Brake problems again!

[Guest bastaad525]

Okay guys, a while back I posted about changing my front calipers and having issues with the brakes seeming a little too soft, and also with the car pulling to the side a little when I'd brake hard.

 

So I went and bled the system very thoroughly at all four corners as was suggested.

 

The pedal did seem to get a little stiffer, though the wheel will still jerk slightly to the side if I brake hard. But I"m not worried about that right now.

 

 

I was doing some... ah... spirited driving this morning on the way home, and did a quick stop from like 60mph. First thing I notice is this horrible SMELL, which I've smelled before and I know that's the smell of burning brakes.

 

Then I roll off and come to a stop light and jsut go to stop normally, and suddenly my pedal is going almost all the way to the floor! I had to pump it a couple times before it stiffened back up and brought the car to a stop. Stopped at 7-11 for a sec, then continued on home and the pedal was back to normal for the rest of the drive.

 

So wtf was that all about??? Did I not bleed them thoroughly enough??? Or is this sign that something ELSE is wrong with my system?? Why the smell of burning brakes? That was very unexpected... it wasn't even THAT hard of a stop, not close to locking the tires or anything like that.

 

And was the pedals going soft just regular brake fade as it occurs on such an old car?

 

Oh and yeah I rechecked the fluid levels they hadn't changed a bit so, no leaks.

[JMortensen]

You boiled the fluid somehow. Fade is when the pedal is rock hard but the car doesn't slow down. BTW, now that you boiled the fluid you NEED to bleed the brakes again ASAP.

 

One stop from 60, no matter how hard, isn't going to boil the fluid. I can't remember your other post too well. Didn't you think you had a stuck caliper or something? You need to put quite a bit of heat into the brakes to boil the fluid. Can't say that I ever did that on the street, but it's happened a bunch of times on the track.

[Guest bastaad525]

No I had to replace my calipers because one of my old ones was stuck. So both fronts are rebuilt. I had my wife pumping the pedal while I was bleeding them, and was watching them move as well and it LOOKED like they are moving evenly... they move so little it's kind of hard to tell. I'm really hoping these newly rebuilt calipers aren't bad

 

 

I really can't understand how in the heck I could boil the brakes from one moderately hard stop either. I've done hard stops before, like when I was doing 1/4 mile runs with that cursed G-tech, and that never happened, though I've had that smell once or twice before.

 

 

You know what pisses me off the most about this car? Things will be fine, and then some problem will pop up, and once that problem pops up it just leads to more problems and more problems... they all start these chain reactions. Like the friggin oil leak. I keep fixing it, and it keeps coming back and getting worse. Now the brakes... they worked fine, now they just keep having problems... fix one and two more pop up.

 

 

So... boiling the fluid is the ONLY explanation for what happened? And there's no apparent reason for why it happened. So I'll bleed them again but THEN what?

[Pop N Wood]

A bad master cylinder will also do just what you described. A little rust in the bore, an old rubber plunger or a spec of debris getting under the plunger will cause the MC to move without building any pressure. The problem can be intermittent like that. Back when I was poor I have driven cars like that for months.

 

Not saying that is your problem but maybe the brakes failing shortly after the overheating is just a coincidence.

[Guest bastaad525]

ugh... the master cylinder was recently rebuilt, but yeah I guess I have to start considering that.

 

 

Well to put it like this, the brake pedal getting soft after hard braking has ALWAYS been a problem, just not ever nearly to this degree.

 

Before I changed the calipers, if I was doing a lot of hard braking I would feel the pedal soften up a bit, maybe I had to push it down a half inch further before it really started to grab.

 

But this time it completely let go, I had the pedal all the way to the floor and had to pump before it came back up.

 

Just kinda weird though that this only happened after changing those calipers.

