Brake Problems

[98laserstang]

I am having some issues with my brakes. I have a 98 sixer with four wheel disc brakes and abs. The rear brakes have been giving me hell for awhile now. The best way to describe the problem is that when I take off from a stop it seems as if the rear brakes are not releasing from the rotor, making a noise as I accelerate. I have checked the brake lines, rotors, brake pads, calipers and I have even bled the system but the problem still persists. I cannot find any leaks and the reservoir has plenty of fluid. After reading my fsm, I have narrowed it down to either being the master cylinder, or the pressure control valve. I know if the master cylinder is leaking it can do so from the inside and I won't see it. My suspicions lie with the pressure control valve, but I cannot find this part ANYWHERE. So basically I have two questions: What do you think may be the faulty part and if it is the pressure control valve is there a place to find one or do I need to find a salvage yard and try my luck with a used one. Thanks for any help you guys may have.

 

[atlanticblue98]

im gonna move this to General Tech, it may get more views by other members and they can give input as the V6 braking system is identical to 94-95 GT's.

 

[JDwhite98gt]

Have you checked to make sure the emergency brake assembly is not locked up? It is part of the rear caliper and you didnt list it as a part that you had checked.

 

[98laserstang]

Yes the ebrake is fine.

 

[JDwhite98gt]

Is it a daily driver? does it only happen after sitting for a while. Could be surface rust. I mean the rear brakes are bretty simple if you know that all the boots are intact, the piston screws down freely, the ebrake (and I'm talking about the spring and leverage arm on the caliper) is not sticking, pads are noce and thick, rotors are not warped, sliding pins move in and out freely, then its not your brakes.

 

[98laserstang]

Yeah it's a daily driver so no surface rust. I did have an issue where one of the pins were seized up, but I fixed that with another pin and a lot of grease. The arm, spring, on the caliper for the ebrake and cable are all fine too. The only thing I am not sure of are the rotors being warped and I have thought about that, but the noise isn't consistent. It may do it at one stop light and then not do it at the next. I guess if the position of the wheel has to be in just the right place to make the noise then the rotors might be a possibility but I really think that the master cylinder or something with the hydraulics is the problem because the brake pedal likes to sink just a little after being fully depressed (spongy feeling). Sorry, I forgot to mention that in the op.

 

[JDwhite98gt]

Squishy brake pedal? Welcome to Mustangs. Well I know the master cylinder can be bled but I have never seen it done. You should try that, and try replacing the rotors they are only 20 dollars a piece or get them turned.

 

[red95r]

I really think that the master cylinder or something with the hydraulics is the problem because the brake pedal likes to sink just a little after being fully depressed (spongy feeling).

My brother had the same experience, pushing on the pedal and hen it wants to go down further. This is the master cylinder is bad for sure.

 

[JDwhite98gt]

More testing should be done before you automatically decide its a bad master cylinder.
Bad Master Cylinder = long mushy pedal
Long mushy pedal does not always = bad master cylinder

 

[98laserstang]

Yeah I have thought about getting the rotors checked and turned down if possible. I also have an extra set if need be. I also did some thinking and thought that maybe if I was to make an educated guess between the master cylinder and the pressure control valve that the master cylinder may be the culprit because the fluid has to come from it to get to the pressure control valve, so if the master cylinder is bad the pressure control valve can't do its job properly. It sounds good on paper anyway lol. Yeah I know the pedals are soft compared to most cars but what I feel when I push it down is that after the brakes are fully compressed there is still travel in the pedal which is why I think it's a bad cylinder. Can bad rotors cause this same symptom?

 

[JDwhite98gt]

No they cannot and i must of missed earlier if u said that there is pedal travel after the brakes are fully applied. I would bleed the brakes again and try to bleed the master cylinder, then replace if necessary

 

[98laserstang]

Anyone know how to bleed a master cylinder? lol

 

[red95r]

Trust me its not worth it. I've been down that route and it was a waste of time.

Just replace it, Bleed it, and be on your way.

 

[JDwhite98gt]

How is it a waste of time to properly diagnose his problem? Its a waste of money to throw parts at the car without a proper diagnosis.

 

[red95r]

If he wants to do it then go for it, he'll only wind up buying the part anyway.

 

[98laserstang]

Well I got the master cylinder out tonight and I will bench bleed it tomorrow or Saturday. I did find out however that as far as the brake pressure control valve is concerned, it is no longer manufactured by Ford. At least you can't get it from the dealer anyway. The dealer told me the part was now obsolete. I am now hoping that the master cylinder is the problem or else I get to try and track down an aftermarket brake pressure valve. I will update with the final verdict once I finish the bleeding process.

 

[blackice]

The E-brake can still be the cause. Easy way to find out if it is the culprit, take the rear wheels off and then dissconnect the cables where the attatch to the calipers. Drive it around. That happened to mine and I left the cable dissconnected until I replaced it. Before I did it, when I'd get out of the car the rotor was basically smoking so I knew either the caliper was locked up or the e-brake was stuck on.

 

[AaRoN]

The master cylinder can be bled while still installed in the car.

 

[blackice]

bleeding the master cyl requires you to dissconnect the two lines comming off of it and installing two plastic fittings with clear tubing attached to them in their places. route the tubing directly into the master cylinder resevoir. once that is done you have to push on the back of the piston into the bore of the master cyl. if the master cylinder is off of the car this is done on a workbench vice with a screwdriver or something similar. if it is done on the vehicle the brake pedal is used. either way the piston is pushed all the way down and let back slowly. do it like 100 times to be sure, but when you dont see anymore tiny air bubbles pushing their way through the clear tubes into the resevoir then the master cylinder is bled. im sure you can find this info online if you google it, or if you stop at an auto parts store and ask to see the master cyl for your car they usually come with instructions on how to bleed new master cylinders