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Ford and Spongy brakes

Discussion in 'Stock 1995 - 2001 Explorers' started by 5.0L96Exp, February 4, 2006.

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    1. 5.0L96Exp

      5.0L96Exp Active Member

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      Spongy brakes - UPDATE.. HCU fluid routing diagram

      Hi all. Just looking for some input/thoughts from other GenII Explorer owners with regards to brakes. Since I purchased my X a year ago it has been plagued by a spongy brake pedal. I have never owned an explorer before, nor driven anyone else’s so I don’t have much to compare to. To date I have done the following maintenance:
      -Replaced brake pads with EBC 6000 pads (front and rear disk brakes)
      -Front and rear rotors were still within spec and not scored, warped, cracked, etc so I did not replace/turn them.
      -Pressure bled the entire system removing all the old brake fluid and filled with new Motomaster Ford DOT3 (288F Wet boiling point). Then gravity bled, then pressure bled again.
      -I have not blead the HCU since I do not have the electronic ABS pump/valve cycling tool. However I have braked hard enough that the ABS turns on then bled the brakes again.
      -All the rubber lines appear to be in good condition and do not bulge or bubble when the brakes are applied
      -Greased all the caliper slider pins with caliper slider lube.
      -All the caliper pistons move in and out freely.
      -Performed pump up test.. ie pump the brakes with the key off until the pedal gets hard, then keeping pressure on the pedal see if it moves after a minute. It doesn’t..

      The one thing I have not replaced is the master cylinder. From what I have read if the brake pedal is depressed and hits the floor it can tear a seal in the master cylinder (ie by extending the pistons beyond there normal operating range). I’m not sure if this is the problem or not. I can say that when I brake hard the tires have never locked up (even with the ABS fuse removed). The most I get is a very very slight voooov sound (I’m sure this is just the rotors that aren’t 100% true), no vibration or pull, to a gradual stop. Don’t get me wrong the truck does brake, but the pedal feels soft the whole time and I can almost make it hit the floor if I push with medium force. I now this sounds like apples to oranges but I had a Nissan Maxima before and the brake pedal was hard as a rock and only moved half an inch. It feels to me like there is a pinhole leak someplace, maybe the master cylinder, but I don’t seem to be loosing any brake fluid. Or that I have air in the system somewhere but like I said I have gravity bled, used a vacuum pump to bleed and pressure bled the brakes 4 or 5 different times now. I don’t know what to do, it just doesn’t feel safe towing a boat with a truck that has such mushy brakes. Any one experience the same problem or feeling.. Is there a rebuild kit for the master cylinder? Thanks for the help.
       
      Last edited: February 12, 2006
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    3. CDW6212R

      CDW6212R Elite Explorer

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      It sounds to me like air in the ABS pump. For reference, I have two 95 Crown Vics, and I added ABS to one, and the pedal has felt soft ever since. I know that air got into that ABS pump, and I have learned that it cannot be bled without a special tool.

      I had EBC rotors and pads on my Mountaineer for 45,000 miles, and the brakes were very good, relatively.

      I suggest that you look into having the brakes bled again, using the special tool which manually cycles the ABS pump while bleeding. It sounds like you have done all of the other proper remedies. I would bet that someone has allowed air to get into or above the ABS pump. That would cause air to get into the pump, etc. Good luck,
       
    4. marragtop

      marragtop Well-Known Member

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      I agree, bleed the ABS. IF it's the master cyclinder, you should be able to make the pedal go completely to the floor by hitting the pedal, letting up slightly, hitting the pedal, letting up slightly ... etc. If this happens, then suspect the master cylinder.
       
    5. 5.0L96Exp

      5.0L96Exp Active Member

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      Looks like I will have to get the dealer to bleed the ABS with thier fancy tools and widgets. Thanks for the help. :).
       
    6. unclemeat

      unclemeat Elite Explorer

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      I would check the vacumm booster lines and connections.
       
