| Author | Message | ||
     Bill Coburn Grand Master Username: bill_coburn Post Number: 241 Registered: 4-2003 |
Has anybody had experience with using silicon brake fluid in post-war Cloud and Phantom braking systems. I am mystified to find that the hydraulics in a Phantom were full of air and totally ineffective. Examination of past service records shows that these systems were bled a year ago and no one would have opened the lines in the meantime. The cups in the master cylinder according to the workshop manual apparently have a sealing arrangement that I now wonder may be incompatible with the more viscous silicon fluid. | ||
| Patrick Lockyer. Yet to post message Username: pat_lockyer Post Number: 1 Registered: 9-2004 |
Hi Bill. Have had problems in the past with the silicon brake fluid. Have had the master cylinder piston stick. have had air and moisture getting past the wheel cylinder rubbers. I have put it down to the fluid effect on the seals and the hydroscopic results within the fluid. Our climate may be diferent than yours. I will not use it at all on disc brake systens. | ||
| Robert Chapman Prolific User Username: shadow Post Number: 71 Registered: 5-2003 |
Hi Pat, I was very interested in your comments about silicone brake fluid,I thought that among the advantages of this type of fluid were that it is not hygroscopic and had a very high boiling (at least 500F) point.Making it markedly suitable for disc brakes. | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 338 Registered: 4-2003 |
Hi Robert, The non-hygroscopic properties of silicone fluids are my understanding of the promised advantages too, and are reflected in the DOT specifications. Although you would hope never to approach them even with disc brakes, the minimum specified dry boiling points are: DOT 3 205C = 400F DOT 4 230C = 446F DOT 5 260C = 500F The only theoretical disadvantage of DOT 5 I have read of is in fact that non-hygroscopic nature. The storyline is that any water which gets into the system will not dissolve, but remains in corrosive droplets. Also, with too much water in the wrong place, it will supposedly vapourise instantly at 100C and the brakes will fail. With DOT3 or DOT4, the water dissolves and simply reduces the performance progressively depending on content as outlined in the DOT surves. This is not my own speculation, and have no view on its validity. It may just explain why the likes of Porsche recommend strongly against DOT 5 in all their cars. True, the industry in general has shunned DOT 5, and surely there must be reasons. If the theory has been proven true, where does that leave non-hygroscopic mineral fluid braking systems I wonder ? Bill, did the PVI originally have DOT 5, or is that a little meddling from Queanbeyan ? I didn't think it was available when that car was manufactured. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 246 Registered: 4-2003 |
Richard/ No it was certainly standard fluid when it was delivered. As far as I can establish I have just pumped the third lot of Mr Cornings fluid through the system. But as you know these systems have two master cylinders on a trapeze. There is a record of the lower (smaller) cylinder having to be removed to re-adjust it. God knows what that was about since the upper large cylinder is initially set to a dimension and the lower one adjusted on the car when all the linkages have been re fitted. At that point the clevis is screwed to just eliminate any free travel between the push rod and the cylinder piston. When I discovered there were no front brakes to speak of I laid under the car with the engine running and in gear and watched while the pedal was depressed. The servo wound itself up to its limit so clearly there was air in the lines then. Assuming the cylinder rubbers were faulty I pulled the lot out and refitted new ones. The cylinders are not original having been replaced at vast expense some years ago. Now it occurs to me that when they installed Silicon fluid at that point the new (probably old stock) cylinders would have had a small quantity of DOT 3 fluid in them for assembly purposes. I wonder what that effect had on the system. Anyway I am still mystified as to how air got into the system. Did the seals at the wheels or the cylinders let it in? In the meantime I replaced all the flexible lines and flushed and bled the whole system with a couple of litres of Silicon fluid. I shall monitor the brake preformance very carefully. Pat Lochyer's observations are in fact born out on various reports I have read on the net and by your own remarks. While the fluid is not hygroscopic if there is any water in the system a mere globule can boil and give total brake fluid. There are also reports of master cylinder piston lockup for reasons I haven't absorbed. By comparison my Armstrong Siddeley has been running on silicon for well over ten years and there has been no problem at all! | ||
| Patrick Lockyer. New User Username: pat_lockyer Post Number: 2 Registered: 9-2004 |
