| Author | Message | ||
     Bill Hart Experienced User Username: bill_hart Post Number: 19 Registered: 6-2015 |
It is my understanding that RR/Bentley uses a brake system licensed from Citroen. Apparently, some Citroen owners use, without ill effects, Mil-H-5606 aircraft "red oil" as a substitute for LHM. Essentally the same stuff, different color. Comparison of red oil and LHM: * Seal compatibility - fine * Non-foaming under High pressures - fine * Viscosity/temperature stability - fine * Lubrication qualities - fine * Corrosion resistance - fine * Volatility - passable * Resistance to thermal breakdown - fine Given that red oil is less expensive and more readily available than LHM, this sounds interesting. Your thoughts? | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 476 Registered: 5-2015 |
I used engine oil and diesel fuel in a Citroën CX because it used to leak so much. Done 10k miles no problem. However that was a car I paid 80 quid for not a Rolls-Royce. LHM has an indefinite shelf life so buy a 20 litre drum. Cheaper in bulk. Also LHM can be used in the power steering. NOT the gearbox though. LHM is a high quality hydraulic oil. Dexron as used in gearboxes has friction improvers which LHM doesn't have. Friction improvers are not needed in power steering. A bit of trivia. LHM is not regulated for specifications. Dot type brake fluids are regulated. | ||
| Jean-Pierre 'JP' Hilbert Prolific User Username: jphilbert Post Number: 125 Registered: 9-2013 |
Bill, I see that you are in the US, and unlike Europe, where LHM is readily available in most fuel stations, you have a very good supply of MIL-5606 aircraft hydraulic oil found at almost every airplane service facility. My thoughts: First, do NOT confuse 5606 and its variations with SKYDROL, which is a phosphate-ester, non-flammable hydraulic fluid. Then, the difference between the airplane systems and our cars are those high precision brake pumps. Incidentally, they are RR specific, they do not come from Citroen. Similar to the pre-1980 RR brake fluid (a special variation of DOT4 mixed with castor oil and sold under the name RR363), LHM is a special brew of mineral hydraulic fluid containing additives to precisely keep our pumps happy. MIL5606 routinely runs at 3000psi, like our pumps (2500psi), but the pumps in airplane work differently (rotational pumps, like the oil pump on our cars). Hence I suspect that this fluid may lack the special lubricant what is castor oil for the glycol-based RR363. | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1647 Registered: 6-2009 |
If you download the RR & Bentley Parts, Repair, Restoration & Other Resources Compilation and search for "Miscellaneous Hydraulic/Braking System Mineral Oil Based Fluids and Their Properties", you will find a table showing the basic properties of all the commonly available automotive ones. You will see that there are not huge differences between them. If the stats for aircraft hydraulic oil closely match HSMO, HSMO+, LHM+ (which is, at least in theory, supposed to be the same thing as HSMO+), or Pentosin CHF11S there is no logical reason that it is not suitable. Since these fluids are actually oil based there is no "additive" that is akin to the castor oil in the glycol based fluids. These oils are engineered to have specific characteristics and it doesn't matter precisely how those characteristics are achieved. If you've got the correct or highly similar (since, as you see, "the same thing" doesn't test out in precisely the same way on different occasions) properties you should be just fine. I have no idea what the specs are on aircraft hydraulic fluid and if someone's got those they'd be interesting to have. Brian | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1648 Registered: 6-2009 |
Just did a search for Military Specification H5606 and found version G for download here. This appears to have been superseded by MIL-PRF-5606H (and its amendments, the latest of which is dated 2006) all of which can be found on this webpage. The performance characteristics and the limits on each are described in nauseating detail in the specifications. Read these, compare them to the same characteristics documented for HSMO+, then come to an educated decision with which you're comfortable. Brian P.S. It appears that virtually any of the commonly available aircraft hydraulic fluids will meet multiple military specifications. Here's one example, Royco 756. There have to be subtle differences, though, since single manufacturers do make different product lines which meet Mil-H-5606. Whether those subtle differences would matter for us is a matter for further investigation. | ||
