No Brakes!

[captinsho]

I recently bought a 93 ATX. I already had a 94 MTX. The 94 had various problems but had a number of aftermarket components so I swapped over what I could. The 94 had a 96 brake upgrad that had around 15K miles on it. For whatever reason last year I started to have problems with the brakes on the 94. The ABS would pulsate when I was not braking near hard enough for it to be engaging. Also I had extremely poor brake pressure.

When I got my 93 ATX a month ago I had to do a tranny swap on it. At that time I also swapped out my front struts (spindles and all) from the 94 MTX and put them on the 93 ATX, as I had the 96 brake upgrade on these spindles and I had Tokiko struts and Intrax spings on the 94.

When I went to drive the 93 I had little to no barke pressure. I bled the system multiple times hand ("power" bled) and manually bled with the pedal. I gained little to no pressure from the bleeding. I drove the car for a couple of days and it started to do the same thing where the ABS would kick in and give me tons of brake pressure while it was pulsating or at other times give me no pressure, pulsate and barely allow me to stop. I figured that it was possible that my ABS speed sensors were bad since this was one component that was swapped with the spindles. I took the speed sensors off the 93 spindles, which the brakes worked fine before the suspension swap, and put them on the 94 spindles. When I hooked them up the sensor (?) that is directly below the master cylinder started to smoke so I disconnected the speed sensors. The smoking went away. It is possible that I damaged one or both of the sensors when I was swapping it from spindle to spinde and thus caused them to ground the system out and create the smoke. Don't know?

My question is if anyone might have suggestions as to why:

1) My ABS is engaging at random times.
2) Why I would be getting smoke from the sensor under the master cylinder.
3) Why I am getting no brake pressure. By the way I did replace one of the callipers, before doing the speed sensore swap, because I thought it might be bad but it did not make a difference.

 

[Denny]

Smoke from under the cylinder? Sounds like the master cylinder is leaking then, that could explain it all

 

[oh_SHO]

Yes the sensor under the mastcyclider is leaking. It is an auxilary shutoff for the CC. Replace the sensor and it should fix that. I don't know what it would have to do with the brakes.

I have a problem with my ABS due to a cracked ABS ring on the front. Sounds kinda like your problem. I don't think the ABS system is letting the front engage like they should since my braking sucks and the rear wheels have more dust than the fronts. I am gonna pull the fuse and see what happens. Good luck.

 

[rangerj]

A couple of possibilities. The ABS has air in it. The master cylinder needs to be replaced. The master cylinder is leaking (smoke). You have a leak somewhere in the system. rangerj

 

[captinsho]

A couple of possibilities. The ABS has air in it. The master cylinder needs to be replaced. The master cylinder is leaking (smoke). You have a leak somewhere in the system. rangerj

If the master cylinder on this car is leaking why would I have had the problem of no brake pressure on the 94 and the directly on the 93 when I did the brake swap? My fluid does not seem to be going low. Also the smoking only happened when I had the ABS speed sensors hooked up, the car was running and parked? When I unhooked them the smoking went away? How do you get air out of an ABS system? Can you bleed it? Any input is greatly appreciated as I have little brakes right now and it is snowing here in MI. If there is anything I am leaving out let me know. Thanks!

 

[SHOZ123]

Disconnect or replace the sensor. It is only the fluid level sensor.

 

[rangerj]

The ABS can be bled but it has to be set in a position so the valves are open to be bled. This requires the proper analyizer capable of communicating with the ABS computer (dealer item unless you know someone who has one). In doing the master cylinder swap it is possible that you pumped air into the ABS. You can try to bleed the ABS and hope that by chance the valves are in the open position.

However, if you had a little air in the system you should at least get a spongy pedal, rather than no pedal pressure at all. When a master cylinder fails the fluid bypasses the piston seals inside the master cylinder, thus not providing any pressure at the pedal. There would not be any leaking fluid because the leak is internal, that is the fluid leaks around the piston seals(cups) inside the master cylinder.

Did you "bench bleed" the master cylinder when you did the swap? If not you may have air trapped in the master cylinder. Did you bleed the lines at the master cylinder BEFORE you did any bleeding at the individual wheels. When you attach the lines to the master cylinder they will have a little air in them. The should be bled by applying pressure and opening up the line connection to let the air out of the line and/or the master cylinder. You tighten the line BEFORE letting up the pedal. Do this to all the lines before doing any down line bleeding. This would prevent air from getting to the ABS as you bleed the lines at the wheels.

So, if you do not have ANY pedal pressure, and you do not have any leaks, then suspect the master cylinder. If you have a little pressure and it is spongy feeling, then you have air in the system somewhere. rangerj

 

[captinsho]

I am sorry if I was not clear but I did not replace the master cylinder, just the calliper, spindles and suspension. Because I was having ABS issues before the swap and after I latter swapped the ABS speed sensor. Since I never swapped the master cylinder is there still a chance that there is air in the ABS system? Also to be clearer the pedal is spongy but BARELEY spongy. Occassionaly I can build pressure. As a matter of fact out of the blue today I was driving home from work and got pressure at one stop light but it went away immediately after that stop. While I was at that light I let of the pedal to ease forward and the pressure went away. Since I have two different master cylinders, one in the 94 MTX and one in the 93 ATX and they were never swapped what is the chance that there is air in the ABS in the system? I am not clear why I would have had such major brake problems in both the 94 and the 93 when the 93 had good pressure before the swap of the calliper, spindles and suspension. My gut reaction would be that there is air in the lines but I mean we bled them like crazy! And no air was coming out!