    7. 5.0L96Exp

      5.0L96Exp Active Member

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      unclemeat can you elaborate a little. I hadn’t thought to check the brake booster per say. I didn’t think it could cause the sponginess. ie if there was a leak in the vacuum line, or a tear in the BB diaphragm I think that would lead to an extra amount of pedal pressure required, similar to when the engine is off and you try to break. I did check the check valve and it seems to be working properly.

      I can sort of understand what you are saying though.. For instance, if there was a tear in the brake booster diaphragm then I would have to apply more pressure on the brake pedal to get the same amount of stopping power. ie instead of, lets say, 10% foot / 90% BB I now need to apply 50% foot (the pedal should still end up in the same place regardless) / 50% BB.

      On the other hand when the engine is off, 3 or 4 strokes and the pedal is hard as a rock and remains hard until I start the engine. This would lead me to believe that there are no vacuum leaks.

      Just had another idea... What if the gasket between the brake booster and master cylinder is leaking? What would happen then? Would air get sucked into the BB and make its way to the intake manifold. How would that affect brake performance?

      UPDATE.. there is no gasket between the MC and BB.

      marragtop I tried "hitting" the pedal a few times (while the truck was parked and running) and I was able to get it to hit the floor, the pedal slowly made its way back to its up most position. What is happening here? Is brake fluid quickly getting past one of the two pistons when I "hit" the brake, then slowly getting sucked back when the pedal returns? I know for sure it is a dual piston MC since there are two break lines coming out of it. If as suspected one piston is faulty then I would only get max pressure on one of the lines. I think this would greatly reduce breaking as only 2 out of 4 brakes is receiving proper pressure. Or berceuse of the ABS valving, maybe all 4 breaks see the reduced pressure.

      I am really starting to suspect the MC. The truck does have 230 000Km on the original MC and BB. Is there a rebuild kit for the MC (poor student can’t afford 199.74 for new MC).
       
      Last edited: February 12, 2006
    8. unclemeat

      unclemeat Elite Explorer

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      I had a similar problem with my brakes. It turns out it was the rubber gramet in the vacumm booster had degraded and was leaking. It is easy to check, A visual will do most of it and a mechanics stethiscope will also let you know if there is a leak.
       
    9. 5.0L96Exp

      5.0L96Exp Active Member

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      I asked this a while back but and never got a reply so I figure I'll ask now as we are on the topic of brakes.

      I know there has been a lot of discussion on this topic in the past so stick with me here. I need to bleed the HCU and I don’t have the fancy Ford T90P-50-ALA tool to do it. Now the T90P-50-ALA works by running the pump for 60 seconds. After 20 seconds you hold the "valve" button for 20 seconds then release it, the pump continues to run for the remaining 20 seconds. You can now bleed the brakes like normal. I would like to know if anyone that has used one of the tools or has access to one and can tell me which valves it activates. There a 6 valve in total. L. ISO valve, R ISO valve, Rear ISO valve, L. Dump valve, R. Dump valve and Rear Dump valve. I imagine that when you hit the "valve" button it activates either the ISO valves or the Dump valves the 20 seconds or some combination. If anyone has had one of these HCU's apart before and can tell me how the brake fluid is routed through the unit that would be a good place to start. Or if I could get a picture of the T90P-50-ALA unit itself, specifically the harness portion (so I can see the contacts) that could also help.


      I am going to make an educated guess and say that the ISO valves are normally closed removing the ABS pump from the hydraulic loop when the ABS is not engaged. When the ABS is triggered the ISO valves open/close according to which tire needs/does not need brakes. During this time the ABS pump is running providing the required pressure to operate the brakes (ie a predictable, regulated pressure that does not depend on your foot). The Dump valves are used to reduce pressure/help control the flow of fluid or act as a reservoir. Now I imagine that air in the HCU unit gets trapped behind the Dump valves (in the reservoirs) and the only way to get the air out is to open the Dump valves along with the ISO Valves and run the motor. And via some magic the air will find its way past the ISO valves, and can be bled out using the traditional methods.