Robert,Richard Bill,You are all correct. However i think i must let you kmow the faults that i have expiereced. First if it going to be used and yes you are all correct it is non-hydroscopic,it becomes deadly with the slightest drop of water as we all no it turns to air when heated as Bill has said. Robert that is why i realy must warn you never to use it in the more modern disc brake systems. Even with duel brakeing becomes unsafe. Now this is my thoughts on how it happens on the older drum brakes,with the fluid not changed every year which is one the reasons for useing it. first the seals get a slight build up of wax type substance,the brakes when used heat up and when the car is driven through a heavy rain storm some water gets to the cylinders past the cylinder dust boots,as the water cools the hot wheel cylinder it then lets a small droplets in, after a short period total brake failure can result. Now being non-hydroscopic the fluid will not absorb the water as DOT4 will. Now we all may say what about LHM+they run disc brakeing system, yes thet do but there non-hydroscopic fluid is far better. It still has to be changed reguarly. | ||
| Robert Chapman Prolific User Username: shadow Post Number: 72 Registered: 5-2003 |
Pat L, Thanks for your "thoughts",that is a very interesting theory.I will definitely store them away somewhere. | ||
| Ashley James Unregistered guest Posted From: 62.255.0.5 |
Silicon fluid is vastly superior in every respect to conventional brake fluid and supposedly never needs changing. The problem with ordinary brake fluid is that condensation forms within the fluid causing rust to form that scores brake parts that many of you describe. The cannot happen with silicon (or LHM) because it is moisture repellant rather than absorbent. Apart from price, it offers major advantages and will not cause the damage that some of you ascribe to it. (Message approved by david_gore) | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 247 Registered: 4-2003 |
I am sorry Ashley but if you troll the net you will find report after report of the effect of water in the silicon stuff. The car I am dealing with is a ceremonial car which for a variety of mechanical shortcomings has been used less and less although the 'maintainers' had no difficulty in keeping the money flowing. Having read all this advice and last night having nothing better to do but combing the net I believe that the silicon use whilst of great benefit in the anticorrosion areas, has a few queries about its performance. When the subject car was built silicon fluid was unknown so the system would not be designed to work with it. The fact that it appears to work must be fortuitous. And the Factory or what is left of it is not about to conduct tests on my behalf to see if the stuff is suitable for these systems. Hence my question in the hope of getting some empirical evidence of its performance. Noting Pat Lockyer's remarks about wax build up I am now tempted to pull the wheel cylinders and re-rubber them! | ||
| Ashley James Unregistered guest Posted From: 62.252.44.64 |
I do not doubt that people have brake problems but I do question the diagnosis. I just do not think it is logical to blame Silicone fluid. (Message approved by david_gore) | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 342 Registered: 4-2003 |
Ashley, I for one do not blame silicone fluid for anything. I am just puzzled why the industry has shunned it. Also puzzling is that the perpetuators, particularly the US military, are trying to convert from DOT 5 silicone fluid to DOT 4. What's the secret ? Is it just cost ? Given the unchallenged success of LHM, also non-hygroscopic, logic tells me that silicone fluid should be much better than DOT 4. With billions of cars out there using DOT 3/4, it can't be all bad though. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 250 Registered: 4-2003 |
Well all I need to know is how the Hell air gets into the brake sytem? | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 343 Registered: 4-2003 |
Bill, Have you checked the one-way valves in the master cylinders ? If one valve doesn't function properly, then air will be sucked in. If, due to a faulty valve, the piston return spring causes low pressure in the master cylinder on releasing the pedal, this will occur. The master cylinder main seal makes a perfect air pump, just like a bicycle tyre pump, under those conditions. | ||
| Patrick Lockyer. New User Username: pat_lockyer Post Number: 3 Registered: 9-2004 |
Bill you certainly did have air in the system and what you have experienced is the main failings of the stuff,and not widely publicised. Now what is the choice dot 3/4 with the water content absorbed and corrosion with pistons etc. Then gradual brake failure possible after 2/3 years through not changing the fluid. Use silicone they say and never change the fluid again. True in a real world useing the car in the summer months. But the moment moisture gets in from the atmophere or as prieviously stated through the wheel cylinders,master cylinder,and being non hydroscopic any moisture turns to air with sudden deadly results. Now we come to LHM Yes non hydroscopic and far superior with citroen, but no problems of the above even with the hotter running disc brakes.Down to Citroen on this one with a clever but simple bit of enginering, All fluid is used and vented on the return from the lubricated pistons with no seals. Now Robert C please let us all no what the LHM Rolls Royce cars have,Ie seals in there active suspension with venting return,or whatever. | ||
| Patrick Lockyer. New User Username: pat_lockyer Post Number: 5 Registered: 9-2004 |
