first time camry owner. brake pedal sinking

[kodiakkris400]

Hey all,

Got my first ever Toyota in the form of a 96 Camry 4 cylinder. About 285k on the clock and still running strong. Had a couple of issues to pass inspection (brakes, brake hoses, CV shaft, valve cover gasket& PVC valve) and in the 3 months I've owned it a control arm bushing and wheel cylinder. Even with its minor problems I still love the car (and its gas mileage). As a former and current owner of quite a few Jeeps I'm no stranger to turning a wrench, lol, and was looking for some insight before I start throwing money at the problem replacing parts.

About a month ago the brake pedal began sinking almost to the floor (feels about 3/4 of the way) before the brakes engaged. Being mechanical as I am, when I first noticed the problem I stopped and looked for a leak thinking that as much as the pedal sank it must be pretty big. I found no leaks or puddles and the fluid has remained constant in the last month. Last weekend I finally got some time to look at it figuring that maybe a spring or shoe came lose in the drum allowing the pedal to sink before catching, but found nothing. I put the car up in the air and had a buddy work the brakes and discovered that the front driver and rear passenger tires would let lose as the pedal stopped sinking,And the other two would hold. When driving the sinking is accelerated by the booster and it seems like the two tires that let lose don't grab at all, unless the pedal is suddenly hit in which case they grab for a couple of seconds then release. At first I was thinking proportioning valve, but it seems like the more I read the master cylinder is going bad.

I forgot to mention about 2 weeks prior to this problem surfacing I replaced a leaking wheel cylinder and the brakes worked fine for the 2 weeks. Also I have bleed the brakes trying to resolve this issue with no results.

Thanks in advance for any help!
Kris

[Mister_Perkins]

I would first remove the bolts holding the M/C to the booster and see if its wet between the back of the master cylinder and the booster. This will be a strong indication that the MC is actually bad.

Make sure to check all of the hoses to the calipers for Swelling.. You've already checked for leakage and didnt find anything, so swelled hoses would be the next check.

If every thing looks good down below it's time to have another look at that master cylinder. With the engine off, hold your foot on the brake pedal, firmly but not all your weight. If the pedal creeps down after you first get it firmed up (assuming you may have had to pump it a few times) then fluid is bypassing the seals inside the cylinder and it will need to be replaced. There is even more of a chance that some fluid has contaminated the diaphram in the power booster, weakening it or even causing a leak. It will then be time for a new booster as well

[JohnGD]

+1

If the drums are properly adjusted, there is no external leak and the brake hoses are not ballooning, then it sounds like the MC is bypassing internally.

Rapidly pump the brake pedal and see if it rises and remains firm. (if MC cups are bad I don't think it will) If it drifts towards the floor then swap it out with an OEM MC. I personally don't use rebuilts.

Originally Posted by kodiakkris400

I put the car up in the air and had a buddy work the brakes and discovered that the front driver and rear passenger tires would let lose as the pedal stopped sinking,And the other two would hold. When driving the sinking is accelerated by the booster and it seems like the two tires that let lose don't grab at all, unless the pedal is suddenly hit in which case they grab for a couple of seconds then release. At first I was thinking proportioning valve, but it seems like the more I read the master cylinder is going bad.