bleeding brakes

[f3cbboy]

just bought one of those reverse bleeding kits for my kawi and was thinking about using it for my ford. i was always told when putting the caliper with the new pads back in place, to open the bleeder and push the pistons back into the caliper with the bleeder open as to not push fluid back into the master cylinder being that the orings in the MC are seated in one direction.

I just did the brakes on the ford and was going to maybe use a reverse method to bleed in that it does make sense - to push air up in the direction that it wants to naturally go. but i will wait and see if someone with more knowledge about this can let me know.

thanks

 

[quads]

Never open the brake bleeders unless you are bleeding air from the brake system. There is no reason to open the bleeders when installing new brake pads. Push the caliper pistons in and put the new pads on. The fluid will go up into the master cylinder reservoir and will not harm the master cylinder. The master cylinder piston won't even move when you do that. Wouldn't matter anyway, as the master cylinder piston is supposed to move both ways - push it with your foot and it goes in - let your foot off the pedal and the wheel cylinders push it back out.

 

[f3cbboy]

thanks for the help quads - i appreciate you replying. sometimes with new pads being thick and the wheel cylinders being pushed all the way of you cant get the caliper and new pads over the rotor. but now it makes sense that i could just push the fluid back into the MC. that is the normal fow half of the time. thanks

 

[SlyFerret]

After you change the pads, make sure you pump the brake pedal a few times to get the pads back into their normal position. I forgot to do that about 6 weeks ago when I changed the pads on our cavalier. I backed out of the garage, pressed the bake pedal, it went to the floor, and I backed into a small tree in the front yard. Luckily it didn't ruin the tree... but it did crack the fiberglass spoiler on the trunk of the car. Not bad, but I know it's there.

I felt pretty stupid... so save yourself the embarrassment!!

-SF

 

[WES999]

You can use a large C clamp to push the caliper pistons back into the caliper. Make sure the reservoir does not overflow.

For bleeding/flushing I bought a pressure bleeder, you attach it to the fluid reservoir and pump it up.
Works better than anything else I have used.

 

[dave11]

What a coincidence this was just discussed on another post here. I'll cut and paste what I said there:

For completeness, let me say that, anytime you compress the brake pistons with a C-clamp, you should open the bleeder screw, and let the fluid be expelled. This keeps the dirty, overheated brake fluid which has been sitting in the caliper out of the system, instead of forcing it to mix with the relatively better-preserved brake fluid elsewhere in the lines. If you do it right, you won’t need to bleed the lines at all.

The system is under pressure, even if just the pressure of the weight of the fluid in the cylinder, and unless you depress and release the pedal while bleeder screw is open, you won't introduce air into the lines, and you won't need to bleed.

 

[Highbeam]

I agree with quad. Get yourself a big C-clamp and compress the piston back into the caliper without opening any bleeders. Don't confuse your projects, there is changing the pads and then there is flushing the fluid.

To swap pads you leave the old pad in place while you compress the piston. This prevents you from damaging the piston face or from putting a side load on the piston. In a pinch I've actually used channel locks pliers. Make sure you put the metal side of the new pad against the piston.

To flush the fluid I use a mity-vac suction device to suck the new brake fluid through the lines. This is scheduled maintenance every two years according to the owner's manual of most vehicles but I admit seldom done. It is amaxing how nasty the old fluid gets in the system.

 

[homebrewz]

I have heard that pushing in caliper pistons with the bleeder closed can potentially damage anti-lock sensors.
Just something you might want to check out. Also, if doing rear pads, some Fords use ratcheted calipers which
screw back in with a special tool. My '99 Taurus was like that. Pushing them straight in will damage them.

 

[f3cbboy]

thats what i was saying as far as pushing the fluid back into the MC. push caliper cylinders back in with a c-clamp channel lock anything you can squeeze the piston with. I was a little unclear with this though, I want to flush the caliper and that leg of the break system (from MC to caliper on that corner of the car) untill i see nice clean fluid. my original question is does anyone "reverse bleed" a car. I have done it on motorcycles, I dont want ot ruin anything in my truck. The reverse bleeder gun is like a gravity fed pint sprayer with a hose that connect to the.. never mind this doesn't accomplish what i want as far as replacing the fuid. Sorry my bad.

 

[mayhem]

Also, if doing rear pads, some Fords use ratcheted calipers which
screw back in with a special tool. My '99 Taurus was like that. Pushing them straight in will damage them.

Very true. Alot of cars do this on the rear brakes. Found out my 94 SHO was like this when the dealer told me I needed new calipers because they were seized up so bad they couldn't get them to go in...they weren't turning them when they tried to push them in.

