Brake Pedal Sinks - 1995 Camry - no ABS

[Kep]

Here lately, when the car is running and I apply the brakes the pedal tends to sink about half way before the brakes engage. Then, the pedal begins to sink if I leave the pressure on (like at a stop light). If I release and reapply the pedal comes back up and begins sinking again. It seems to sink faster when I am pressing the pedal softly and sink slower when I press harder. When the engine is off the pedal is much firmer but it still sinks very slowly.

I have been searching on the forum and there appear to be similar problems but several remain unanswered. Suggestions have included the master cylinder, air in the lines, internally leaking cylinders (Can someone instruct me how to test for this?), bad proportioning valves, bad brake boosters, bad calipers, bad caliper bolts, sticking brake pads and bad hoses. There may be others that I haven't found yet.

I am going to begin tracking this problem down and I was hoping to get some opinions on the best sequence to check all of these and maybe some ideas on what kind of tests would demonstrate a problem or exonerate a system. I have a 1995 Camry 5SFE 4cyl automatic without ABS. Front discs and rear drums. I have not noticed any fluid loss in the reservoir nor have I seen any leaks.

Thanks for your input.
Kep

[gottarollwithit]

Let's see if i can help clarify.

What's the history of this problem? Did this just magically start happening or did this start occuring after doing something to the brake system?

Start by taking a peek at the brake fluid. Make sure you have enough of it and it should be clearish yellow. If it's brown then it's real old or you have an opening in the system allowing crap to get into your fluid. Make sure you're not leaking fluid anywhere - inspect throughly.

I really doubt that you have air in the system and that a brake bleed is going to fix your issues. Air in the system will feel like your brakes are squishy and have to press harder on them to stop. Low probability of bad hoses - occasionally a flap can form inside the hose and cause the slowing/stopping of fluid from retracting. This kinda holds the calipers in the "stopped" position.

Lift the entire car and put it in neutral with the parking brake off. Try spinning each each wheel manually. They should all rotate easily without much resistance. Lots of resistance indicates a sticking caliper. Your issues don't sound like you have caliper problems.

It sounds a lot like a master cylinder or a booster problem. This is just my 2 cents, but i'd bet that if you're not subject to any of the probs above, it's a faulty master b/c you're probably still getting good stopping power, just the pedal sinks when you're stopped which might be from a leaking master.

[hill8570]

Since your fluid levels aren't dropping, sounds like your master cylinder seals are getting leaky.

[Kep]

Thanks for the fast replies. The problem just started on its own. I started noticing it about a month ago. I haven't done any maintenance on the brake system for well over a year. I just checked the resevoir. It is full but the fluid looks filthy. I expect that it is the original fluid (I bought the car used about 14 months ago.)

Kep

[JohnGD]

Normally you should feel brake action almost immediately. But if you are going down 1/2 before brakes applied then I would suspect the primary piston cup of the master cylinder is a goner.

With engine off. As you apply light pressure, the pedal gradually sink towards the floor is a telltale sign. Firm pressure helps to seal the cup to the bore.

If there is air in the lines, then rapidly pumping the brakes should get the pedal height up, but this won't be the case with leaky cups.

I'd plan on getting an OEM Toyota master cylinder. Castrol GT LMA (Low Moisture Activity) brake fluid or Valvoline Synthetic. Get a set of metric flare nut wrenches from local Harbor Freight if you don't have them and feel fine of doing this replacement. I'd actually prefer flare crowfoot with a torque wrench.

I'd even open up the lines at the MC and pump the pedal. See if you get pressure at the ports. (I'd bleed the complete system afterwards).

Originally Posted by Kep

Here lately, when the car is running and I apply the brakes the pedal tends to sink about half way before the brakes engage. Then, the pedal begins to sink if I leave the pressure on (like at a stop light). If I release and reapply the pedal comes back up and begins sinking again. It seems to sink faster when I am pressing the pedal softly and sink slower when I press harder. When the engine is off the pedal is much firmer but it still sinks very slowly.

I have been searching on the forum and there appear to be similar problems but several remain unanswered. Suggestions have included the master cylinder, air in the lines, internally leaking cylinders (Can someone instruct me how to test for this?), bad proportioning valves, bad brake boosters, bad calipers, bad caliper bolts, sticking brake pads and bad hoses. There may be others that I haven't found yet.