[Here comes trouble]

I had a bad master cylinder in the silver Z for years with bleed off resulting in mushy brakes....After an occasional "pump up" the brakes would work fine for a couple hours use but out of habit I would occasionally pump them gently while driving in case I had to stop. When I finally replaced front and rear brakes, I replaced the master cylinder from a parts car and had no more "bleed off" in the master cylinder during operation of the car. If you are not leaking somewhere in the system.... Bleed the brakes also at the two master cylinder bleed off points. Disconnect the vaccum booster and see if your problem seems the same without it's use. Next time at the JY grab yourself a front/rear brake proportioning vave off a Z firewall for a little parts changing to see if this is the problem.(Take a metric 10 mm flare nut wrench) Sounds like a master cylinder problem if not leaking somwhere.

[Guest bastaad525]

yeah definatley not a leak, my fluid levels haven't changed a bit.

 

 

i was wondering about that proportioning valve... man I'm REALLY scared to try to get that thing out, I have a bad feeling those old hard lines aren't gonna put up with too much movement.

 

When I bled the brakes I bled all four corners and then bled the master cylinder at both bleed points. Actually, as per the Haynes manual, I bled from the master cylinder FIRST, then did the rear passenger, rear driver, front passenger, and front driver brakes.

[mark]

Did the calipers come with pads already loaded? Buy some good pads, use some dot 4 fluid (valvoline syntec is a good one for the street) and bleed the brakes again.

 

Good luck, Mark

[Guest bastaad525]

Nope not loaded... I just bought Auto Zone lifetime warranty pads... never had any problems with them before.

 

 

So I should switch from Dot 3 to Dot 4 fluid??

[JMortensen]

Why do you get all the bizarre problems Bastaad? Bad karma or something? No pad should have problems with a single 60-0 stop. I think changing out pads is barking up the wrong tree. Besides, if the pads were gassing, the pedal would have been normal, but the car wouldn't have slowed down at all. The master is a possibility, but I have yet to see a bad master that was fooled by the light steady pressure test. If you put light steady pressure on the brake pedal and it doesn't sink to the floor, then its probably not the master IME. If you somehow managed to boil the fluid, that leaves 2 possibilities. Either the brake fluid you used was contaminated somehow, or somehow even after you bled the system you still had a lot of moisture in the lines. I still think that either of these scenarios is really unusual. You should check for a stuck caliper. Just jack the front end up and spin the wheels. Same with the rear. Rear should have very light drag from the shoes, front should spin freely. If not, something is hanging up, and if something is dragging while you're driving that might be putting heat into the brakes causing your problem.

 

Maybe your car needs an exorcism...

[wheelman]

I agree with Jon, it sounds like you boiled the brake fluid somehow.

 

How old was the fluid you put in the system?

Did you flush the entire system during or after the caliper install?

How did the fluid look, was it dark brown, clear tan or somewhere in between?

What type of fluid did you use?

Did you replace the rear shoes along with the front calipers?

How badly does the wheel jerk when you apply the brakes?

Do you have to maintain pressure on the steering wheel to keep the car straight while braking or does it straighten itself out after the initial jerk?

 

Maybe the rears are shot so the fronts had to work harder, getting them hotter and in combination with moisture in the fluid it boiled?

Maybe the fuild in only one caliper boiled? The one doing more of the braking, which causes the jerk.

 

Wheelman

[fastzcars]

Bastaad, I live in L.A. but I work in Burbank. I could bring my Power Brake bleeder kit, and help you bleed the brake's. I would need to do it after work. Did you change the rubber hoses to the calipers and

[Guest bastaad525]

Jmortensen - dude I dont know why I've had so much weird crap with this 240. You know, before this I had my '81 ZX for like 6 years, and had the built up high compression N/A motor in that. That car never gave me any problems... only one time did it ever 'strand' me and that was when the fuel pump went out which was my fault because I KNEW it was going to go out, it was acting weird and making noises for like a month, and I just dragged my feet changing it. Other than that... no problems, always started right up, always got me where I needed to go, and being my only car at the time, never had to be down for long lengths of time to fix big problems. Every job I can ever remember doing or having done on that car was a one day job and every job, when done, was DONE... it didn't keep having problems after that.

