Soft-ish brake pedal

Maintenance/Repairs
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1

2004 Camry 4-cyl AT, PB; 98K miles

Brakes seem to work fine; pads/shoes were recently checked. However, when idling at a stop, if I push down unnecessarily hard on the pedal, it slowly goes further toward the floor. Lifting foot off and reapplying force returns it to same initial condition. Been that way for a year or more; not getting noticeably worse.

Am I seeing a leaking MC; or air in the brake lines; or is this normal? (Friend with similar car is out of town, so I can’t do comparison test right now.)

2

Sounds like air in the system but could be a failing MC or booster, too. Bleed the brakes first to see if there is any air there and if there is any improvement. Next step would be to disconnect the brake booster and drive (carefully! - no power brakes) and do a few stops and hold the pedal (forcefully!) to see if it drops the same. If it does, likely one set of seals in the master has failed. If not, the booster is likely at fault. Hope this helps.

3

A quick way to determine if the master cylinder is starting to leak internally is, when the engine cold start the engine. Step on the brake pedal and see if it sinks like you describe. If not the master cylinder is starting to leak internally.

What happens is as the heat under the hood increases the bore in the master cylinder expands. If the seals in the master are worn it allows the brake fluid to by-pass them. The brake pedal sinks until the seals reach a point in the bore that isn’t as worn and the brake pedal stops sinking.

I’ll bet that when summer comes and temperatures are higher, and the temperature under the hood gets higher the problem will become worse.

Anyone else ever notice that master cylinders always fail in the summertime?

Tester

4

I will say something now, which others may disagree with . . .

That particular generation of Camry, 2002-2006, never had a particularly impressive brake pedal feel, even when new

I have a 2005 Camry, myself. I bleed the brakes every 2 years. I gurantee you 100% there’s nothing wrong with my brakes, front to back, mechanical or hydraulic. Anyways, I believe @galant also has a 2005 Camry, and has much the same experience as me

5

@db4690
Yes, indeed. I have done everything to the brakes on this car and it is mushy at best. You get used to it as long as you don’t drive another car. Now my wife is driving it mostly and whenever I get back in it, on the first tap of the brake I have a mini panic.

I also took it in to the dealer for a coolant flush and asked them to check the brake system up and down. They said everything is perfect except that the car has aftermarket pads and rotors. I have put ones that were better than OEM, but I guess dealers have an issue with everything aftermarket. They did not want to change them either, at least they were being honest.

6

The OP states the sinking brake pedal started occurring a year or more ago.

Hmmmm? I wonder why the brake pedal wasn’t doing it before that time?

Tester

7

It’s entirely possible OP didn’t notice it until then

I owned my car for quite some time before I noticed the driver’s seat has an adjustable lumbar support

On my mom’s car, she didn’t notice the steering wheel was shaking at highway speed . . . due to rims that needed balancing . . . until I drove the car and pointed it out to her

8

And it’s entirely possible that the master cylinder is starting to fail.

Tester

9

@Tester you’re right that the brake master may be failing

But I have one of those Camrys, and so does @galant and we know they didn’t have a great pedal feel to begin with

And I also know that many people don’t notice things for quite awhile, even though they’ve always been that way

And I also know that even with a brand new master cylinder, bench bled and everything, if you’re stopped at a light, if you want to, you can “push right through” if you’ve got a real lead foot

A few years ago, one of the guys in our fleet was complaining that he could push his brake pedal right through, stopped at the light

Even though I could find nothing wrong with his truck, or the brakes . . . he had hydroboost, by the way . . . I decided to replace the brake master, just “to make him happy”

Of course, it didn’t change everything. After bench bleeding the master and doing a brake flush with the diaphragm brake master, nothing changed

I gave it back to the guy, and he brought it back. I told him to show me his problem. He started the engine, got in the truck and pushed his solid lead foot right through, so to speak. I explained that was normal. I wish I could explain in a better way why it’s normal. I knew right then and there that the guy was probably up to something

Anyways, I told him to leave the truck and I’d check it out again. Of course, everything was normal.
I talked to the guy’s boss, and it was an enlightening conversation. The boss explained that the guy was a demon driver, with a lead foot, and that he’d crashed several vehicles already, due to his driving habits. One more crash, and he was fired. The guy was a demon driver, and didn’t want to admit to himself . . . or anybody else . . . that the crashes were all his fault. He was looking for that needle in the haystack, so to speak

I explained to the boss that the guy’s brakes were in tip top shape. Plenty of meat on the rotors and pads, no runout of any kind . . . I measured, so I know, fresh brake fluid, no leaks, no air. I even told him the guy’s truck stops on a dime, and the brakes were in better shape than some of the other trucks, which happened to be true.

The boss said he’d take care of it. He had a talk with the guy. I don’t know what was said, but that guy never invented any bogus stories about supposed defects again. The next time he complained about something, it was something tangible, and it was obvious he wasn’t making it up. I think it was an engine oil leak.

10

Thanks for the replies.

Tester – By “a year or more” I mean that I have noticed it at least that long. But I don’t usually push so hard on the brake pedal, so it could have been that way forever and I might not have noticed. You are right, could be MC failing (unusually warm weather today; I’ll try your cold test later this week). And the Camry owners are right, too – it is a quirk of their cars.

11

Mustang above suggests a good idea to disconnect the power booster as an aid to diagnosis. Just curious, does this mean to simply remove the booster vacuum source line from the booster and plug the end of the line up temporarily. Or is disabling the brake booster more complicated than that?