I am going to begin tracking this problem down and I was hoping to get some opinions on the best sequence to check all of these and maybe some ideas on what kind of tests would demonstrate a problem or exonerate a system. I have a 1995 Camry 5SFE 4cyl automatic without ABS. Front discs and rear drums. I have not noticed any fluid loss in the reservoir nor have I seen any leaks.

Thanks for your input.
Kep

[JohnGD]

14 year fluid in the brake system? That's a big no no. These should be changed no less than every 2 years. You're likely to have 3% moisture in there already.

If that's the case, I'd consider changing out the wheel cylinders and at least rebuild the calipers with new rubber parts. (I don't rebuild wheel cylinders). Even consider changing out the rubber brake hoses while at it.

If you do your own work, every year at <$10 a quart and some of your time. That's Castrol GT LMA or Valvoline Synthetic DOT 3/4 for me.

Originally Posted by Kep

Thanks for the fast replies. The problem just started on its own. I started noticing it about a month ago. I haven't done any maintenance on the brake system for well over a year. I just checked the resevoir. It is full but the fluid looks filthy. I expect that it is the original fluid (I bought the car used about 14 months ago.)

Kep

[archibald tuttle]

Kep,

So, I had the first symptom but not the second when I went to fix my 95 camry wagon with a soft pedal in the first place. Then it finally started losing fluid but this was actually a second problem not an exacerbation of the first.
Kind of like when your alternator goes and the low battery sulfates and leans on your starter while you're trying to remedy the problem and you end up replacing all three.

So I don't believe that, in my case, the one symptom caused the other but bad things happen in threes (hopefully good things too).

I believe the soft pedal came from caliper pins hanging up. When I pulled stuff apart the brake pads had that angular wear pattern and I had to pound the pins to get them to move, so I believe the rotor was kicking the pads out after each application so you had a little more travel to apply the brakes as the pads skewed and maybe water absorption could have contributed to less than perfect hydraulic force.

Now, I have to admit I use the if it ain't broke don't fix it school of brake maintenance so I've had a few rigs that have had some pretty murky looking brake fluid. But I generally figure that, in a car that age, something will break often enough to get me some fluid exchange. And I do use DOT 4 low moisture absorption.

So in my case, the follow on problem was a very small leak in one of the 90 deg. bends coming out of the Rear proportioning valve that always rot. They did on earlier gen camries and they do on these.

Now your secondary symptom, travel to floor, could be master cylinder bypass, and if you have really gruesome fluid it may have attacked the master a bit. Although when I took my master apart, it was clean as a whistle inside, no leak out the back and didn't seem compromised. Because of the continuing symptoms after I replaced the leaking brake line, I replaced the master, but that didn't cure the symptom so, in my case, I believe the master was fine all along.

But, as I mentioned on the thread I started the problem turned out to be that the new pads I put on were too tight on the inside of both front calipers. I actually had a friend putting the front on while I was messing with the brake line replacement, but I'm not sure I would have thought they were too tight. I would have noticed they were tough going in, but aside from lubing the tabs, I might have let it go. As soon as I ground off the tabs to allow easier travel in the caliper the brakes and then pedal slowly drops problem went away. A toyota dealer's service manager had suggested I look for pad hang-up and he was right. I still haven't figured out how it the pad hanging up could keep causing that problem, cause I figure it would stick once applied as well as during application, so you'd get hot brakes and slow release to alert you to the problem, but that is not what I experienced. And you couldn't pump it up, it kept doing the same thing over and over.

Oh well, it's fixed. Now I'm trolling the web looking for the answer as to how it made that symptom.

Sounds like you got to start jacking up corners of the car and looking into stuff.

Report what you find.

Brian

[ghettosled]

Originally Posted by archibald tuttle

Kep,

But, as I mentioned on the thread I started the problem turned out to be that the new pads I put on were too tight on the inside of both front calipers. I actually had a friend putting the front on while I was messing with the brake line replacement, but I'm not sure I would have thought they were too tight. I would have noticed they were tough going in, but aside from lubing the tabs, I might have let it go. As soon as I ground off the tabs to allow easier travel in the caliper the brakes and then pedal slowly drops problem went away.

thats funny, i ran into the same problem when doing my last brake service. i thought it was strange i had to grind down the backing plate a bit and so i just chalked it up to having a slightly defective/out of tolerance part. didnt realize someone else had the same problem. on a side note, i bought the parts from napa.