How to change brake fluid on cars with ABS?

[Titanium_Alloy]

Hi guys,

I'm thinking about changing brake fluid in my 02 Grand Am with 2.2L engine. It has ABS system. I’ve heard that you need a special flushing procedure for ABS brakes. Some tool is hooked up to an ABS unit and is cycled through the flush. I also heard that only dealers have this tool. On the other hand some people say just do a regular flush, then go on the road and activate (i.e. brake hard) ABS function to get the old brake fluid from ABS unit. Second approach seems kind of simplistic and not very scientific. As I understand fluid from reservoir goes into ABS unit directly and then goes into brakes. ABS unit, I assume, works under high pressure and any incorrect flushing might damage it. I also have high doubts about power flushing under external pressure because it might damage valves and some other components in ABS. What's your opinion/experience/knowledge on that? What would be your recommendations?

Regards,

 

[road_rascal]

I've been flushing brake fluid out of my ABS equipped vehicles for years using just a MityVac pump. If you're replacing the master cylinder on an ABS equipped vehicle it is my understanding that you do need special tools to activate the valves to prime the cylinder (does that sound right?). Otherwise it's the same procedure as non-ABS brakes.

 

[ZR2RANDO]

I'm not sure about any diff in the flushing procedure..you're just pushing new fluid through the system. Someone else may give better details on that.
I do know that you need to USE the antilock feature periodically to keep it working though. Get on a dirt road somewhere and drive forward and try to lock up the tires...make sure all the skid marks (or actually the lack of skid marks) is the same...do that a few times. The mechanism needs to pulse the calipers rapidly and I have read that sometimes that mechanism needs some exercise...don't want to test the feature out on the highway behind a big truck for the first time now do we?

 

[Mark in NY]

You can do this without much effort. You just have to assure the master cylinder does not run dry and pump air into the ABS unit. If that happens then it does have to be pressure bled according to a specific procedure.
Otherwise just have a helper pump the brakes as you manually bleed it and you will be fine. Since the fluid down at the front calipers degrades first due to the heat, the first fluid you pump out will be the worst.
Castrol LMA DOT 4 fluid has been my own preference for years.
Capable of withstanding higher temps than the std fluid without degrading and the low moisture activity nature of it helps reduce system corrosion. If you keep cars a long time you can notice an improvment.

 

[n8wvi]

I've only done it one way for years, and it only requires one person (me

). I just open the bleader screws and let 'em drip, making sure to not let the resivoir go empty. When the drips are the color of the fresh fluid, I'm done. Take a bit longer maybe, but very simple.

Dave

 

[Titanium_Alloy]

Thanks guys for advice. It seems like I'll be doing a regular flush without dealer rip-off. Mark, I'm planning to use ATE Blue because you can keep it for 3 years and it still will have a high boiling point. Castrol LMA is my second choice because it's 2 times cheaper than ATE and has very properties compared to other off the shelf products.

Regards,

 

[Ken4]

I've never had problems bleeding brakes on my ABS vehicles. But maybe an older vehicle might bleed easier with the engine started.

 

[labman]

Having replaced the aged, worn rubber parts in the calipers before they caused a problem, I was ready to bleed the brakes on my 92 Grand Am with ABS. I sent my son in for the shop manual. He said "Dad, you have done this before, why do you need to read the book?" I replied, "Not on this car". I would at least lay ahold of a Chiltons, if not a good book before bleeding any newer car with ABS.

That drip bleeding does seem to work. Another time, late one night, I decided to finish the job in the morning. I went out to find all I needed to do was tighten the bleed screw. Just never, never let the reservoir run dry.

Wheel cylinder pistons and more and more of caliper pistons as the pads wear, operate outside of the areas in contact with the bulk of the fluid. They only see the film of whatever was put on them when installed. They are also most exposed to the unfriendly atmosphere. Replacing the brake fluid may not even clean out the bottom of the bore, let along that critical, highly exposed area. Maybe that is a good argument for rebuild over replace. That way I know I have a generous coat of silicone grease between the bore and piston in addition to a fresh, new boot to keep out oxygen and moisture. My 77 LUV still has the original steel pistons in the caliper, despite never having the brake fluid changed.