      If there is anyone that has used one of these tools before can you describe the sounds made by the HCU.. ie the motor is running, I hear valves cycle on and off every xx seconds… or maybe the valves simply open then close 20 seconds later..

      I plan on putting together a electronics watchamacallit to simulate the very expensive Ford tool. Ill post the results.
       
    10. CDW6212R

      CDW6212R Elite Explorer

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      Hello, contact Glacier here. He has some experience with the ABS diagnostic tools. He may be able to steer you to a workable tool. Good luck,
       
    11. 5.0L96Exp

      5.0L96Exp Active Member

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      UPDATE: I am on crack.. I have come across a hydraulic fluid routing diagram for the HCU and I can now explain in detail exactly what happens when the ABS is activated (well a heck of a lot better than I could before). A picture is worth a 1000 words so I won’t even attempt to explain in detail what happens. Email me for the pic since I can’t seem to post it.

      It is also worth mentioning that the DUMP valves seals can fail and allow brake fluid to enter the accumulator. This IS VERY OFTEN confused with a failing MC since they give the same spongy pedal feeling.
       
      Last edited: February 12, 2006
    12. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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      I was just wondering if your vehicle has a brake proportioning valve like the older models before ABS was introduced? It's not too common for them to go bad, but any part could break after a while. This balances the pressure of the fluid in the front, and back.
       
    13. 5.0L96Exp

      5.0L96Exp Active Member

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      With 4WABS the HCU controls proportioning under normal and ABS braking.
      Please correct me if I am wrong.
       
    14. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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    15. Mbrooks420

      Mbrooks420 High Voltage. Elite Explorer

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      He has 4wabs, and 4 wheel disc brakes. RABS were just for the 91-92 I think. I think that in 93-94 you could get 4wabs. 95+are all 4wabs, with 4 discs.
       
    16. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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    17. CDW6212R

      CDW6212R Elite Explorer

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      I have never seen a modern vehicle without a proportioning valve. The factory proportioning valve in all vehicles is not called a proportioning valve.

      As far as I know, all Ford vehicles have a combination valve, which contains the "proportioning valve." All vehicles need it, including ABS vehicles, because ABS does absolutely nothing under normal operation. ABS only functions when adequate pressure is applied to stop a wheel from turning. BTW, that is the cause of some ABS malfunctions; if you never use it, it becomes attriphied.

      These later Ford vehicles have the proportioning valve function built into the master cylinders by design. Regards,
       
      Last edited: November 21, 2006
    18. 5.0L96Exp

      5.0L96Exp Active Member

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      So where is the combination valve? Is it built into the MC or is it part of the HCU assembly. I would tend to think that it is integral to the dual outlet MC's. But then again it could just as esily be part of the HCU.. I dont know....
       
    19. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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      Do you have a repair manual, or CD of your vehicle? If not, maybe you could get a diagram from the dealer. They usually give you a free printout if you ask them (usually, but not always). I would also suggest downloading the Ford CD from WWW.Fordcds.Com.
       
    20. 5.0L96Exp

      5.0L96Exp Active Member

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      I have a copy of Hanes, the Ford CD and a copy of Mitchel OnDemand. None go into the detail I am looking for. Its kinda like asking for the schematic of the Anti-theft (RAP) module. I can find out which wires plug into it but I cant see whats inside the box.
       
    21. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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      I think the only 2 options are to either get a copy of your brake system from the dealer, or just trace all of the steel brake lines until you find that proportioning valve. You could also call the dealer, and ask them how much one of them is. If they have one in stock, you could go there to take a look at it. It will give you an idea as what to look for.
       
