Air in brake fluid?

[beezanick]

I just changed my brake fluid today. I used a presure bleed kit, and have done the procedure many times before, on other cars, sucsesfuly. However, after completing, the pedal felt spongey. I assumed I had got air into the system somehow, so checked all of the calipers again. Only fluid came out - no air. I am at a loss as to what has happend and how I could have got air into the system. Could it be somthing else, or is it worth me having the job done profesionaly?

 

[Bondiblu]

I had the same after changing the rear disks and a seized rear caliper (brakes didn't seem spongy before). The front disks were quite worn too, but because I hadn't touched them I assumed they weren't causing the spongy problem. After seeking advice, I fitted new front pads and disks and all sorted ( I didn't bleed the system further).

 

[beezanick]

Ok, thanks. The front pads do need changing soon. I hadnt heard of that causing spongy brakes before. My assumption was that I must have got air into the system as they became spongy after bleeding, but wernt before.

 

[Nath.]

Did you bleed the system in the correct order? I have heard about the master cylinder seals folding back on themselvs whilst pumping the pedal but you obviously didn't do that as you used a pressure bleed kit.

You didn't shake the bottle of fresh fluid before you added it did you. it must be left to settle for a day or 2 and never left with the bottle top off.

 

[beezanick]

No, used a new bottle of fluid which wasnt shaken.

Out of interest, what happens when the master cylinder seals get folded back on themselves?

 

[Nath.]

^^^^^They do not make a proper seal and fluid passes by them causing a spongy pedal and or the need to pump the pedal to get a firm feel.

 

[beezanick]

Oh, I dont think thats whats happened, but ive just booked a oil change with seat on friday so will ask toem to check it out. I cant think of anything ive done wrong, and ive changed brake fluid many times before fine.

If it was the seals, I guess its a big job. Having to get at the master cylinder ect?