My brake pedal is sinking to the floor when pressure is exerted on it (standing on brakes at traffic light). This only occurs at very low speeds or when competely stopped, on the freeway it seems fine so far.

The pedal doesn't sink by itself, only when pressure is exerted, and as far as I can tell the level of brake fluid in the resevoir has not dropped.

Is it possible air has gotten into the lines somehow? I am not sure how that could have happened. I don't think the MC needs replacing as the symptoms don't seem that severe.

 

replace your brake master cylinder.

 

I would try bleeding the lines first, and if that doesn't help then sounds like you need to replace the MC. My car had the same syptoms when I needed an MC.

 

maybe your symptoms are not that severe YET, dont wait for them to get to the severe point. Its a true sign that your master cylinder is gone.
they are not that expensive, i replaced mine on my crx for $30

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by Vitt1 &raquo;</TD></TR><TR><TD CLASS="quote">I would try bleeding the lines first, and if that doesn't help then sounds like you need to replace the MC. My car had the same syptoms when I needed an MC.</TD></TR></TABLE>

My old 91 Integra did the same thing, and bleeding the brake lines did the trick. I'd try that first. Good luck fixing it.

 

Hmmm ... posts seem pretty conclusive. If the Master Cylinder is the problem, would there be a gradual drop in the level of the brake fluid in the resevoir under the hood?

You guys are right, I need to get this taken care of before my brake pedal drops to the floor while I am on the freeway.

 

<TABLE WIDTH="90%" CELLSPACING=0 CELLPADDING=0 ALIGN=CENTER><TR><TD>Quote, originally posted by 95GS-R &raquo;</TD></TR><TR><TD CLASS="quote">Hmmm ... posts seem pretty conclusive. If the Master Cylinder is the problem, would there be a gradual drop in the level of the brake fluid in the resevoir under the hood?

You guys are right, I need to get this taken care of before my brake pedal drops to the floor while I am on the freeway.</TD></TR></TABLE>

yes, if the master cylinder is gone then you either have brake fluid leaking outside of where the mc mounts to the vacuum booster or its leaking inside the vacuum booster. i would think if there was AIR in your lines, your fluid level in your reservoir would increase. you could try bleeding each wheel, starting from the furthest one from the master cylinder (thats at least how your suposed to do it on mine, but ive heard different from different cars).
it might save you some money, but i would say 90% of time this occurs its your master cylinder

 

took my car into the alignment shop recently. and they told me the same thing.

MASTER CYLINDER

i have all the same symptoms as you. in a 92 DA

 

 

you can also rebuild your MC, buy a rebuild kit, maybe 10 bucks.

 

The MC can leak internally by not holding pressure in the internal seals and not leak outside at all. An easy way to verify is when it drops, try pumping it up. If it goes up and then drops again, probably the MC.

 

you know what...if it i sleaking internally you also want to make sure that your vacuum booster is not damaged, a way to test it, is after you replace the MC, with the car off, pump the brake pedal 10-15 times, hold your foot down on the brake pedal and then start the car, if you feel the pedal drop slightly then your vacuum booster is working properly.