 

[oh_SHO]

Just a thought and it may not have anything to do with your problem... Does it feel like the brake booster is working?

 

[captinsho]

I am not possitive how to answer that? Like I said I get pressure some times. If I pump the brakes enough I get pressure, although it never feels like full pressure? I there a way for me to test to see if the brake booster is working?

 

[oh_SHO]

Well power brakes use vacuum from the engine as the booster or whatever. Do the brakes feel different after you've started the engine? If the vac hose to the motor was leaking you may notice difference in performance.

 

[rangerj]

Unless you pumped the master cylinder dry you should not have gotten air in the ABS. If you have pressure by pumping up the pedal, and the pressure is lost, that is the pedal fades to the floor, this is a classic sign of either a leak or a failed master cylinder. If you do not have a leak and you are not loosing fluid, then the master cylinder is suspect #1.

You did everything right. You bled the lines "like crazy" and checked everywhere for leaks, and did not find any. But you still cannot get a firm pedal. Plus the pedal fades to the floor and will get some pressure when pumped up, but eventually fades away. Two words, ie MASTER CYLINDER.

The fluid is bypassing the piston cups inside the master cylinder so that pressure is not being applied to the lines or the caliper pistons, ergo no brake pressure or sporatic brake pressure. rangerj

 

[captinsho]

I really do appreciate all your help. One question: why would I have gotten pressure yesterday at one point, even though it went away, but most times I do not get pressure. I just want to make sure that before I replace the master cylinder, which may require me bleeding the ABS system (?) and will not be inexpensive, that I rule out any other components. It for sure would not be any of the brake components I swapped (Callipers - one if which is brand new, ABS speed sensor) or something I could have done in the swap? It just does not make sense that I would have had pressure before the swap on this vehicle and not after the swap. Especially since the other car, which I took these components from, did not have brake pressure. It just seems like too much of a coincidence.

 

[captinsho]

By the way I can build pressure. As soon as I take me foot of the pedal, after building the pressure and holding the pedal into place, the pressure is gone. Even if I immediately press the pedal again within the next 2 seconds. This is beginning to frustrate me 'cuz I have no brakes, or heat for that matter (whole other thread)! I just can't believe that it is not due to one of the components I have swapped since it was prevelant in both cars.

Note that the 1st care that I stole the parts from started having this problem shortly after I replaced the clutch in it (94 MTX). I don't think this happened but I MIGHT have allowed the fluid level in the master cylinder to go too low in both cars when I did the tranny removals. If this happened what all issues could I have caused and how can I trouble shoot to fix the problems? If I did get air in the ABS system would I be able to build pressure but not keep it?

 

[rangerj]

Captain,

Satisfy yourself that there are no leaks at any of the brake components, ie the calipers, lines, connections, master cylinder, ABS pump, and the resevoir. You checked the resevoir and you are not down any fluid, right?

You did it right. Stop second guessing yourself. It does not have to be because of something you did. We are talking about a 10+ year old car and its components.

Here is my theary on what has happened to your car based upon my experience with many other cars over the last 45 years. In the duel safety master cylinder there are two sets of pistons with rubber sealing cups. The master cylinder is in essence split into two seperate hydrolic pumps.

Because folks do not flush their brake fluid regularly crud build up inside the master cylinder and gets rubbed against the cylinder bore surface. This ends up putting scratches in the bore, AND wears the rubber piston cups.

The crud builds up around the cups and maintains a the seal to a degree. So, when you bled the brakes "like crazy" due to the caliper swap, the crud got flushed out in the bleeding process. Now the fresh clean fluid escapes around the piston cups due to cylinder bore wear and/or scratches AND rubber cup wear.

When you pump up the pedal the fluid pressure flares out the rubber cups edges and you get some pressure due to a temporary seal. The seal is soon lost and the pedal sinks to the floor.

So, If you do not have any leaks, and you do not have air in the system due to the bleeding "like crazy", then you have a bad master cylinder.

You do not have to get air in the ABS when you change a master cylinder. Open and close (just loosen a 1/4 to 1/3 turn) the lines attached to the master cylinder like they were bleeders.

Get the air out of the master cylinder and the little bit in the upper end of the lines BEFORE you bleed anything else. Then you will not push any air into the ABS when you bleed the calipers. If you do the master cylinder bleeding well enough you should not have to bleed the lines again.

If you are not clear on any of this get back to me and I'll take another shot at explaining it. rangerj

 

[felophnx]

Hi,
I realize this post was from a while ago, but I had similar problems with my 95 SHO and I had the brake sytem bled several times by Sears. They were telling me that they thought it was the Master cylinder and wanted to change it, but before I agreed to let them do it I bit the bullet and brought it to Ford. They diagnosed it as the exciter rings which the ABS uses for sensing wheel slip. It was like $20 for the parts, but the labor was at least $150. I had the same problems with little pedal pressue, ABS sputtering at times.
Good luck,
Tom