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Master Cylinder? Rotors? Help my 2004 Corolla! Help us?!

Hi everyone,

We have a 2004 Toyota Corolla which has been having a mysterious, and probably very dangerous problem. The car is an automatic, no anti-lock brakes, and has about 125k miles on it.

It started a few months ago, the brake pedal began to feel stiff and the car had trouble accelerating. The front driver’s side wheel would completely seize, the whole car would vibrate vigorously, struggling to even get up to 35mph. The steering wheel would jerk clock-and-counter-clockwise rapidly, and you could feel the vibrations moving the brake pedal up and down too. Also, we were hearing a bumpity-bumpity-bumpity sound which changed its rate with the speed of the car. When this happened, there would be a burning rubber smell, sometimes even some white, noxious smoke coming from beneath the front, driver’s side wheel well. We took it to our garage, and they replaced the calipers, pads and the brake hoses. We asked the mechanic if maybe the bumpity-bumpity sound was the rotors, and he insisted it wasn’t that.

Although this helped the problem, it didn’t completely solve it - now the car wasn’t seizing up in the same way. Instead, what is happening is that the car will be fine, then it seems that if the driver needs to brake a lot in a short period (lots of red lights, traffic jam, etc.) the brake pedal slowly goes stiff again and the tachometer goes to 3k at 50mph on a flat. The vibrating came back, and when driving slowly it feels like a lurching - like the driver is pumping the brakes (but isn’t). If the brakes are given a chance to rest - either by highway driving for a time, or parking (ie not braking!) - the pressure seems to release and the pedal loosens up again.

The scariest thing is that I don’t know how far the pedal will travel at any given moment - it might feel that I only need to move the brake pedal half-an-inch to brake, but the next time it will depress almost to the floor. It is freaky and dangerous.

We had some doubts about the mechanic who worked on the car, so we took it to another place. They replaced the rotors and front tires, and once again, it seemed better. The bumpity-bumpity sound definitely went away. But once again, slowly the problems came back. Or, alternately, maybe we only notice it when we need to do a highway trip, since most of our driving is on local 25mph roads.

Now the car is seizing up again. Last night, with the car off, just sitting in my driveway, I pumped the gas pedal. With each pump, the pedal moved less and less, until it finally felt extremely stiff and didn’t travel far enough to activate the brake light.

The first mechanic who saw the car thinks it is the master cylinder. He said there is a valve there that must not be releasing correctly. What seems to be so perplexing about this problem is that it is intermittent - the car will drive just fine, then it will seize up, shake and struggle. Then it feels fine again.

Anyone have any thoughts on this?


The problem could be in the brake booster or the engine, not the master cylinder or the wheels. If there is a bad vacuum leak, it could be causing the engine to stumble horribly, and the brake pedal will stiffen up as the brake booster loses vacuum.

When you pumped the brake pedal, was the engine running? Pumping the brake with the engine off will use up the vacuum stored in the booster, and the pedal will stiffen. This is normal. Once the engine is started, the pedal should return to normal feel. If it doesn’t, you should replace the booster first before replacing the master cylinder.

Ah, okay, well the car was stopped when I pumped the pedal. But the rest of the story stands - the pedal gets stiff, then releases after a period.

Is there a way to determine if it is the brake booster, the engine (God forbid) or the master cylinder before we pay to have this done? It seems to me that the mechanics I have encountered take a “shotgun” approach, which is very costly to us.

Thank you, Busted Knuckles.

when a booster go bad you will feel a still brake pedal and the car maybe hard to get stopped. because the booster works on engine vacuum
and inside of of the booster there is rubber disk and they ware out or just get old and split and is causes a big vacuum leak and this will cause your engine to run rough or not even run. this will cause your engine to vibrate. you can do a check on the master cylinder to see if it is leaking or an inside seal has broken insdie .start engine, push down on brake pedal and hold it in place, if it slowly moves to toward floor and finaly hits floor you have an internal leak with seals in master cyl. if you have to keep brake fluid in master cyl the seal at the push rod going to pedal through fire wall is bad look under dash at rod from pedal into firewall or where the cyl bolts to car under hood I do not know why some shops have a hard time with brakes system , my thoughs are they do not want to take time to test and test. they can charge for this time and in the end it save customer time and money

