Problems! DOT 3 Synthetic Brake Fluid Yay or Nay?

[J33Pfan]

Problems! + DOT 3 Synthetic Brake Fluid Yay or Nay?

Greetings!

Having brake problems with my 2002 Liberty 165k miles 4WD V6 ABS. Drums in rear.

I replaced both front brake lines after Right Front blew out at caliper end. (It was rust rotted where rubber hose meets the metal tube) Calipers work good.

I was using DOT 3+ brake fluid with no issues. When the brake hose broke, all the fluid left the reservoir, so I had to refill & bleed but I switched to DOT 3 Synthetic.
I used a compressor powered vacuum bleeder that worked great last flush. I bled brakes per factory instructions. I could actually see the air being bled out.

After bleeding with reservoir full. The pedal felt great with the engine off.

After starting the engine I pumped the brakes. ...After a few pumps, the pedal went to the floor and got stuck there. I shut the engine -the pedal eventually back came up. Afterwards the pedal is spongy soft and braking is poor. No Brake Light indicator. (I've never seen this before)

I dont know how old the Master cylinder is so I'm ready to change it being its age is unknown and pedal hit the floor.

Questions
1) Do I need to bench bleed the old master cylinder or is the vacuum bleeding the way to go. Do I need to bench bleed the new master cylinder?

2) Is DOT 3 Synthetic the problem?

3) Does this sound like a bad Master Cylinder? ("pedal went to the floor and got stuck")

Thanks you your input!

 

[cplchris]

i wouldn't blame the brake fluid for the issue, but a spongy pedal is indicative of air in the system or a leaky seal in the master cylinder. i would try bleeding the brakes again.

i had a similar experience when i used my motive power bleeder for the first time, I'm not a fan of it because it was a pain to get the cap to seal properly and the fact that it didn't work right the first time, I have always heard people speak highly of the motive bleeder but I wasn't impressed at all.

 

[duderz7]

Did you also bleed the rear brakes? With the master going dry, I would if you haven't already.

 

[J33Pfan]

Did you also bleed the rear brakes? With the master going dry, I would if you haven't already.

Yes, everything was bled as per the Manuel. With the vacuum bleeder you can view the bubbles as you bleed.

 

[J33Pfan]

Is there a proportional valve that needs to be reset or bled? where is it? or is it a Junction Block? and where is that?

 

[tjkj2002]

Is there a proportional valve that needs to be reset or bled? where is it? or is it a Junction Block? and where is that?

If the master went dry I'd be changing it and having ABS the prop valve is part of the ABS module which needs to be bleed via a scanner that can access that function(your looking at $2000+ scanners for that old).

 

[Lancer]

I had a similar problem after a fluid flush and change. Its either air in the system - especially the ABS, or a seal is leaking or both. I had both, so the seals were replaced and the system properly refilled. As for fluid, I use either a synthetic Dot 4 or 5.1. The fluids are never an issue if they are uncontaminated.

 

[J33Pfan]

If the master went dry I'd be changing it and having ABS the prop valve is part of the ABS module which needs to be bleed via a scanner that can access that function(your looking at $2000+ scanners for that old).

just noticed this post needed an update to help others with similar ABS MC Brake problems.

I replaced the MC as the old one was questionable. The new MC came with a reservoir but the Fluid sensor wasnt compatible and I had to use the old reservoir to get the dash BRAKE light to go out.
The brakes have been working fine with no issues.

I just Bled the ABS module with my new $120 FOXWELL 630 Scanner. Its all good!