iLJ

Hello folks,

So my rear steel brake lines were rusty and after sanding the rust off, brake fluid began leaking out. Mechanic swapped the lines but could NOT bleed the rear brakes. The front brakes bled fine. The brake pedal is soft. My front brakes work, my rear brakes do not. We agreed there is some sort of safety feature on the car which prevents all the fluid from being sent to the rear and thus leaking out, to preserve the front brakes. Some forum trawling tells me this could be a shuttle valve / combination valve restricting fluid. Another possibility is the ABS pump needs to be flushed via STAR / scan tool.

Has anyone experienced this on any mercedes model, and know how to let fluid and thus air back into the rear of the car?

All info is appreciated,
Luke

chassis

WIS does not call for ABS actuation. WIS makes no mention of a "safety feature". Mechanic needs to check his work.

Consider that there is something in the new pipes blocking the bleed procedure.

Open the system at the junction between old and new pipes and confirm you can force fluid out with pressure on the reservoir (with a bleeder device).

Then reconnect the new pipe to the old, disconnect at the caliper and check that you can force fluid through. Last is to reconnect everything, open the caliper bleed screw and repeat.

iLJ

He opened the pipes and bled as you suggested. All sound.

iLJ

To clarify he did as suggested but still no bleeding from the rear. I will try to activate ABS to flush out a potential air pocket, and will also try to force a valve (if theres one there) to go back open. Both solved by slamming on brakes repeatedly.

In the meantime anyone with advice, please do post.

iLJ

Update: Turns out mechanic was pumping brake pedal to bleed, didn’t use a pump. Suspect a pump will do the trick.

chassis

WIS is posted in my signature for brake fluid replacement.

Find a new mechanic because he doesn’t know what he is doing.

iLJ

Fixed. Air was trapped in the ABS lines going to the control module. It got in there when I drove the car on low brake fluid.

juanmor40

Usually, brake fluid work should be bread and butter for dedicated mechanics; therefore, drive carefully until satisfied everything is correct, i.e. something loose, till some air in the system or else.

Enjoy your drive,

iLJ

Yes, but to be fair, I drove with my brake fluid too low and it must've been low enough to allow air into the ABS lines connecting to the rear. My fault.

Senecat

Don't do that.

Ifari

I am having a similar problem with my '92 W140 300SE after changing rusted/busted brake lines and replacing a front caliper.

Now the rear brakes will not bleed and the pedal is nearly on the floor.

How exactly did you get the air out?

Thanks

Rickman30

You will need a pressure bleeder, pumping brake pedal does nothing. https://www.fcpeuro.com/products/pow...motive-mot0100

Ifari

I appreciate the heads up...Thanks for the link.