| Bill Hart Experienced User Username: bill_hart Post Number: 20 Registered: 6-2015 |
To Brian Vogel and others, go to: citroen.cappyfabrics.com/tony.html for a dissertation on the subject. | ||
| Jean-Pierre 'JP' Hilbert Prolific User Username: jphilbert Post Number: 127 Registered: 9-2013 |
Good article but one sentence made me smile: ''Rolls Royce used DOT 3 in bottles labeled RR 363'' | ||
| Brian Vogel Grand Master Username: guyslp Post Number: 1649 Registered: 6-2009 |
JP, Why? RR363 is a DOT3 fluid, it just has the extra lubricant (ethoxylated-propxylated castor oil) for the pumps. It is not in any way an inaccurate statement to call RR363 a DOT3 fluid. Since this guy is a Citroen specialist I don't think he was motivated to dig into the details of what the "plus" was with regard to RR363, but that "plus" doesn't change the fact that it is DOT3 (and, I believe DOT4 compliant, too) fluid. One could use RR363 in any system that requires DOT3 fluid but you'd have to be crazy to do that just based on the expense. Bill, I'm intimately familiar with that article and had a long private exchange with its author several years ago. This is one of the reasons, but not the only one, that I am perfectly comfortable with my decision to use YAK363, a 90% DOT3 brake fluid and 10% pharmaceutical grade castor oil mix, in my SY cars that are both RR363 era. Brian | ||
| Bill Hart Experienced User Username: bill_hart Post Number: 21 Registered: 6-2015 |
I'm going to replace the front brake hoses on my Turbo R, which will entail a brake bleed. I have decided to top up the reservoir with aircraft red oil which, except for the red dye, seems to be very similar to LHM. Wish me luck. | ||
| Jean-Pierre 'JP' Hilbert Prolific User Username: jphilbert Post Number: 128 Registered: 9-2013 |
well, what made me smile is that the author believed that RR simply re-labelled DOT3 as RR363, like they nowadays re-label Italian Parma ham as ''product of Turkey'' to circumvent the Russian ban on EU food. I surely appreciate the fact that the author was not concerned about being 100% on the technicalities of our cars ))) | ||
| Robert Noel Reddington Grand Master Username: bob_uk Post Number: 479 Registered: 5-2015 |
Changing the front hoses. Discharge the hydraulic pressure by pumping. Hold the pedal down with a length of wood between pedal and seat. The idea is that the brake valve will close of the return port to the reservoir and no fluid can flow. Open up 4 caliper nipples slowly just in case some pressure is lurking around. Change pipes any trouble cut old pipes so a socket can be used. Release brake pedal. Observe bleed nipples when they flow a bit close nipples. Start engine and take a squirt from each caliper. Replace any dodgy rubber nipple boots. Available from Anne Summers sex toy catalogue. If you are going to change the hydraulic fluid. Retract all 16 caliper pistons. This will put most of the fluid into the reservoir. While changing the hoses don't apply the brake pedal. This will allow the fluid from the reservoir to run out. Then simply fill up with new fluid and allow a bit to run out. Then close up the nips. Start engine apply brake to reset the calioer pistons and then top up and then a quick squirt from each caliper. LHM is a very high quality hydraulic oil especially formulated for Citreon. All Citroen and RR pumps are plunger pumps like diesel injection pumps. The first prototype of this system used diesel injection pumps. The Citroen uses a Swash plate plunger pump or a similiar set up as RR. I understand that LHM is expensive and hard to source in the USA. Naturally one is looking for alternative oils. One oil that springs to mind is JCB hydraulic oil usually sold in 25 litre drums. Another is Shell tellus range of hydraulic oils. Be very cautious with aero red oil. Some types are most definitely not compatible. Aero stuff has to work in conditions that are different from cars. So the boffins put additives in aero stuff that suit the conditions. These additives can detract from the lubricity of the oil but the additive is essential for the conditions so they do a trade off. A trade off that is not needed for a car. However if the Citreon guys say its Ok then most likely it is. It's pointless asking an oil company because they will say use LHM. An aside comment. Often people think that because something is used in motor racing or aeroplanes that it must be better than what is used on cars. For instance Castrol R racing oil. This must not be run for over say 200 miles then allowed to stand idle because the oil gums up. Great for racing useless for anything else. |
