[TeMPOraL]

AFAIK in Poland, it's common knowledge among experienced drivers you should park on gear in lieu of handbrake in winter and/or a wet weather, especially if you plan to keep the car parked for more than a couple of hours.

We didn't know it until recently, which is how we ended up with blocked rear wheels after the car stayed parked for a couple of days, one of which was rainy. The process of unlocking the wheels damaged the brakes, so we also ended up with two visits to repair shop (one to hot-fix them before a trip home, another to fix them properly).

[spongeb00b]

I left my first car parked on my sloped drive for 2 weeks while on holiday. When trying to drive it for the first time I found the handbrake seized on. My dad was all “give it more gas” to try and free it while reversing down the drive. Suddenly there was a bang and jolt and the sound of escaping air. The front spring had been pulled until snapped and punctured the tyre...

[salawat]

Out of curiosity; why force it if you suspect it of being frozen on? I'd get an extension cord and a hair dryer/heat gun and warm the brake cable/linkages and rear brake assembly. You'd just have to get it warm enough to get an ice fracture started, then the force of actuating the brake should do the rest if it's an old fashioned one.

Just be careful, and make sure your electrical cord is in good condition, and you should be fine. Bonus points in that you get an excuse to nab the Mrs./Ms. hair dryer for a good laugh when someone inevitably sees you giving your car a good blow down.

I'd be incredibly leery of trying to force anything through engine output/mechanical vibration alone. Always try undoing the environmental complication first. It's much less prone to causing costly repairs, and easier to do than it seems. A car cover that goes to the ground, and a beefy enough space heater underneath the cover in the morning might do the trick too. Although winds can make the heat gun/hair dryer + point heating work better.

Brake fluid doesn't freeze, but any water it manages to have pulled out of the air will. In fact if you have too much water in your brake lines from moisture absorption from the atmosphere because you were fiddling with the master cylinder, or using fluid that had a chance to absorb significant moisture, you could get large enough concentrations of water to get some crystallization started. Normally though, hydraulic brake systems in good condition shouldn't have a problem with that. In the unlikely event you do, the amount of ice shouldn't threaten the physical integrity of the system, and warming the brake lines would resolve it. Note that having enough water for that to happen gas probably made your braking sponge though, and you should really flush your brakes at that point when you get a good dry day.

[spongeb00b]

The problem wasn’t cold weather, this was the middle of summer!

They were just stuck on too hard. At that age I didn’t know any better, and my dad who was the one encouraging me to gun it was never that mechanically minded.

Over 10 years later I now do all maintenance and servicing on my cars myself, so yeah if it happened again I would not have been doing that!

[TeMPOraL]

In that situation I mentioned, our uncle (an experienced driver) helped us unlock the wheels by essentially making the car rock back and forth. Standing outside, I was horrified - I didn't even realize the suspension system has such a large range of motion, and I'm pretty sure that if I tried to reproduce it on a toy car, I'd break it into pieces. But after few minutes of this dance, with two loud bangs, the brake disks let go and the stuck wheels started to rotate.

We drove the car straight to the mechanic after that.

[mdavidn]

Yes, that's true of automatics as well. If you suspect the brake shoe or cabling could get wet and freeze, you should avoid leaving the handbrake engaged.

[squiggleblaz]

Oh, so it's not "brake and in gear", but "in gear only"?

[TeMPOraL]

Yes, at least in the manual case I described above. The issue is that the braking mechanism itself will get stuck if it's left engaged and then gets wet.

[onefuncman]

I thought this was prevented by brake fluid being hygroscopic?

[blattimwind]

Classic handbrakes use a braking wire and don't use the hydraulic breaking system (so it's somewhat redundant, actually). Also, the brake fluid is inside the system and can't prevent the brake cylinder or the brake pads from seizing.

[AstralStorm]

The difference is the handbrake will seize off rather than braking, which means the car is usable or at least easier to haul.