Brake bleeding

[etc1006]

I finally got the seized bleeder out of my left front. Had to use the torch. Replaced the bleeder screw. Now I can finish it the way they list in the manual. My question is, is there a way to do the pump/master cylinder part without the special tool? Kinda like doing the EEC test or fuel pump jumper? I can only imagine how much THAT is, even if its available... I'm still not happy with how soft the pedal is. And I've already been throught the better part of a quart bottle. I had to replace the rear hoses, did that with low mileage used ones(I'm on a budget right now) and they bleed out. We think the rear brakes are the reason the car got abandonded. As everything else back there looks new. TIA

 

[shoebilly]

Crack the lines one at a time at the master. Never let the fluid level go too low.Master has to be done first, then the wheels

 

[etc1006]

What about the pump? The Chiltons says something about using the tool to cycle the pump for so long.

 

[Shoaz]

Really all the tool does (well, the Thexton unit, anyway) is open all the valves in the ABS so that when you bleed the system you're also bleeding the ABS pump.

 

[rcsavage]

dont want to hijack but lets say that air got up into the master cyclinder. same procedure?

 

[SonicRiot]

Yes, same procedure.

If you bleed the master and base brakes, the yucky stuff will still stay in the ABS pump, but will generally not hurt the rest of the system. I replaced my fluid, but left the ABS alone becuase I have two bad WSS and the ABS doesn't work currently. It's on the list!

 

[rangerj]

As long as you do not get air in the ABS pump there is no need to bleed it. If the master cylinder is pumped dry it has to be bled. Fill the master cylinder and let it sit for several hours for the air to work its way to the top. Not all of the air will escape so you have a friend hold pressure on the brake pedal and open the lines on the driver side of the master cylinder, one at a time and let air and fluid escape. Close the line before the fluid stops comming out. do this a few times then bleed the rest of the lines starting with the left rear, then right front, right rear, and finally the left front. If the master cylinder was pumped dry, or bled out, then this could take several bleedings to get all the air out.

If the ABS has air in it you can try bleeding it but only the valves that are in the bleed position will bleed out the air. If you get fluid out of an ABS bleeder it was in the right possition. You can try activating the ABS and try the bleeder until you get it in position to be bled. Otherwise you have to have the tool that sets the valves in the bleeding position, or have the ABS bled by a dealership or repair shop that has the tool.

 

[etc1006]

Yeah, thats the whole mystery of this... I don't know if the m/c was dry. I did notice what looked like a Ford replacment part sticker on the side of it today. LIke I said the whole rear setup looks new, so I dont know how long the system sat while th p.o./shop did the work... I guess I'll try for the nuts under the hood first and go from there. Hopefully I can get the pedal to my satisfaction.

 

[nkb93]

If the ABS has air in it you can try bleeding it but only the valves that are in the bleed position will bleed out the air. If you get fluid out of an ABS bleeder it was in the right possition. You can try activating the ABS and try the bleeder until you get it in position to be bled. Otherwise you have to have the tool that sets the valves in the bleeding position, or have the ABS bled by a dealership or repair shop that has the tool.

When you say "get fluid out of an ABS bleeder", are there separate bleeder screws on the ABS unit itself?

 

[etc1006]

You can "bleed" up to the connection of that nut. You know if you're checking to see if fluid is coming that far... Like at the union of the rear hard lines and rubber lines. Just by cracking the nut you're bleeding the line, just keep a rag under it. My main Q was how to bleed the ABS pump as I didn't know the service history of the work that was done to my car. I didn't know if there was a "shade tree" way of bleeding the pump or not...

 

[klauspass]

Eric,

Not to diminish any of the advice in this thread, my 1990 SHO has just been re-shoed on all four corners including the master cylinder. Revamp included front bearings and hubs, all hoses, all calipers, all rotors, all pads and a master cylinder.

I was foolish, for my assumption was that the parts would be in stock at the auto store when I ripped everything out. I pretty much waited a week to get everything in and by that time all the remaining brake fluid was on the garage floor. After reassembly, the brakes would not bleed, all I got was fluid and air.

Since my ABS was on the blink and the shuttle valves were not being excercised, I assumed again that I was bleeding straight. Pedal remained soft through 3 quarts of brake fluid. The fluid needed changed anyways. My economy brake job turned into a vast expansion of tools to my already SHO tool collection including a vaccum bleeder, Alldatadiy.com subscription (screw chiltons) and and ABS Bleeder.

Below is the FORD recommended bleeding sequence. On the 1990 SHO, the master cylinder is a tandem unit. The primary (rear) circuit feeds right front and left rear brakes. The secondary circuit (front) feeds left front and right rear brakes.

Bleeding with Antilock Brakes

The master cylinder and hydraulic control unit must be bled using ABS test adapter T90P-50-ALA or equivalent. If this procedure is not followed, air will be trapped in the hydraulic control unit which will eventually lead to a spongy brake pedal.

To bleed the master cylinder and HCU, disconnect the 55-pin plug from the ABS module and install the ABS test adapter to the wire harness 55-pin plug.

Place bleed/harness switch in bleed position.

Turn ignition to ON position. At this point the red OFF indicator should turn on.

Push motor button on adapter down to start pump motor. The red OFF indicator should turn off and the green ON indicator should turn on.
Pump motor will run for 60 seconds once motor button is pushed. If pump motor must be stopped before 60 seconds, press abort button to turn motor off.

