91 Cont. Brakes slow to release (updated)

[My Money Pit]

Update, slow brake release problem solved. I have included the orginal post below for reference for others with similar problems.

I replaced both rear wheel ABS sensors as they were rusted away completely hoping this would solve the problem but it didn't. The problem was resolved by replacing the Hydraulic Control Unit which consited of the pump, motor, and valve body as a remanufactured unit. I purchased the unit from the Car Quest Auto Parts chain for a reasonable price of $360.00 and installed it myself. Brakes now release within approx. 4 seconds. Total cost of repairs since problem was first encountered comes to just under $1000.00 which is 400-800 less than what Ford quoted me origninally for the HCU only. I hope this information will be usefull to someone with similar brake problems.

(Original Post)
About a month after replacing all four brake calipers and rotors I noticed it felt like the brakes were dragging. Within another week one of the rear calipers had frozen and welded itself to the rotor. Luckily, my local parts store provided new rear calipers and a rotor under warranty. While installing the new calipers and immediatetly after bleeding, I can not rotate the wheel even with two hands and my full body weight. If I wait 30 seconds I can just barely turn it, and if I wait 60 seconds I can turn the wheel freely with one finger! Touch the brake pedal and the process starts over again. This happens on both rear calipers. The front calipers are also tight but not nearly as tight as the rears. The car now sits in my garage. I have recently replaced the leaking Master Cylinder hoping it would solve the slow release problem, but it had no affect. The brake warning light and ABS light seem to be functioning normally. When I described this problem to Lincoln they immediately said I need a new Hydraulic Control Module....$1400 to $1600 repair.....Ouch!

[Bluegrass]

Thanks for the report and the source of the replacment part. I am curious about you brake release time of 4 seconds or do I missunderstand? The release should be complete and imediate or I would think the ABS function could not work by quickly modulating the calipers in a slick surface traction condition.

[My Money Pit]

After bleeding the 4 calipers and test driving for 15-20 minutes I decided to check for release time again. I jacked up the right rear and had someone apply the brakes (with engine running). As soon as they released the brake pedal I was able to rotate the wheel with two hands, and after 3 or 4 seconds (1 rev of the wheel) I was able to rotate it with one hand. There still seems to be a slight drag, but it feels normal to me (like any other brake job).

During assembly with the caliper piston completely retracted, the brake pads had plenty of clearance on both sides of the rotor. I don't think the calipers are supposed to retract to a position that provides clearance on both sides of the rotor during normal braking/release, or should they? My experience with disc brakes of all types still seem to ruba little bit after release. I have always assumed this to be normal and have never had any problems caused by this in the past. Should I be thinking differently about this condition?

[Bluegrass]

Sound ok to me. I was just cocerned about them draging hard. Yes, they will contact the rotors normally at rest. Any sleight disc wobble or change as they rotate will cause the pads to back off enough not to drag. Your still in the breakin peroid so they will drag a little till the surfaces settle in. Don't heat them up to quick or a glaze can take place.

[My Money Pit]

Slow release problem is back again. I can smell the burning brake pads. 4 seconds right rear, and 10 seconds left rear. Decided to replace flexible brake hoses for the heck of it. Air flows freely through new hoses. Old hoses were blocked. Cut away 1 inch segments and found it blocked near the "crimped on" mounting bracket near center of hose. Won't even pass 120 PSI shop air! Didn't have time to bleed brakes today. I'll post results in a day or two.

[My Money Pit]

Well, finished replacing rear brake hoses and bleeding all 4 calipers. WOW, what a difference, when bleeding the rears I got three or four times as much volume of fluid out of the bleed screws than before. Rear brakes are no longer dragging.

Note to Bluegrass: Brake release is now definetly "immediate"......no more two or three seconds or 1 or 2 revs of the wheel. I mean release the brake pedal and the calipers are free with no hesitation at all. :D

Going to replace the front hoses too, just for the heck of it.

[Bluegrass]

Great to here. I had a car once that exhibited the same kind of fault except it was in the front and would cause the car to randomly pull either way. The front hoses develped a leak between the inside and the outside layer and balloned up. This would keep the pads hard against the discs without appling the brake. The uneven pressure would apply different amounts of pressure to each side, so you never knew what would happen next. I'm sorry that you replaced the master complex and the cost involved. Some times we all take the long way home. ;)

[My Money Pit]

Originally posted by Bluegrass
quote:The rear brakes are supposed to auto adjust by application of the emergency brake, to compensate for wear. There is a special assembly internal to the brake lever that allows an adjustment to reset it's position and move the inner pad closer to the rotors without locking up. This is the area, when replacing the pads, that requires the piston to be retracted in order to get the new pads to fit on over the rotor because the piston has adjusted its self inward as the old pads wore thinner. When setting pad clearence, this is where the special tool in used to turn the piston back in, then test fit the new pads for the reqired clearence.

During my "slow to release" problem I dis-connected the parking brake cables from the calipers and haven't re-attached them yet. In regards to the self adjustment feature, is there any harm in leaving them dis-connected for awhile longer? I have a broken vacum line labeled B/R under the hood and I think it is for the Parking Brake Release but I'm not sure. I was planning on fixing the vacum hose before I tried re-connecting the cables.