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Do you have some documentation to back this up? Not to put you on the spot here, but I'm just curios about where you heard this. If there is a TSB I would like to see it.
Actually there is a great amount of fluid movement when you push pistons back in. Worse yet, sediment, that tend to build up in the large caliper bores can get pushed back through the system and lodge into the small dump valve orifices. This so concerns most manufacture that screens are placed in most ABS unit inlets and outlets to prevent contamination.
Maybe this has Ford confident that this can't happen, this is why I ask. But what happened if you plug up a screen? You could probably clean it out but not till after your remove the ABS unit.
I would say, to be on the safe side you are better off pushing the fluid out of the bleeder. If you plain of flush with fresh fluid after installing your new pads, why push that old fluid back through the system.
Mike
BRAKE FLUID-- Ford does not recommend changing DOT 3 fluid or flushing the system. Ford says their recommendation is a "risk versus benefit" assessment because there's a potential for doing more damage than good. If sediment or contamination from the master cylinder is pushed through the ABS unit, it can cause big problems. Flushing the system also increases the risk of air entrapment and leaks, says Ford.
Ford says their brake systems are engineered to tolerate brake fluid contamination of up to 3 percent moisture without fluid boil (which is close to the saturation point for DOT 3 brake fluid). If the fluid has more moisture, it probably has some liquid water in it and should be changed.
Ford said they measured the water content in 7 to 10 year old Ford vehicles and found that the water content was actually quite low: only 1 to 1-1/2 percent. So based on their findings and the design target of 3 percent water, they see no need to change the fluid for preventive maintenance.
Does pushing the caliper pistons in when changing the pads push contaminants from the calipers back toward the ABS unit or master cylinder? Ford says no. There's not enough movement or migration to cause a problem.
BRAKE FLUID-- Ford does not recommend changing DOT 3 fluid or flushing the system. Ford says their recommendation is a "risk versus benefit" assessment because there's a potential for doing more damage than good. If sediment or contamination from the master cylinder is pushed through the ABS unit, it can cause big problems. Flushing the system also increases the risk of air entrapment and leaks, says Ford.
Ford says their brake systems are engineered to tolerate brake fluid contamination of up to 3 percent moisture without fluid boil (which is close to the saturation point for DOT 3 brake fluid). If the fluid has more moisture, it probably has some liquid water in it and should be changed.
Ford said they measured the water content in 7 to 10 year old Ford vehicles and found that the water content was actually quite low: only 1 to 1-1/2 percent. So based on their findings and the design target of 3 percent water, they see no need to change the fluid for preventive maintenance.
Does pushing the caliper pistons in when changing the pads push contaminants from the calipers back toward the ABS unit or master cylinder? Ford says no. There's not enough movement or migration to cause a problem.
Interesting that a company that in my experience has had some of the worse problems with internal system corrosion would say this, but I can't say it surprises me. Your article here is old, 2001 but all through the '90's I saw problem with Ford verticals, like seized up calipers, bad dump valve, rusted up wheels cylinders, and fluid warning lights stuck on, all with the nastiest blackest brake fluid you ever seen. But this is Ford and maybe why we all own Toyotas.
But I will also give you and Ford this, I have never seen a ABS unit damaged from the fluid being pushed back to the master. But the warnings make sense, it is posible and why take a chance. It's just as easy to push the fluid out the bleeder.
And then there is more resent findings about brake fluid: Industry Adopts Brake Fluid Replacement Guidelines, Bill Williams, Brake & Front End, May, 2004
Since Ford made these statements it has been found that copper contamination is more of a reason to change your fluid then moister contamination. Still most manufactures do not give fluid change intervals. (Take a good look at the pictures of internal corrosion)
From someone who has opened up hundreds if not thousands of brake system in his life, I can tell you it's a good idea to change your brake fluid at lest when you replace brakes pads.
Mike
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"That the automobile has practically reached the limit of its development is suggested by the fact that during the past year no improvements of a radical nature have been introduced." (Scientific American January 2, 1909). Moderator Brake Forum
I don't doubt Ford's claim on their brake system tolerance. All Econolines I've seen will turn brake fluid dark in < 20K. Many will run fine with no brake flush at 100K.
