99 Brake job caliper bleeding question

I will probably do my brakes this weekend. I just have a question on pushing the caliper pistons back in with a C-clamp. There seems to be an issue as to whether I should open up the bleeder valve or not when I compress the piston. I did a search on this and everyone seems to have mixed opinions. Some say you should open the bleeder valve to prevent the dirty brake fluid being pushed back into the caliper and possibly the ABS. Some say it's not necessary risking getting air in the line and not opening up the system. I don't think Ford even mentions opening up the bleeder in their procedure manual. Jusy wondering what everyone else thinks. Has anyone had problems by not bleeding? If I do need to bleed, can I use the one-man vacuum brake bleeder they sell in Auto parts stores? Thanks.

Reply to
Mikepier
Loading thread data ...

IMO, it probably isn't necessary for the reason given, but I'd do it simply because the most contaminated fluid in the system is right there in the calipers and wheel cyls. Why leave it in there? I'm a big fan of changing brake fluid whenever I have to do brakes, but just clearing the contamination from the calipers is better than nothing, and you should be able to do it without getting air in the system. H

Reply to
Hairy

I just compressed the caliper pistons like normal and have had no problems. If I'm not mistaken you need a special tool to properly bleed anti-lock brakes.

HTH Steve

Reply to
sehaare

anti-lock

I know about the special tool for the ABS, but I thought that was only if the ABS ran dry or if the ABS was changed. I thought as long as you keep the master cylinder full and you don't run it dry, you can do bleeding as you would on any car. The Chiltons book I have mentions the tool, but does not mention to use it if you are bleeding brakes at the caliper.

Reply to
Mikepier

Special tools for ABS? The ABS system has nothing to do with changing the pads. The ABS is all controlled close to the master cylinder. The only thing that has to do with ABS at the calipers is the plastice "notched" wheel and the sensor itself. Unless you are doing a major break overhaul then messing around with these items is crazy. If you ask me of course. I have ABS and I change the pads myself pull the rotors and turn them if necessary and I have yet to have any problems nor have I ever bled the calipers when returning the piston to reset position. You do have to make sure that you open the master cylinder reservoir before pushing the fluid back through the system.

Searcher1

Reply to
Searcher

The brake fluid should be changed at regular intervals..... it is hygroscopic and will readily absorb moisture from the air and other sources. The moisture in the fluid can indeed affect the integrity of the metal lines, the calipers and the wheel cylinders. Aditionally, the moisture content reduces the boiling point of the brake fluid exponentially. When retracting the caliper pistons is an ideal time to change out a good deal of old fluid.

Resist the urge to use that old, open container of brake fluid that's been on the garage shelf for umpteen years. I usually recommend that DIYers buy several small containers of brake flluid rather than one large container. Discard any containers with broken seals, saving only those containers that are unopened.

The tone ring (notched wheel in technospeak) is usually made of ductile iron due to this materials magnetic properties. A bias voltage is applied to the wheel speed sensor circuit turning the speed sensor into a tiny electromagnet. As the poles of the tone ring pass the sensor, the magnetic field is disturbed changing the reluctance of the sensor..... the PCM reads these disturbances as a frequency.

One should always try to gain knowledge on those systems being repaired or serviced. Should the brake hydraulic system be breached in such a way as to allow air into the HCU, a capable scan tool will be needed in order to purge the control unit.

To minimize the mess when retracting the calipers, a length of vacuum tubing or even aquarium tubing can be installed over the bleeder screw with the other end inserted into a clean container (I use a high-tech plastic pop bottle) with a small amount of fresh brake fluid - enough to cover the end of the hose. This will minimize the possibility of air getting back into the caliper.

Remember.... stopping our cars is likely the single most important thing we can do with them. We always have one more chance to start them - I've never seen anyone get a second chance to stop soon enough.

HTH

Reply to
Jim Warman

Jim,

I value your advice greatly and have a few fairly > The brake fluid should be changed at regular intervals..... it is

I have often heard this theory before, but fail to see how the moisture absorbed by the fluid will cause corrosion inside the sealed brake line. In fact this is supposed to be one of the main reasons to avoid the DOT 5 silicone oil. That stuff will not absorb the moisture so it will remain water in the lines which will boil even earlier and cause even more corrosion.