Ask current shop if they can do the following for free: Let them have car long enough for them to see symptoms rear head. As soon as it acts up they quickly get car on lift and see if a wheel is hard to turn by hand. Quickly break bleeder screw on the caliper at that wheel. If wheel all of a sudden breaks free it’s the master cylinder pistons or something in the vaccuum booster not retracting. If

wheeel doesn’t break free it’s the caliper- yes, they’re new but you could have a bad one esp. if it’s a rebuilt unit. Grabbbing calipers often need to get nice and hot before they act up. If it’s caliper they should replace it free. Then take car and see how it goes.If symptoms continue, I agree w/your shotgun statement, so don’t pay current garage anymore $. Doubtful that current mechanic will charge

you nothing to get brakes working properly now, so maybe hit “home” at bottom of this page then on homepage around right center click under “find a reccomended mechanic”. Let new mechanic have car for a couple days- if you can, so he can really observe the symptoms, or else it’ll never get fixed right. He should check engine manifold vacuum- 15-20 inches of mercury @ idle @ sea level

is good; subtract 1" for every 1000’ of elevation. Cruising along around 40 should see 10-15". He could easily run a long hose from manifold vacuum source to gauge and tape gauge to windshield, to see what happens to vacuum when symptoms rear their head. If calipers are OK it’s a tough call between master cylinder and booster cause on the one hand boosters don’t go bad as often as master cylinders,

and occasionallly pedal goes almost to floor indicatig master cylinder. On the other hand the intermittent hard pedal would indicate bad booster. You can’t rule out that it’s both, either. (Groan) Compromise: mechanic could, since he has to remove M/C from booster to replace booster, put M/C in vise and push on primary piston 50, maybe 100 times to see if it jams. If it doesn’t, it doesn’t prove

anything, but if does, M/C definately is bad. Call first and ask someone close to the nuts and bolts of the operation (foreman, or mechanic who’s gonna do job) if you can have a few minutes of their time. Be prepared w/all salient info. (Your OP is good.) Impresss on them how important it is to you to get to the bottom of the problem. Depending on how much you need your car, you maybe could give the

person a day or two to turn the situation over in their mind, that would be N/C to you. Sometimes it’s hard for a tech who’s in a rush to think perfectly clearly and logically “on-the-spot”.

You can check the booster for yourself, its easy enough. With the engine off, step on the pedal three times. The first time it should go down like normal, the second time it won’t go as far and the third time even less. A couple more pumps of the brake pedal should not be much different that the third, maybe a little on the fourth. Now hold you foot on the brake pedal and start the engine, the pedal should immediately go down to its normal position. I suspect that your booster will pass, they are very reliable and often last 20 or more years.

I think your master cylinder is bad and it was the cause of your problems all along. I would recommend that your mechanic either put a rebuild kit into your existing master cylinder ore use a brand new Toyota master cylinder. I have found through experience that reman master cylinders and non Toyota master cylinders reduce the brake effectiveness of Toyota cars. I suspect that it has to do with valving, that the remans and the new non Toyota master cylinders use a universal sized valve that is not adequate. For some reason the remanufactured Toyota master cylinders have the outlets drilled and machined out and universal outlets installed so they can fit a number of vehicles, not just yours.

BTW, in defense of your first mechanic, I would have first suspected a brake hose or caliper too.

this is kinda a shot in the dark but take the proportioning valve off and clean it out

Well, first off, I’d like to say thank you SO MUCH to everyone who has responded. It is much appreciated.

With the engine off, I hit the brake pedal three times, each time stiffer than the next. Start the car and the pedal goes down. Drive the car for a bit, and it’s more like the pedal felt when the car was off and I’d hit it two times.

Another thing - we pulled over when the brakes got stiff and I got out of the car to see if I could find anything under the hood. While my wife sat inside the car (which was not running) she said she heard a moderately loud clicking sound coming from the front of the car. This was not the sound of a hot car cooling down, this was something else. And after this clicking, and the resting of the car, it drove fine again for a while.

The front brakes don’t go through the proportioning valve.

He may have meant metering valve but I doubt this car has one.

Hi Everybody,
Just wanted to post a follow up - our mechanic (the first one) replaced the master cylinder and the car seems to be happy now. It’s a great relief. He told us the previous garage did the wrong things and we should hassle them for a refund of some kind. They had replaced the rotors, which our mechanic said were not the problem, but that they had been warped because of this situation. However, the rotors were not replaced this time, our mechanic instead saying we should wait until we need new brake pads to do the rotors too.