Maybe it's the area I'm in, Ohio river valley. But Fords here have tremendous brake issues. Keeps the brake shops busy. Some model may have improved in the past 7 years, but friends with Ford trucks still see problems like internal system corrosion and slide pins seizing up (common on Super Duties).
Also rotors rusting over is a big problem here. I just resurfaced two rotors on a Mazda Protegra (shares brakes with Fords Escort) this weekend. A daily driver but the rotors where 70% covered over with rust and was pulsating badly.
Mike
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"That the automobile has practically reached the limit of its development is suggested by the fact that during the past year no improvements of a radical nature have been introduced." (Scientific American January 2, 1909). Moderator Brake Forum
It's a definite no-no to reset the caliper pistons without cracking the bleeders open. Yes, most ABS units have screens, but the moisture that tends to accumulate in the caliper's piston bores will corrode the internals due to the DOT3 brake fluid's hygroscopic properties. Vacuum bleeding the old fluid is cheap insurance against brake system problems.
If your not cutting the rotors, it's a good idea to at least check the rotors for uneven wear and run-out and then, if it's all ok, rough up the rotor surface with some 120 grit sandpaper. This will enable the pads to seat quickly and give you better initial braking performance.
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2007 Tundra 5.7 4x2 RCSB slate metallic
2005 Corolla - all stock, cause it's the wifes
1986 Mustang GT - the stereo is under the hood
1990 Corolla - cause it was really cheap
It's a definite no-no to reset the caliper pistons without cracking the bleeders open. Yes, most ABS units have screens, but the moisture that tends to accumulate in the caliper's piston bores will corrode the internals due to the DOT3 brake fluid's hygroscopic properties. Vacuum bleeding the old fluid is cheap insurance against brake system problems.
If your not cutting the rotors, it's a good idea to at least check the rotors for uneven wear and run-out and then, if it's all ok, rough up the rotor surface with some 120 grit sandpaper. This will enable the pads to seat quickly and give you better initial braking performance.
None of the OEMs feel that it is necessary to open the bleeder when retracting the caliper piston. When Ford was asked this question during the Big 3 Brake Symposium in 2001, they stated that there isn't enough fluid movement in the system for any problems to occur.
For modern day brake pads, smoother is better. OEMs generally want the surface finish to be under 100 microinches. 150 grit sandpaper is a good way to improve the finish quality after resurfacing the rotor on the lathe. IMO, if the runout and thickness variation are not close to perfect, I'd resurface or replace the rotor.
I like the logic on the fluid feedback and possible contamination.
Would just loosen the bleeder screw while pressing the pads back not allow the fluid to flow out the bleeder instead of back up the line?
Path of least resistance.
Just a side note.
Rear brake drum removal for service / inspection.
Located a pair of threaded (possibly metric) holes near the center.
This allowed you to screw in a matching bolt applying pressure to the axle plate, which forced the drum out.
As I have stated I have never seen an ABS unit directly damaged by pushing in the piston of a caliper, but I have seen master cylinders fail. I have seen sediment pushed into compensator ports and lodged under seals causing internal leaks. It was also very common for Ford Rangers to set a code on the rear ABS dump valve (old Ranger had rear only ABS) The code was for a stuck dump valve that would not return home due to crud in the brake fluid. I've seen many combination valve failures due to grit in the fluid sticking the valves.
And consider this. On Toyota vehicle (and now most) if you never add fluid the life of your brake pads you will usually find that the brake light comes on about the time the pads are worn out. This means your brake fluid reservoir is at the low line. Now if you simple push in the pistons and install new pad you will find it's back at full. This means you are pushing all this fluid (the amounts can vary from vehicle to vehicle) back through the system into the master cylinder and through the tiny compensator port. I would consider this a substantial amount of fluid to push through the system.
I know your just quoting what a manufacture stated, but I don't buy it. It's risky business. This (and many) manufacture is known for little support after the warranty expires, so what would they care if you damage an ABS unit during a brake service. Their concern is the extra cost of labor or brake fluid changes that may happen under warranty.
Better to leave sleeping dogs lay (or in this case crud) or at lest flush it out.
Mike E
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"That the automobile has practically reached the limit of its development is suggested by the fact that during the past year no improvements of a radical nature have been introduced." (Scientific American January 2, 1909). Moderator Brake Forum
Re: Autozone brake pads
Linear Mode
