Ok Guys I need some help from the super wrenches on the brakes of my 2000 F150 XLt 2wd 106K.... cause my mechanics are useless it appears... Long story so bear with me.. the basic problem that no one can fix is, 90pct of the time the brakes are fine, then the pedal dops about 1.5 to 2 inches before catching. skeers the sheet outta me. Here is my 6 months story

I took my truck in to Mech #1 in July 09 for rear pads and rotors.. then all the problems started. Turns out I needed axle seals as well so I did those too. Guy said the fluid was really dirty so we did a flush too. Got the truck back and had a great pedal for about 10 miles then whoosh.. almost no brakes. Pumped it and they came right back soild and stayed solid for a while.. then did it again. No warning.. just whoosh. this continues to be the problem throughout

Mech #1 is a freind and didnt hose me around on the money at all and tried his best to fix it.. it went like this

Took it back, oh we need to bleed it agian
Not fixed took it back
Oh yer MC must be bad, we replaced it and bled it
Not fixed took it back
Oh it just needs bled again
Not fixed took it back
Hmmm bad MC we will replace it again and credit you
Not fixed took it back
Oh it just needs bled again
Not fixed took it back
Hmmm rarely happens but maybe we got 2 bad MC, bought one from a different supplier.. gotta be fixed now.
Not fixed took it back
Oh it just needs bled again
Not fixed took it back
Wait we found the problem Your ABS pump is bad we replaced it with a used one and now you are all good... (turns out the light in the dash was burnt out so I didnt even know I had ABS for the last 3 years I owned the truck lol)
Not fixed took it back, but I have ABS now..
Oh it just needs bled again
Not fixed had enough of Mech #1.

Took it to a Merlin brake shop I trusted and have used in the past and they screwed me.

Oh you need 2 front calipers, bleeder screws are all jacked up and rounded off we cant get them loose. Ok.. thats BS but the truck has 106K on it.. ok replace them and get the dang air outta the system.
Not fixed took it back
Oh it just needs bled again
Not fixed took it back
You have a bad MC, no I dont I have had 3 new ones problem is EXACTLY the same. Oh we looked at it the rod behind the MC was bent by the other guy, we straightened it out, now it fixed for sure.
Not fixed took it back
Oh it just needs bled again
Not fixed took it back
full system flush and check problem the same...um... take it to Ford we dunno.

I have had it. Other than now having ABS where I had none (which is really cool in the snow BTW), this has been a complete waste of my time and about $1200. have done a ton of research on here and found nothing similar. I would say ABS module but the problem occured BEFORE he replaced the ABS pump and fixed the ABS system... Please help... I am ready to sell the truck. I have still been driving it and just been REALLY careful. No close calls yet but I cant leave it like this. Sorry for the long post but its all questions you would have asked I assume.

Once again the PROBLEM is.. Great brakes 90pct of the time, then the pedal travels before engaging. then its fine for a while and then happens again. From cold start doesnt do it till near the end of my 9 mile drive to work, same place almost every day. Only warning is pedal softens a little first sometimes then the next stop it aint gonna be there unless you pump it. Stop an go traffic no problems. ride a mile or two with not hitting the brake, it may or may not happen. But its not infinately reproducible. Most of the time I dont think the techs drove it long enough to have it happen. Although the Merlin guy finally said it did it on one of his test drives..then he looked at me confused and said take it to Ford... thanks.

SO any thoughts would be appreciated...I am a fairly competant mechanic but dont do ABS systems. I keep feeling its air trapped someplace that they arent getting out of the system but I am prolly wrong. Its been bled manually and with a power bleeder and still the same.

 

Did any of these guys re check the original work done to the rear pads and rotors? disassmble and re check that work.

 

What would you look for? What could be wrong that would cause a failure 10% of the time? I think it has to be getting air somewhere. A line, the MC, or a wheel cylinder.

 

Thanks for the thoughts so far guys..rear brakes are disc and yes the rear calipers were pulled and rechecked. I am on mC #3 so I really cant see it being that. Doesnt seen like a booster problem either... is there a valve somewhere in the system I am missing that could be failing under pressure? Something in the ABS module? As far as i know its been bled at the pump. i ahve considered a bulging line, but where would I start replacing lines.. they all look ok... Have seen posts with guys saying the lines suck and stainless is the only way to fixit.. just seems odd it would start after the brake flush

 

Had an Explorer do about the same thing after replacing a rear caliper. It ended up having air trapped in the abs and the only way we could get it out was to borrow a knock out box from the local Ford dealer that would run the abs while bleading it.

