Lycosaurus
Well Known Member
I bought the EPDM o-ring kit from Charlie Kuss a while ago, and had upgraded my BUNA N caliper and master cylinder seals with these o-rings, as well as changing out the pilot brake lines with teflon-lined hoses. The intent was to use DOT 4 automotive fluid, since it would mitigate a fire should the aluminum lines or caliper seals rupture at the wheels.
I have since done a little more research, and see that DOT 4 is only used in a sealed system, due to issues with moisture absorption. This fluid is highly hygroscopic, and it is typically recommended that it be flushed out every year or two, when used in a sealed system. Even moist air permeating the pores of the hoses will supposedly degrade the fluid over this time.
In our RVs, the brake system is open to the air, with a breather located at the the top of the firewall forward fluid container. I believe that this fluid would deteriorate very rapidly (weeks), since it is recommended that once opened, the remains of a bottle of fluid be discarded.
Seems that the upgrade to DOT 4 fluid is not for me (unless somebody here can convince me otherwise).
A compromise is the use of mil-h-83282 fluid, which is still flammable, but has a higher flash point than mil-h-5606. As it stands, it would seem that my EPDM seals are compatible with ester fluids (DOT 4, Skydrol), but not with the mineral base (5606) or synthetic hydrocarbon based (83282) fluids.
Here's a link for seal compatibility: http://www.lumaco.com/oringmat.htm
This leave me with the choice of using Skydrol and keep the present EPDM seals (I hear Skydrol is quite a skin irritant, though MSDS downplays this), or change the seals out to Viton (anybody sell a seal kit?) so I can use mil-h-83282. I would prefer not to go back to BUNA N, as it has a low temperature rating.
Skydrol is mildly hygroscopic (has an ester formulation), but also acidic (not sure this is really compatible with our aluminum lines.
Skydrol FAQ: http://www.skydrol.com/pages/faqs.asp
Not sure where to go from here. Leaning towards changing seals to Viton and going the mil-h-83282 route.
Comments?
Edit:
Skydrol seems to be compatible with aluminum.... see http://www.skydrol.com/pages/materials_chart.asp
also from http://www.skydrol.com/pages/faqs.asp
I have since done a little more research, and see that DOT 4 is only used in a sealed system, due to issues with moisture absorption. This fluid is highly hygroscopic, and it is typically recommended that it be flushed out every year or two, when used in a sealed system. Even moist air permeating the pores of the hoses will supposedly degrade the fluid over this time.
In our RVs, the brake system is open to the air, with a breather located at the the top of the firewall forward fluid container. I believe that this fluid would deteriorate very rapidly (weeks), since it is recommended that once opened, the remains of a bottle of fluid be discarded.
Seems that the upgrade to DOT 4 fluid is not for me (unless somebody here can convince me otherwise).
A compromise is the use of mil-h-83282 fluid, which is still flammable, but has a higher flash point than mil-h-5606. As it stands, it would seem that my EPDM seals are compatible with ester fluids (DOT 4, Skydrol), but not with the mineral base (5606) or synthetic hydrocarbon based (83282) fluids.
Here's a link for seal compatibility: http://www.lumaco.com/oringmat.htm
This leave me with the choice of using Skydrol and keep the present EPDM seals (I hear Skydrol is quite a skin irritant, though MSDS downplays this), or change the seals out to Viton (anybody sell a seal kit?) so I can use mil-h-83282. I would prefer not to go back to BUNA N, as it has a low temperature rating.
Skydrol is mildly hygroscopic (has an ester formulation), but also acidic (not sure this is really compatible with our aluminum lines.
Skydrol FAQ: http://www.skydrol.com/pages/faqs.asp
Not sure where to go from here. Leaning towards changing seals to Viton and going the mil-h-83282 route.
Comments?
Edit:
Skydrol seems to be compatible with aluminum.... see http://www.skydrol.com/pages/materials_chart.asp
also from http://www.skydrol.com/pages/faqs.asp
The basestocks of Skydrol hydraulic fluids are blends of phosphate esters, which are mildly hygroscopic. In order to keep moisture in the air from absorbing into the fluid, fluid containers should remain closed when not in use. Vent holes on reservoirs should fitted with dessicant breathers to absorb moisture from the air.
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