Richard,if the return valve did not work correctly then the pedal would stay down,help no brakes. only after a long time would the pedal return sucking air in the system. Unless i miss understood Bill i thought he was able to bleed the brakes to indeed find the air pressent already in the system,with the pedal returning on each and every pump. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 251 Registered: 4-2003 |
Thank you all for your contributions. The one way valves are part of the replacement kit. I think what I am going to do is closely monitor the performance of the brakes and any sign of air, I'll scrap the stuff and go back to DOT 4 even if it has to be changed regularly. The latter is not that much of a hastle. Last night I was talking to an ex-mechanic who recalled that use of silicon invariable gave a softer pedal in a conventional braking system. That presumably would be air in the sytem on installation. They do warn you on the container to not shake the stuff up before use! The other mystery which Richard raised is why is the US military scrapping it. THAT would be a contract that Dow would not like to lose! | ||
| William H. Trovinger II Grand Master Username: bill_trovinger Post Number: 154 Registered: 8-2003 |
Bill; Your question about the intent of the US military is interesting. However, even as a strong support of the Military I think that the chance of finding an answer to this question is about the same as raising J. Edgar Hoover so he will tell us who really shot JFK.  I would suggest that the conversion to ABS being done on later model HMMWV (military version of the Hummer H1) was tested NOT using DOT 5 and the time and cost requirements to retest the conversion system made it impractical. Also understand that the US DOD does like, as much the same everywhere in it’s system as possible. Therefore if they have some equipment that requires DOT3/4 then they would want all systems to use DOT3/4 less chance of a grunt in the field mixing things up. Best regards, Bill | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 303 Registered: 4-2003 |
Well my friends 'Happy New Year'. The saga of the silicone goes on. I have the dear old Phantom back and thought I would whip off the brake drums. Lo there is a nice deposit of a white waxy material nicely coating the linings. The area under the wheel cylinder dust covers is dry and there is no evidence of loss of fluid from the reservoirs. But despite the denials above, the stuff on the linings can only be a brake fluid deposit.If I am correct it would go a long way to explaining why the brakes are somewhat desultory silicon being an excellent lubricant! I will clean the shoes thoroughly and probably paper the linings to get as much stuff off as possible and see if that helps but I worry about impregnation (don't we all)!. Lastly I can't get an unequivocal assurance that I can change the system back to DOT4. Apparently the two fluids are incompatible but what happens does everything rot or disintegrate? Please talk to me you all!!! | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 219 Registered: 9-2004 |
Bill Happy new year to you. Regarding doing the change back to DOT4,you will have to change all the wheel clyinder master cylinder rubbers as well as the brake hoses. Not sure what type of servo you have? But the rubbers in that will need to be changed if it is the vac type. All the pipe work should be flushed with meths oh what great stuff that is! If a change either way is done without the above the rubbers will swell or become soft etc. Not completly sure on the white waxy coating. sometimes oil from the hub can go a whiteish colour if it is cold and damp, but no it must be DOT5 as you are in the hot summer time,lucky you! | ||
| Richard Treacy Grand Master Username: richard_treacy Post Number: 522 Registered: 4-2003 |
Having passed an eye over the amazing Phantom VI in Bill's garage last weekend, I was mighty impressed. Bill deserves to be very proud of his work on this car, and he tells me that the new valve stem oil seals have wiped out oil consumption completely. Bravo. Now, how about a spanner or two on that lovely S2 sitting nearby ?? The motor is out and begging TLC to the same standard as the PVI, and of course to the standard of the Silver Dawn all those years ago. For Pat: of course the servo is a Silver Cloud mechanical type: there was never a vacuum type in sight. There was no perceptible sign of fluid leaks: remember, Bill is a perfectionist afterall. The Commonwealth of Australia is truly lucky to have found someone to take on this splendid car. Now, what happens when that speed camera goes off, and only a crown appears on the photo ? There is quite some intrigue about the apparent demise of DOT5 fluid. I'll have a look at my files and try to throw some light on this panacea which seemed to fail in practice. As for changing back to DOT4, I would chance it: simply flush the system thoroughly and go for it. This car covers very low mileages and is under Bill's constant watchful eye anyhow. Stating the bleeding obvious (no pun intended), of course the one-way valves in the master cylinders are there to stop air entering the system at the wheel cylinders when the brakes are released: I'm sure that Bill has checked them. RT. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 308 Registered: 4-2003 |
