| Author | Message | ||
     Richard Greene Experienced User Username: benzjag Post Number: 15 Registered: 12-2012 |
After installing my new brake pipe for System 1 (in center of car) on my 78 Shadow, I tried to bleed the system. I started the car, held the brake pedal down while bleeding. I bleed the right (passenger)accumulator first, then the front calipers. When a I tried to bleed the upper cylinders on the rear calipers, I get no fluid (with the pedal still continously pressed). Each time I press the pedal, the brake system light 1 will come on for a few seconds & go out. I do feel a slight pulsation in the pedal when the light comes on. The System light goes out immediately when starting the car. HELP! Richard 1978 Shadow | ||
| David Gore Moderator Username: david_gore Post Number: 2054 Registered: 4-2003 |
I wonder if the rear pressure limiting valve has jammed shut due to hydraulic hammer from the rear bleed valves being opened abruptly rather than slowly and smoothly. I would try depressurising the accumulators by a normal warning light test and then tapping the pressure limiting housing with a hammer to return the ball inside the cylinder to the open circuit position. When you start bleeding the system, just crack the bleed nipple slightly until some fluid escapes and then gently press the brake pedal slowly to prevent a sudden rush of fluid through the pressure limiting valve pushing the ball against the seat shutting off the fluid flow. This is one job where it is highly desirable to have a trustworthy assistant. | ||
| Richard Greene Experienced User Username: benzjag Post Number: 16 Registered: 12-2012 |
Just got this text from my Rolls dealer. My question is where is the "g valve"? "The reason the rear brake calipers will not bleed is the G Val has air in the Val. Come down slow on the pedal with the bleeder valve open 2 remove the ir. Once it starts to bleed you can close it then normal." | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1913 Registered: 6-2009 |
Richard, It's in the brake actuation linkage, AKA "the rat trap." See section G8 of the RR363 cars workshop manual. Also, here's the illustration of the rat trap from chapter G10:  See item 10 in the illustration. Brian | ||
| Vladimir Ivanovich Kirillov Grand Master Username: soviet Post Number: 503 Registered: 2-2013 |
This may be a long shot but if the above info does not solve your problem check to see if the car has any flexible rubber brake lines going to the rear and that fluid is going through them. I did find on one car not RR/B that the flexible rubber hose had deteriorated to the point that no fluid could pass through it. That's one car in 45 years !! | ||
| Omar M. Shams Grand Master Username: omar Post Number: 656 Registered: 4-2009 |
Dear Vlad, you are totally correct. I had that too on my Green Wraith II. The hose looked ok from the outside but internally it is totally blocked. That problem was only sorted when I chose to replace all the rubber hoses as a precasutionary measure. I would neever have ben able to diagnose such an oddball problem. Omar | ||
| gordon le feuvre Prolific User Username: triumph Post Number: 113 Registered: 7-2012 |
Also need to check reservoir filters are not blocked, if you have not sure of cleanliness of reservoir in general. | ||
| Richard Greene Experienced User Username: benzjag Post Number: 17 Registered: 12-2012 |
Finally, today I was able to get fluid at the rear calipers. After bleeding, the brakes are now fine! I started the car and had my friend open the bleed screw at the caliper. I then pushed the pedal very slowly a couple of times and had fluid.The brakes then bled as did the front. My Rolls mechanic said what actually happens is by pressing slowly the pedal the ball in the g valve will not rise up and close the port to the rear caliper. Hope this helps someone as I never heard about this. Appreciated all who helped. Brian, the diagram was excellent. I now know where that g valve is located! Richard | ||
| Hubert Kelly Prolific User Username: h_kelly Post Number: 197 Registered: 3-2012 |
Never knew that. Thanks Richard it's news to some of us ie me | ||
| nicolas@nucoltd.com Unregistered guest Posted From: 102.115.234.40 |
WE HAD REMOVED THE BRAKE ASSEMBLY ABOVE AND WHEN WE HAVE CONNECTED THE BRAKE PIPES WE DO NOT HAVE ANY PRESSURE ON THE CALIPER FOR BLEEDING, CAN YOU PLEASE MENTION WHICH PIPES THAT SHOULD BE CONNECTED TO EACH OF THE CONNECTIONS ON THE DISTRIBUTION VALVES AND YOU HAVE IT ON A DRAWING WOULD BE GREAT THANKS NICOLAS (Message approved by david_gore) | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 3013 Registered: 06-2009 |
Nicolas, What is the chassis number of the car you're asking about? There are differences between the SY1 series that used a master cylinder and SY2 series that did not. Brian | ||
| Robert J. Sprauer Frequent User Username: wraithman Post Number: 587 Registered: 11-2017 |
The valves and piping at the valves are shown in the workshop manual including the colour bands. | ||
| Geoff Wootton Grand Master Username: dounraey Post Number: 2190 Registered: 05-2012 |
Nicolas Just to re-emphasize what Brian and Robert have said, we need to know the chassis number of your car and also, there is a lot of important information in the workshop manual. The two maps of the distribution valve connections below are what I created for my car a while ago when I was blanking off the height control system. My car is an SY1. 1974, chassis number SRX18501. These diagrams are not valid for the series 2 and possibly for very early cars.    All the usual disclaimers apply. If your car is an SY1 and these diagrams are useful to you I can send more legible versions through email, if you pm me. There is a filesize restriction on this site, hence the loss of resolution on the images. Geoff |
