My wife's firebird has the front disk brakes (power). The fronts are really touchy and will pull hard to the side if pressed hard. She doesnt want to drive it now. was there a proportioning valve in the system? I replaced the master cylinder a while ago with one off the shelf. Did I get the wrong cylinder? Is it different with front disk brakes?
Seems like the fronts grab a lot sooner than the rear brakes and pulls to one side.
If your car came from the factory with front disk brakes, this is what your master cylinder and booster should have along with the valve on the frame rail. note there is a distribution block under the master cylinder and off to the right is a front brake proportion valve.
So which side does it pull to? Sounds more like a caliper and/or flexible hose problem. That's where you should start. A master cylinder won't cause a pull to either side.
So which side does it pull to? Sounds more like a caliper and/or flexible hose problem. That's where you should start. A master cylinder won't cause a pull to either side.
X2 Usually a caliper or rubber hose issue.
-=>Lee<=- Due to budget constraints the "light at the end of the tunnel" has been turned off!
If the flex hoses have never been changed that is the place to start. Even if they are not the problem, they should be changed. Don't forget that there is also a flex hose at the rear that should be changed too, as long as you are bleedng the system .
Thanks for all of the input. This is a car with the factory front disc brakes. I know it has the squarish box that is like a splitter and a wire comes out the side. Is the roundish item that is at about four o,clock the proportioning valve? It looks like I have that. I would guess it is a time to change the flexible brake lines... :-)
And it pulls to the right. And when I say pulls... it will lock up the front brakes hard. Can a proportioning valve go bad? It just seems to much front brake. If I make a quick stop... as in half pedal, it can send you thru the windshield :-(
Let me know if you have any more ideas and I will let you know what I find out.
I will have to post a pic. We painted it a color called blackish red... which is black in the shade but turns into a metallic cranberry/burgundy in the sun! And it is a convert with an added 400 hood and rear spoiler.
>Seems like the fronts grab a lot sooner than the rear brakes and pulls to one side< >And it pulls to the right<
It could be the assend of the car is trying to spin around, not the front brakes pulling, so the first thing I would check is the rear shoe adjustment.
Why do I think that the assend is trying to spin around? It’s a waste of my time to explain why, and if my suggestions aren’t considered worth investigating, I’m wasting my time to even make a suggestion, correct? Also, because I’m not a mind reader, I would have to check basics before moving on, and that’s hard to do while sitting behind a computer. So if I don’t know a thing about the basics, I’m wasting my time to make suggestions, also correct?
Go to 16:57, and listen to the amount of shoe-to-drum drag. It’s not a case of too-much drag, not-enough drag, or spot-on drag; again, why should I waste my time explaining? 16:57 is in the ballpark, and this is the ONLY youtube video that has drum brakes adjusted in the ballpark, obviously the reason why everyone has so many problems with drum brakes.
By the way, my car has manual drums. One-quarter brake-pedal travel will lock up all four wheels. If your pedal is goes half way, the pedal is going to the floor, an excellent indication that the rear brake shoes are way too loose.
I have the front discs on my car, but no booster. From what I have heard, the proportioning valve can indeed go bad. I would start with the basics though, like mentioned above. I just re-built my calipers, and replaced the flex hoses on mine because it sat for so long. The caliper pistons and seals were shot!
It will be interesting when I get the Muncie back and get her on the road- hopefully the brakes will cooperate!
By the way- do you still have the factory 4 piston calipers like mine or were they replaced with the single piston design? Keep us updated on what you find out.
Cant wait for summer... 68HO4004spvert Sleddog Iowa
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Had one caliper get so hot that something happened to the rubber seal and wouldn't release all the way. Went out and bought a new one and things are good as new. They are pretty cheap. Or you could rebuild it yourself. A rebuild kit is like $5. Just saying that after you replace everything else and it still pulls you might change out the caliper.
dougb, Did she have these problems before you replaced the master cylinder? If not, re-bleed the entire system. If so it's not likely the master cylinder. She may have two separate problems, one the rears do not activate and two the fronts pull to one side, or it could be that the caliper which is grabbing is the cause of both symptoms. The rear brakes [as stated above] should start to activate before the fronts. This keeps the car sort of straight when braking and reduces the tendency of the rear passing the front. A faulty proportioning valve, faulty metering valve, rear shoes out of adjustment, air in the system, incorrect installation, defective rear flex hose and a faulty master cylinder can all be reasons for the rears to not activate before the fronts. The metering valve holds pressure off the front system until threshold pressure is reached in the rear. If this valve is faulty you could be getting full pressure to the front before the rears activate. The proportioning valve allows more pressure to the front than the rear as the front will not lock up with the same pressure as the rears. If this valve is faulty it may be the fault. If the rear shoes are too far away from the drums they may not get enough fluid to move them into contact with the drums with one application of the brake pedal. The brake hose may have an interior breakage stopping flow of fluid to the rear cylinders. If you have air in the rear brake circuit that will compress rather than move the shoes. The piston in the master cylinder that activates the rear brakes may be defective bypassing fluid rather that building pressure for the rear brakes.
My experience tells the most common cause of brake pull is air in the opposite brake. The earlier disc brakes were known to have pistons slightly tip in the cylinder and not release or not activate. If one side does not activate the brakes will pull to the opposite side. The flexible hoses may also start to deteriorate internally, when this happens a small piece of hose may partially dislodge and act like a check valve, stopping fluid flow to or away from the caliper. If such a hose stops flow to a caliper it will pull to the opposite side, if it prevents flow from the caliper there is pressure in the caliper before pedal activation and will pull to that side when an application is made. Does one side of the front brakes drag when the pedal is not being pressed? If so that could be the side with a faulty hose or caliper.
Are you sure you have a disc/drum master cylinder? Drum/drum master cylinders have a residual pressure valve in the output ports. A little ball check valve which holds a small amount of pressure in the front and rear brake circuits. This is not used in disc brakes. Disc/drum master cylinders only have the valve in the rear brake output port. If the front disc circuit has a residual pressure valve it will hold pressure and cause brake drag and other problems such as fronts activating too soon.