So this morning i decided to change the brake pads of my trusty felly
The original pads were where bosch but were worn down to 1/4 of the material and also cracked and patrially  lifted of the backing plate
And i went ahead for the installation 
I greased the guide pins i showed great care for the hydralic line neither kinked it nor hung the caliper from it and generally i did a very carefull job
I sligtly unscrewed the reservoir cap and pushed the pistons in gently and very minimal amount of fluid was lost (from overflow)
Then i pumped the brakes a couple of times and the pedal seemed to go down a bit more than it previously did
I took the car for a test drive and it appeared that it could actually lock both front wheels very well just the pedal was a bit softer
After a bit of driving the pedal appeared a bit harder 
Is there air in the system and how the heck did it got in?
*Some say that this is normal for new brake pads
So is it?
The pads i installed were brembos

Your disks wore down with previous pads. When putting new pads in, it takes some time to brake pad face to wear to match disk wear pattern. Until this happens you will feel bit sponginess. This is also why pedal got better later because pads have being bedding in.

Pretty normal thing.

Edited 11 August, 20187 yr by TonisT

That makes sense so i will keep bedding them in

Read this article for better understanding and doing the bedding in process.

 

I think its better to open the bleed nipple when pushing the pistons back in, otherwise your pushing the more contaminated fluid back up towards the reservoir. 

8 hours ago, SuperbTWM said:

I think its better to open the bleed nipple when pushing the pistons back in, otherwise your pushing the more contaminated fluid back up towards the reservoir. 

But still is that enough to cause this sponginess i mean sponginess is caused by air a fluid contaminated or not will be incompressible though i am aware that old dirty fluid will have degrated performance i am not sure about the felling of the brake
Can you please explain how that can happen

11 hours ago, SuperbTWM said:

I think its better to open the bleed nipple when pushing the pistons back in, otherwise your pushing the more contaminated fluid back up towards the reservoir.

There is no such thing as "the more contaminated fluid". Brake fluid degrades as a whole from moisture and should be replaced every 2 years.

4 minutes ago, RicardoM said:

There is no such thing as "the more contaminated fluid". Brake fluid degrades as a whole from moisture and should be replaced every 2 years.

Have you never bled a brake caliper? The fluid that comes out first is always a bit darker than what’s been sat in the lines. Makes no sense to me to push all that dirt that has migrated past the seals into the rest of the system. 

 

 

6 hours ago, SuperbTWM said:

Makes no sense to me to push all that dirt that has migrated past the seals into the rest of the system.

What are you talking about ? "dirt that has migrated past the seals" ??

You are describing a different issue, a brake fluid leak from worn seals, because you can't "convince" otherwise pressurized brake fluid to not leak out while dirt gets happily in. It's basic physics. Not to mention brake fluid has a big power of penetration and will pour out every pore it finds. The OP didn't report any leaks. It's common practice to push brake calipers in while observing the fluid max level in the reservoir.

 

The fluid "a bit darker" you're describing is due to corrosion from degraded brake fluid and moisture but that is a different kettle of fish. The OP has nothing against replacing old brake fluid with new one IF that's the case. While I always recommend that, I don't find necessary to open the brake fluid circuit for a brake pads replacement job.

29 minutes ago, RicardoM said:

 

The fluid "a bit darker" you're describing is due to corrosion from degraded brake fluid and moisture.

 

7 hours ago, RicardoM said:

There is no such thing as "the more contaminated fluid". Brake fluid degrades as a whole from moisture and should be replaced every 2 years.

 

So the darker fluid isn't more contaminated?

 

Nowhere did i say this was the issue the OP was having so i'm not sure why you are going on about it, I was merely stating that something which maybe common practice could be improved upon by not pumping all the cruddy fluid back into the system.

Isn't the darkness of the 'caliper cylinder fluid' just tiny bits of the square-section seal?

I can positevely assure that there was absolutely no leaking from the pistons and their outer (dust) seal seemed in very good condition
As for the reservoir its a smidge above the max line so i dont bother taking any fluid off and as for as i am concerned more fluid is not going to harm the brake system in any way

3 hours ago, SuperbTWM said:

I was merely stating that something which maybe common practice could be improved upon by not pumping all the cruddy fluid back into the system.

You are the only one that KNOWS there is cruddy fluid into the braking system of the OP. You are the only one that feels the need to purge the fluid on a brake pads job. It happens I don't agree with your opinion because you made false assumptions. I would think it is safe to say that OP has enough data to choose the best advice and decide what to do next.

 

3 hours ago, Wino said:

Isn't the darkness of the 'caliper cylinder fluid' just tiny bits of the square-section seal?

I am glad you asked and joined our discussion. I value your opinions most of the time. I will try to answer your question below.

 

From my knowledge a perfect (ideal ?) brake pads job requires the following steps:

• Examine the brake fluid for humidity and contamination. There are cheap solutions for that. Replace brake fluid if necessary.
• Skim the brake disc. This is better than having to bed in the brake pads because you will have 100% braking efficiency immediately after the brake pads job. Moreover, there will be no warpage of the brake disc. The downside is not everyone has access to a lathe or a brake shop. Also some people are not happy to pay for this extra job.
• Clean thoroughly the part of the caliper piston that sticks out. It will be dirty and rusted. Thus you will avoid damaging the square section seal when pushing back the piston. It is a good idea to change the seal too if you will replace the brake fluid. Not cleaning the piston will result in shaving tiny bits of the seal and contaminate the brake fluid. So Wino is right.
• Clean the parts of the caliper that brake pads will ride on. Grease them with very small quantity of copper grease. Also use copper grease on the back of the pad that will come in contact with the caliper piston to avoid brake squealing. 
• Make sure the sliding pins are free to move, have enough silicone grease, and the rubber boots are tight.
• Degrease then install the brake pads. Torque accordingly all related bolts. 
• Degrease then install the brake disc.
• Put a small amount of anti-seize grease on the side of the disc that will touch the wheel.
• Install the wheel and torque the bolts according to specs.

22 hours ago, RicardoM said:

You are the only one that KNOWS there is cruddy fluid into the braking system of the OP. You are the only one that feels the need to purge the fluid on a brake pads job. It happens I don't agree with your opinion because you made false assumptions. I would think it is safe to say that OP has enough data to choose the best advice and decide what to do next.

 

 

 

I'm not sure what you are on about, all I did was make a general statement about the way I like to bleed brakes, I never mentioned the OP at all. You do know this is a forum and its whole purpose is for discussion?

 

On 12/08/2018 at 17:42, Wino said:

Isn't the darkness of the 'caliper cylinder fluid' just tiny bits of the square-section seal?

 

Thanks for your input.

 

Edited 13 August, 20187 yr by john999boy
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