 

just wanted to make sure there was no mechanical malfunction going on with a faulty repair. Since this started with an initial repair that its safe to assume that it is from that repair. Although coisidence seems to happen when least expected.

Could this "pedal loss" feel anything at all like an ABS action? Does this vehicle have 2,3,or 4 channel antilock brakes? The reason I ask is could the ABS sensor in the rear got messed up or even the ones in the front. Just throwing things out here.

 

replaced the flexible rubber lines on the truck yet? They can swell up under pressure and the swelling causes pressure loss to the caliper/wheel cylinder

vacuum line to the brake booster?
brake booster itself?


you should also be able to bleed the ABS on the lines coming out of the ABS pump, outgoing lines to the wheels. Crack the lines same as you would on each corner

 

Thanks fellas keep the ideas coming. I am thinking Blue Screw is onto something. Tim there is no pedal vibration at al like ABS, just a quick smooth drop before engaging. Not sure on the ABS channels, its a '00 standard XLT so prolly 2? Patman the rubber lines are factory, they are a concern to me but dont feel spongy in any spots I can tell . and wouldnt that just cause a spongy pedal all the time? I would think a bad hose or even two wouldnt cause a big drop like that. I dunno.. I keep hoping somebody has had the same problem and knows exactly what it is. I may have to take it to Ford to get bled out to rule out air in the ABS

 

Ok, update for anyone who cares...

After futher review, I am thinking more and more its air in the ABS modulator. With all the work thats been done and haveing work done upstream of the ABS and the ABS pump replaced, I think there is air hiding in there.

I called Merlin this morning and asked if they specifcally bled the ABS system. There answer was it was power bled through the ABS. So that doesnt rule out to me that the ABS was specifically bled correctly.

I called the stealership this morning also.. $150 to bleed the whole system, The service mngr says yes there is a specific procedure for bleeding the ABS modulator and that would be where he would start based on my symptoms.

I am now looking into this "specific procedure" to see if its doable by myself. Doesnt look so. The knockout box that Blue-Screw mentioned was mentioned in this link off of an Explorer website, http://www.explorerforum.com/forums/...ad.php?t=80910 interesting info on these kinda boxes if nothing else. These look really old school, cant I just use a high quality mechanics scanner to cycle the ABS while its being bled? or should I just let Ford do it in shop?

 

Yet another post for those keeping score... found this on another Ford truck site so I didnt post the link but its great info.. might not fix my problem but might help someone else.. ABS Hydrolic Control Unit bleeding procedure...

Here is the actual brake bleeding procedure.

If equipped with the 4 wheel anti-lock brake system and the Hydraulic Control Unit (HCU) has been replaced or is suspected of containing trapped air; bleed the brake system using the procedure below. Conventional brake system bleeding cannot remove the air trapped in the lower portion of the HCU. If a spongy brake pedal is present and air in the hydraulic control unit is suspected, use the following procedure:

1. Bleed the brake system as outlined in the conventional bleeding procedure.
2. Connect a New Generation Star (NGS) tester or equivalent scan tool, to the serial data link connector below the instrument panel as though retrieving codes.
3. Make sure the ignition switch is in the RUN position.
4. Follow the instructions on the NGS screen. Verify correct vehicle and model year go to the "Diagnostic Data Link' menu item, choose ABS Module, choose "Function Tests", and choose "Service Bleed."

5. Bleed the right-front wheel as follows:
---A. Open the caliper bleed screw and pump the brake pedal for 3 seconds. Repeat the procedure again.
---B. When the fluid runs clear, begin the program and continue to pump the brake pedal.
---C. Continue bleeding for approximately 1 to 2 minutes after the program ends and then tighten the bleed screw.
6. Repeat the bleeding procedure to the left-front, left-rear and finally the right-rear wheel.
7. Remove the pressure bleeding device and adjust the brake fluid level.
8. Road test the vehicle and check for proper brake system operation.

 

At work we use a Genysis Scanner to accomplish this. My Grandprix is supposed to be the same way but there is a trick to doing it without the scanner. Not sure about our trucks though. You already know it has not been done right, so my opinion is take it to ford and get a complete system bleed. I know you hate to throw more money at it but you need to completly eliminate air being in the system to contimue troubleshooting if thats not.

 

This is happening to me right now!! So far every caliper has been replaced, ABS pump replaced, Master Cylinder replaced, brake system flushed, brakes bled to death like 500 times! Anyone figured it out yet!

 

Turned out to be a bad brake booster for me. Very uncommon fail but the symptoms fit. I had it replaced and have been fine ever since. Hope that helps.