It was a Froda dealer too...they really should have known better. Saved myself $1100 by doing it myself.

 

[Highbeam]

Mitsubishi eclipse is like that too. Silly design that you need to twist the piston. The large majority of calipers are not like that and the ones that are I believe are only on the rear as it is part of the mechanical parking brake system.

As for the "reverse" bleeding well the mity-vac vacuum bleeder is sort of like a paint gun and sucks brake fluid through the system to include the caliper. I have used this method with great success on several modern vehicles. It is amazing how nasty the old brake fluid is.

 

[Gooserider]

Not sure what the incoherent post above was about, but you don't want water ANYWHERE near the brake system innards.. There are two problems w/ brake fluid and water, both bad...

Brake fluid is hygroscopic - it absorbs moisture, including water vapor from the air... This is why they tell you to only use fluid from a sealed container, and why your brake system itself is sealed up w/ rubber gaskets on the lid and so forth...

1. Pure brake fluid has a very high boiling point, the exact number depends on the DOT grade number - when it absorbs water the boiling point lowers, DRASTICALLY... This can cause the fluid to boil under hard extended braking - such as descending a steep hill or towing a trailer in heavy traffic... When the fluid boils it turns into vapor, which is compressible, this makes your brakes go mushy, and then fail altogether until they cool down...

2. Clean brake fluid is an oil, and while it will attack paint, it is harmless to brake system components, and even acts as a preservative coating. When it absorbs water, it becomes mildly corrosive, and will attack the insides of metal brake lines, and more importantly, the sealing surfaces of brake pistons and cylinders... It is likely that if you bleed the brakes on a regular basis you will never have to replace a caliper or brake cylinder. If you don't, you have good odds of needing new calipers every brake job or so...

Gooserider

 

[John_M]

Gooserider's description above is an accurate and excellent introduction to "Brake Fluid 101". Allow me to add just a little more info. for those who like to experiment: DOT 3 and DOT 4 brake fluids have a glycol chemical base and can be mixed in the same system without damage. When water is absorbed by the DOT 3 and 4 fluids it tends to distribute itself evenly throughout the fluid. DOT 4 fluid is just a little less hygroscopic than DOT 3 and may have a very slightly higher boiling point.

You will also find DOT 5 and other brake fluids on the shelves of NAPA, Advance Auto and other supply stores. DOT 5 fluid has a silicone chemical base and is definitely NOT compatible with DOT 3 and DOT 4 fluids. DOT 5 fluid is not hygroscopic but moisture will still enter the system through the air, flexible brake lines etc. This moisture is not absorbed by the DOT 5 fluid but will tend to "pool up" and settle in the lowest parts of the brake lines. This small pool of water will tend to rust the lines from the inside.

Once a system has been filled with DOT 3 or 4 fluid those fluids must be continually used in that system. The same is true of DOT 5 fluid. If DOT 5 fluid is introduced into a system or comes into contact with rubber components which have been exposed to DOT 3 or 4 fluids, the chemical incompatability of the two chemical bases will cause all rubber components to eventually harden and fail. This may happen in a couple of months or a couple of years but it will happen. If you are currently using DOT 3 or 4 fluids in a hydraulic system, continue to use that same fluid. If using DOT 5, continue to use that same fluid in that system. DOT 5 fluid is used mostly in military, racing and other very high heat applications where brake fluid is changed on a regular basis.

Google "brake fluid" and you will find lots of helpful and informative sites.

John_M

 

[f3cbboy]

incoherent post above is about when i was in the middle of the write up i realized that i was talking about replacing the brake fluid not bleeding the brakes...

i am relativley new to forums and sometimes it is hard to get a point across for me in writing.

 

[granpajohn]

^I'd be willing to bet that the "incoherent" one was Pook, er..cycloptic pendulum.
He has his own private language. Well loved by all, but a bit difficult to get used to.

 

[Gooserider]

^I'd be willing to bet that the "incoherent" one was Pook, er..cycloptic pendulum.
He has his own private language. Well loved by all, but a bit difficult to get used to.

Bingo....

Gooserider

 

[RustyShackleford]

Check out www.speedbleeder.com ...

 

[Hogwildz]

Luckily, I never had the screw in type calipers.
I always used a big C clamp and one of the old pads taken off against the piston(s) surface compress, pull old pad off put new ones in, reinstall caliper, done. Never had any problems doing it that way.
And yes, pump the pedal a few times while done, I have had the scare of forgetting to let the pressure build up, but luckily, never hit anything.