| Author | Message | ||
     Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 562 Registered: 9-2004 |
How about running Dot5[silicone]in the dot4 RR363 system cars,after a total brake overhaul hoses and all the rubber components including the caliper seals. As the system is allowed to breathe,the one failing that could have arose was the more micrscopic ammounts of air due to the make up of the chemistry of dot5. As for the high pressure pumps the dot5 fluid looks ok on the lube side. Any thoughts on this interesting mod that i will consider at the next brake overhaul in the autumn. The car has still its original high pressure hoses at 32 years and just now one ram hose is looking as it may be starting to fail close to the ferrule. To date i have only had one diaphragm and three bouts of recharging of the nitrogen within the spheres. Has this anyone done this or looked into the posibility of it. | ||
| David Gore Moderator Username: david_gore Post Number: 567 Registered: 4-2003 |
Hi Pat, Bill Coburn has published a lot of information in Tee One Topics about the problems with silicon brake fluids especially the fact that water and silicon are not miscible [ie do not mix together but remain separate]. This can cause total brake fade problems if moisture gets into the system from condensation/over-enthusiastic hosing of the engine bay etc - the water will boil very readily and turn to steam meaning the fluid is now no longer incompressible to apply the brakes. If the use of silicon fluid was appropriate; I would have expected this to have been highly popular by now. Not a change that I would consider doing without a lot of consideration and experimentation by those more wealthy than I [to pay for the repairs if it doesn't work!!]. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 563 Registered: 9-2004 |
Hi David, Off the cuff i think Bills dealings were with the Phantom. That had the twin master cylinders with the rubber seals also drum brakes. The Shadow is a different type of beast with the master cylinders that have no seals just a fine tolerance of the working high pressure parts. However the SS1 does have the third master cylinder but that system could also possibly be converted without to much trouble. The hydralic pumps would also be ok even though the running of DOT 5 in a car with the Abs pump is a no go due to the pump speed. Hoses are ok as are the caliper seals etc. Any unlikly pooling could be delt with by cracking the bleeders one a year to check if the fluid is not venting with the reservoir caps. Will do a tempeture change check on the fluid within the the system next. | ||
| David Gore Moderator Username: david_gore Post Number: 570 Registered: 4-2003 |
Hi Pat, Yes they were with the Vice-Regal Phantom however he also mentioned the problems the US Military had with the Silicon fluids as they were the main driving force behind their use. The water vaporisation problem and consequent loss of brakes apparently has caused a "loss of interest" in Silicon fluids. | ||
| Larry Halpert Prolific User Username: larry_halpert Post Number: 87 Registered: 9-2003 |
Wouldn't LHM mineral oil be better to convert to, as it has already proven itself in this type of system? Larry | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 564 Registered: 9-2004 |
Hi David i had forgot the military prob, will try and find more about what caused the specific prob they had with silicon. Prehaps the systems let the water in when vehicles were used in certain water terains. Hi Larry yes that would be my first choice however the new seals etc for the SS1 are not compatible for LHM [mineral oil]. Have done some tests on LHM and they swell up. | ||
| bob uk Unregistered guest Posted From: 80.3.64.11 |
This has jogged my memory. The problem with silicon is that water does not mix and tends to pool in one place -- at the lowest point--. This slug of water lowers the boil point of the system to that of water 100 c . Dot fluids absorb the water and the same amount of water does not lower the boiling point as much. In master cylinder type systems this is an accident waiting to happen. Because the stoke of the master cylinder has not got enough volume to cover the "gap" The same applies to LHM. However the later citreon 2CVs had LHM and a master. Constant pressure systems such as the Shadow have enough reserve volume of fuild under pressure to still swash the steam and work the brakes. I have driven constant pressure vehicles where system has not been bleed and has massive amounts of air, the brake pedal feels normal but there is a small delay and eratic braking effort. If the slug of water does boil while the brakes are on the steam cannot escape