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Locked Up Brakes, Can't Find Fix

Hi, I have a 2003 Subaru Forester, manual transmission. Last week, there was one day where I was driving and I felt like the ABS system was being weird-when I would brake it would feel like I was braking on ice, but the roads were dry. The next day, as I was backing out the garage the car wouldn’t move for a minute-but then I got going and I thought everyone was fine. Drove a few blocks to the store, went in, came back out and the brakes were locked up and 3 out of the 4 tires wouldn’t spin (both front tires and the rear passenger tire, rear driver side tire was fine). Had to get it towed, was told by the shop that the brakes needed cleaned up and the calipers replaced, so did that. Drives fine for two days, and then two days later the same tires lock up again and I have to get another tow, etc. This mechanic tells me it’s the ABS pump, and he released the lines in front of me and the tires started spinning so that seemed like it was right. That was Friday, today is Sunday and it’s been fine since then and I’ve driven about 270 miles, but then this evening as I was leaving the store the brakes weren’t locked up, but they felt…stuck somehow, like the car was being bogged down and it was jerky getting out the parking lot…then it drove fine the short way home but I am worried to drive it any significant distance again in case the brakes lock up yet again and I have to get another tow. Should I be worried? What on earth could be causing this? Any advice greatly appreciated!

I think you have a bad master cylinder and there is something wrong with your drivers side rear brake and it is not working.

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How much does master cylinder repair/replacement usually run? Also, when the brakes are working or for the past year I’ve been driving the car, it doesn’t feel like I have a bad brake…I’ve had brakes go out on me before and the car will usually pull to one side while I’m braking or otherwise feel weird while I break, wouldn’t have a brake out be something you’d notice while driving?

It seems improbable that 3 calipers would fail at the same time. I doubt replacing the calipers did anything other than release built up & stuck (for some reason) pressure in the hydraulics. I think what I’d do if I had this problem is temporarily disable the ABS and see if the problem goes away. On many vehicles that possible by disabling the ABS fuse.

Other things that could cause it are the ideas presented above by old-timer, or you could actually have multiple problems going on b/c the brake fluid somehow got contaminated. Or the parking brakes are sticking is one problem and a caliper or ABS sticking is another.

Is the ABS dash wash warming light on? If so, there’s a possibility of faulty wheel speed sensor(s).

OEM master cylinders tend to run about $200 ea, and don’t take long to replace, maybe an hour labor. So around $300.

You would probably feel if a front wheel is not working but not necessarily a rear one. Jack up the drivers rear wheel, stepping on the brake should instantly lock it up. I cannot think of anything that would lock op 3 out of four brakes.


I rarely use my parking brake, and since only one of the rear wheels is locking up I don’t think that’s it. ABS warning light is off, my check engine light was on for ages but since the ABS pump was replaced has been off and so far has stayed off for just under 300 miles (don’t know if the shop did anything extra that would have made that go off).

I’ve dropped a lot of money trying to fix this problem in the past week, so my plan for now is to drive my beater car until I have enough money to get to a mechanic I trust and get a good diagnostic test for this, because I can’t afford to keep getting my car towed every other day. The brakes only lock up after I’ve parked, if that makes a difference-I’ve never had them lock up in traffic or an a stoplight.

I’m wondering if one or more of the brake hoses might be partially collapsed, acting as a one-way check valve


Your mechanic should have checked for retained fluid pressure in the system before replacing those brake calipers. Your master cylinder is probably damaged from contaminated fluid, did someone add something to the master cylinder reservoir a week or two before this problem started?

Nope, nothing had been added anywhere in the engine to the car in quite some time, except for windshield washer fluid, which I am confident I put in the right reservoir!

How many years since your last oil change?

Ha, years? Not quite that long…I just had it changed this most recent time in the shop, prior to that it had been about 6,000 miles.

When they locked up, have you stepped on the brake pedal again to see how the pedal feels, and if so, was it really hard and would not go down at all? Did you try again later after things cooled down some or just let it get towed? When the mechanic released the lines right in front of you, how long had it been since they had locked up?

What I am suspecting is that @oldtimer_11 is right. It is the master cylinder and it has something to do with heat. I suspect that you press the brake pedal while putting the shifter in gear, then release the brake and let the clutch out. It is when you press on the brakes at that time that the lockup occurs.

I have stepped on the brake pedal when they’ve been locked up to see if that would get them to release, and I wouldn’t say that the pedal felt hard. I’m trying to remember some specifics, but I guess I would say it feels the way it usually does when you step on the brake when the car is not moving. I’m sorry if that’s not very helpful. I haven’t tried to wait until things cooled down. When the mechanic released the ABS lines, it had been probably about an hour since the brakes locked up.

And yep, you’re correct, both times it’s happened I’ve been trying to leave a parking spot so I have the clutch and the brake pushed it, shift into first or reverse, let off the brake and start releasing the clutch…

Have your mechanic disconnect your hillholder and your problems will be solved. And ask him about those calipers that didn’t need to be replaced…


Ding ding ding, it seems like we have a winner! I did go and talk to my mechanic today and he showed me the calipers from my old vehicle, they were corroded as xxxx (I live in northern Wisconsin, the salt and calcium chloride the heck out of everything), so while that wasn’t the cause of my problem they did need to be replaced now or in the near future. He said that when he manually released the hillholder, the brakes released so it seems like that’s it. Do you know much about that system? How much to repair/replace? Can it just be disabled and the rest of the brakes, including the parking brake, will work fine? Also, I’m still feeling a little confused because like I said earlier, the rear driver’s side tire never locks up, do I just have a bad brake back there or is something else causing it?

There is a button to turn the hill holder on and off, but I don’t think that it affects the front brakes, I thought it set the parking brake. Look in your owners manual for a complete description.

Gah, mine’s too old to have the dash button to disable the feature. Seems like it’s not hard to do mechanically but I still don’t want to screw anything up.

I just googled “2003 Forester hillholder disable” and there’s all sorts of stuff in forums about your problem. The hillholder locks the pressure in your brake lines while the clutch is pressed when you are stopped with your foot on the brake, and is supposed to release when you release the clutch fully. Yours is sticking. Do some research, show your mechanic the printouts and disable it forever.

Sounds like you’ve got to the bottom of it OP. Good for you. Brake lock ups can be caused by mechanical things sticking and/or by the hydraulic system not releasing pressure when it should. Sounds like yours is the hydraulic system not releasing pressure.

I’ve driven a manual Subie in San Francisco before, and the hill-holder clutch comes in very handy on those steep hills.

The hillholder and parking brake are two entirely separate systems on your car. Late model Subarus have electric park brakes operated by a pushbutton on the dash, but yours is an entirely mechanical system. And the hillholder is a simple cable actuated hydraulic valve. Nothing electric about it.

It’s easy enough to disable, just have your mechanic remove the cable from the valve and you’re done. It’s not too expensive to replace though and it’s a nice feature to have if you live in a hilly area.