hard brake pedal

[brelandt]

For about the last 2 years or so my 04 tacoma has had periods when the brake pedal would be hard. The pedal has almost no travel. The truck stops just fine. I press the pedal as hard as I can and sometimes the pedal gives and feels normal but most of the time it does not give. Then for months on end there will be no issues what so ever...!
I replaced the front pads and greased all the parts. Even removed them again a year later and regreased them. none of the brake hoses are hot after use. The fluid appears good and is filled properly.
I did a booster check. I first checked for vacuum leak with carb cleaner. Then I took the hose off and checked it. seems fine. Cleaned the one way check valve. It also appears to work fine. then I pressed the pedal several times then started the engine. The pedal travels about 2" when the engine starts. After warming the engine I press the pedal and each time I do it seems to travel the same distance to the floor. Then holding the pedal down I shut the engine off and count to 30 and the pedal stays put. It may travel down but if it does it's no more than a fraction of an inch.
The only thing I can think to do is change the fluid. Truck has 76K but has done this since at least 45K.
Am I missing something? Thanks!

 

[scurvy]

Sounds like a vacuum leak or the brake booster is bad... I'm suspecting the former, possibly even a hairline crack that's only there once it's warm under the engine bay.

When was the last time the fluid was changed? I don't think it could be a contributing factor, but IME it should be changed every two years.

 

[Tim4mods]

I agree! Sounds like the booster is going bad I just replaced one on a 68 chevy truck it had been acting funny and then the pedal got stiff and wouldn't move I checked everything and ended up having to replace the booster and it fixed my problem.

 

[brelandt]

Originally Posted By: scurvy
Sounds like a vacuum leak or the brake booster is bad... I'm suspecting the former, possibly even a hairline crack that's only there once it's warm under the engine bay.

When was the last time the fluid was changed? I don't think it could be a contributing factor, but IME it should be changed every two years.


Never been changed. Needs to be but can never find anyone I trust to pump the brakes for me!

I'm thinking it's the booster as well, but just can't seem to make it fail. Hate to spend good money changing parts just to say I changed it so that can't be the issue. I also failed to mention that at times I have a rough idle. However, the 2 issues do not seem to happen at the sametime everytime. Sometimes the idle acts up but the brake works and sometimes it idles fine and the brakes act up.

 

[brelandt]

just thinking. I went a year with the front O2 sensor out. It pulled a code for the heat sensor. Truck ran just fine. I wonder if this caused the engine to run rich and fuel entered the diaphragm? Just a thought?

 

[beast3300]

Originally Posted By: brelandt
just thinking. I went a year with the front O2 sensor out. It pulled a code for the heat sensor. Truck ran just fine. I wonder if this caused the engine to run rich and fuel entered the diaphragm? Just a thought?


Not likely the booster only sees vacuum. Heater circuit isn't a totally failed O2, just a slower to get ready O2.

It's hard to judge what a hard brake pedal feels like without in person. Brake pedal height is controlled by the rear brakes so if you have seized wheel cylinder that will give you a high brake pedal as well.

 

[mechtech2]

Sure sounds like the booster is faulty.

 

[brelandt]

Originally Posted By: beast3300
Originally Posted By: brelandt
just thinking. I went a year with the front O2 sensor out. It pulled a code for the heat sensor. Truck ran just fine. I wonder if this caused the engine to run rich and fuel entered the diaphragm? Just a thought?


Not likely the booster only sees vacuum. Heater circuit isn't a totally failed O2, just a slower to get ready O2.

It's hard to judge what a hard brake pedal feels like without in person. Brake pedal height is controlled by the rear brakes so if you have seized wheel cylinder that will give you a high brake pedal as well.


When it happens the pedal only moves maybe 1/2" no further. The truck stops but it takes a little longer. I can place the weight of my body on it by lifting my butt off of the seat. At times this forces the pedal back to normal but most of the time the pedal will not budge. Then like I've said the next day it's 100% fine and will stay that way for weeks on end.

 

[brelandt]

Bought a bottle of DOT 3 and decided to change the fluid. It is the factory fill from Sept 2003! I tried gravity bleed. started with the right rear and only a little tiny bit came out. So I got someone to pump the pedal. again very little. So we tried it again and this time nothing came out. So i switched to the left rear and it bled fine. Also the fronts bled perfectly. Tried the RR again afterwards and still no fluid.
I'll take the tire off tomorrow as it's way too hot today. I think I just might have a frozen wheel cylinder.

 

[brelandt]

Took the rear drums off. After 7 plus years the shoes are still 3/8" thick and no gouging on the drums. Had my assistant press the pedal and the wheel calipers work fine. No signs of any leaks or anything.
Put everything back together and called it good for now. Wait and see if and when the hard pedal issue occurs again.