Occasionally hard brake pedal

[Mateo8]

Recently when I have gone to drive my '97 4runner I have noticed that the brake pedal is rock hard when I go to start the car. It is a stick v6, I recently replaced the master and the slave cylinder to fix a weird feeling clutch. When driving the car, occasionally the pedal is hard (like when I go to start it) and braking performance is non-existent. I did blow out a rusty brake line in the summer, but it is full of fluid and there are no leaks under the car.

This is not a real "problem" for me as I do not need to go back into the office on a daily basis, but the day is soon coming when I need to go into the office everyday and cannot take the BMW as it is RHD and I need to access a gate on the way in and out of the parking garage. I have read some threads saying it is the booster as it is most likely the original and the 4Runner has 280k+ on it, I believe that to be the culprit. I have had success when I blip the throttle before I go to put in the clutch and then blip it when I start to brake, but that is a bandaid for a cut that requires stitches.

Does this match up to other owners experience, and if it does, which brand is recommended as a replacement?

 

[mtbtim]

That is a sign of a brake booster that's going out. Check the integrity of the vacuum hose running from the intake plenum to the brake booster.

This video was done on a FJ80 Land Cruiser but it will give you an idea of how to handle the swap if your brake booster is bad.

<iframe width="560" height="315" src="https://www.youtube.com/embed/KqugF6hLAMY" title="YouTube video player" frameborder="0" allow="accelerometer; autoplay; clipboard-write; encrypted-media; gyroscope; picture-in-picture" allowfullscreen></iframe>


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[19963.4lsr5]

For me the issue was the check valve in the booster.

Same exact symptom


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[Buckaroo]

Had this problem when the weather was cold - it was also the check valve.

 

[octanejunkie]

I tried swapping the check valve on my hard brake pedal but that didn't resolve it, I ended up swapping the booster.

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[brillo_76]

The only hard pedal I ever experience is very cold weather for like 2 to 5 seconds on startup. Then all is fine. So I expect vacuum lines, check valve or booster going so I agree with the others.

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[JohnMc]

Adding to the 'check valve' opinion from above. I had the exact same symptoms, on cold starts (at first, very cold) and gradually getting more frequent. The check valve is cheap and easy to replace, and my brakes worked 100% normally after. They just get sticky over time.

 

[cleanrunner]

sounds like a booster.

 

[Mateo8]

I will watch the video right now, if it is the check valve, that sounds a lot easier and cheaper to replace. Hopefully that is the case, if not, I am mechanically inclined and should be able to get the problem solved in short order. Thank you everyone for the quick replies, I will let you know how it goes