| Author | Message | ||
     richard george yeaman Prolific User Username: richyrich Post Number: 151 Registered: 4-2012 |
Hello All. I was out this evening helping a friend who was having difficulty bleeding the rear struts/dampers on a 1986 Silver Spur he and his man had fitted new gas springs I was asked to go because I knew where the bleed valve was and also because I could read Tee one topics number 82 and 24 all to no avail. having put a considerable weight in the boot/trunk engine running and the bleed valve open no joy would be grateful for any help!!! Richard. | ||
| Randy Roberson Prolific User Username: wascator Post Number: 196 Registered: 5-2009 |
Is the rear pump pumping? Is the link to the height control valve connected? | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 762 Registered: 6-2009 |
The first thing I'll say is that I've never tried to bleed an HSMO car. That being said, I'll share my experience with my two SY cars in the hope there may be some commonality. I have never, ever been able to get much more than a drop or two of fluid out of the bleed points for the rear rams, which I believe are analogous to the gas spheres & shocks on the SZ cars, using the load weight in the back technique. It seems to me that once the car rises and the height control valves close, there just not enough pressure from the weight of the car itself to cause it to sink and expel fluid. I have always found that I have to open the bleed screws first, activate the control arms of the height control valves to make the car believe it's had a lot of weight placed in the rear, then I get gushers from the bleed screws. If I then close off the bleed screws and wait for the car to rise and stop rising I can't get more fluid out if I crack them open again. I can only get them to bleed again if I reverse the position of the height control arms, let the car come down at least somewhat, and open the bleed screws before pushing those control arms back up again. Perhaps an analogous technique for the height control on an SZ car might coax things along. If you try this do report back. I think if you don't have a pressure light illuminated the brake pump not pumping is an unlikely cause. If the equivalent of the height control valve control arm is not connected correctly, making the system think it's perpetually in a fixed position, that could be a definite issue. Brian | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 1179 Registered: 6-2006 |
Hi, Is the weight of the car on the wheels and did the rear end rise up at all when the engine was started? The engine will have to run for at least 5 mins. If the rear did not rise them you will need to make sure that the rear pump is working and that the linkages to the rear height control valve are connected. Was the rear of the car up before they started the job? Did they release the fluid through the nipple on the sill before they started? did they get a pint out? If they didn't but the car has risen then check that the pipe leading to the remote bleeder on the inside of the sill is still connected. This pipe is prone to rusting and many cars have their bleed nipple at the other end of that rise under the boot floor. It's best to remove the old pipe but I've come across some left complete with block and nipples. Also note that the valves are damped so once the ripple is noopened and the initial fluid has gushed out, you need to wait another 10 to 30 seconds for the valve to open and fluid to flow. If you've done all that already, come back to us after checking the rear pump. Good luck,Paul. | ||
| richard george yeaman Prolific User Username: richyrich Post Number: 152 Registered: 4-2012 |
Hi,Randy Brian and Paul. Thank you for your response this car has always had this saggy look since the owner has had it. this current work that they are doing they have fitted New spheres to the front and New gas springs to the rear. I got the mechanic to bleed the rear brakes and there was plenty of fluid came from them assuming the back pump does both systems as in my SY car then it appears to be working when the bleed nipple on the inner cill was loosened there was a dribble of fluid came out about an egg cup in total I looked for a height control valve but couldn't find it as I am not familiar with SZ cars they also replaced one of the struts with a second hand one that appears to be leaking. he car was lifted on a two poster ramp and let down on to its wheels the bleed nipple was loosened and the boot filled with all sorts of stuff and one big person sitting on the boot floor and with the engine running for quite a long time all advice appreciated. Richard. | ||
| richard george yeaman Prolific User Username: richyrich Post Number: 153 Registered: 4-2012 |
Hi all. I found where the height control valves are by the way of the technical library there also was mention of two priority valves that wont let the height control valves work if the pressure is needed in the braking system sounds very daunting I am glad I only have a SS1. Richard. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 764 Registered: 6-2009 |
