Long Brake Pedal With Engine On

July 3, 2010

Hi all,

The car is a 2004 T25, and I've been doing my own service on it since the warranty lapsed. I have good (20+ years) mechanical experience on several cars, but unfortunately no manuals for this car so I do everything just using experience/judgement.

The problem is that recently I've realized that with the engine running, the brake pedal, when pressed quite hard and without letting up the pressure, will go down much farther than I think it should. In normal driving it stops quite fine, brake application is prompt and the pedal seems firm with usual pedal pressure. It's only when specifically pushing quite hard that the pedal moves too far. It does not pump up with repeated quicker hard presses, or at least not much.

"Recent" work include a flush of the brake fluid last summer, and changing the front pads about 3 months ago.

At no point have the hydraulic lines been opened, apart from the bleed screws obviously when doing the fluid flush last year. The fluid flush last year also did not take the level in the reservoir too low, as far as I could tell.

There is no fluid leak at the calipers that I can see, however I've not tried to inspect the entire run of the brake lines.

I only noticed this long pedal after the car had sat for about a week, and I was on vacation driving a different car. I probably noticed the difference because of being accustomed to the other car.

This morning I bled the brakes with a pressure bleeder, giving generous time for bubbles to get out, but none came out at all.

The pedal behaviour is exactly the same now.

(I would note that my previous flush last year was done using the open bleed/push pedal/close bleed/release pedal routine.)

Visually, the pads are in tight contact with the rotors on all 4 corners, and I can't see any reason for long brake travel because of that or because of sloppy wheel bearings.

I am a bit concerned that either I have air somehow in the system that is being difficult in not coming out, or that the master cylinder seals have started to leak internally. (It looks to be a bit of a challenge to get the MC out, by the way...)

Has anyone experienced this sort of thing with a T25 and know how it got fixed.

Thanks

Neil

Madrid

July 4, 2010

The problem is that recently I've realized that with the engine running, the brake pedal, when pressed quite hard and without letting up the pressure, will go down much farther than I think it should. In normal driving it stops quite fine, brake application is prompt and the pedal seems firm with usual pedal pressure. It's only when specifically pushing quite hard that the pedal moves too far. It does not pump up with repeated quicker hard presses, or at least not much.
Neil
Madrid

Is the car a diesel? If so then Im led to the believe this is normal. Something to do with the brake assit and the way the vacuum works on the brakes.

Have a search on the forum I think Parts-King answered some questions abouts this recently.

July 5, 2010

I suppose that's the way they are built.

http://www.toyotaownersclub.com/forums/index.php?showtopic=108258

July 5, 2010

The problem is that recently I've realized that with the engine running, the brake pedal, when pressed quite hard and without letting up the pressure, will go down much farther than I think it should. In normal driving it stops quite fine, brake application is prompt and the pedal seems firm with usual pedal pressure. It's only when specifically pushing quite hard that the pedal moves too far. It does not pump up with repeated quicker hard presses, or at least not much.
Neil
Madrid
Is the car a diesel? If so then Im led to the believe this is normal. Something to do with the brake assit and the way the vacuum works on the brakes.
Have a search on the forum I think Parts-King answered some questions abouts this recently.

Don't know if yours is a diesel or if it's new enough for this to be the norm, the only other thing I can suggest is to check your brake flexible hoses to see if they are ballooning under pressure.

July 6, 2010

The problem is that recently I've realized that with the engine running, the brake pedal, when pressed quite hard and without letting up the pressure, will go down much farther than I think it should. In normal driving it stops quite fine, brake application is prompt and the pedal seems firm with usual pedal pressure. It's only when specifically pushing quite hard that the pedal moves too far. It does not pump up with repeated quicker hard presses, or at least not much.
Neil
Madrid
Is the car a diesel? If so then Im led to the believe this is normal. Something to do with the brake assit and the way the vacuum works on the brakes.
Have a search on the forum I think Parts-King answered some questions abouts this recently.
Don't know if yours is a diesel or if it's new enough for this to be the norm, the only other thing I can suggest is to check your brake flexible hoses to see if they are ballooning under pressure.

Thanks so far everyone.

The ballooning hoses also occurred to me later in the day after I posted the initial query, but I haven't been able to round up the wife to check the hoses while the pedal's being pressed hard. I hope to get that done this weekend.

Re diesel or not, it's the gasoline 2L version.

I just read the linked post (sorry, I didn't find it when I searched before writing the inital post) and it's interesting for sure.

My testing has been with the car stationary, yes, but it was initially triggered by a long pedal on the road when I had to try to haul the car down quickly (somebody deciding to lounge into a roundabout in front of me). Clearly I'll have to check again on the road also to confirm if that is happening again now after the bleed (even if no air came out).

I'll get back once I have more from my end.

Regards

Neil