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Comment by giantg2 | Hacker News Reader

I found the brake fluid freezing comment interesting. Quite a bit conflicting info on it when I do a search.

Some places say the fluid doesn't actually freeze but becomes too viscous to function properly. Others say it's condensation in the vacuum booster line, effectively making them non-power brakes. And still others say the fluid itself won't freeze, but the water it absorbed will.

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Anecdata: I live in Minnesota. It is cold here ( https://en.wikipedia.org/wiki/List_of_Minnesota_weather_reco... ) -- and here in my fourth decade of life, never had an issue with brake fluid. I've seen issues in the cold with: electronics, radiator fluid, washer fluid, ignitions, batteries, tire pressure, bushings, plastics, even fuel back when EFI was less common, but never issues with brake fluid.

Road salt is our big problem here, but that's true for everyone who has winter.

FWIW my neighbor has a Tesla and loves it...

I think the colder areas don't use salt, right? Like some areas of Alaska are too cold for salt to work.

In the context of minnesota, road salt is used on most flat or heavily trafficked roads. Steep inclines and intersections all use grit or small gravel instead or or in addition to salt.

True, but the second half of the sentence was that it was true for everywhere with winter weather. I was just pointing out that it isn't necessarily the case.

Edit: and also, some areas are not using salt for environmental reasons, like Portland.

Yeah, outer portions of Minnesota avoid using salt near wetlands as well- most states do, I think. You have to get pretty far into northern latitudes before salt stops working well enough to abandon it, though. Mixing sand or grit helps warm it up in direct sunlight enough that it can still be beneficial below zero F.

Once you get below -20 C (-4 F) salt loses a lot of effectiveness. Here in Edmonton we had a few weeks of ~-30 C and the roads were polished to an icy shine, there was no getting away from it and no amount of sand or salt helped for any amount of time.

> Road salt is our big problem here, but that's true for everyone who has winter.

Not if your municipality uses grit instead of salt.

So they have two problems.

>Road salt is our big problem here

Road salt problems always makes me wonder how much the vehicle plays into that.

I've driven 20+ year old cars without a spot of rust while there are vehicles that are 5 years old with rust problems.

I think the real variable when it comes to road salt issue is vehicle quality.

>I think the real variable when it comes to road salt issue is vehicle quality.

It depends on how much the OEM wants to spend on fancy paint and coatings, how much the vehicle's use degrades that coating, how much salt the vehicle is exposed to, what kind of salt (liquid stuff gets everywhere much more effectively) and what if any steps the owner takes to mitigate the salt.

You can make generalizations like "Volvo loves to galvanize stuff and Toyota DGAF" but without controlling for the life the vehicle will have that doesn't really let you make predictions about a specific vehicle.

I feel like your two paragraphs conflict.

To add to the confusion, there are two main kinds of brake fluid:

The classic, pro: works well even under high temperatures resulting from prolonged braking. Con: absorbs water over time and must be replaced fairly often even if not stressed.

New kind, pro: does not absorb water and does not degrade as much on its own. Con: braking action gets "spongy" when the fluid heats up from prolonged braking.

Doesn't DOT 5 also have the issue of not working as well with ABS due to compressible nature of the fluid?

The amount of brake fluid that actually moves when you press the brake is trivial and with the forces involved it could be as thick as grease and still work mostly fine.

Unless you actively mix it with water (like you do antifreeze) you are going to have a hell of a time getting glycol based brake fluid to absorb enough water to freeze at any earthly temperature. Maybe if you ran a system without the cap on the reservoir for decades in a very humid climate you could do it but even then I think the odds are long at best.

I vote condensation.

My understanding is that the water contaminated fluid tends to concentrate at the bottom of the systems. With 20% of cars having systems with 5% water, that seems like the concentration could be higher in parts of the system. So I agree that it's probably unlikely (and only even possible in artic condidtions).

All may be true - DOT 5 brake fluid is silicon based and will not absorb water at all, the others will. Which is why DOT 5 is often found in military trucks.

Yeah, but the claims I saw were including DOT 3, 4 and sometimes 5. At least here in the US, DOT 5 seems to be pretty uncommon.

3 and 4 (and 5.1) absorb water so who knows what that does at super low temperatures (but it’s rated pretty low as is).

I know power steering fluid gets too viscous and can blow out the hoses on a Dodge Avenger because it can’t get through the cooler.

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