After 20 seconds of pump motor operation, push and hold valve button down for 20 seconds then release.

Brake lines may be bled in the conventional manner. Ensure lines are bled in the following sequence:

Right Rear.
Left Front.
Left Rear.
Right Front.

The ABS test adapter T90P-50-ALA can be purchased from RCM at http://home.earthlink.net/~rcm_automotive/index.html. Just e-mail Mark. I believe I paid $89 and I know he has a few left. Or you can by a Thexton unit for $200. However, Thexton no longer manufactures this unit and when they did, it sold for $39.00. RCM is also an excellent source for parts and quite reasonable I might add.

 

[klauspass]

Just for purposes of clarification.........

Both the Thexton and FoMoco T90P-50-ALA HCU brake bleeders do a tad bit more than open valves. During the sequence that the units are acivated, the brake bleeders run the HCU accumulator pump for a timed 60 seconds, pressurizing the brake system to as high as 3000psi. After 20 seconds you press a button to shuttle the valves electrically for 20 seconds. If there is air in the HCU and the Master Cylinder, you will see it bubble in the Master Cylinder reservoir. After 40 seconds, you release the valve button and the adapter runs the HCU for another 20 seconds to represurerize the accumulator and then turns off at 60 seconds.

Some folks say you can achieve the same level of service by simply driving the vehicle, repeatedly braking and activating the ABS and then bleed again. That will work, however, I would not recommend this procedure.

 

[etc1006]

Hey, great info. Now you know what I was getting at about not know if the system sat open during repairs. You got pm, nice to see another person close to me with a SHO.

 

[Markus]

Just for purposes of clarification.........

Both the Thexton and FoMoco T90P-50-ALA HCU brake bleeders do a tad bit more than open valves. During the sequence that the units are acivated, the brake bleeders run the HCU accumulator pump for a timed 60 seconds, pressurizing the brake system to as high as 3000psi. After 20 seconds you press a button to shuttle the valves electrically for 20 seconds. If there is air in the HCU and the Master Cylinder, you will see it bubble in the Master Cylinder reservoir. After 40 seconds, you release the valve button and the adapter runs the HCU for another 20 seconds to represurerize the accumulator and then turns off at 60 seconds.

Some folks say you can achieve the same level of service by simply driving the vehicle, repeatedly braking and activating the ABS and then bleed again. That will work, however, I would not recommend this procedure.

Where were you 18 months ago when I needed info on bleeding the ABS?


I've spent the last 18 months (on and off) trying to figure out exactly what the ABS bleeder did. I think finally figured it out last week after finding some resources about the Teves Mk IV ABS system on the net. It seems that there is a circuitous loop between the master cylinder resevoir and the HCU. There seems to be a third line from the master cylinder to the HCU and I think it is through this line that fluid is moved from the HCU to the master cylinder. Is this correct? Now for a theoretical question. If the brake fluid in the master cylinder is noticably cleaner than the fluid in the HCU, will I notice a change in colour of the fluid in the master cylinder during the 20 second period when the tool cylces the valves?

I determined the existance of the third line both visually and from the following quotation from the service manual regarding removal of the master cylinder:

For ABS vehicles, disconnect hydraulic control unit (HCU) supply hose at brake master cylinder and secure in a position to prevent loss of brake fluid.

I just received the Ford Rotunda tool from RCM and I will be bleeding the brakes at the weekend.

 

[klauspass]

Hi Marcus,

Sorry for the late response, just back in town. Yes, regarding the third line. But the third line is only a supply line to replenish the HCU reservoir. The dirt you see or the change in fluid color comes from the HCU fluid reservoir back through the exiting master cylinder lines. The master cylinder reservoir continually supplies the HCU reservoir.

The HCU consists of a valve body assembly, pump, and motor assembly and brake fluid reservoir. During normal braking, fluid from master cylinder enters the HCU through two inlet ports. The fluid passes through four normally open inlet valves, one to each wheel. When the ECU senses wheel lock, the ECU produces a pulse to the appropriate inlet valve that closes that valve. This prevents any more fluid from entering the affected brake. The ECU senses the wheel again; if the wheel is still decelerating the ECU then pulses open the normally closed valve that decreases pressure trapped in line. This last part is important, this is the pulsating sensation that you feel in the pedal when the ABS is activated.

The ABS test adapter T90P-50-ALA, opens all four channels. It basically pumps HCU reservoir fluid back through the master cylinder. The HCU reservoir is replenished from the master brake cylinder reservoir. If the HCU was never activated for the recommended bleeding process, you will probably have quite a bit of OEM fluid in the system. The HCU reservoir is small but has roughly 16” x ½” in line that connects to the Master brake cylinder reservoir. Combined, you probably have better than 6 ounces of fluid. At best, if you activate the system by repeated breaking, you would have to have all four wheels lock for a minimum of 20 seconds and you would be lucky to move 1 ounce.

I personally evacuate all the fluid from both reservoirs, refill, bleed the Master cylinder, run the test adapter TWICE, evacuate the dirty fluid from the Master cylinder reservoir, refill and then vacuum bleed the entire system as described in the previous thread. I end up using 2 quarts of brake fluid in this process. This by the way is not just the SHO ABS but in principle applies to all ABS systems.

Hydraulic systems generally don't move fluids; you pressurize and transfer movement from the brake pedal to the compression of the calipers. Air in your system reduces fluid volume. This results in extra pedal travel or a soft pedal.

You move fluid when evacuating or bleeding.