skhan

I am having some trouble getting my front brakes bled fully. I have run through a lot of brake fluid trying to get all the air out. Whats happening now is, there are very tiny bubbles and there is a noise that comes from the caliper when I am bleeding the front brakes. There are no leaks in the system. I have also tired a new brake caliper, but still the issue is there. The air is not getting in the system from any where. I have emptied out the lines for the front and have had to rebleed the front brakes. Is there a different bleeding technique if the lines were fully empty?

My rear brake are perfect. Bled them with same technique and same equipment and had no issues. Something is special about the front ones.

Here is the link for the video I made, please copy paste the link and put up the volume. you should be able to hear the noise and see the bubbles with each pump.

https://drive.google.com/file/d/1l3x...ew?usp=sharing

Fredtoo

How are you pushing the fluid through the system?

skhan

By pumping the brake peddle.

Fredtoo

I do not see where you are closing the bleeder screw between each purge.
Did I miss something?

skhan

no I am not closing the bleeder between each purge, am I suppose to? I have the other end of the tube submerged in brake oil, there is not air getting in the tube from where its purging the brake oil from.
Even then do I need to close the bleeder in between each purge?

Fredtoo

You need to close the bleeder.
The air that you are seeing is sucked in from the really small clearance between the threads on the bleeder screw and the caliper.
You should be doing this.

Pump 2-3 times
Hold brake pedal down
open - then close the bleeder

repeat until bubbles are gone.

skhan

Okay I can try that too, just to put it out there, I performed the bleeding on the rear brake exactly the same way as I stated above, and had no issue. So I am not sure why the front ones are acting different.

flyeri

I also think it is drawing air in around the threads. This is due to a venturi effect caused by the fluid flowing through the bleeder. That is what the noise sounds like to me anyway. Take the bleeder out and put some thick grease around the threads to seal it. Then use the pump, open and close method that Fredtoo described above. Post your results please.

Fredtoo

Be careful with grease and brakes.
Most greases are not compatible with the rubber seals used for brake fluid.
Using a thick silicone based grease would be OK

skhan

The brake oil being so harsh, is there a specific type of grease that I should use? I dont want the grease to get jammed and destroy the caliper over time because of being in contact with brake oil. Just being cautious.

Fredtoo

I don't use any grease.
Just bleed them like I described before.

skhan

Alright, I will try that in the evening today and get back to you guys with results.

danh77

flyeri

The threads on the bleeder are not internal to the system and not in contact with brake fluid and do not seal the system. The bleeder tightens against a seat, metal to metal, and seals the system. The grease is only preventing and air leak around the threads during bleeding, not sealing brake fluid in the system. You only use a small amount of grease on the last threads the bleeder. When you screw it in it pushes most of it to the outside making a small buildup around the bleeder on the outside of the caliper. None of it ever enters the brake system. After bleeding simply wipe off the excess. Vaseline will work just as well or you can use plumbers tape on the bleeder threads for that matter. Even though the brake fluid will soften the tape over some time it is not providing any sealing function after the bleeding is done and the system is closed. No harm will come to your brake system.

Fredtoo

In a perfect world, you are correct.
however,
You do not know how much grease someone is going to pack onto the threads of the bleeder screw, or if they will pack it into the bleeder hole in the caliper.
I can not support the idea of putting a hydrocarbon grease anywhere near the fluid path, if it can be avoided.

Any oil or grease that gets into the system will soften or swell the seals. In extreme cases, it will turn the seals into mush.

flyeri

Fredtoo,
I went back to edit and tried to share some more info. I agree that you can never tell what someone might do so I wanted to make it more clear. I did not want to give advice that could backfire, especially on brakes. I also saw that my post sounded bit brusk, so my apologies. You must have been replying as I did my edit. As I think about it, if brakes are bled as you have described, and I do it that way too, any contamination in the bleeder, grease, dirt, etc would be pushed out. I can't see how anything could get sucked back inside. However, the op's method would allow for reintroduction of contamination. So with that said you have a very valid point.

Fredtoo

No sweat dude.
We have a thick skin up here.

skhan

I did try to Pump 2-3 times, Hold brake pedal down, open - then close the bleeder. I still was hearing the bubbles noise and seeing the tiny bubble. Its such a mixed result that its hard to say if its getting better or not. One time it would be less noise and less tiny bubbles and the next bleed goes back to more tiny bubbles and more noise. Not sure why it continues to go on.

After doing some more research, I did read, some people suggest letting the car sit so the air can rise and then bleed the brakes again. Or even drive it (if brakes are safe enough) and then bleed the brakes again and that should take care of it.

So after bleeding the brakes with the technique described above I did take the car out for a quick drive. Brakes arent too bad but I believe there is potential for improvement. So I will be buying more brake fluid and bleeding them again. I want to achieve as much braking capability as this car can give me.