Well Richard with all those nice words I am going to become even more insufferable. As a little prophylaxis I will give the old girl a further careful bleed mindful of problems of aeration. And I have to confess that the coating on the liners is, I think and you agreed an accumulation of dirt that collected during its rear brake only period. With a few cans of a marvellous brake cleaning fluid, and liberal use of fine sand paper on the glazed surface and some fine wet and dry inside the drums, I am hopeful of a considerable improvement in performance. Stand by for further bulletins when the lady gets to her feet again. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 246 Registered: 9-2004 |
Bill is the brake pedal returning with clearance on each and every pump or does it stick down a little? Do not Chance it with regard to flushing and changing back to dot4. All the rubbers must be changed or they will swell etc with total failure. Flushing the system of dot 3/4 and filling dot 5 is ok but not the other way round. At least the servo being mechanical will be ok. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 312 Registered: 4-2003 |
Thanks Pat I am sure that is good advice. Having just done the master cylinders I will put up with the foibles at least for a while!! | ||
| whunter Grand Master Username: whunter Post Number: 136 Registered: 10-2003 |
Going from silicone to DOT 3 - 4 or RR363… Acetone is the only thing I use to flush silicone out. Absolutely every trace of silicone must be removed. All rubber throughout the system must be replaced. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 322 Registered: 4-2003 |
Well the axe has fallen. As far as I am concerned the silicon comes out and stays out. Yesterday, largely as a fussy after thought I decided to bleed the brake hydraulic systems on the Phantom just to assure myself that Pat's cautions were not applicable. It seems they were. Another $86 for a litre of fluid and my mate and I started on the laborious task. The primary circuit bled OK but while the fluid I put in was bright blue that which came out was cacky in colour and this is fluid that has not been in the system 2 months!!! On to the second circuit and it would not bleed. This is the smaller master cylinder and clearly the piston was not returning to its stop to allow replenishment. I then noticed that the larger master cylinder was leaking (after 2 months and 500 miles!!) As Patrick would say crumbs!!! My command of expletives is much better and I used it to the full. Out came the cylinder again and lo both rubber seals were noticeably swollen and jamming the piston. I rang Paton Brake Replacements (PBR)in Melbourne who manufacture most if not all of our hydraulic seals and by happenchance got to talk to a fellow who had actually used silicon and worked on RR's. He was adamant that if you use silicon you MUST use special composition seals NOT rubber or whatever the standard material is used for these items. He confirmed that otherwise the seals will swell which is precisely what has happened to these new seals I have just fitted. This advice also suggested why the colour change in the fluid - the colour is dissolved seal!! So tomorrow out come the master cylinders again, all the wheel cylinders, the new flexible brake hoses and the special hoses from the reservoirs to the master cylinders. There are also the gaskets in the top of the reservoirs that will need renewing. The lines then have to be flushed. I was going to use high pressure methylated spirits (US denatured alcohol)but is acetone really the solvent Bill H? It is highly toxic and God knows where I will get it but if that is the requirement so be it. Could you please confirm this? | ||
| David Gore Moderator Username: david_gore Post Number: 382 Registered: 4-2003 |
Hi Bill, You can buy bulk acetone at Bunnings at least in 500ml cans and they can order in larger sizes if needed or I would try Blackwoods. You will need to keep both shed doors wide open and use a fan to force-ventilate the work area together with a good supply of aspirin/paracetamol handy as the exposure to the fumes over time can give you massive headaches. Also if my memory is correct, acetone is highly flammable so be wary of explosion/fire risks [make sure the fan is upwind so it is not in the fume path!!] | ||
| whunter Grand Master Username: whunter Post Number: 137 Registered: 10-2003 |
David is correct. Acetone burns at the first hint of spark or flame. Silicone is incredibly difficult to remove from a hydraulic system. Every slightest trace must be removed or it will contaminate the system again. The rubber flex hoses must be replaced; they are saturated and contaminated beyond recovery. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 323 Registered: 4-2003 |
Good old Bunnings David! I had traced through the www that cleaners' suppliers stock the stuff for cleaning something and that was my next stop. I must say I am confused as to its flamability. What was the stuff that used to be put in those metal fire extinguishers that you pumped. They were used a lot on HM ships and the contents were great for getting off grease spots off a uniform. Hence when they were needed they were often found to be empty! I have a gadget not used for some years for testing the lubrication sytem on newly built engines. It is an old gas cylinder with appropriate outlets which you can fill with oil and connect it to the oil galleries in the block. Turning the crankshaft slowly and you can see what is being oiled and how much. I propose using the same set up but use acetone and flush the lines at pressure. I thought a fairly vigorous primary flush with a strong detergent may also help and then finish up after the acetone with methylated spirits and compressed air. I will certainly be replacing every bit of consumable as I detailed before. I started this morning and whipped all the brand new hoses off and got them to the local brake man to make new ones. He also confirmed acetone as the solvent, Bill, thank you. What an embuggerance but hopefully the end result will make it all worthwhile. I found the origin of the installation in a file dated 1983 where the local Department had picked up on the anti-corrosive properties and directed that all low mileage high value vehicles would be so equipped. But I should mention that my old Armstrong Siddeley Whitely ran the stuff for 20 odd years without any trouble. It's a puzzlement!! | ||
