I just checked my H36/HK36 pplservice manual. Page 59 specifies that DOT3 or some equivalents are used. They emphatically state that MIL5606 is not to be used. I have always attributed this to the belief that the seals and O rings in the master cylinder were incompatible with 5606. If the master cylinder is a Cleveland part, I wonder if anyone has a Cleveland part number. I have always thought of it as a BMW part--like the gas cap.
Other serial number birds may have differing specifications in their service manuals. I have no clue why Hoffman chose DOT3 fluid, but I can't imagine any such manufacturer buying Cleveland brakes and then disassembling them to change out O rings due to an incompatibility issue. Nor, I wonder if Cleveland would make such a change on the assembly line, for certification reasons. My H36 arrived with automotive brake fluid. I put new tires on and rebuilt the brakes, operated without any issues for about fifteen years, then rebuilt the brakes a year or so back when I installed new tires. Upon disassembly this was purely preventive maintenance because I hate the drill of removing the wheels from the fairings. In both instances of disassembly I used MS O rings. I saw no softening or significant deterioration after years with DOT3. I live in a fairly dry climate, so absorption of water doesn't seem an issue for either the H36 or thousands of autos here. My sophomoric understanding of hydraulics tells me the issue of water in brake fluid is that it changes into a vaporous state at about 100 degrees C. As with brake fluid, it is not compressable in fluid state. If the brakes get hot--above that temperature and there is moisture in the slave cylinders or in adjacent lines, one could have soft brakes or even failure. In comparison, corrosion may be the lesser concern. The fluid in the brake system does not circulate, so I wonder if it wouldn't take many months of water absorption before the fluid at the slave end of the system had an issue. This may be the case with most autos in the states that can go decades without brake fluid replacement. It is a rare spot of maintenance here (we have our foibles, including our elections.) Once, when I requested brake fluid change, the shop didn't even get the reason. Michael Stockhill Polson MT On Jun 24, 2018 3:25 PM, "Rob Thompson" <amessageto...@gmail.com> wrote: I just found this useful and comprehensive table of how different rubbers are effected by different chemicals http://mykin.com/rubber-chemical-resistance-chart-3 It says that Nitrile rubber is OK with glycol.... but as the auto brake fluid absorbs water over time it must adversely effect the Nitrile O rings as Nigel says. With Nigel's experience in hydraulics I would take what he says as being the most practically accurate. I have always bought genuine Cleveland nitrile rubber 0-rings for the the H36 brake system and used the mineral oil that is recommended for them. You need to pump a lot through to get the bubbles out so the mineral oil saves a fair bit of cash. You can use Automatic Transmission Fluid. Sounds like Glycol based fluids may be OK but on the condition that you need to change them regularly if you have genuine Cleveland seals. And make sure no one gets them mixed up when topping up the system! Rob regards Rob Rob Thompson 0429 493 828 (Please note that my new email address is amessageto...@gmail.com) On Sun, Jun 24, 2018 at 10:05 PM, Nigel Baker <ni...