So when leaving work today in '94 Legacy 2.2L auto, I almost ran into the side of a coworker at about 5 mph because the brake pedal 'locked up' or got stuck.

 

It was a strange feeling. It didn't feel like a lack of boost, it more felt like the pedal mechanically jammed up. It wouldn't go down. I pressed pretty hard but there was next to zero braking.

 

So I pulled off slowly into another parking lot to see what was going on, and then the pedal seemed to be working normally again. I tested it a couple dozen times and it seemed alright. So I left and it didn't act up any more on the 30+ mile drive on the way home.

 

It was pretty cold out, for here anyway, at about 8F. Wasn't there a TSB or recall or something for this kind of issue on this era in cold weather? Or what else could be causing this? I mean if this happened at much higher speed, having like zero brakes suddenly would not be good. I didn't even think about pulling the parking brake though for some reason.

 

I did the booster checks and those were oK.

there is a condition, cold related, where basically the thing (master, or booster or something) freezes up. i have heard a few possible solutions but nothing definite.

 

so the best advice, if you can't find a solution, is to test your brakes before you need them. it usually does not last long but colder may be worse.

The few clues you have given would be indicative of moisture in the lines, freezing up.

 

I would drain the entire brake system, bleed all new brake fluid all the way to each caliper piston.

 

Brake fluid is one thing that draws/attracts moisture. It must be totally sealed when stored. If a cap is loose, or a seal is bad, it will draw moisture in.

 

So, check your cap condition, and the seal on the fill resevoir, after completely flushing ALL the old fluid of your brake lines.

Edited January 4, 201214 yr by bheinen74

Thanks, I will definitely be testing the brakes more before I get going, esp when cold! I did forget to mention that it has all fresh brake fluid. I had just finished changing it a couple months back and what do I discover but the rear lines had rusted and were leaking, so it got new rear lines and then new fluid again on top of that.

 

I took the hose off the intake manifold for the booster and sprayed some metal protector (wd-40 basically) in there, not sure, I know some people said there could be a problem with that check valve, but I don't think it would cause this, since it felt mechanically jammed (not just no assist).

 

I couldn't find a TSB about it, though I know I read something about it somewhere some years back......

Used to have this problem on my old Ranger. The brake booster had moisture in it, and it would freeze when it was cold. Anytime it was below freezing I had no brakes. Had to let the truck warm up before I could move the pedal at all. :-p

I replaced the brake booster and it fixed it.

Hm that's interesting. Maybe I can get the garage nice and warm, then pull the booster hose off and put a slight nitrogen purge from my cylinder on it for a day or so to try to dry it out. I wonder if it would hold a high vacuum? Like putting a refrigeration vacuum pump on it, then if it is warm enough the moisture would boil out?

 

It didn't do it today, but was about 18F. I've had this car for a few years but I don't remember it ever happening before.