| Author | Message | ||
     Mark Anson Prolific User Username: bentleybloke Post Number: 80 Registered: 11-2004 |
Hi All hope someone can help. My brake pedal is nearly on the floor on my Shadow One after the vehicle has been standing for some time. The low pressure brake system fluid level light has now come on. I want to bleed the brakes so the car will have a better pedal whilst I move the car around during its restoration. I have read through some of the emails on brake fluid and brake work but I have not found a step by step guide in how to bleed the low pressure braking system. Some people I know say do it with the engine running some say use a pressurised bleeding system. What is the method (step by step) you use? Also what bleed nipples and what order do you open them to get the best result? Many thanks Mark | ||
| whunter Prolific User Username: whunter Post Number: 160 Registered: 10-2003 |
There is no fast way to bleed the hydraulic system. Go to the following URL http://www.swammelstein.nl/techinfo.htm Look for G07-G10 Bleeding the Hydraulic systems Down load and save Scanned sections of the Silver Shadow workshop manual (in ZIP files with tif images) | ||
| bob uk Unregistered guest Posted From: 81.168.83.66 |
To bleed the manual master cylinder. Pressure bleeding will not work because there is not really a way to fit the equipment to a Shadow. Vacuum bleeding will work. Engine not required. However if the brake pedal is going down then the master could be faulty. These are not expensive and best replaced rather than rebuilt. They are easy to fit as well. To bleed. Between the frames of the rat trap is a spacer which when the brake is applied stops 2 prongs which stops the master push rod going any further. This is a safety feature. When the prongs hit the spacer the compensator in the linkage puts the power brakes on. To bleed the master cylinder this spacer needs to be removed so that the cylinder gets full travel. Because the master is at an angle an air bubble can get trapped by the output port. So remove the front wheels and drop the car down at the front and lift the back up. Pump the pedal and then open the bleed nipple for the lower calliper pistons on cars with a pressure limiter ( about 1972 on ) and the upper on cars without. (1966 to about 1972 ). Bleed as normal cars. Adjusting the master cylinder push rod. If after bleeding if the pedal stills feel low it may mean that the push rod is too short. Adjust the push rod so that the clevis pin can still turn, but this is hard to judge. SO as a check the rear wheel must turn by hand if not the rear brakes may binding due to the master being held on a bit. Also as the car warms up the rear brakes can come on even if the rear wheels turned by hand as above. SO leave rat trap off drive car for at least 5 mile if the rear brakes do not bind then the settings is not too tight. If the brakes start to bind , stop car shorten push rod slowly until the brakes release. Safety first be carefull car could roll and run you over. Also if any of the hoses on the master system are old change them because I have seen people spend days trying to get a good pedal and I come along pop new hoses on and they are gobsmacked when 5 mins later I have a good pedal. You can use normal DOT 4 fluid for testing and bleeding but once you have the system right drain the tank down and refill with RR363. Note for Dave Gore. It you do not like the last comment delete it. Hi Bob, I have no problems with your advice as it is a good and economical way to test the system provided sufficient bleeding [the rear height control rams in particular] is done at the end of the job to ensure RR363 fills the entire system. Kind regards David (Message approved by david_gore) (Message edited by david_gore on October 19, 2005) | ||
| Gus Brogden Experienced User Username: gus Post Number: 37 Registered: 2-2008 |
Hi, I am replacing the accumulator to frame high pressure hose on SRF31065. Any idea where downsteam I should bleed when I'm done? Thanks. | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1112 Registered: 4-2003 |
All points down stream of the accumulator. This is a good time for flushing if there is crap in the system. Consider flushing with DOT 4 and finish with RR363 | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 315 Registered: 6-2006 |
Gus, unfortunately the frame hoses are the entry point to both main systems. You should bleed the whole system really. If you wanted to try just a single point bleed, I'd go for BOTH callipers on one front wheel. Open both nipples and apply tubes BEFORE starting the engine. Wedge brake pedal down BEFORE starting engine. Ensure she's topped up and then start the engine. In theory this should isolate any air and pump it straight out before it has a chance to go elsewhere. Of course problem may occur because the AIR in the flex pipes may not have read the theory books!  Any delay in the brake pedal will mean a complete bleed of the brakes (less mater cylinder if you have one) Bill, we posted at the same time there! Good advice for all. I think Gus has just changed his fluid though :S (Message edited by paul_yorke on 02 May 2009) | ||
| Gus Brogden Experienced User Username: gus Post Number: 41 Registered: 2-2008 |
