You don’t need a mechanic, you need some signs;
It seems to me, in every one of those scenarios where you have a problem with the brakes (ice, rain, hopping a curb), you are in a situation where you could lose traction and the ABS could activate, which might explain the difference in brake pedal feel. If the brakes never act up on dry pavement (or hitting a curb), I don’t think there’s a problem, it’s just the ABS kicking in.
Hi, Nevada_545, thanks for the warning sign, which is useful in any circumstance. But there does have a problem with the brake, as that slippery response lasts much longer than it should have.
I looked up brake booster (there are so many breaks that I corrected in the original post!). Although my brake was not hard to press (one of the main symptom of a brake booster failure), I found some information regarding a bad brake booster check valve, which causes brake feels spongy (this was exactly what it feels like each time when it occurred) besides hard to press. Also, when waiting at the red light, I sometime feel the brake gradually gets soften (or there is a pressure change) when the vehicle is totally not moved. Is this normal?
No, it’s not, and that usually indicates a bad master cylinder.
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OK, to sump up what everyone said so far, it seems that
- the master cylinder that newly replaced could still be a bad one
- brake booster (including check valve)
- ABS (which I still need to look into a little more). My manual says that ABS light should flash on and off when I start the engine. I do not even see that or I do not know which one is ABS. I tried to step hard on brake yesterday (although the road was not too wet and I did not hear the sound of ABS kicking in), there was no light coming on and I did not remember seeing any light on in the past.
It is not normal. All of the symptoms you’ve described so far could be caused by a bad master cylinder. I know you said you had it changed, but do you know if they used a new one or a rebuilt one?
I am yet to find out if they used a new one or a rebuilt one. The repair shop was quarantined last week.
I did one more test and it seems that I now can reproduce it: On a wet day, if I step on the brake hard, it loses brake, which will continue to feel spongy. But if I now step on the brake even harder, stretching leg even further, the brake seems to become working again. Does that sound like a bad master cylinder?
Do you have any issues with the brakes on a dry day?
That is the antilock brake system engaging, you are braking too hard for road conditions. If braking requires stretching your leg, you need to move the seat forward. The brake pedal is higher than the accelerator pedal, how do you accelerate?
That is normal. When the A/C compressor cycles off, the engine vacuum increases and you will feel more brake boost.
No, it sounds like your ABS is operating.
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