Brake bleeder leaking after changing fluid.

[atikovi]

I'm changing the brake fluid in a Mercedes S550 after replacing the rear pads and rotors. Right rear went fine. Left rear bleeder was very difficult to loosen even a little, and after I tightened it back, it was leaking out of the center. Calipers are aluminum. With a lot of effort, I got the bleeder all the way out for examination and I see a lot of aluminum fused to it from the caliper.

Would a new bleeder screw work? Do I tap the hole first? Or do I need a caliper. Not too expensive but would be next week before I get it.

 

[JohnnyG]

You can try that, since the bleeder valve seats at the very tip. I'd be very careful when re tightening, your not going to have much thread left. Try to get it just where it stops leaking under hard braking.
Otherwise, it's time for a new caliper.

That's pretty typical of threads galling in aluminum, it wasn't your fault that it happened.

 

[BHopkins]

It seems that it would be worthwhile to try to run a tap down the hole first. What have you got to lose, except the cost of a tap, if you have to go out and buy one? And your time, of course.

Do you have a forming tap in the right size? I doubt a typical cutting tap is going to do anything to correct the threads, that close to the bottom of the hole.

 

[atikovi]

I need this but can't find it locally,

Snap-on Store

shop.snapon.com

 

[The Critic]

You need a new caliper. The material on that screw is material that is now gone from the caliper. A tap will clean-up the threads that are left, but the section that is missing material will now be a larger void.

 

[Astro14]

You need a new caliper. The material on that screw is material that is now gone from the caliper. A tap will clean-up the threads that are left, but the section that is missing material will now be a larger void.

+1

But I got 50 bucks that says he runs a tap in it, gets it to barely hold, then foists the car onto an unsuspecting buyer.

 

[atikovi]

Screwed in a new bleeder and it's not leaking anymore even after holding my foot on the brake. Will check again in a few hours

 

[The Critic]

Screwed in a new bleeder and it's not leaking anymore even after holding my foot on the brake. Will check again in a few hours

Wait till it heat cycles for a while.

This is a very bad idea - if it loses brake fluid, you can have a brake failure.

 

[BHopkins]

Screwed in a new bleeder and it's not leaking anymore even after holding my foot on the brake. Will check again in a few hours

Were you able to tighten it to the torque spec?

 

[The Critic]

Were you able to tighten it to the torque spec?

It doesn't matter. If you're missing that much material, even if it torques ok now, it may not be enough to hold torque after heat cycling.

I have ran into this scenario multiple times. Sometimes the fastener will loosen on its own after a few thousand miles.

 

[SammyChevelleTypeS3]

I'm changing the brake fluid in a Mercedes S550 after replacing the rear pads and rotors. Right rear went fine. Left rear bleeder was very difficult to loosen even a little, and after I tightened it back, it was leaking out of the center. Calipers are aluminum. With a lot of effort, I got the bleeder all the way out for examination and I see a lot of aluminum fused to it from the caliper.

View attachment 210976

Would a new bleeder screw work? Do I tap the hole first? Or do I need a caliper. Not too expensive but would be next week before I get it.

Not your fault. You can bet that was installed long ago without any of the "break bleeder valve" anti sieze lube you can find at any auto parts places. Maybe you can get away with something like this (in right size) before you end up needing to replace the caliper which is likely where you are with that much metal galled out....

1/8 NPT Brake Bleeder Assembly (2 piece) - Pegasus Auto Racing Supplies

Our 2-Piece 1/8 NPT Brake Bleeder is a direct replacement for Wilwood caliper bleeder assemblies. The outer sleeve has an internal seat for the bleeder screw.

www.pegasusautoracing.com

 

[The Critic]

Not your fault. You can bet that was installed long ago without any of the "break bleeder valve" anti sieze lube you can find at any auto parts places.

Umm, you don't want to use any anti-seize on these screws. Anti-seize has a petroleum base and if any of that migrates into the fluid, you will have serious issues with the rubber components.

 

[atikovi]

Wait till it heat cycles for a while.

This is a very bad idea - if it loses brake fluid, you can have a brake failure.

Thought you would have known this, but all cars sold in the U.S. since the mid 60's have dual brake systems. If one part fails, the other one is still working. And since the front brakes have the majority of the stopping power, a rear brake going out is even less of an issue.

 

[The Critic]

Thought you would have known this, but all cars sold in the U.S. since the mid 60's have dual brake systems. If one part fails, the other one is still working. And since the front brakes have the majority of the stopping power, a rear brake going out is even less of an issue.

What happens to the brake pedal when a bleeder screw is open? It goes to the ground.

 

[atikovi]

The bleeder isn't open now. And you think the caliper rebuilders do it any different? If a new bleeder screw goes in and seals, they send it.

 

[paulo57509]

The bleeder seals on its conical surface. Even with buggered up threads, as long as the new bleeder tightens up it shouldn't leak.

 

[xmanjeff]

id get a new caliper on there , murphys law , its gonna go at the exact worst possible time , usually when you need to brake , you need to brake

 

[SammyChevelleTypeS3]

It doesn't matter. If you're missing that much material, even if it torques ok now, it may not be enough to hold torque after heat cycling.

I have ran into this scenario multiple times. Sometimes the fastener will loosen on its own after a few thousand miles.

Right...... Brakes are nothing to take even the slightest chances with.

Umm, you don't want to use any anti-seize on these screws. Anti-seize has a petroleum base and if any of that migrates into the fluid, you will have serious issues with the rubber components.

Agree with you. No one should be putting just anything (lube or sealant) on those threads. Not on the "valve" threads as they are not what seals, they seal on the conical mating surface. It is certainly not recommended to put anything at all on the bleeder valves. The stuff we used on the valve body threads was at first a copper/graphite based anti seize and then went to a 100% synthetic/ceramic anti seize product. Just put a tiny amount on the threads before inserting into the calipers. Never had any issues. No one should plan to or have to keep removing the complete valve assembly out of the calipers. I have heard guys who live in the northern/winter time "salt belt" removing to clean or even replacing the valve assemblies when doing brake jobs to prevent seized parts. Glad I never experienced that type problems.
That one is strange looking to me the way the galling took place in the center. Not cross threaded or it would look different. My guess is some type of metal shavings or trash got in there as that valve assembly was installed whenever?

 

[SammyChevelleTypeS3]

What happens to the brake pedal when a bleeder screw is open? It goes to the ground.

Had one leak already. I can attest to that-goes to ground.

 

[SammyChevelleTypeS3]

Amazon.com right now has pages and pages of brake bleeder assemblies, bleeder valves, bleeder valve caps, bleeder kits with hoses to all sorts of brake tools etc.... They have all types of really non expensive tools, kits and accessories to make doing brake jobs easier for the
guys who want to do quick home brake jobs but do not have access to a shop or a garage full of tools. Auto zone used to have in stock all sorts of loaner or rental tools as well for the home/garage mechanics.