Technical Front brakes full of air, can’t purge!

[turbo500]

Hello and happy new year to you all! I’m writing to you from the distant year 2017, while most of you are now in 2018

I’m having issues clearing air from my front brake lines. I recently managed to install new rear drums, that I’ve been struggling with for months.

The fronts were changed a while back, new drums, new pads, new copper lines, rubber lines, banjo bolts, brake cylinders, and also new brake pump. When I did those, I bled the brakes and all seemed fine.

Now, with the new rear rotors, I bled the system again, and the rears seemed fine. I did the fronts, and both were full of tiny, fine bubbles. The bubbles stayed in the drained fluid as well. I was unable to clear the fronts.

I read somewhere that the issue could be with the new lines, meaning there is an air pocket somewhere and the only solution is to use a vacuum bleed system or compressed fluid bleed.

Anyone have any suggestions to what I may be doing wrong?

Thanks in advance, and happy new year!

[ame]https://youtu.be/LZ5Bg7cRDuo[/ame]

 

[IanEmery]

Anyone have any suggestions to what I may be doing wrong?

Thanks in advance, and happy new year!

https://youtu.be/LZ5Bg7cRDuo

Hi, and a Happy New Year to you.

Looking at your video I see that you are using an incorrect technique to bleed the braking system. You need to close the bleed screw after each push down on the brake pedal, ie, 1/ open the bleed screw, 2/ get your helper to push the brake pedal down, 3/ now close the bleed screw, 4/ helper now releases brake pedal,5/ check fluid level in brake reservoir. Repeat as necessary until fluid is clear of air bubbles. Hopefully this will clear your system.

 

[El cargador]

Alternatively you could use a pressure system to bleed them. Years ago I made one for my Mini. Get a spare reservoir cap and a spout like the throw away one on a silicone tube,drill a hole in the cap and pass the spout through. Attach a length of brake hose to reach the nearest wheel then attach a valve attachment to clip onto the tyre valve.then you will have constant pressure in the brake system and just need to open the brake cylinder nipples. Hope I explained this well.

 

[turbo500]

Thank you both. Will try the first method hoping it clears.

 

[F123C]

I met someone who was having difficulty in bleeding air from his brakes. He was new to car maintenance and hadn't bled brakes before.

First thing he'd do before topping-up the reservoir was to give the can of brake fluid a good shake to mix the contents......

Remember this when transporting cans of fluid, probably best to let them sit for a while before use. How long? hint - see how long it takes for the bubbles to disappear from the container of (aerated) brake fluid bled from the system....

AL.

 

[portland_bill]

As well as the advice above, don't open the bleed screw too far, or it can allow air to bleed past its thread, adding it to the bled fluid. So that way you'll never see the end of it.

Also, with drum brakes, it is often beneficial to back off the adjusters, all the way, to ensure the wheel cylinder piston is deep in the cylinder. Stops it keeping air in the cylinder if the chamber is smallest.

 

[MLW]

As they others have said two basic techniques.
1. Close the bleed nipple on the UP peddle upstroke. This is because it sucks air in via the nipple thread. Unbelievable but true.


2. Go £20 and get a pressure bleeder. Every time I did mine my wife and I had an argument. This was the solution. Only pressurise it to about 17 lbs per square inch or it blows and fluid is everywhere. I use to blow just air through first to get all the old fluid out. Then fill up with fluid and simply open the nipple like a tap. It is one way and it all comes out. Best £20 I ever spent. I still have it after 30 years.



Two tips,
1). Stand the fluid for 1-2 days where it can't get knocked and 'gently' pour it in. I use to use a litre and double bleed it, i.e. twice = 8 nipples.
2. Unscrew all the bleed nipples first and put a smear, just a smear, of copper grease on the threads. In 10 years time they will still undo.

 

[turbo500]

Thank you MLW, and everyone else. I think I managed to solve the issue. I ended up doing each one from scratch, closing the nipple before releasing the brake pedal.

I'm trying to get a pressure bleeder, as I will be changing more copper lines in the near future.