old man neri

Okay,

Sorry to bug you all on Christmas but driving to work last night (about 150mi) in the heavy rain I had a very very odd brake problem.

Background
I rebuilt all 4 calipers about a month and half ago due to a sticking caliper. First time doing it but all seemed to go well. I bleed brakes, pedal felt different as expected but it came back to the way it was after driving a while. Bleed again about 2 weeks ago, some air came out, and pedal felt even nicer.

Currently

Driving the car almost every day in various weather conditions from above freezing to horrid blizzards. Brakes fine. All of a suden last night I get in my car after we have a 'thaw' and the brakes have good pressure but it's just not 'grabbing'. That is to say, there is no slowing down. I hit the pedal again and it works. Odd, I think to myself, maybe some snow or ice fell on it and I squished it out of the way. Brakes function normally from then on.

I get gas and begin my road trip. Driving through the city everything is fine. I get on the highway and drive for a bit. I then have to apply light brakes....the car wants to dive to the side. I release and apply the brakes again, it brakes normally. Again, all this time there is normal pressure.

After some more experimenting on this trip it seems that if I use the brakes every minute or two there is no problem but if I got several minutes without braking either it will want to dive to a side or it just won't slow down. Normal pedal feel/pressure through out. Also, if I apply the brakes after not using them for several minutes but press the pedal twice they seem to work. But if I press the pedal only once and hold it takes about a second for the brakes to all of a sudden start grabbing.

WTF?

Future Plans

Well was stuck at work today (still am) so there is not much I can do. Tonight I am going to try to get it up on the hoist to see if I can notice something odd. Actually, I am hoping the problem just mystically went away but I doubt it. I might try to push the individual pistons in and out if I can, maybe there is something funny there.

I can't buy brake fluid tonight but maybe tomorrow night after work. I will then try to bleed the brakes. Got to start somewhere.

Lastly, I have to go on a very long road trip with this car soon so this problem needs to be resolved quickly.

Thank you all for taking the time to read this and I thank you all for any input or advice you might have. I hope you all had/are having a merry Christmas

-matt

GothingNC

How old are the brake hoses?

john

old man neri

Would have to check the POs records but I do believe about 2yrs old, maybe less.

MDL

Matt, first, find a job closer to home and move further south.

At first it sounded like you have a vacuum leak in the system, until I got to the part about it pulling to one side. I had similar issues with my 69 Camaro but it did not pull to one side, but it was intermittent as yours seems to be. Turned out to be a bad booster. Are you sure the road did not make it pull? Not trying to be a wise guy, but are you sure you installed the piston with the notch in the correct position?

Is it possible that brake fluid is somehow getting on the pads?

Sorry your having problems at Christmas!!!

old man neri

Actually I live 'on base' so my job is about 100 yards from where I live. I was visiting family for Christmas eve. As for moving South, well.... that might be easier said than done.


Positive.


Pretty sure, give or take a few degrees. Like I said, it worked fine for over a month until all of a sudden it didn't. Could it have rotated? I will make sure to check it out though.

I certainly hope not but thanks for the suggestion and I will take a look. I looked a the reservoir level when I first noticed the problem and it was fine.

It's all good. Could always be worse, saw a car flipped over in the snow when I was driving down.

Thanks for taking the time on Christmas to help me
-matt

SirPzalot

There are lots of possibilities. How old is the master cylinder ? A loose wheel bearing that pushes the pads back ( symptom should be a lower pedal, comes up with a pump, possible pull to one side).
To check for wheel bearing play the wheel must be in the air, use a bar or 2x4 under the tire and repeatedly lift upward a small amount while feeling for the slightest play. There should be NONE.
Brake hoses can do strange things...the inside can swell creating a valve action that doen't allow fluid movement, more so they don't release pressure ,holding the caliper on or dragging the pads. If one pad is dragging and gets real hot it won't grab as well as the cool pad, this would cause a pull to one side too. Try driving the car with light use or no use of the brakes and then feel each wheel center . You are looking for one that is too warm=dragging caliper.

old man neri

Interesting suggestions, I will give them a try.

Update

Problem no longer exists. It just went away. Maybe it was weather related? Drove through a lot and a lot of deep snow, worked fine. Parked car with wet snow impacted in all the wheel wells. The temperature then rose to just above freezing and there was a very very heavy down pour. Could the pads/rotors just get to wet yet it not be hot enough to get rid of the water? Does this make any sense.


I think it needs another bleed but again, that is apparently expected after rebuilding all 4 calipers. The other thing I noticed is that if I kill the engine while the car is moving (key still in to make sure steering doesn't lock) and keep using the brakes on-off-on-off...etc there is no change in feel or brake force. In other cars I have after 3 pumps with the engine off the pedal becomes like a rock due to vacuum loss.. But I think it has always been like this....is this normal?

-matt

GothingNC

Maybe you had some ice build up since the weather condtions changed from aboive freezing to below causing the caliper to stick.

What kind of brake pads are you using?

John

old man neri

The standard Mintex ones from Pelican. I just DD the car and people said that was the pad that was right for me.

Ed Hughes

I wouldn't call it a night on this. This sounds like a classic "air in the system" to me. Having to pump the brakes up after non-use seems to tell us that.

So, where is it? I'd go back over everything. Also, it would be interesting to know how you bled your brakes. When do it manually by pumping with the pedal, if you go too crazy, you can damage the M?C internals. There's a seal on the M/C piston between the front and rear circuits. If, during the bleed process, that piston travels too far from the pedal being pushed to the floor, that seal can be damaged which causes screwy things.

I'd go back and bleed well again. Using a plastic mallet or screwdriver handle to tap the calipers as you do it. This should dislodge any air bubbles that traveled out to the caliper.

One last thing...not knowing if you had the M/C off or maybe replaced , you need to bench bleed that to get the air out of it, otherwise you can bleed and bleed and bleed and still find air in the system.

Seems like too important a component to let it go.

old man neri

Ed,

I did the pressure bleeder method, the Motive one. I did hit the calipers with a mallet.

I never had the MC off, I did, however, take the calipers off and a lot of fluid drained out. I don't know if that could have affected the MC. How do you bench bleed? Is it necessary if you use a power bleeder?

What puzzles me is why all of a sudden.

Thanks and Merry Christmas Ed!
-matt

Ed Hughes

Could be weather related, something could have given way. Another thing that happens sometimes is that when a major bleed is done, and the aforementioned piston "resets" itself in its new position, that the seal can damage itself. If your original on the M/C, that could be the problem.

A bench bleed is basically manually working the piston on the M/C to pump fluid into it. Basically, you're priming the pump.

MDL

Matt, Did you use brake fluid in the Motive One pressure bleeder?

old man neri

Yes. Why? Was I not suppose to?

MDL

The power bleeders are designed to be used WITH brake fluid as you have done. I'm sure you have seen the debates here whether it is necessary to use the brake fluid or just leave the bleeder dry and use air pressure to push the fluid, but sense you used it properly as per the instruction by the people who designed the darn thing we don't have to go there.