| whunter Grand Master Username: whunter Post Number: 138 Registered: 10-2003 |
Hello Bill Use only acetone; it will leave clean metal behind. Acetone eats rubber and plastic, almost as well as water breaks down sugar. Never allow acetone to touch paint, it will strip it to bare metal. A good flush by a mechanic with the correct tools "done out of doors" takes two or three working days. I will not go faster, my safety and the cars safety demand time. A respirator, gloves and form fitting goggles may save your life. This stuff is blasted dangerous to work with. It will burn eye tissue or lung tissue given a chance. Never lay in a puddle of acetone, it will burn skin and cloth. Please read the MSDS for acetone. http://www.google.com/search?hl=en&q=acetone+MSDS DANGER! EXTREMELY FLAMMABLE LIQUID AND VAPOR. VAPOR MAY CAUSE FLASH FIRE. HARMFUL IF SWALLOWED OR INHALED. CAUSES IRRITATION TO SKIN, EYES AND RESPIRATORY TRACT. AFFECTS CENTRAL NERVOUS SYSTEM. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 324 Registered: 4-2003 |
Thanks very much Bill. I have bought 4 litres for starters and a good respirator. Will get the goggles tomorrow. I remember now that the fire extinguisher stuff was carbon tetra chloride the 50 year old memory is going slowly!! Interesting stuff this silicon particularly when you see what it does to paint jobs! | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 325 Registered: 4-2003 |
Well the whole brakes on the left side are out. I removed the wheel cylinders and had difficulty getting the pistons out. Eventually they emmerged coated with shaved wheel cup. Seems the cup swelled wqith the silicone to the point that when the piston was pushed back it sliced a a little bit off the edge. The cup itself was very soft and spongy. Neither side had any actual leakage. The residue in the bottom of the cylinder was interesting. See both pics if I can get them in/on!  | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 326 Registered: 4-2003 |
Well that was exciting, Patrick you are not the only clever one!!! Now for the image of the piston coming out of the cylinder.  | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 327 Registered: 4-2003 |
Well now I have found where to put the caption so I'll try another - ain't this fun. This pic was a funny shape but within the allowed dimensions. You get the caption by putting the arrow/curser on the pic. This should show the shaved wheel cup  | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 329 Registered: 4-2003 |
Now John Dare after all that excitement I can get back to that Porsche of yours. I have had an Armstrong Siddeley Whitley for over 20 years and sold it recently. It has had the Dow Corning Silicon fluid in the brakes all that time. The brakes have never given me any cause for alarm and seem to perform as they were designed. Having missed a turn off on a rally I had the experience of having a full pedal stop from 87 mph (yes it was flat out)and I stopped without skidding which I think it was incapable of doing. But there were no repercusions or dimunition of the braking. My only curiosity was who was having harp practice while I was giving the old girl her head! I also found the instigator of the Phantom's silicon on a file. Seems a government department got all excited by the new stuff in 1983 and directed it be put in all low mileage high value prestige vehicles. This was done by York Motors on direction/request and the saga started. | ||
| Patrick Lockyer. Grand Master Username: pat_lockyer Post Number: 279 Registered: 9-2004 |
Bill well done you have a great camera and you can use it well with the standard of pictures. That dot5 sure is proveing troublesome. Get the old girl back on Dot4 and im sure all will be well. | ||
| Bill Coburn Grand Master Username: bill_coburn Post Number: 378 Registered: 4-2003 |
Thank you Patrick. Just a SITREP as they say in the Army on the silicon saga. Had the old girl out for the Federal Rally last weekend and took the opportunity to check for leaking master cylinders and wheel cylinders. Nothing. I am using RR363 simply because I have it. I do note that after some use the fluid darkens slightly which helps to see it but I imagine this could well be dye from the various new rubber pipes. This has happened on a number of Cloud cars which of course all have glass reservoirs. The slots on the Shadows don't seem to show the change. In short all is well to date after some 350K and a couple of months. It will be due for a service in May and I intend flushing it again as a precaution. If I have to pull those master cylinders out again I will find a nearby cliff and facilitate a face to face meeting with Henry!!! |
