Over the last few months, I found out that I have a brake pulling problem that gets worse with speed... Yanks hard to the right, especially when braking hard at speeds of 40+. Naturally, I think.. "well, the left front isn't working... gotta be the caliper"...(they are about 5 years old).

I went through the whole manual brake system about 5 years ago, calipers, pads, hoses, MC. Everything worked ok, not GREAT but decent...and it always stopped straight...although it never had enough power to lock the brakes... So now here we go again..



Round 1

Install rebuilt front calipers from O'Reilys Auto, turn the rotors and install Wagner Lifetime Ceramic pads. I bled the whole system with my Motive pressure bleeder and got decent pedal. (mine has NEVER had a rock hard pedal, but decent feel and always atleast 3" from the floor at max braking.)...

Car still pulls hard to the right under hard braking.

Round 2

Replace rear calipers (they were only 5 years old with not even 10k miles), clean up rotors with scotchbrite (these were also new 5 years ago), install new Wagner Ceramic pads. Bleed the system again.. No visible air bubbles, same decent pedal feel..

Car still pulls hard to the right under hard braking.

Round 3

Replaced the rubber brake hoses (also 5 years old) with Russell stainless braided brake lines. Bled the system with the Pressure bleeder and the two person method. Verified good flow at all four calipers, the front having a lot more pressure.(As they should). Thoroughly cleaned the rotors/calipers and checked the pads for contamination.

Car still pulls hard to the right under hard braking.

So now I am at a loss. This leaves me to believe maybe I have a steel line problem, (slight restriction) or maybe the proportioning valve is messed up? I know it only controls the front/rear bias but maybe its getting plugged up on the left front circuit or something? Does it actually do anything from left to right? It has about 157k miles on it.


When bleeding the brakes, I get no visible air bubbles after using both the Motive bleeder and the 2 person method...Doing two passes of each.. It appears to have a pretty strong fluid shot at both front calipers but..Obviously, something is wrong on the left side.

Notes:
*Both wheels spin freely with normal drag in the air
*Brakes bled with no visible air bubbles
*Pedal feels the same as it always has. (Decent feel/hard at bottom)
*Never been able to lock up the brakes no matter what, but it stopped well enough and always stopped straight until recently.

I'm trying to get this thing ready for a 3k mile road trip to Bowlingreen and Deals Gap in July and I need some GOOD, reliable brakes. Any help is GREATLY appreciated...

I'm not opposed to buying anything new, but I keep searching/reading about how good the stock brakes on C3s are and mine has NEVER been GOOD....Just liveable... I have receipts back to late 71' for caliper replacement etc etc..so this thing has ALWAYS had bad brakes...

 

Could be something with the suspension. Like sloppy control arm bushing bushing for instance. Braking puts force on it, alignment changes and it pulls.

I had a rear TA that was loose at the front mounting point. Felt OK driving but when I hit the brakes it moved, toe changed, and car pulled.

 

I replaced the control arm bushings, ball joints, idler arm, tie rod ends etc etc back in '06, about 20k miles ago.... In early 2009 I replaced the steering control valve and hoses while I had the engine out. Then in 2013, I noticed the lower control arm bushings were splitting so I pulled the arms, replaced the lower bushings only, uppers looked perfect. At the same time, I installed new front coil springs and KYB shocks and had it all aligned.

The rear suspension was completely rebuilt back in 2010. Tracdogg rebuilt my trailing arms and used all of the Tom's Diffs big axles/bearings etc etc. Has about 10k miles on this stuff. I did check the wheel bearings for up/down play and they are tight. I checked the shims in the trailing arms today and they are all still there and everything looks perfect in the bushing pocket.

I have read something about adjusting the steering control valve and I don't recall doing anything like that . I just put it on and it worked. I greased everything back in 2013 when I did the bushings, only a couple thousand miles since then.

The car drives straight, and runs straight under acceleration.

 

Sounds like you have done a lot, I did not see you check the rotor runout though.

And if your power steering valve needs adjustment, you can jack up the front, crank the engine and the front wheels should stay centered, ck posts here, and Jim Shea stuff.

Interesting the lower control arm bushing split, might be a good clue. I thought lower bushing should be good for more than 20K.

Good luck with finding the problem.

 

How about rigging up a pressure gauge to see what sort of pressure your getting at each caliper, doing so would confirm weather or not you have a blocked hard line.
Was the car ever a power brake car and converted to manual brakes? If so the rod needs to move up higher on the brake pedal so it has more leverage.
Kinked line?......
How about bypassing the proportioning valve......testing purposes only......just to see if its causing troubles.
How about the master cylinder, any chance of an air bubble trapped in there? You should be able to lock them up.
My car can easily lock up all four, with just normal 1977 power brakes/calipers/linings. Something is wrong with yours.
Just some ideas to try.....

Hope you find something

 

Its always been a manual brake car. Not sure about the pressure gauge, I'm sure its possible. However for such a simple brake system, this kind of BS shouldn't be this difficult. I am suspect of the proportioning valve but...Looking in my old 1970 service manual, it doesn't appear to have much to do with Left/Right fluid control... I suppose a left side hard line could be corroded but...When I was bleeding the brakes, it had a good fluid shot out of the left....

I suppose I could try swapping rotors from the right to the left and see if it changes anything... If I have a run out problem with the left rotor, put it on the right side, maybe it would start pulling to the left...if so, then I know its all in the rotors..--But honestly, if it was run out, I'd think the pedal would go soft from sucking air in the calipers. When I turned the rotors, I didn't pay attention to which one went where...but it pulled to the right before I turned the rotors also.

 

Oh well, just trying to brain storm some ideas, this is not good, but you know that already.

