I live in Fairbanks, Alaska, and drive a 1993 Subaru Legacy. In seriously subzero temperatures, my brakes tend to freeze, so that when I put my foot on the brake pedal, it won’t depress at all. It feels like a rock! The car will actually stop, but only with considerable force and not very fast. My mechanic says there is no solution, as brake fluid thickens and freezes at certain temps. (My car has ABS brakes, thus synthetic brake fluid is not an option.) I have found a partial, but not foolproof, solution is to keep depressing my brakes every 100 yards or so. The weird thing is, I have been driving in Alaska for years and never had this problem before until my second winter with this car. I’m thinking there just has to be a solution, as this is quite dangerous. I’m wondering if there is a way to wrap the brake lines, even with heat tape? Just trying to get creative here, so I can avoid an accident.
When was the last time you replaced your brake fluid?
A good point. Pure brake fluid does not freeze even in Alaska temperatures. But it does absorb water. It is possible there is enough water in the fluid to puddle and turn solid. If the brake fluid has never been changed since the car was built some 15 years ago, it is most certainly due.
OK, now think about this…Do you realize how cold it would have to get to freeze a petroleum based product? The brake fluid is not freezing. The rotors are being glazed over with condensed water and snow and when you drag the brakes you are keeping the rotor warm enough to heep the condensation from building up on the rotor. There has to be a simple cure for this like replacing the brake pads because they are worn just enough to allow too much of a gap between the pad and rotor. Otherwise this would be a huge design oversight, and I would look into another car.
I had the lines drained and brake fluid replaced in January.
I had the lines drained and brake fluid replaced in January. It didn’t help.
OK, two things. One is we’re talking air temperatures of between -20 and -60, which means the air temperature around the brakes and lines at high speeds is going to be a lot lower than that. Two mechanics have told me this is a common problem and that the brake fluid is indeed freezing. So I don’t know. I insisted they look at my brake pads, and they said I still had plenty of pad left. So I don’t know what to think.
where do these posts go???
i wish i had more experience about how the cold affects the car.
since your brakes DO work; after “standing” on them, i suspect the brake booster is either failing, or getting no vaccuum assist. the vaccuum is probably lessened (or more likely frozen.)
any work done on the car related to the vaccuum system prior to this becoming an issue?
keep every one informed. i would like to know the outcome. FMI, FYI
Putting a bottle of brake fluid outside can verify it is getting thick. One flush may not be sufficient to get all the water out. I have had propane lines freeze because of moisture. It wouldn’t take much to block small diameter brake lines. A problem with the vacuum valve sounds like a possibility.
At one point, there was a factory recall on Subaru master cylinders because they did exactly what you describe, under the weather conditions that you describe. However, I don’t recall the exact model years for the recall–only that it applied to some models made prior to circa 1998.
Since factory recalls don’t expire, I would suggest that you check with a Subaru dealer. It is just possible that you can get a new, updated design, master cylinder free-of-charge.
air blowing on something does not make it colder. Unless it is wet, like your skin.
I did a search for brake fluid freeze. Found lots of specs, but only one specified freezing point, as Less than -40?F
You are mistaken…brake fluid is hygroscopic, meaning it absorbs water. It can freeze (although songcatcher posted he changed the fluid) and it can boil while in the lines.
Being glazed with condensation is not it. What happens when your brakes are left in a cold, humid place? They grab and in a matter of 2 or 3 applications of the brakes…good as new.
Also the gap between a rotor and pad is not big enough to accumulate a lot of snow/ice. Modern calipers are designed to have the pads back off very slightly to reduce drag but there are plenty of disc brakes out there that are designed to have the pads in slight contact with the rotor.
The brakes lines were drained; but, what about the brake fluid/water in the brake caliper cylinder? Sure, during the brake fluid drain, the bleeder screw may have been used to bleed the brakes (maybe, not).
ALL of the old brake fluid has to be removed, and new fluid put into the brake master cylinder before the bleeding begins.
A spreader could be used to push (and, hold) the caliper piston completely in, to (completely) evacuate all of the brake fluid/water in the caliper cylinder. Or, shims could be put between the fully pushed in caliper piston and the rotor, before the bleeding begins.
The brake calipers have to be able to float, freely, on the guide pins. The guide pins must be free of adhered rubber, and the pins and guides, must be free of rust, and other crud. The guide pins must be an easy slip fit in the guides. They must be lubricated with a high temperature, and low temperature, special grease.
It’s possible the caliper piston seal isn’t pliable at low temperature. This is particularly true if the seals are made of crapola rubber from China. I have a distrust of Chinese products; since, I’ve seen so much crapola from them. I hope that they, and their importers, are offended enough to improve their products.
I can’t see the brake hoses surviving that many Alaskan winters. Rubber, even synthetic rubber, and cold, do not love each other.
“One is we’re talking air temperatures of between -20 and -60, which means the air temperature around the brakes and lines at high speeds is going to be a lot lower than that.”
Not really. It can cool metal to -60 faster but it can’t cool it below -60. The wind chill effect ONLY applies to exposed skin at 37? C.
The brake fluid will get a little thicker, but that should not be the problem. Also it is not water in the fluid that makes it more viscous when cold. It should not be a problem at -60? F.
Hey…have the tech test the booster
What happens when you, “keep depressing the brake pedal every 100 yards, or so”? Do the brakes become normal in feel and stopping ability?
See if you have a replaceable check valve in the vacuum line for the brake booster. It may be sticking.
The rock-hard pedal indicates a problem with the brake booster, probably a frozen check valve in the vacuum line.
I think we’re wasting our time. Songcatcher isn’t communicado. Why should we be?