@limbachaustralia.com> wrote: > I think your right on the DOT 5 Konrad. Silicone lubricants are fine on BN > seals and Silicone Grease is used to lube BN seals in food processing > machinery as it is non toxic so compatible. > > The H36 mm does say DOT fluid but either some have been changed over at > some stage eg by the Thai Airforce and others or depends on when it was > built. There is a mix out there that I have seen. > > > > *Characteristics of common braking fluids*[6] > <https://en.wikipedia.org/wiki/Brake_fluid#cite_note-DOT-6>[5] > <https://en.wikipedia.org/wiki/Brake_fluid#cite_note-epic-5> > > *Dry boiling point <https://en.wikipedia.org/wiki/Boiling_point>* > > *Wet boiling point* > > *Viscosity limit* > > *Primary constituent* > > DOT 2 > <https://en.wikipedia.org/w/index.php?title=DOT_2&action=edit&redlink=1> > > 190 °C (374 °F) > > 140 °C (284 °F) > > ? > > castor oil/alcohol > > DOT 3 <https://en.wikipedia.org/wiki/DOT_3> > > 205 °C (401 °F) > > 140 °C (284 °F) > > 1500 mm2/s > > glycol ether <https://en.wikipedia.org/wiki/Glycol_ethers> > > DOT 4 <https://en.wikipedia.org/wiki/DOT_4> > > 230 °C (446 °F) > > 155 °C (311 °F) > > 1800 mm2/s > > glycol ether/borate ester > <https://en.wikipedia.org/wiki/Borate#Borate_esters> > > LHM+ > <https://en.wikipedia.org/wiki/Hydropneumatic_suspension#LHS_versus_LHM> > > 249 °C (480 °F) > > 249 °C (480 °F) > > 1200 mm2/s [7] <https://en.wikipedia.org/wiki/Brake_fluid#cite_note-7> > > mineral oil > > DOT 5 <https://en.wikipedia.org/wiki/DOT_5> > > 260 °C (500 °F) > > 180 °C (356 °F) > > 900 mm2/s > > silicone > > DOT 5.1 <https://en.wikipedia.org/wiki/DOT_5.1> > > 260 °C (500 °F) > > 180 °C (356 °F) > > 900 mm2/s > > glycol ether/borate ester > > *Wet boiling point defined as 3.7% water by volume.* > > I have just looked up Matco and yep can use DOT 5 but not 5.1 so same with > the other DOT series fluids. Same chemical problem. > > http://www.matcomfg.com/MASTERCYLINDERCAP10MC4X-idv-3835-5.html > > Thus Diamond must change the seals or they get them special order. Same > problem exists with Cleveland. > > > > Cheers. > > Nige. > > > > > > > > *From:* dog@lists.riverland.net.au <dog@lists.riverland.net.au> *On > Behalf Of *Konrad FDU > *Sent:* Sunday, June 24, 2018 8:57 PM > *To:* dog@lists.riverland.net.au > *Subject:* AW: [DOG mailing list] NO AUTOMOTIVE BRAKE FLUID IN H36 > > > > Hello Rob, > > > > my MM for the Super Dimona specifies DOT4 as break fluid. So does TOST > which also is a Cleveland break. It is not specify DOT 5 that you might > refer to and is silicone based (not DOT5.1 which again is glycol based) . > > I would not call DOT4 or DOT3 water soluble. It is hygroscopic and accepts > to accumulate the humidity from the air but water degrades performance and > boiling point. This is why break fluid is changed regularly or checked for > water. > > > > regards > > Konrad > > > ------------------------------ > > *Von:* dog@lists.riverland.net.au [mailto:dog@lists.riverland.net.au > <dog@lists.riverland.net.au>] *Im Auftrag von *Rob Thompson > *Gesendet:* Sonntag, 24. Juni 2018 11:59 > *An:* dog@lists.riverland.net.au > *Betreff:* Re: [DOG mailing list] NO AUTOMOTIVE BRAKE FLUID IN H36 > > Hi Michael, > > So you have been running water soluble auto fluid in Cleveland brakes for > 17 years? > > Interesting. I didn't think the rubber bits would go OK with a > water/glycol based fluid. > > Make sure you label the reservoir very clearly what type you are using. If > someone adds the wrong type you will get a horrible mess! > > > regards > > Rob > > > > Rob Thompson > > 0429 493 828 > > (Please note that my new email address is amessageto...@gmail.com) > > > > On Sun, Jun 24, 2018 at 9:26 AM, Michael Stockhill <sto...@gmail.com> > wrote: > > I believe the service manual specifies automotive type fluid, likely for > the motorcycle type master cylinder. No problem with Cleveland O rings in > slaves for last 17 years. > > > > Best > > > > Michael Stockhill > > > > > > > > > > > > On Jun 23, 2018 3:01 PM, "Rob Thompson" <amessageto...@gmail.com> wrote: > > Just a reminder to everyone and Martin from K1W1 land. > > The H36 uses hydraulic brake fluid. Auto fluid is water based and will > wreck the seals and system. > > > > regards > > Rob > > > > Rob Thompson > > 0429 493 828 > > (Please note that my new email address is amessageto...@gmail.com) > > > > >