This has been quite an education for me. Maybe I can get a federal school loan to pay for the repairs, instead of using credit. Anyway, thanks everyone.

Glad it worked out. BTW, for those below, Toyota calls the proportioning valve a metering valve, and you have one but they rarely ever go bad, and they are for the rear brakes only.

Well, here we are a few months later, and the problem has returned. Our mechanic, whom we were doubting, replaced the master cylinder and the car seemed to be okay. But while driving on the highway about a month ago, the car started to vibrate. It got to a point where we would drive on the highway for 15 minutes and the vibrating really began to feel violent. The steering wheel shakes back and forth, and it’s pretty scary. We pull over for 15 minutes and give it a rest - then it’s okay again.

We took it to a dealer. They told us there was somehow some oil in the brake fluid, compromising the rubber parts in the system. Now how did that get in there? They told us to take the car back to our mechanic and have them repair it for free, that they should warranty their parts and work. Of course, our mechanic says, “I didn’t put oil in there” - but nobody else was in there! The dealer said they would charge us $1400 to flush the system, put in new calipers, plane the rotors and replace the master cylinder.

So now the question is, should we take the car back to the guy to apparently screwed it up, because he should make right by us, or should we just suck it up, have the dealer fix it and be done with it? We want to find a mechanic who specializes in Toyotas, so we have a third option, but I don’t think that’s a part of this equation. Or is it?

What would you do?

Yes mineral oil products will cause the rubber parts of a brake system to swell. When that happens to the master cylinder the primary cups expand to cover the compensation ports so brake fluid cannot return to the reservoir as heat causes it to expand causing the residual pressure to rise and the pedal to feel like the brake is already on. Once mineral oil gets into the system it has to flushed very well to make sure it is all out. The calipers and wheel cylinders have to disassembled; cleaned; and new rubber parts installed or use new or rebuilt units. The lines have to be flushed before the new units are installed. Also look at the proportioning valve as it has rubber parts. Each time you get the front calipers locked on you run the risk of warping the rotors so those probably will have to be trued or replaced. Yes, it probably will cost $1400 to do all this work.

You have to find out if the mineral oil getting into the system is ongoing. Is anyone topping off fluids when they check or change the oil? If you have been topping off the brake reservoir yourself, throw the old can away and buy a fresh can from a reputable company. You have to make sure that however the mineral oil got into or is getting into the brake reservoir that it doesn’t happen again.

Good luck on this.

“should we take the car back to the guy to apparently screwed it up”

Which one? If I followed your posts correctly, the car was worked on by two different mechanics.

However, since the problem apparently occurred before either of them worked on your brakes, if I were you, I would go back through my maintenance invoices (you do save them, I assume) to see where your car was serviced prior to the beginning of the problem. Did you ever use a fast oil change place?

Whoever topped off your master cylinder prior to the beginning of the problem is undoubtedly the one who contaminated your brake system with motor oil. Unfortunately, proving this after at least 5 months is going to be somewhere between difficult and impossible.

If I were you, I would have a competent mechanic perform the repairs recommended by the dealership. And after that, I would be very careful about where the car’s maintenance is done. DO NOT go to a quick oil change place!!

Ah, well now it’s all making sense, and it might go back a ways, then. Maybe about two years ago, our brake light came on. We took it to “Dealer A” for an oil change and to deal with the light. They told us we needed new brake pads, they filled the fluid reservoir and changed the oil. The place was unpleasant, and I walked out of there feeling that I’d been scammed. A few weeks later, the brake light came on again, we took it to “Local Mechanic A”, as we were also due for an inspection. (We were new to the area and also first-time car owners, so we didn’t have a relationship with a mechanic yet). “Mechanic A” told me that he felt the dealership had “done too much” to the car (ie ripped us off) and that they had forgotten to return the cap onto the brake fluid reservoir. We figured it was a cheap little part, we didn’t complain to the dealership. Just figured, have the mechanic order the part for $5 (?) and be done with it. But perhaps that was the point at which our brake system became contaminated?

So that’s when “Local Mechanic A” worked on it, couldn’t solve it, then off to “Local Mechanic B” who also failed, back to “Mechanic A” who replaced master cylinder which worked for a piece and then most recently over to “Dealer B”, which was a much more pleasant (and seemingly trustworthy) experience than “Dealer A”.

I want to thank everyone for being so helpful and forthcoming with your knowledge.