Brake trouble

[sparkydave]

I did the 60,000 mile service on our '05 Legacy this weekend, including changing the brake fluid. No problem, I've changed brake fluid before on ABS equipped cars, and overhauled all the hydraulics on my collector car, so I'm familiar with working on them. I sucked out the fluid in the reservoir, refilled it with Valvoline Synpower DOT 4 fluid, then had my wife push and hold the brake while I opened the bleeder on each wheel, then closed off the bleeder and had her release the pedal. I had a piece of tubing on the bleeder and let enough fluid out until I got new fluid coming out of them. Probably went through a dozen cycles on each wheel before I got clean stuff out, but the reservoir always had plenty of fluid and was never in danger of getting low. Followed the order given in the Haynes book (RR, LR, RF, LF). In all, took about a pint of fluid to change it.

 

Here's the disconcerting thing: The pedal feels softer. Not to the point of being dangerous or hard to drive, but it does seem to take a little more travel to stop. I thought it felt a little soft when I test drove it, but I figured I was used to my car and didn't drive this one often enough. I didn't think much of it until my wife said the pedal feels soft to her. I can't imagine how any air would have gotten in, since the reservoir always had plenty of fluid in it, and the the tubing was full of fluid at all times.

 

Could it be that there's still some old fluid that isn't getting along with the new stuff? It says it's compatible with DOT 3, and DOT 3 and 4 should be able to mix. Any other thoughts? I guess the next step would be to bleed again and see if it's any better, or maybe even go back to DOT 3, but having the pedal feel different isn't very encouraging.

[Rooster2]

I don't think it is any brake fluid compatibility problem. The difference between Dot 3 and Dot 4, is that Dot 4 has a higher boiling point, and therefore has a higher performance capability.

 

It sounds unlikely that you introduced air into the brake lines while bleeding, but you may have accidentaly done so. Suggest you do a quick rebleed, paying attention to any bubbles you might see in the clear tubing as the fluid is bled off. If you bleed off any bubbles, then you have solved your problem.

 

BTW, I use a "one man bleeder kit." It is pretty slick, and used properly, will not allow air to back flow through the bleeder valve.

 

Hope you get her fixed.

[porcupine73]

Followed the order given in the Haynes book (RR, LR, RF, LF).

No that's not the right bleed order for Subaru. Haynes manual is wrong. That is the bleed order for many domestic vehicle makers but not Subaru.

 

 

Here's an article about bleeding Subaru brakes: http://endwrench.com/images/pdfs/BrakeFluidSumm02.pdf

[sparkydave]

Thanks Porcupine, looks like Haynes was a big help (NOT) in this case. Guess they got it wrong for Subaru. Thanks for the article. Is there a better description of the "Sequence Control"? The steps in that are confusing at best. For example, I understand connecting terminals 3(K) and 6 (L), but it says "set speed at 2 MPH or less" (stop the car??), and "within 0.5 seconds after ABS warning lamp goes out, immediately after ignition is turned to on, depress brake pedal and hold" Note: when ignition switch is set to on, the brake pedal must not be depressed (isn't that what the step just said to do??). Then it goes on to say the "sequence control" is complete when L terminal is separated from ground and K terminal is separated from ground. Say what?

[sparkydave]

Never mind, I found a translation that's much more descriptive. Thanks a bunch!

[brus brother]

I run the tubing into a small bottle with brake fluid in it so there is no chance of sucking back any air.

[Rooster2]

I run the tubing into a small bottle with brake fluid in it so there is no chance of sucking back any air.

 

I do the same thing with that "one man bleeder kit" that I have. That is very important, not to let any air get sucked back up the drain tubing into the bleeder valve.

[Rooster2]

For what it is worth, I bled the brakes out on both my Subie Legacy OBWs last summer. I bought both cars used, all brakes pads were still good, but brake fluid in the reservoir had the color of ice tea. It looked pretty bad, so I changed it out.

 

I never knew anything about any brake wheel bleeding sequense. I just bled out any which wheel, that I felt like bleeding out at the time. Both cars have anti-lock braking systems. When I finished, I had no brake issues; brakes on both cars worked just fine.

 

Guess, I don't understand all the fuss about the bleeding sequense being so important. Please fill me in, I would like to learn something.

[porcupine73]

I think Subaru specifies that bleed order as it has the best shot at getting any air in the lines out in one bleed of all four wheels. If there is already no air in the lines, especially near the master cylinder, then the bleed order is probably not so important. When TCS, VDC, and ABS are involved it can be more steps and the order may be more important especially if air is trapped in the hydraulic unit. Nonetheless, if the bleed order were not important Subaru would not specify a particular sequence.

[nipper]

It used to be the longest brakeline was first, shortest last. This is to keep air from being moved from one line to another.

 

Now with 4 channel ABS, all the wheels are isolated from each other for the most part. SO its the closest first (doesnt really matter unless you have an odd issue like yours).

 

ABS for the most part is a passthrough system, so it doesnt need to be bled.

 

Now with the NEW systems that can apply the brakes, I am not so sure.

 

nipper