Re: Brake Fluid woes...

better get flushing before it f***s all the seals in the system Steve the grease

There is an argument (which I won't be drawn further into) that water can pool in the system and cause localised problems, rather than being absorbed into the fluid as with conventioanl types. Not having shiny cars with nicely painted bulkheads, I stick with DOT4, however I might feel the advantages of silicone outweigh the disadvantages if I ever get a car with a tidy engine bay.... Cheers, Bill.

-- Rarebits4classics .......just what you've been looking for

PO Box 1232 Calne Wiltshire SN11 8WA United Kingdom

The PO did have a Cit DS as well so I did wonder but he was well clued up so I doubt he'd have done that and all the calipers seem fine..... Also they mix okay...whereas silicon fluid does NOT mix at all with Dot 4 stuff... Anyone ever seen any green Dot 5 ?

Jonners

Presumably (this is not an argument I've presented myself), the same way condensation appears on the inside surface of body panels when cars are kept outside in the winter. Is silicone fluid lighter or heavier than water, ie will the water sink if it gets onto the surface of the fluid? I can see the reasoning behind the argument, but I don't know whether it's likely to be a problem in the real world. Cheers, Bill.

-- Rarebits4classics .......just what you've been looking for

PO Box 1232 Calne Wiltshire SN11 8WA United Kingdom

In article , William Davies writes

No, that doesn't hold up. Condensation forms because the air that is in contact with the cold panel contains considerable amounts of water. Given that Silicon fluid is not hygroscopic this will not be the case inside the brake system.

It's probably lighter, so water would sink, but only if it's liquid water. In other words this mechanism doesn't apply unless you leave the bonnet open and the reservoir cap off during a rain storm.

No it's not.

I've also never had any problems with seals swelling due to use of silicon fluid, even on the (many) occasions when I haven't replaced them before changing from DOT4.

Dunno about water, but silicone fluid is certainly lighter than the crap that comes out with it when bleeding the brakes, as I've noticed half an inch of slightly darker stuff at the bottom of the jam jar once it's had time to settle. I think that's just general dirt from within the system, as there's never the clear threshold you'd get between water and oil. Of course, one other advantage of silicone, is that clean fluid can be reused.

Since silicone brake fluid is not hygroscopic, we are only concerned with condensation. The brake system is sealed except for a very small breather hole in the reservoir cap. Given the small air volume in the reservoir, and the small air exchange through that "pin hole" in the cap, I would think the amount of condensation would be negligible. And if the car is garaged, the air in the reservoir may never go through dew point - hence no condensation at all!

-- Bob Donahue (Still stuck in the '50s) Email - snipped-for-privacy@insightbb.com