    22. 5.0L96Exp

      5.0L96Exp Active Member

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      I still think we are on different pages here. There is no proportioning valve per say. The "proportioning" is built directly into the HCU and MC. That is, the MC determines Front to Rear brake pressure (via different pri/sec spring rates), the HCU determines (while ABS is activated) the pressure applied to the FL, FR, and rear brakes. ie the HCU can raise/lower pressure to the FL, FR and rear brakes as needed to prevent skidding. There is no way "proportioning" could be after the HCU since the HCU has 3 outputs, 1 for the FL, 1 for the FR, and on for the Rear brakes. It simply doesn’t make sense. Also, there are only 2 lines into the HCU, one from the MC primary and one from the MC secondary.

      However, the original question remains. Which valves open/close when the VALVE button is pressed? And where does the air in the HCU end up after the 60 seconds. It seems to me, from the HCU fluid routing diagram that when the pump is running, the DUMP and ISO valves are opened, the accumulators will fill with brake fluid under pressure forcing any air around in a loop. Unless of course the HCU is designed with some sort of loop de loop routing that causes the air to get stuck in the primary leg. Once all the air is trapped in the primary leg, (the DUMP valves are now closed restricting fluid from entering back into the accumulators), the brakes are bled normally starting with the RR, RL, FR, FL.

      If anyone has the name and number of a Ford dealer that is willing to let you talk to a tech and ask all sorts of questions it would be greatly appreciated. I have yet to find a dealer that is willing to answer any technical question, or any question that would in any way make them liable. ie The moment you so much as mention brakes, abs, airbag, cup holder, floor mats they tend to freak out and tell you to they will have to look at it and replace the parts as needed.
       
      Last edited: February 14, 2006
    23. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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      My local Ford dealer is the type that if you ask any question, they tell you to ask one of the mechanics. If you go to a mechanic, they say that no customers are allowed in the service area due to insurance regulations. If you say that you have a technical question, they tell you to go into the office. The office tells you that no customers are allowed there, because it's reserved only for mechanics to look things up in their manuals. If you ask a mechanic to look something up for you in their manual, they tell you that they don't have the book anymore on your vehicle, but you should schedule an appointment to have it serviced. If you ask them how they would service it without a manual, they tell you that all of their information comes up on a display on their scanner once they hook the vehicle up to it. I think they have a minimum of $75 just to look at it. After customers get such a run around from them, I can't understand why anybody would give them business.
       
    24. CDW6212R

      CDW6212R Elite Explorer

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      Well, color me surprised at Ford. I look at pictures that I took of my 99 V6 Explorer, and the brake lines do go straight from the master cylinder to the ABS unit. The proportioning valve function is evidently integrated into the MC now.

      The combination valves of past have always been very very reliable, hardly ever fail parts. That may be why it would be included in the MC now. But anyway, that leaves the master cylinder as a more important part now.

      I have a good Ford tech that I sometimes can catch to ask questions of. He would likely try to help with the Ford ABS tool. Still may I suggest that you send Glacier a PM, and ask for his help with the ABS functions. He has some knowledge of those tools, etc.
       
    25. 1-Dragon

      1-Dragon New Member

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      I found this on the web http://www.sccoa.com/forums/archive/index.php/t-29670.html

      Duffy Floyd says :
      08-22-2003, 10:40 PM
      Ad if you go to the Ford Shop Manual it tells you to bleed the Brake Master Cylinder and ABS Hydraulic Control bracket you have to use the Ford T90P-50-ALA ABS Test Adapter or air will be trapped in the ABS Hydraulic Control Bracket which will lead to a spongy pedal.

      On EBay you see a Thexton tool which does the same thing as the above mentioned special tool sold often for less than 29 bucks. Search on Teves ABS and you should be able to find one.

      I didn't find one on ebay though but this might help U



      UPDATE:

      I found one on ebay 5 items available at $38.95

      http://cgi.ebay.com/ebaymotors/THEX...ryZ43989QQssPageNameZWDVWQQrdZ1QQcmdZViewItem
       
      Last edited: April 12, 2006
    26. BrooklynBay

      BrooklynBay Staff Member Moderator Elite Explorer

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