 

I should clarify a little bit about that day and the possibility of boiling the fluid... there was only the one REALLY hard stop from 60-0 (consider it an emergency stop... was braking just short of locking up the tires). But up to that point I had been driving kinda nutty for about an hour, so had been giving the brakes a workout, to the extent that you could 'normally' work out a set of brakes while driving on the street. So... I dunno if that was abusive enough to get the fluid to the edge of boiling and then that final stop just put them over.

 

About the master cylinder... as I've said, it was rebuilt about 2-3 years ago. And no, if I do slow steady pressure, it wont sink to the floor. In normal driving and testing, it feels fine, and will only to down about 1-2". Considering that none of these problems occured until immediately AFTER changing the calipers, it doesn't make sense that it would be a screwed master cylinder. If it were, I'd be having these problems before. And trust me, I've put my brakes to the test several times

 

I will check for a dragging caliper again, though as I said i did check to see if they were moving when my wife pumped the pedal, and they definately looked to be moving evenly.

 

 

Wheelman - I'll answer your questions in order.

 

- 1. I used brand new fluid to replace the fluid I lost while bleeding the system.

- 2. it was not my intention to completely flush the system, but after having bled it three times, I think I can consider it flushed that is to say, all the old fluid has been bled out and replaced with new fluid.

- 3. the old fluid looked okay, I've seen really old nasty fluid before and this wasn't like that... it was still clearish. But it was old, last time I replaced the fluid was 2-3 years ago when I replaced the master cylinder. Keep in mind, that is 2-3 very low mileage years.

- 4. I forget the brand, I think STP or whatever Autozone had, DOT 3 fluid is what I used.

- 5. I didn't touch the rear brakes at all, until the very last time I bled them (I've bled them a total of 3 times since replacing the front calipers). According the Haynes manual, the front and rear brakes operate completely seperately and independently. So if I only opened the system in the front (which I did) I would only have to bleed the fronts, so that's why I did that.

- 6. the wheel doesn't jerk that badly at all... I'd say it rotates only about 1/2 to 1", it's more like just a light shudder, and it's only if I jab the brakes... if I apply pressure normally it doesn't do it. If I brake hard and steady, the car goes straight with my hand off the wheel, it doesn't pull to one side. The wheel has been jerking to the side like that since immediately after replacing the calipers... not just after that episode where the pedal went all the way to the ground.

 

 

Now one thing to keep in mind, is that the reason I replaced the calipers is because one of my old ones WAS definately stuck. And even with a stuck caliper, I never had any of these things happen before, the wheel jerking or the pedal getting so soft it went to the floor like that.

 

 

 

Fastzcars - sure if you have the time and we could arrange it I'd greatly appreciate the help in rebleeding the system. If anything, just to be sure I'm doing it right... if someone else verifies that, and I still have problems, then I know there's something else wrong and it's most likely to do with those calipers, so will end up trying to get them replaced.

 

And no, I didn't change the hoses, as I had replaced those about 3 years ago as well, so they are relatively new.

[cygnusx1]

If your fluid was really hydrated (old and watery), you could very well have boiled the fluid. Even if you did boil it, a simple brake bleed (fluid change) will cure the problem.

 

Soft pedal can be, bubbles in the fluid, bad master cylinder, pads/shoes getting pushed away from the rotor/drum by warped/bumpy rotating hardware, flex in a pressure line or mechanical brake component.

 

Do some braking and compare temperatures of the wheels/brakes to see if one is working harder than the rest. If they are different, you have a problem.

 

IF one of your brakes is working harder than the rest (stuck pistons), it may very well have boiled the fluid at that corner and caused the burning brake smell...and soft pedal. Which way is the steering wheel pulling (hands-off) when you apply the brakes? That is pointing you to the overworked brake.

[Guest bastaad525]

it jerks slightly to the left if I JAB the brake pedal kinda hard. Under normal braking, or even if I brake HARD (like I did that time that the pedal went soft) but steady, it doesn't pull to one side at all.