Richard, Just FYI, the height control system is reversed from the SY arrangement on the SZ cars (at least through 1986). From Chapter G of TSD4400: The inboard hydraulic reservoir supplies hydraulic system mineral oil for the number 1 system. From the reservoir, mineral oil is supplied to the front brake pump, which in turn supplies hydraulic system mineral oil under pressure to the vertically mounted accumulator, the upper distribution valve, the front brake calipers on the front wheels, the upper cylinders of the rear brake calipers, and the rear suspension struts. (emphasis mine) It's system 2 on the SY cars that provides height control, but system 1 on the SZs. See Chapter G of the Workshop Manual (TSD4400) on PDF page 6. If I recall correctly, and I believe that I am, Richard Treacy has offered that both the SY and SZ series cars can have their brakes and hydraulics bled much more simply than the workshop manual method. I think that information has been posted on these forums. I did an extended write-up based upon his method that's specific to the SY cars: Flush and Bleed Your Silver Shadow/Bentley T Hydraulics/Brakes the Easy Way. The principles are so similar, as are the bleed points that are used, that it's easy to figure out how to use this method on an SZ car (doing the respective fluid name change and knowing that it's the gas springs being bled rather than a height control ram and the change in location of the bleed screws for same). Brian P.S. I could not find a post by Richard on these forums (or at least not easily) but, being the record keeper that I am, I copied what he either posted on the RROC-US forums or e-mailed to me directly. The first comment was because SRH33576 has one bleed screw port filled with a sawed-off bolt rather than a bleed screw. Here are his observations: You can safely do a 99.99% calliper bleed by letting the air out at the Bundy tube olive union nearest to any broken bleed nipple and on the same circuit. That's an old trick with broken bleed nipples on all makes of cars. It even works a treat with master cylinder systems. Don’t forget to fit new rubber caps to the nipples on completion to save them seizing for next time. Incidentally, these brake systems don't mind a small amount of air, unlike on most braking systems. Only the master cylinder on the early SYs is sensitive to air or water vapour. That is because the distribution valves open the brakes to pressure and a virtually unlimited volume of fluid to achieve proper braking, not simply a fixed quantity of fluid as with a conventional master cylinder. Much is written in the manuals about bleeding techniques. I have been bleeding our T-Series for decades the simpler way with total success since I last did it by the book yonks ago. That means once every 6 years at the latest when I fit all new hoses and caliper seals in accordance with scheduled maintenance. What’s more, you may bleed all the hydraulics without a whingeing assistant. 1. Where fitted on early cars, bleed the master cylinder/rear brake halves first in the conventional manner. 2. Pressurise the system. If you are in a hurry, bleed the accumulators by all means. Alternatively, let them have a few days of use and they will bleed themselves. Being a system recirculating through the reservoir, all air is dispelled very soon. That’s quite safe for the reason above. 3. Once the accumulator circuits are purged as described in 2., with the system pressurised, bleed the brakes at the calipers as follows. Place a short plank between the seat and the brake pedal with a towel as protection. Move the seat forward so that the brake pedal has, say, 15lb pressing onto it. Crack each brake system nipple at the calipers in turn until they run clear, then again once each in sequence for good measure. Brakes done. 4. Finally, load the boot/trunk with 1cwt or more or set the rear height temporarily very high. With the system pressurised and on Fast (door open or whatever your particular model needs), open the bleed nipple at each ram in turn until the fluid runs clear and a bit more. Do it again after waiting for the rear end to rise again. Job done. All that stuff in the manual about low-pressure and high-pressure bleeding and all over the place is B****cks, It is mainly to scare of the uninitiated, but introduces many silly and unnecessary risks. Almost every service specialist I know does it the way I describe. To quote one in my hometown “these cars have the easiest brakes on earth to bleed.”. The same applies to SZs. Forget all the intermediate bleed points. If you just do it properly at the end points (calipers and struts) that does the job more safely, quickly and easily. (again, emphasis mine) | ||
| richard george yeaman Prolific User Username: richyrich Post Number: 154 Registered: 4-2012 |
Hi Brian. thank you for your input I have read the Hydraulic section of workshop manual and as you say the role of the pumps on the SZ cars are indeed the reverse of the SY cars I will relay this information to my friends mechanic. typically Rolls Royce change for the sake of change Richard. |
