Brake bleeding problems with 1997 Taurus

[cjhepburn]

Don't worry my ego, it's shot. I'm eating humble pie simply by posting that I have no idea why the brakes are doing this. I've gone through the system several times, there's no leak and the level in the master cylinder isn't dropping.
I found this youtube video. It shows exactly what the pedal is doing (0:32) and it's the result of air trapped somewhere.
http://www.youtube.com/watch?v=giENZskoE6w

 

[AVB]

They had the brake calipers on the wrong sides in that video. I made that mistake on a Ford truck a long time ago. You can't get the air out if the bleeder isn't at the highest point of the caliper.

 

[Scott_Tucker]

Originally Posted By: Tegger
Originally Posted By: cjhepburn
I forgot to mention that I replaced the master cylinder too

Did you bench-bleed the new MC, or just throw it on dry?

Do you have rear discs? If so, do the calipers incorporate a parking brake, or is the parking brake separate from the caliper (drum-in-hat, etc.)?

Has a mallet been employed at any point at any location during the bleeding sequence?


This. If you did not bench bleed the master cylinder, that is your problem.

 

[yonyon]

A sinking brake pedal is always a leak. It could be an external leak or an internal leak, but it's a leak. Rinse away all dribbled brake fluid with water, dry it all off, then check for external leaks.

If you can't find an external leak, you've got an internal leak. It is not safe to assume your new master cylinder is working properly. Plug it off and check for a rock hard pedal. If you've got one you're back to an ABS problem.

 

[cjhepburn]

Originally Posted By: yonyon
A sinking brake pedal is always a leak. It could be an external leak or an internal leak, but it's a leak. Rinse away all dribbled brake fluid with water, dry it all off, then check for external leaks.

The internal leak is interesting... I'm thinking the only internal leak could happen at the MC, right?

Here are the events as they happened. My father panic stopped and the one of the brake line blew out due to corrosion. I replaced both brake lines. After that I've been fighting the problem with a spongy brake pedal. I bled the brakes until I'm blue in the face. I then thought something else must have happened. I replaced the MC and that didn't change the symptoms. I bench bled the MC in place and then connected the brake lines. My father has been driving it this way for about a month. In that time the brake fluid level hasn't changed. I drove the car today and tried locking the brakes on a gravel road. I felt the ABS kick in. I drove it back to the garage and bled the brakes one more time today using the MityVac. There was no improvement. I have no idea where else to look. I've been up and down the brake line, there are no leaks. The only thing I haven't done is address the possibility of the ABS holding on to some air because I don't have the tool to operate it in service mode.
That's my story and I'm sticking with it.

 

[andyd]

For sure, the the ABS is a complication. I have managed to dance around in my cars. I waste a qt of BF just keeping the MC full while replacing the lines. The Rat has some sort of valve that prevents the rears from locking up. The valve wont open if it doesn't see enough line pressure. I use either a gravity bleed or a I rig an airlock on the bleeder with a piece of clear tubing and a small bottle 1/2 full of BF. Either, gives me a better pedal than the traditional 2 person process. Assuming it is trapped air, maybe a pressure bleeder would work. I would also be joining a Taurus forum and picking their brains.

But I think you have a fitting that is dragging air in. RE-using fittings is [censored] shoot. Especially if a vise grip was used to take them apart. It can oval a fitting. Whatever, please post a follow up when you resolve this. Good Luck.

 

[cjhepburn]

I've been thinking about this. When I started this job, I was expecting to borrow a bubble flange tool from AZ but found out that didn't have it. The only place I could get it was Amazon so the brake lines were left open at the proportion valve for a few days. My hypothesis is, in that time, enough BF drained out to let air into the ABS lines.
As far as it leaking, everything I touched stayed dry, the level in the MC hasn't changed, and I'm not pulling any more air out of the system, with yesterday's bleed.
It's going to the shop, I'll let you know what they do to fix it.

 

[Gito]

Originally Posted By: NHGUY
A Motive Products pressure bleeder would do it.

Plus 1 on using the Motive brake bleeder

 

[outdoorsman310]

there was a taurus in the shop with no pedal. i think a line broke but I am not sure. I know we had to change both rear wheel cylinders. it needed shoes and i think drums