Some more ideas, for what it is worth, did you turn the rotors on the hubs (in other words, are the rotors still riveted on the hubs, like original?)? I would still check the rotor runout, good idea to always do, I say after any brake work.

And I think you are on to something, even though more work, I agree, I would try swapping parts one at a time from right to left to try to isolate the problem. Logically troubleshooting one part at a time is a pain, but a good practice.

Hard to believe the brake lines would be a problem, not much flow huh?, but installing new front brake lines would be fairly easy. And maybe you have a cracked weld or something in the suspension moving that is supposed to be fixed when you brake hard. Is there a way to flex the tire/front end with a cheater bar and see if something is moving that is not supposed to?

Hope you find it and best of luck.

 

Id certainly swap the rotors side to side, Ive seen brake pulls fixed by turning rotors many, many times. Swapping them side to side is free and would eliminate a rotor finish problem as the culprit.

 

Sounds like the master Cylinder or brake proportioning valve is not functioning properly... The fact that you cannot lock the brakes is a big signal something is not right with brake pressure- you should be able to lock the brakes easily. Fix that issue first since low inconsistent brake pressure will cause severe pulling. Checking rotor runout is probably not the issue since a fresh brake bleed will have strong brakes right after it was done with slight rotor runout with loss of pedal feel with some miles.

 

couple things, first, is the MC correct? Did someone (PO) use wrong length pushrod? Not having enough pressure to lock up with all new parts is NOT normal.

Second, they DO make a pressure tester for just this kind of diagnosis. I have one, it is a sensor that goes between the pads. Find a good grake shop that has a "Brake equalizer pressure tester" like this: http://www.autotoolexpress.com/waebeq0197.html

I have the Waekon, but Snap-on and BLue point make them as well. This is the proper way to diagnose without throwing parts at it...

 

Great info! Thanks for the link. That's definitely a good tool to have.

The MC was a new (not reman) from O Reilys about 5 years ago. I had gone thru several remans back to back and they either leaked out of the rear, seaped from the lid (pitted surface) or wouldn't bench bleed well. This new one seem to work fine... But maybe it is a little soft. I think it's lifetime warranty, maybe I'll get another new one and try. All that is left is that MC, proportioning valve or the steel lines themselves.

 

I'm not sure about the MC push rod, I've never changed it. No telling if it's been changed or not thru the years. The brake pedal seems to ride in the correct range and has a small amount of "soft" before it gets firm so.. I think the rod is probably ok.

 

Still think something is loose in the suspension (front or rear). Spend some time under the car with a pry-bar and see if you can make anything move.

 

I would suspect the proportioning valve, but never seen one apart to know how fluid is routed through it. I do know on my 71, it contains the low pressure switch.

I would also ask these two things: Are you bedding the pads in? There could be some funny wear between them.

Is the road you are on perfectly flat? I know depending on tires size sometimes c3's like to pull on bad roads.

 

The pro valve only meters front and rear bias, not left and right. To check your left and right bias, find a dirt road or rock parking lot and slowly lock up the brakes. Check the skid marks (not the ones in your pants)
You'll see which well has more braking. If they're just about even, you'll need to find something in the suspension. Start with hub bearings control arm and even the frame for cracks. A big pry bar will be your friend. Any flex is suspect.

Oh and the cheap Russell brake lines made my chevy truck very hard to stop. I couldn't lock the wheels up but when I went back to rubber, I got my brakes back. I don't know why but that was my experience.

 

Alan,
I have PB. I swapped out my PB master c for a manual brake master c from Lonestar per traccdoggs advice. That helped me and gave me more pedal pressure. Just recently I was at Zwede's and we performed a simple test and it looks like my booster is probably leaking/not holding vac.
I did this due to my low vac from the cam.
But I am still able to lock up the front brakes. Not sure about the back, if they do I don't know it, but I would imagine if your back lock up that could cause you to lose control more easily.
I have always read its difficult to lock up the back brakes with stock C3 brakes.
I recently bled all 4 corners with motive brake bleeder. I flushed about 40 ozs of new brake fluid thru system.
Take a rubber mallet and lightly beat on the prop valve... other wise pull it and take it apart. Maybe its corroded.

 

Sometimes sticking pistons (pistons that don't retract fully) can cause the pads to rub/grab more as they heat up.....could be happening on the right front......I would definetly do the braking-in gravel-test/or even sprinkle a bag of sand in the corner of a unused parking lot to see if the brakes are not grabbing equally after they are thoroughly heated up.

 

ajrothm, you have a PM

 

So today I decided to swap rotors from left to right, just to see if it makes any type of change, I seriously doubt that it does but...it was free so..

Here is the rotor, great condition visually and very smooth


Well in the midst of putting the left caliper back on and squeezing the pistons in by hand to get the caliper/pads back on the rotor, one of the pistons started squirting fluid they the seal. So I ran to O Reilys and got another caliper and got it on and all back together, but I ran out of time to bleed it before I had to come to work. Tomorrow morning, I'll pressure bleed the caliper and see what it does.



I also ordered a new MC (lifetime warranty on mine) and I'll try swapping that in a few days after I drive it with the new caliper/rotor swap.

If none of that solves it, I'll dive into the proportioning valve and hardlines.... After that, I have nothing else to check...

Fingers crossed but... I have my doubts.

 

If your pads aren't contaminated, the rotor isn't glazed and your mechanicals are otherwise up to snuff, I'd be looking very closely at a chassis problem. I went through the same thing many years back with a pull to the right that was getting progressively worse. It turned out the lower control arm bracket welded to the frame had broken. It was too slight to find when the problem first started but it did eventually show itself prominently as the bracket actually bent far away from the frame and the car was undriveable.