HELP Bad rebuilt master cylinder?

[Cap'n 2jz]

I've been fiddling around with my 1988 camry DD for a couple weeks now fixing everything that broke (all in the same week) timing belt water pump, calipers and new cv boots.

Now my biggest problem: No matter what I do, the brake petal is spongy and goes to the floor. It started when I pulled my 2 calipers to rebuild them. I used a BECK/ARNLEY rebuld kit. All went well. The originals were sticking, a little bit of rust on the pistons. I cleaned them up and put them back together with the new seals.

Bleed the 4 wheels (2 person, pedal pump style) to flush some new fluid into the lines. Then after bleading: pedal is soft, goes to the floor.So I went and bought a new master cylinder figuring the other one blew out while doing the manual bleeding.

Put the new one on after bench bleading it (with the shitty kit them give you to do it) I put it on the car, and SAME problem. Pedal is way loose, brakes barly and the pedal is at the floor.

So I figured, seeing as the little plastic fittings they give you to bleed the master and crappy, I made my own. Took the master off, and RE-bench bled it again. To no avail! :32:

I adjusted my rear brake shoes figuring maybe they were too loose. Then Re-bled 4 wheels --> started Rear passenger, ended drivers front. SOFT GOES TO THE FLOOR :SM130 (1):

But the pedal feels somewhat ok when the car is OFF. as soon as you turn on the car with the vaccum assist the pedal goes to the floor.

I am only assuming that I got a bad rebuilt master?

comments, ideas? I need to get this car back on the road...too much wear on the supra for nothing

[supra_toy]

bad booster?

[Cap'n 2jz]

how do you diagnose that.

why would it just break after I changed my calipers and re-bled my system? I'll check for a vacuum leak. most likely cause if it is from the booster.

any other ideas?

[supra_toy]

Well there is the master, slave, and the booster. Air in any of those would give you a spongy pedal but it ordinarily wouldn’t be bad enough to have it so the pedal goes all the way to the floor. Did you see allot of air when you bleed the brake lines? Were all the air bubbles gone when you finished? Sometimes I find it helpful to use some clear plastic tubing so as to see the air bubbles better when bleeding the calipers. My other mechanic suggested that the master may not have been bleed properly (although I doubt that’s it) It is possible that you got a poorly rebuild master cylinder and that the new one is bad. Is the reservoir level staying constant? Any leakage past the caliper piston boots?

hth

will

[Cap'n 2jz]

I went to the auto parts store and they gave me another one. I bled it intensely in the bench. Then I bled the car intensely.

The pedal feels better.....I have yet to take it out to really try it.

will post an update

And no, I didn't see a lot of air. that what was driving me insane.

[Cap'n 2jz]

ok. tested and failed

maybe its just me....

2nd new master cylinder, full blead of the system (again for the 5th time)

What I'm thinking --> I drove the car knowing the calipers needed to be rebuilt. Obviously the calipers were staying stuck to the disc, so that caused me to have a stiff pedal. I maybe got used to that stiff pedal and that is what is actually driving me insane?

The brake booster is fine, I have full power brakes at all times with the engine running. The pedal just feels so low. I know the brakes are crappy on this car, but come on, after a full front overhaul how can it be this shitty??

This is driving me nuts. I adjusted the rear shoes until they were tight, so its not coming from there, NO AIR in the system FOR SURE. But still a pedal that is squishy and feels like it goes to the floor when braking...

what is my next step. Ive been all through the TSRM for the Camry, my last resorts are to replace the rear wheel cylinders and the proportioning valve. The problem is, this is my shitty DD and I dont want to dump all this money into it if its not going to help!!

[Sean Chung]

Did you check the brake booster to master cylinder pushrod clearance. There should be zero play, but no pressure on the master.

[Cap'n 2jz]

fire wall side I would imagine?

[Cap'n 2jz]

ok, more info found.

I could be looking at a bad portioning valve, but seems very unlikely... Not mentioned in the TSRM, how do you diagnose this?

After some research on the net I see people having problems with the rubber lines getting clogged with junk. Could be possible because one of my rear wheel cylinders doesn't piss out like the others, it just spurts then drips. More crap to check. Obvious diagnosis: take off the line and see if there is shit clogging it, then take wheel cylinder apart to inspect.

I will also check the pedal adjustment as per Mr Chungs suggestion.

[CarFreek]

Try bleeding brakes again with nose down on car. Get the backend up as high as possible with all four off the ground. Not sure about Camrys, but a LOT of other cars have a slight incline to master cylinder, and this can sometimes allow air to stick around. Check fittings/lines for leaks and pinholes, also. The symptoms sound like booster, though. Does Camry have air valve in Booster line?

[Cap'n 2jz]

I'll check in the morning for the valve.

if it was a booster, wouldn't you expect there to be a lack of power brakes? or for it to be inconsistent?

[Sean Chung]

remove the two nuts that hold the master cyl onto the booster. pull the master away from the booster, and there will be a push rod inside the booster that pushes the master. that rod is adjustable. if there is any gap, the pedal will have to take up this extra travel before it pushes the master.

also, when you rebuilt the calipers, were the slides sliding freely. that is a very common cause of low pedal. I would not worry about checking booster problems. booster problems cause a hard pedal.

[alfun]

remove the two nuts that hold the master cyl onto the booster. pull the master away from the booster, and there will be a push rod inside the booster that pushes the master. that rod is adjustable. if there is any gap, the pedal will have to take up this extra travel before it pushes the master.

also, when you rebuilt the calipers, were the slides sliding freely. that is a very common cause of low pedal. I would not worry about checking booster problems. booster problems cause a hard pedal.
I am about to install my brake master cylinder and power brake booster. Do you use a SST to set the push rod inside the booster? Do you know of a good way to set it without the SST?

