| Author | Message | ||
     Kevin Lagden Yet to post message Username: kevin Post Number: 1 Registered: 7-2009 |
I am now the very proud owner of a 1975 Shadow 1, a car I have, since the age of 6 (i'm now 50)always wanted. The car is being serviced on Thursday 16th July to have the braking and hydraulics looked at and where necessary adjusted. The only warning lights to come on are the braking system lights, although on the test drive all felt fine. I am wary of brake failure, but what if any time do you have when the light first appears before they fail. More to follow on this forum I am sure, I fully intend to get this fine old lady up to scratch, body work all immaculate and few minor trimming issues but other than that I am one very happy chappy who has finally realized a childhood dream Kevin | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1143 Registered: 4-2003 |
Well welcome to the strange world of addicts Kevin. When you say you are going to have the car 'serviced' given the warnings coming up in the hydraulic department, to me it is a bit like having a broken leg and deciding to go to the doctor for a check up. To answer your question, as long as the engine is running you should have brakes. But be warned that these old cars often have the original fuel pump which so many owners and 'service' people ignore and they stop (the pumps not the people). So the engine stops and you are out of stop! Briefly the hydraulic pumps which are buried under the inlet manifold in the centre of the engine and are driven by the cam shaft, these pump brake fluid into high pressure containers bolted onto the lower left rear side of the engine. These containers known as accumulators have a diaphragm across them with high pressure nitrogen on one side. The brake fluid from the pumps fill the accumulators from the other side of the diaphragm,further compressing the diaphragm and the nitrogen. When you apply the brakes some of this brake fluid in the accumulator by now under great pressure is released into the brake lines and applies the brakes. To warn the driver that the pressure in the accumulators is below a safe level, a pressure switch is fitted to switch on the warning lights you have seen. In time the nitrogen leaks out until the accumulators are simply unpressurised vessels full of brake fluid. With these accumulator full and the pumps trying to push more fluid in, the pump pressure (providing the engine is running) is all that is available to apply the brakes. Can we refer you to our Technical Library rrtechnical.info where you will find the complete workshop manual, look at section G and all will be clear! | ||
| David Thomas New User Username: davidthomas Post Number: 8 Registered: 5-2007 |
Kevin! May you have many many years of happy motoring - just as I am now having in my Peacock Blue 1975 Silver Shadow SRH 20104. Like you, owning a Rolls Royce was a childhood dream - sadly only realised after 40 years of doing so. David | ||
| Andrew Lark New User Username: drew Post Number: 7 Registered: 6-2009 |
G'day Kevin and welcome to the forum. I'm also new to RR ownership and new to this forum - I'm sure you'll find lots of friendly help here and also don't forget the Technical Library at http://rrtechnical.info as Bill has mentioned. With the braking system, as I understood it; if the twin high pressure hydraulic systems happen to fail there is a third backup system that is a straight hydraulic system with no power assistance, giving you good old fasioned 1940's hydraulic brakes (like my '49 Morris!) except with discs all 'round, the pedal effort required is significant. So if the high pressure systems (x2) fail you still have some braking ability. I might have the wrong handle on this, anyone please correct me if I'm not giving the right info. Cheers, Andrew. ----- 1973 Rolls-Royce Silver Shadow SRH15138 | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1144 Registered: 4-2003 |
Andrew You are quite right for your car but they dispensed with that I think a little before the Shadow II. I was too lazy to look it up and can't remember. Even so I recently had a Corniche with the master cylinder which failed, the accumulators where also shot! Don't throw Kevin lifelines! The master cylinder applies a pair of pistons on the back wheels actually to give the brake pedal 'feel' Trying to stop with them is just preferable to putting your foot out the door!! | ||
| Kevin Lagden New User Username: kevin Post Number: 2 Registered: 7-2009 |
Thanks for the advie guys, I appreciate it. Not being technically minded and never really had my hands dirty under any bonnet, I am fully prepared to learn all I can. I will certainly make good use of the technical info to brush up. For piece of mind I am getting the car checked out by a recommended source from NSW owners club, so I'll let you know what the report is. Do you know if there are evenings, days/weekends where one can learn more about the technical aspects? | ||
| Jan Forrest Frequent User Username: got_one Post Number: 86 Registered: 1-2008 |
As I posted in the technical forum (Brakes) The Old Girl (SRH24518) doesn't have a master cylinder, just the big spring to give 'feel' to the brakes. Also, if you have access to a cylinder of dry gas at the correct pressure and the correct hose and connector, it is a fairly simple matter to repressurize the accumulators - usual precations apply, of course! | ||
| Bill Coburn Moderator Username: bill_coburn Post Number: 1145 Registered: 4-2003 |
Well Jan here is my Jeremiah side coming out. Repressurising the system in an unknown car would in my humble opinion be a little unwise for two reasons. The first is if the diaphragms are punctured through being left uncharged for a long time and the diaphragm being forced into that neat charging hole with appropriately sharp edges, recharging will simply blow the gas back into the entire system and nullify all main pressure braking. This problem occurs to some extent even with 'intact' diaphragms through the minute and unavoidable passage of nitrogen through the diaphragm. This is corrected by simply bleeding the brakes. The second hazard in my experience is the structure of the accumulators themselves. They can rust which weakens them. The rust occurs through the system absorbing water and this in turn is allowed to sit stagnant for long periods. There is a least one event of which I am aware where the accumulator exploded before the pump push rod snapped, which was attributed to internal corrosion. I have no problem with recharging although it is a fairly awkward procedure from the point of view of access but given the critical nature of the system I would want to know just what state the it was in before re-charging. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1802 Registered: 4-2003 |
Bill, Would you agree with this ? If it's a bit low, say 700psi discharged and 30 brake pumps charged, then a recharge with Nitrogen may be a Good Thing Citroën-style. If it's so low that the pressure is below, say, 200psi and 10 pumps, then it's like trying to raise the Titanic with a can of Spray Fresh in the ballast tanks ? Better complete the heart transplant before attempting the blood tranfusion. RT. | ||
| Jan Forrest Frequent User Username: got_one Post Number: 87 Registered: 1-2008 |
I see your point, Bill. But if the accumulators can cope with the pressure from the hydraulic pumps - ~2.5k psi - then 1.0k of gas is hardly likely to 'push them over the edge'. Awkward? Hhmmm ... a complete sod is more like it  Obviously, if the membrane is punctured the gas side will not hold pressure and hopefully bubble up into the reservoirs and *hissss* out of the caps. | ||
| Trevor P Hodgkinson Experienced User Username: wm20 Post Number: 21 Registered: 11-2006 |
It can also send a pressure wave back through the system. I bought a S1 with no padding under the bonnet. The owner told me that shortly after having the accumulator recharged the system "exploded" and deposited the contents of the master cylinder into the padding. It also blew off the filling caps. It was a mess. As to stopping the car with nothing but the pedal pressure. it can be done on flat ground, but it isn't easy. The third car we bought had the warning lamps removed and on the way home from the purchase the car stalled, no brakes. I pushed so hard on the pedal with both hands on the bottom of the steering wheel to get more leverage on the pedal that I bent the wheel. It did stop but from about 40 kph it took well over 100 meters and to make things even more interesting the flexible linkage on the steering broke on one side and made a direct short on to the power cable to the starter and suddenly the very cheap car started to look very expensive. |
