how humid is too humid for brake work?

I've never heard of such a thing nor ever had any problem from doing brake work in less than ideal weather. Then again I don't usually let the MC sit with the cap off. It's open just long enough to fill it. The difference in how much water is absorbed must be extremely tiny if any.

I've never really put much thought into it; I usually just schedule maintenance for a warm day. Unfortunately, you can't always schedule repairs, and apparently even changing the fluid regularly can't keep hoses from bursting :(

nate

It's not the heat, it's the humdity.we have plenty of that around here. cuhulin

75% humidity at 32* would put the dew point at about 24, not very humid.

Use Castrol LMA brake fluid and don't worry about it.

My brother's oldsmobile didn't seem to like aligning itself with warm sunny days either.

Unless you let the system stay open for a long time (several hours, or days), this is just BS.

There is a time rate of absorption, certainly, but this is not a big deal. Do what you have to do, but get finished in reasonable time. ;>)

By the way, Nate, I am considering a Cayman.. What have you heard or what do you think of them??

Too humid is when you walk out the door and you're soaked instantly, or when even a beer is too warm...

I want one, but they're so far out of my price range that I really haven't done my research :(

nate

A.C., not brakes. The desiccant bag in the Receiver/Driers, Accumulators will suck moisture in.

The Cayman was offered in Dallas for $42,000-45,000 a couple of weeks ago.. I suspect a person could make that deal most of the time.. Not cheap, but not insurmountable.

Back to the topic....

I am really a little surprised that "water scavengers" are not added to brake fluids. Such chemicals are known, certainly. Maybe they have found that issues like boiling point, corrosivity, or compatibility with elastomeric seals were a stumbling block.

Even an inline "filter drier", or sidestream unit, would be easy to conceive.

Once you start to get discoloration in the fluid, and solids, you know that oxidation has started. Solids also promote the corrosion reaction. I have seen tons of the old cast drum iron brake cylinders, as well as master cylinders, destroyed by this. The alloys used in calipers seems to tolerate the problem a bit better.

I think the issue is that the fluid does not circulate, but only moves back and forth in the pipes slightly as you apply and release the brakes. Otherwise we'd all be using non-hygroscopic brake fluids with water separators built into the plumbing.

I suppose you could build a brake fluid circulation system, but the number of added check valves, pumps, etc. would be silly.

Now if you have an ABS-equipped car, you might be able to put a water separator on the return line to the rewervoir (I think? I'm talking off the cuff here and haven't completely thought this through) but you'd need to have regular ABS activation to get any benefit from it...

nate

My take on brake fluid is that whether or not moisture becomes an issue is very dependent on the type of driving you do. The guy who drives his car a

100 miles a day or 30000 miles per year can go the entire life of the vehicle (say 10 years and 300K miles) without ever changing the brake fluid and there won't be any problem with corrosion. The guy who drives his car on weekends and parks it for the winter is going to have nothing but trouble with things like pitted cylinders and brake lines that rust from the inside out and that can happen in just a couple of years with that type of driving. For that type of driver changing the brake fluid every year is the only way to avoid those problems.

-jim

If it's not air-cooled, it's not the real thing.

--scott