Thanks gents, I thought that way after I thought about the system. My good invisible being, they are an expensive hose. I can see why people change all hoses but these. I found an aftermarket one and it was still stifling. Considering the proximity of the exhaust pipe, I never want that hose to pop again. I will dutifully change it at every hose service. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 316 Registered: 6-2006 |
Gus, not sure why yours went, but the only leaking ones I have come across were due to them touching - either each other or something else. It can be tricky to get all the accumulator hoses not touching, but it's very important that all 4 are apart. Anybody that has had them off should check for interference between them. | ||
| Gus Brogden Experienced User Username: gus Post Number: 42 Registered: 2-2008 |
Mine was touching nothing. It looks (to my eye) like an original hose. It suddenly started leaking at the ferrule, and it was a large one. It emptied the resevoir in a minute. It's on SRF31065, so it was probably over 30 years old. It was due to be changed anyway. I'm just glad it happened in my driveway, and not on the road. My neighbors have seen me tow enough vehicles in and out of here, so far they haven't seen a Royce towed. I hope to keep it that way. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 317 Registered: 6-2006 |
LMAO - a lucky break. Well at least my neighbours only see cars being towed in! I've seen cars where the fluid has sprayed out through the wheel arch in a fine mist and ruined the paint down one side. Not good! I wish R-R had gone over to LHM earlier! Mind you , the change over was a real mess - even with a completely different shape reservoir and car - the amount of cars that were contaminated were a nightmare! | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1116 Registered: 4-2003 |
Interesting. Paul have you noticed that the new children - neither use LHM??? | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 318 Registered: 6-2006 |
Tis true Bill. Although I think they use a separate hydraulic fluid now. Some mystery fluid again. RR2000 or something??? I don't have many that I repair but have not had brake problems yet. Well . . . apart from rusty brake pipes already failing MOT's - Can't imagine what they will be like in 40 or 50 years! I guess they have gone over to mass produced tried and tested systems a lá BMW etc. so they should be fine. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1698 Registered: 4-2003 |
Bill, That's because the new kids on the block don't have high-pressure braking systems with distribution valves. They have conventional braking systems, and those are totally unsuited to silicone fluids (DOT-5) and LHM alike. Like DOT-5, LHM is not hydroscopic, a feature assumed to be a good thing in the past. That theory hit a sudden and ugly brick wall decades ago for all but competition applications, with new fluid at each meeting, and in systems such as SYs and SZs. Thought to be the bugbear of conventional brake fluid for a long time, being hydroscopic turned out to be its huge quality afterall. The problem with non-hydroscopic fluids is that inevitably moisture still enters the system, albeit in smaller amounts, and does not diffuse throughout the entire system. Instead, with LHM and DOT-5, mosture congregates as droplets in the most unfavourable places. Notably, that is in the callipers at the hot-spots behind the pads, the lowest altitude in the systems, where the droplets cause corrosion and boil unexpectedly on heavy braking. Boiling droplets may cause total brake failure due to steam vapour locks. That happens on a conventional system when it runs out of capacity as the brake pedal hits the floor. On some cars with conventional braking systems, this is known to happen in both braking circuits at once without warning the first time. When the Arnage T was first tested by Top Gear, precisely that happened. I know first-hand of a Morgan converted not long ago to silicone for a very brief time until the same thing happened. On an SY or SZ, along with most Citroens, the systems are remarkably tolerant of degraded fluids and moisture. Hence they are often neglected as the brakes work fine with no detectable loss of feel or effectiveness long after the fluids are spent. Boiled fluid or vaporised moisture droplets are not serious problems as the pressure loss is simply topped-up by the distribution valves. The capacity of the accumulators, and being topped-up by the pumps at all times, effectively gives an unlimited capacity to push fluid back down the brake lines. Any pressure loss due to vaporisation is automatically compensated for by the distribution valves passing more fluid to maintain pressure. That is why LHM is fine in SZs. Even Citroen has changed to conventional brakes on the C5. They run conventional DOT fluids for the brakes for this very reason. So, although moisture degradation of a conventional hydroscopic brake fluid is undesirable, it is better than the alternative potential total brake failure with LHM or DOT-5 silicone. Many found that out in the 1970s when DOT-5 was supposed to be the panacea. It cost the US Military tens of millions of dollars to correct, and the correction programme is still going on. Hydroscopic fluid has disadvantages, but the enormous advantage is that moisture degradation is dispersed molecularly throughout the system, and only causes a gradual, non-critical, lowering of the fluid's boiling point over time. The slow degradation in boiling point is corrected every two years when the fluid is routinely completely purged anyhow. RT. |