 

And the fluid definately isn't old and watery it's all new now and was all new the day that that happened.

[Sumo]

It could be that you just managed to buy a bad rebuilt caliper, it's not unheard of because it happened to a friend of mine once.

[VRJoe]

I suspect there are a few things happening at the same time.

 

1- Pulling to the Left - The Left caliper could be sticking closed or the Right caliper could be sticking open. Also if it's still drums on the back, check that they are properly adjusted.

 

If you smelled burning brakes it is possible that one caliper is bad and is not applying enough pressure forcing the other to do the majority of the stopping.

 

If the pads got hot enough to smell they might have been damaged. Cooked pads can cause all kinds of interesting symptoms. Check them and change if necessary.

 

Clean the Proportioning valve.

 

2- Master Cylinder - Could be bad, did you Bench Bleed it after rebuilding it.

 

3- Fluid - Change it, it sounds like it's gone bad.

 

Hope that helps,

 

 

- Joe

[srgunz]

Funny thing you should say pedal returned to normal by itself. A similar situation just happened to me on this Thursday.

Had the rear struts off and had everything put back together and bled the brakes on Thursday. The pedal was perfect. I always use Ford Motorcraft fuid. $3.95 a pint and 550F rated.

After I rejet the carbs as well, I take it for a test drive.

As I am backing out the drive, WTF, the pedal goes almost to the floor but had some brakes. I took it out anyway and about 5 minutes later I did

a full throttle 1st thru 3rd gear. All of a sudden my pedal came back to normal again. I have driven the car all weekend with no further problems.

My M/cyl is fairly new also with about 2000 miles on it.

I am still figuring this one out as well.

[Guest bastaad525]

the stuck caliper theory just doesn't seem to make sense.

 

a) before I replaced the calipers with the rebuilt ones, one of them DEFINATELY had a stuck piston, and yeah the car would pull to one side under hard braking, not just jerk the wheel, but PULLLL continuously until I let off the brakes.

 

I've tested several times and it doesnt' do that now, I can brake softly or extremely hard with my hands off the steering completely and it will go straight, just the steering wheel will shudder for that one instant when I first hit the pedal. But the car goes straight.

 

c) I watched the pistons while I had my wife pumping the brake pedal, and they seemed to be moving properly and evenly. Though they move so little it's kind of hard to tell.

 

d) I still doubt a bad master cylinder since it seemed to be working fine before I swapped the calipers.

 

 

I still want to give bleeding it one more try, as soon as I can arrange to take FastZcars up on his offer to help me out with that power brake bleeder.

 

If that doesn't fix it I give, I'm just gonna bite the bullet and take it back to the shop yet AGAIN. I'd rather pay the big bucks than keep pullin my hair out chasing problems. I still can't believe that what should have been such a simple job is turning into such an ordeal, and has now kept the car off the road for like what... three weeks now? I HOPE it's not a bad caliper because after all this time I wonder if they'll be willing to exchange them for me....

[Guest bastaad525]

sorry for the double post guys... I know this is a long shot but the thought occured to me that I should ask anyways.

 

Is there any possibility that a slight difference in the hard brake line to each caliper could be causing this? The reason I ask is because, when I was removing the old calipers I ended up cracking one of the S-shaped hardlines that connects directly to the caliper.

 

There is a place right down the street from my house that custom does hose and hardlines, and I brought the broken one to them and they made me another one. However, I noticed that, where the line was flared, the hole diameter was reduced quite a bit, compared to the original piece.

 

I'd say the hole diameter was reduced by around 1/16 to 1/32 of an inch... I really can't recall but it was a significant difference.

 

 

Could this be the cause of the wheel jerking if I jab the brakes? Maybe it just takes that fraction of a second longer for the pressure to equalize between the two?

 

Could this be causing the pedals to work unevenly and cause all these problems?

 

If you guys think it's a big deal I can make it a point to hunt down a replacement from a JY or something.