I am also sure I have fresh, clean brake fluid at the very bottom of the bore, where any pits form. Bleed screws are always at the very top, but inlets may not be at the very bottom. Fluid may run right through leaving old crap at the bottom.

 

[carrera79]

On my ABS SAAB you bleed the front brakes normally. With the rears you leave the screw open and hold down the pedal. The ABS pump does the work.

 

[Kestas]

Labman, I agree that the seal around the piston is the most critical area of the hydraulic system. I'm intrigued. How do you prep the cylinder with silicone grease? This is the first I've heard of anybody doing this. Doesn't the silicone get mixed with the brake fluid or attack the seals?

 

[labman]

I specify silicone grease because it is very inert. It neither swells rubber, or absorbs moisture and oxygen. You can use it on any kind of rubber, even silicone rubber. It wets and lubricates the rubber, but is not absorbed. It also resists water, alcohol, brake fluid, and hydrocarbons. When you are rebuilding brake parts, you put a glob on you finger and rub it on everything, cups, O-rings, bores, pistons, boots, caliper bolts, and especially bleed screws. Caliper pistons are particularly prone to rust and corrode in the area between the O-ring and the boot. Even the best, intact boots let some moisture and air in. A steel piston, coated with brake fluid absorbs them and may rust through the chrome plating. The caliper continues function normally until the piston is pushed back in when new pads are installed. Then it binds in the bore, or causes the O-ring to leak. This is why many brake jobs go bad quickly or cost twice the quoted price. I am not sure calipers need to be rebuilt/replaced with new pads every time, but never should be allowed to go 5 years.

When I worked at a brake shop, we always had a big tube of Sylglide from NAPA. We used it on everything we rebuilt, cylinders, calipers, antique HydroVacs, vacuum brake boosters, HydroBoosts, etc.

 

[vvk]

The procedure depends on the car. Sometimes you need special equipment (BMW comes to mind), sometimes you need to follow a special procedure (old SAAB systems) and on some vehicles there is nothing special -- just follow the common brake fluid procedures. Read your repair manual.

 

[Kestas]

Then that settles it. I'm using silicone grease to butter all my wheel cylinders and calipers next time they're apart. The three cars I drive are 9, 13, and 33 years old. If I can put off caliper work until the brake pads need changing, it would help delay brake work until it's needed.

 

[Titanium_Alloy]

Hi once again guys,

I found this post on Grand AM owners board. This is a post by other member. What do you think about it? Does it seem right or a big BS?

_____________________

How to Bleed the Brakes
As Most of you probably know the Braking system on a vehicle is based on "Hydraulics" (Liquid does not compress) Now of course if you get air in your brakes they will not work right.

How do I know if there is air in my Brake lines?
You will get a very spongy feeling on the brake pedal, remembering that liquid does not compress but air does. So when you are applying the brakes you are compressing the air in the lines.

Doing a "Dry Bleed" on our cars requires a pressure bleeder and OBD 2 Scanner.

If you don’t use an OBD 2 scanner you when you bleed the brakes you will be bleeding the positive side of the ABS System. The first time your ABS Valves open, guess what? More air. So you need a scanner to lock the ABS Valves open for the bleeding process.

Even changing the brake pads will require you to crack the bleeder screw, if done the right way. The reason you have to crack the bleeder screw is because, if you just push the piston back you are pushing the crud that is in the braking system back into the ABS valves. And this might cause an ABS Failure. This rarely happens but it is a possibility.

But to just get some air out of the calipers that might have got sucked in, you will first need 2 people. One to pump the brakes and one to open the bleeder screw. Start by first pumping the brake peddle about 10 time to build pressure, then open the bleeder screw, then once all the fluid/air has come out close the screw. Do not let up on the brake peddle before the screw has been close tightly or else you will suck in more air! The process should be continued until all the air is out and you get a steady stream of fluid coming out. If it is just a simple brake job, one to two times should do.

DONT DO'S!

As I said when DO NOT let up on the brake pedal when the bleeder screw is open you will suck in a lot of air!

If you have high Miles/KM on you car and you have never opened the bleeder screw before be sure not to break it off they tend to seas up after a wile.

If you are cracking the bleeder screw when the caliper is off DO NOT tip it upside down! Once again you will just suck in lots of air.


