: 349 Registered: 4-2009 |
If I may ask the question that was first asked by David in a slightly different way, maybe we can get a more targeted response from the experts. Assuming that the car is straight and the rear laden, it should be possible to get oil comming out of either rear height control bleed nipples - not just one. The discussion about accumulator pressure working on a bleed nipple should apply equally to the other side if the car was restarted and the system pressures normalised. I think that in a perfectly set up car, either bleed nipple should discharge equallly when opened. Could the fact that one nipple is not flowing be due to the height control valve lever adjustment not being correct? | ||
| David Gore Moderator Username: david_gore Post Number: 1328 Registered: 4-2003 |
Hi Omar, The nipples should only bleed fluid when the rams are pressurised; if the mass of the car is being carried solely by the springs, the rams will not be pressurised and will only bleed if the springs are subsequently loaded and compressed. If my memory is correct, the accumulators are isolated from the rams when the height control valve is in the neutral position; this is why it is necessary to load the rear suspension before bleeding the rams. I think your suspicion that one of the height control valves is not set correctly is correct - my suspicion is that the incorrectly set valve is the one on the side of the car where bleeding was successful. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 606 Registered: 6-2009 |
David, I believe your memory is correct. Unless the height control ram is in the process of being "adjusted up" there's no incoming pressure much like there is no incoming pressure to the brakes unless the brake pedal is depressed. I have always found bleeding the height control to be a hit-or-miss proposition, particularly if you're doing it alone. While you can get the rams to raise or lower easily, to bleed them you must have a bleed screw open when they're trying to raise the car (or at least that's been my experience). If you have the car "pre-set" to fast level when you start it you're never going to get to the bleed screws before that leveling is complete. You do have the option of having a bleed screw already open and "ready to bleed" when you start the car then you need to get back there to cut off the flow and let the ram raise the car again. This is not particularly easy at all when you're trying to do this work with the car on the ground. I've never had access to a "drive-on" ramp-type lift on which I could do all this a bit more easily. I've also never had luck creating a "boot in the air" situation and getting the system to bleed then by opening the screw, though it seems like this should work. The height control system is self-bleeding, much like the accumulators, if (and I emphasize if) it is activated repeatedly. This doesn't often happen in actual practice, but you can do multiple "up and down" activations by hand to get repeated in then out flows of fluid (and air) directly back to the reservoir. Brian | ||
| David Lacey Experienced User Username: dlacey Post Number: 17 Registered: 11-2010 |
All, I also understand that the rams will self-bleed, but the result of my 'improper'(!) bleeding operation is positive, the creaks have gone and now I just have a light clicking noise on a bump/compression of the rear end. Still worried by the side-side difference in behaviour & accept that this could be an adjustment needed to get things trim. |