Also, If there is no air (oxygen) will the parts corrode (oxidize)?

This is certainly true, but for those not interested in performance driving (racing, etc.), at what water content does the boiling point become low enough to be significant to the average Joe?

Don't get me wrong, I am a proponent of flushing brake systems at regular (2-3 year) intervals. I just know that there are many, many cars on the road that have *never* flushed the brake fluid and they seem to get by OK.

If this were an important safety item, you would think there would be some sort of a check for fluyid age or moisture content when doing the annual government mandated safety inspections.

True.

This is another piece of advice that I often see repeated, especially in shop manuals and such. But I wonder how many of us really leave "open" containers of brake fluid around? I would be too fraid that the container might spill. That stuff is no good to get on your cars' paint.

If they do really mean that the container cannot be opened once (seal broken), used, and then resealed tightly and stored, then I do not understand the merit of this advice, other than perhaps to sell more new containers of brake fluid. Surely a container that has the cap screwed on tightly is just as impervious to hygroscopically absorbing moisture as one sealed at the factory? The small volume of air allowed in the container upon resealing, even at high relative humidity conditions, would be insignificant.

Just doing a little "thinking out loud" here. Not trying to be a smart@$$ at all. Enquiring minds, and all that...

-Fred W

Reply to
Fred W

Hi, Fred..... I'll try to give some insight into the reasoning...

Even though the water is emulsified in the fluid, it can still do it's dirty work..... years of witnessing rusty wheel cylinders and calliper bores (and the odd perforated brake line) attest to that. AFAIK, DOT5 isn't hygroscopic and one of it's major downfalls is that it doesn't bleed easily.... once fine air bubbles become entrained in the fluid the resist coalescing and coming out (these bubbles are formed by simply pouring the product).

The minimum spec boiling point for dry DOT3 is 401 deg F. Most brand name fluids exceed this spec but not by a great deal, IMHO. The heat load imposed during a good downhill coast or stop and go driving can raise the fluid temperature significantly, reducing the available buffer zone for panic manoeuvres. As little as 6% moisture content can reduce the boiling point of the fluid to about 260 F. A dragging brake can really through a wrench into the works.

Racers get real familiar with brake fade quite often but brake fade isn't just a concern for racers. It can and does happen on the street and it is a condition that we have a means to avoid or at least reduce - changing fluid. Most of us will find a need to service our brakes at roughly the same time that a fluid exchange would be a wise service - making opening the bleeder when retracting calipers an easy way to start the process.

As far as storing fluid is concerned..... a refractometer can be used to measure water content but low water concentrations can turn the task into guesswork. When it comes to such an important system as the brakes, I can't see saving a buck or two as being worth the gamble....... not to me, not to my customers and not to my family. The foil cap under the brake fluid lid is hermetically sealed.... the same can't be said of the little cardboard or plastic disc taking it's place. Let's not forget that temperature variations of the container may have it "breathing" quite regularly.

The question isn't whether we can or can't use fluid from an open container - it is a question of whether we SHOULD or not. I'm in a position where I cannot and will not take that chance. The liability concerns alone are enough to weaken the knees.

It remains a question of safety and fresh fluid from a sealed container is about the safest thing we have when it comes to brake fluid...

Reply to
Jim Warman

The official Ford recommendation on changing brake fluid is that it's not needed other then what is done during normal pad/shoe/brake service. Ford based their recommendation on studies that showed moisture content in brake systems rises to about 3% fairly quickly and then stabilizes. Changing the fluid just provides new fluid to fairly quickly absorb it's 3%.

I agree with your thoughts >Jim,

-- Elbridge Gerry, of Massachusetts:

"What, sir, is the use of militia? It is to prevent the establishment of a standing army, the bane of liberty. . . Whenever Government means to invade the rights and liberties of the people, they always attempt to destroy the militia, in order to raise a standing army upon its ruins." -- Debate, U.S. House of Representatives, August 17, 1789

Reply to
AZGuy

MotorsForum website is not affiliated with any of the manufacturers or service providers discussed here. All logos and trade names are the property of their respective owners.