Vacuum Bleeders
If you only have yourself to bleed the brakes you could try a "Vacuum Bleeder” This tool will literally suck the air and fluid out of the lines. There is no pumping needed. The problem with these is that they tend to suck air from the outside around the threads on the bleeder screw. In my opinion they suck. But there may be better ones than I have use out there.

Hope this helps for all your Brake bleeding needs. It is a fairy simple process. Good luck

______________________________


Regards,

 

[XS650]

quote:

---

Originally posted by Titanium_Alloy:
Hi once again guys,

I found this post on Grand AM owners board. This is a post by other member. What do you think about it? Does it seem right or a big BS?

Regards,

---

Makes sense. It's resonably close to what my 96 Corvette manual says. The manual instructions more complex and involve some special equipment.

 

[Titanium_Alloy]

I'm kind of worried about the whole procedure involving OBD 2 scanner. It seems like the only place to do a proper brake bleeding would be at GM dealer. On the other hand I don't even know if dealer's techs use proper bleeding procedure.

 

[XS650]

quote:

---

Originally posted by Titanium_Alloy:
I'm kind of worried about the whole procedure involving OBD 2 scanner.

---

I don't think there's much to worry about unless you have air in the ABS device.

I got my 96 Chevy last November. I doubt the fluid had ever been changed. I did a thorough flush job on the glop in the system using the pump the brake pedal techinque. Then drove the car a week including a few intentional ABS braking applications and repeated the flush.

Despite starting out with real cruddy looking fluid, what came out during the second flush was only slightly discolored. The pedal is also rock hard now, although the steel braded lines probably helped a bit. It's one of the firmest brake pedals I have had in any car. Not doing an OBD II bleed on the ABS didn't seem to hinder anything in my case.

BTW, when you think your pedal feels good, let the car sit overnight without moving it, but tap the wheel cylinders with a screwdriver handle a few times do help any microscopic bubbles migrate up. Then do a quick rebleed. It seems to give a bit firmer pedal. It just takes a few squirts because you are only getting some new small bubbles out the the wheel cycinder that are already near the bleed valve.

 

[Russ]

quote:

---

Originally posted by Titanium_Alloy:
I'm kind of worried about the whole procedure involving OBD 2 scanner. It seems like the only place to do a proper brake bleeding would be at GM dealer. On the other hand I don't even know if dealer's techs use proper bleeding procedure.

---

When I was in the business, the only thing we ever did was bleed the brakes using the standard procedure, and then bleed the ABS unint using the scan tool (all that means, is that the unit is cycled - an equivalent of a harsh stop with the activation of the ABS system), and another round of "regular" bleeding. I never had any problems with this method, and never heard of any. So unless the manual calls for some kind of exotic procedure, I would follow the advice found in this thread.

 

[slalom44]

There are a few other methods to bleed your brakes:

Install Speed Bleeders. They're one-way check valves that allow you to pump the brakes and let you flush your brake lines by yourself.

Put a plastic tube over the bleed screw, and put it into a cup with a little brake fluid on the bottom. When you pump the brakes, the tube fills up with brake fluid and since there's no air to suck in, you can bleed the brakes by yourself. When done, just tighten the bleed screw and you're done.

A third way: Remove the cap on your reservoir and clamp some type of cover with a hose attached to an air compressor. Have only a few PSI of pressure in the air compressor tank. Make sure you don't get any dust in your reservoir when you do this. Then you can loosen each bleed screw one at a time and watch the brake fluid come out. Tighten the bleed screw and you're done.

 

[FowVay]

I bought a Motive power bleeder several years ago and it is the way to go. You thread the cap onto the fluid reservoir, you pump up 10 - 15 psi (or whatever is allowed by the manufacturer of the vehicle) on the canister, and you let it push the fluid through the system. It makes brake fluid replacement a breeze. It eliminates the need to do a bench bleed on a newly installed master cylinder and it seems to eliminate all traces of air in the system. It is actually made to fill with brake fluid so that your system won't run dry but I've never felt the need to dump a quart of brake fluid into the container. I just keep my eye on the reservoir and top-off the reservoir after each wheel is done.

It's been one of the best tools I've bought.