[Cap'n 2jz]

remove the two nuts that hold the master cyl onto the booster. pull the master away from the booster, and there will be a push rod inside the booster that pushes the master. that rod is adjustable. if there is any gap, the pedal will have to take up this extra travel before it pushes the master.

also, when you rebuilt the calipers, were the slides sliding freely. that is a very common cause of low pedal. I would not worry about checking booster problems. booster problems cause a hard pedal.

yes the sliders WERE sliding freely. I cleaned and greased them to do so.

[Cap'n 2jz]

ok I did some more diagnosing.

Here is what I found.

Removed the front drivers caliper. Pumped the brakes, cylinder DIDNT MOVE and wasnt leaking.

So I put a vise grip on the line. Pedal stays hard. Changed the caliper on the other side, it works fine.

So I'm not getting enough pressure on the front drivers caliper, its not letting enough fluid in to move the piston....

what is causing it? Proportioning valve? I have 1 little one with one entry and 2 exits going to the proportioning valve, then the valve with all the exits for the wheels.

which is the most likely culprit of my problem?

[Sean Chung]

I would check for brake pressure at the right rear. If it is a diagonal split system, and the proportioning valve moved, you would lose pressure there as well.

[Cap'n 2jz]

yes, there is a lack of pressure there!

so its my proportioning valve!

[Sean Chung]

Have you checked that you have pressure coming out of both lines on the master? I would start at the top and trace where you are losing pressure.

[Cap'n 2jz]

re-bled the master on the car today, both clear vinyl tubes I'm using to bleed it fill with fluid and it bleeds properly, there is pressure to the proportioning valve. then no pressure after that....

took the valve off, tried to clean it and blow it out with compressed air, I also cleaned the little splitter block that splits into 2 out-puts that go into the prop valve --> No use. Put the prop. valve back on the car: re-bled master on the car, then tried to bleed the system. Front right, full pressure, rear left full pressure. Front left no pressure rear right no pressure (as it was before) some fluid drips out, but barely from the front AND the back.

[Sean Chung]

Sounds like you tripped the safety in the valve.

[Cap'n 2jz]

can we un-trip this safety...

[Sean Chung]

In the center there is a cylinder that if the system loses pressure (i.e. a broken brake line) pressure on the other side will move it to block off that circuit. That is why they do a split, so you still have one front brake and one rear brake in case of failure.

You may able to apply pressure to the side that got blocked off while releasing pressure on the good side and get it to move back. The tricky part will be not letting it move too far and block the other side. You only want to move it back to center.

[Cap'n 2jz]

compressed air with some custom fittings to apply equal pressure on both sides?

how often does this stuff happen, I've never heard of this type of failure before!

what about reverse bleeding? forcing fluid back through the non functioning lines to force the cylinder back.

[Cap'n 2jz]

ok so I got another proportioning valve. 2 weeks by mail, it didnt solve the problem....

I replaced 1 of the wheel cylinders because it had a seized piston....that didnt help...

I bought 2 brand new calipers and installed them......its not working


I've changed every single piece of the braking system, and I get no pressure on the 2 opposing lines and the pedal drops to the floor

I'm fucked I cant figure out what it is..........Its been over a month now I've been trying to fix it and I just cant

does anyone have any more suggestions? I cant just keep throwing pieces at it, its already been done.....

my next step is to buy a vaccum bleader and see if I can get it to work this way.....

[Don L.]

I'm a little late to the dance on this one, but have your disconnected the driver front caliper from the brake line, and checked to see if fluid shoot out of the brake line when pressing the pedal? Just wondering if perhaps the fitting to the caliper gets blocked or crushed, it stops fluid from going into the caliper, also might stop pressure from going to passenger rear.

I'm just tossing out an idea, I had my own brake issues recently, and Frank C. helped me with that. I definitely understand the frustration! I now have a spare MC, all new brake lines, 4 rebuilt calipers, and new brake pads.

Don L.

ps: don't waste money on a vacuum bleeder. Borrow one if you must, but save your money.

[Cap'n 2jz]

thanks Don, I appreciate any and all ideas anyone can give me!

I'll check for an obstruction. I spoke with a mechanic yesterday and he brought up an interesting point. My pedal is really low, he said maybe the master cylinder isn't returning back to its correct position, so it cant recharge itself. I'm going to check that this afternoon

[KesekiSupra]

from my experience, theres no such thing as a "good" rebuilt master cylinder. i wouldnt trust something as important as my brake system to "rebuilt". its new or nothing to me. ive had so many rebuilt master cylinders fail, its not even funny....

[Don L.]

The MC is pretty well sprung to return to static position after pushing in its piston (as in activating the brakes). Seems odd that the problem is the MC.

It seemed suprising to me, but as Frank mentioned to me on my brake problems, the brake pads as they rest against the rotors move extremely little when pedal is applied. If things are misaligned slighted (due to uneven pads, hanging up spring clips, etc) the pedal can feel mushy. Your situation may be different, but it points out how such a small misalignment in the system can feel like the whole braking system is screwed.

In your situation I was looking mainly at the calipers and the attachment of the calipers to the brake line. Those are the parts that you initially handled, so most likely areas to inspect.
I hope you can figure this mystery out, and let us know what it was, it probabably will be a simple thing and we can all collectively hit ourselves on the side of the noggin'.

Don L.

[supra_toy]

if the primary piston cup in the master cylinder is leaking that could cause the pedal to go to the floor, but no pressure at the opposing lines indicates a pressure differential switch...