past the brake valve until the brakes are released then it bubbles back to the reservoir via the brake valve dump line. When the brakes are re-applied freash fluid replaces the water that got boiled away. So the system is self purging of water to a certain extent. The Shadow 1 has a master which I should think would never get hot enough to cause boil fad. even if it did the other 2 systems will easily stop the car even if the hoses blew on the master cylinder -- It will still give you a bit of a fright though. The above tells me that providing the dot 5 silicon does not rot any rubber parts then it should be ok. HOWEVER THE USUAL DISCLAIMER APPLY AND THIS IS A DISCUSSION DOCUMENT ONLY. The problem that the military had with silicon is that they lay vehicles up for periods of time some times years. They expect the vehicle to be operational and read for driving across a battlefield under fire. The water will rot out the system. When I was about 15 I tried to bleed out a Mini clutch using sowing machine oil. The seals lasted about 30 mins and failed badly --- oil every where. The seals looked twice as big and like black brussels sprouts. Should have used condensed milk or better still dot 3. This is how learn -- muck it up first then read the instruction ! (Message approved by david_gore) | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 1016 Registered: 4-2003 |
Not again ! Maybe, but why bother while DOT5 silicones have been all but abandoned worldwide for good reason ? Many a Silver Shadow is laid up for weeks at a time, a situation not suited to silicone fluids for a start. Rumbling even on this site suggest that brake calliper seals in RR363 systems outlast the mineral oil ones as well for that matter, but I have never heard of any sane person attempting to use DOT3/4 or RR363 in an SZ. Nor have I heard of any honorable doctor experimenting with transfusing a blood group A patient with blood group O except in a dire emergency, even though it is theoretically safe in most cases. Were there a problem with using the right stuff perhaps some research would be sensible, but there is patently not in the case of our braking systems. Leave the darned system alone and use the correct fluid please. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 583 Registered: 9-2004 |
Richard hang on,my last CX did over 350,000 miles with out any replacment caliper seals running LHM. Just no probs at all including the speed adjusted power rack,wheels balanced correctly of course. Can you say that on any system useing DOT 3/4 RR363. Now the Shadow 1-2 has RR363 fluid change every second year with new caliper seals every eight, Would be nice to cut out the real probs of DOT 3/4 RR363. Bob as you say the venting of the fluid in the reservior would take care of any moisture within the system an keep the system in good shape. Think the SS2 will be a good candidate. Not the SS1 at the moment. | ||
| bob uk Unregistered guest Posted From: brig-cache-4.server.ntli.net |
I have noticed that LHM calipers are more likely to leak than DOT calipers. The trouble with silicon is also that once fitted it is bugger to get rid of. No matter how many flushs the stuff stiil lurchs aorund awaiting to contaminate something. (Message approved by david_gore) | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 609 Registered: 9-2004 |
Silicone Dot 5 has been installed successfully so far in another Shadow, great news! Well done Alan D. Reading your posting on the caliper seals question on the RRBEW I have found it is ok to use the existing seals after a total flush of the DOT4 363 and filling the system with DOT 5[silicone] however the reversal will not work they will swell. The only possible worry long term is that if any pooling of water droplets occur this will be in the calipers being the lowest point, easy to bleed off if ever needed. As the system is well vented in the reservoir with the pressure full flow returning i think this may well be ok. Great news to hear you have bit the bullet and all is well. Do contribute to this great site you have much to offer. Regards Pat. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 671 Registered: 9-2004 |
Well well,a long talk at swindon to-day. Confirmed no supply date now given for RR 363. It may well be dead. Should have been December. Use Dot 3 with additives confirmed with get you out of jail recipe. Do not convert to LHM. Inappropriate comment deleted by moderator - unnecessary remarks about specific individuals will not be tolerated and a continuation of this practice may result in temporary or permanent suspension/withdrawal of privileges by the management. (Message edited by david_gore on 17 March 2007) |
