| Author | Message | ||
     Koby Millo Yet to post message Username: kobym Post Number: 1 Registered: 7-2011 |
Hello, I am new in this forum, and would appreciate your help. I’m helping a friend who is a professional mechanic to restore his 1976 Silver Shadow. We had no previous experience with Rolls-Royces, but we have tried to learn the hydraulic system as deep as we could. Like many, we have a brake issue… Most of the system was rebuild – calipers with new pistons, accumulators, hoses, distribution valves etc. But – faulty rebuilds are always possible… We still have few problems: When the brake pedal is pressed and released, all 4 wheels remain locked. After slightly releasing any one of the caliper bleeding nipples, the brakes are immediately released. Another issue which might be related – we have put pressure gauges to measure the 2 hydraulic pumps. When the engine starts running, pump A goes up to 2200psi, but the 2nd pump B goes only to 300psi. When we stop the engine, the gauge on pump B is going slowly up to 2000psi, and when we start AGAIN it goes up to 2200psi like pump A. After 1 day that the car is left still, pump B goes to 200-300psi (while pump A stays high, but goes down after 2 more days). Any help or insight would be highly appreciated, especially on the locked brake issue. Regards, Koby | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 748 Registered: 6-2006 |
Hi and welcome Koby, Has your car got a master cylinder? If so it may be that the rod is too long. If not check that there is some free play in the pins that operate the brake distribution valves. Does opening any rear brake nipple also free out the brakes? Regarding the pressures - Hmmmm. Remove the accumulator flex pipe and put the gauges in there and see what readings you get. If the readings you quote are already with the flex pipe out, then clamp the return hose. Remove it and add a hose to the return pipe. Run the engine with the gauge in and see if fluid exits the return pipe at the 300 psi reading. If it does then the accumulator valve is faulty and not seating correctly. If it is not then the problem is more likely to be pump based. Are the reservoir filters clean and teh feed hoses in good condition? | ||
| Jan Forrest Prolific User Username: got_one Post Number: 206 Registered: 1-2008 |
Firstly a '76 Shadow shouldn't have a brake master cylinder. Braking effort is supplied by a position dependent distribution valve. If the brakes stick on then either the pistons are binding in the calipers (unlikely for them all to do so) or the flexible hoses have collapsed internally (ditto) and aren't letting the excess pressure drain back away from the calipers. Two other thoughts comes to mind: Did you fit Shadow 1 seals and refill the hydraulic system with LHM brake fluid? Alternatively did you fit the seals for a late Shadow 2 model but still filled it with RR363? Either would result in a completely trashed system and the system would have to be completely flushed before replacing all the seals again. | ||
| Koby Millo New User Username: kobym Post Number: 2 Registered: 7-2011 |
Thank you all for the comments and advices - will give it a try and will update. Best regards, Koby | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 749 Registered: 6-2006 |
"Alternatively did you fit the seals for a late Shadow 2 model but still filled it with RR363? Either would result in a completely trashed system and the system would have to be completely flushed before replacing all the seals again." Eh??? | ||
| Jan Forrest Prolific User Username: got_one Post Number: 207 Registered: 1-2008 |
Unless the seals were made from Viton or a similar synthetic rubber they wouldn't be able to withstand the corrosive effects of the vegetable based DOT standard fluid that makes up the majority of RR363. People who run diesel engines on veg have been having this problem for years. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2359 Registered: 4-2003 |
Careful. Viton would last about 10 minutes with RR363. I know, as I tried it in 1986 when Crewe was selling a rogue batch of nitrile sphere o-rings instead of EPDM o-rings for these cars. The rogue nitrile ones were lasting 3 months, so I tried some viton ones in desperation thinking that this new NASA wonder material must be the answer. The Viton ones failed within a week. By the way, just days afterwards, the Space Shuttle Challenger blew up (January 28, 1986) when its Viton o-rings blew out. I have never used Viton since except on valve stem seals. Not that Challenger used RR363 !! but Viton was immediately on the watch list. Since then I sourced the correct EPDM o-rings from Crewe once they corrected the error with no further problems. That's one reason why the table is in the Technical Library. http://rrtechnical.info/sz/o.pdf RT. | ||
| Paul Yorke Grand Master Username: paul_yorke Post Number: 750 Registered: 6-2006 |
Jan - I'm fully aware of the importance of the correct seals - but what are you implying about late Shadow II seals being wrong for R363? | ||
| Chris Browne Experienced User Username: chrisb Post Number: 49 Registered: 2-2010 |
Hi gents, Aren't we in danger of thoroughly confusing our new member, Koby, by giving out over complicated advice. If I am mistaken, I would happily withdraw this post, cap in hand, but is it not the case that ALL Shadows from day one, with the exception of the final 50,000 series, run on RR363? Or to make it even simpler, if the car has an oblong metal reservoir, it is RR363, if it has round reservoirs, it is LHM. Please respond immediately if it is not as simple as this but my understanding is that it is! Kind regards, Chris | ||
| Jan Forrest Prolific User Username: got_one Post Number: 208 Registered: 1-2008 |
Perhaps there was a rogue batch of Viton around in the 80's or the formulation has been changed in the intervening decades. However it's now the recommended material for diesel injector pump seals when overhauling them for running older engines on veg oil. I haven't heard of any failures from the use of Viton in this application and I'm an active member of a couple of 'Alternative Fuels' forums (my Toyota hasn't had as much as a tankful of DERV run through it in the last 2 years despite covering 10's of K kilometres). Anyway; to get back to this case: IMHO the brakes sticking on may be the best clue we have. It's highly unlikely that this would be caused by all the piston seals or flexible hoses failing at the same time unless there was a mismatch between the brake fluid and the 'rubber' being used in their manufacture. Fortunately Crewe originally placed large warning stickers on the reservoirs to aid owners/servicing mechanics as to the dire consequences of using RR363 in a system meant for LHM and smaller ones on the earlier reservoirs advising the use of RR363 only. Even so, some owners/mechs may have thought that the two fluids are miscible and that the later LHM is just a superior version of RR363. I'm sure we've all heard tales of this happening and the inevitable consequences! On further reflection, though ... A relatively large particle of solid contaminant in the wrong place could just about block the low pressure brake line returns to the hydraulic reservoir. I can only advise him to try to check out which fluid and what seals were used and if they're matched and only then try to flush the braking system again as detailed in the manual. | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1307 Registered: 4-2003 |
Hmm somewhere in Topics I recounted an earlier Shadow that would not move. This result was caused by seized pistons in the distribution valves. So whenever the engine was started the brakes went on. As the car had to be moved the solution was to open the bleed valves and drive on the handbrake to get the car where we wanted it. A bit messy but it worked. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 2360 Registered: 4-2003 |
Certainly for vegetable oil, and certainly for diesel, probably even for LHM, but certainly not for polyethylene glycol which is the basis of RR363. | ||
| Jan Forrest Prolific User Username: got_one Post Number: 209 Registered: 1-2008 |
I stand corrected. I hadn't taken into account the inclusion of PEG in RR363. It still indicates that the wrong seal material could cause some of the problems if not all of them. If it were my car I'd be inclined to remove one or two of the new ones and check them for damage. The distribution valve would be my first port of call. |
