Brake Problem - Possible Airlock??
 

Hi, my old brake callipers gave up the ghost recently (one of the pots ceased) so I decided to replace them with second hand standard ones. My car Is a MY94 STi RA Import.

The problem I'm having is that I've bled the brakes at least four times now, in the correct manor (farthest away from master cylinder first) and in the correct way, building pressure on pedal, releasing nipple slightly to let fluid and air out, then tightning, then repeating the precedure on each wheel, but I still have a pedal that whilst the engine is running travels about half way before any pressure to the brake is applied. There seems to be no brake travel when engine is off, when pumped up.

I've heard that a possible failure in master cylinder can occur if expieriencing these symtoms, but it was fine before I done the front calliper change.

Could the callipers I've replaced be faulty in some way, or Is there just still air in the system some how, like an airlock or something.

The brakes still work fine, but there is a lot of play in the pedal, which isn't good as can cause a delayed reaction in a sudden braking situation.

I have the MOT coming up soon and I need it done pretty sharpish.

Any help would be appreciated.

Thanks.

Just a simple check and easy mistake to make,Are the bleed nipes on the top of the calipers? If there at the bottom the calipers are on the wrong side and makes it almost impossible to bleed them properly

No, they are definitley at the top 0f the callipers, so what do you think would be the problem I have??

probably not bled properly. It's very easy to get air into the system when you change a caliper. I would be ready to put around 500ml through the caliper you changed to make sure all the air is out, you need the nipplie well open so the fluid can travel fast enough to take the air with it. Remember to keep the resevior topped at all times.

Paul

Did you have somebody sat in the driver's seat pumping the peddle? It's impossible to bleed the system properly unless you have somebody helping, or with one of those brake bleed tube kits from halfords.
If you built the pressure up yourself, then went and released the nipple, some air would have crept back into the system before you're able to re-tighten the nipple.

The brake pedal needs to be pushed down, giving a high flow of fluid from the nipple. Then just make sure you do the nipple up before the pedal reaches the floor. Again, a £5 brake bleed kit that clips onto the nipple is available from halfords, enabling you to operate the pedal yourself.
Hope this helps.

I had the same problem in the end I got a one mad bleeding kit from halfords for a fiver a a big tub of blake fluid did the back the the front first. Alls fine now

Yea, I had my brother operating the pedal whilst I was bleeding the nipple. I have one of those one way valve system bleeders, and there was a small amount of air bubbles coming coming from each calliper when they were bled. This ran to clear fluid after about three or four bleeds per side, so I gather they were done.

So do you think I should go no holds barred and get myself a large tub of brake fluid and keep bleeding each calliper until theres definatley no air left in the system?

yup, that would be the sure way of doing it.

Tap the Calipers with a rubber mallet as well, As the little blighter air bubbles can get trapped & not travel to the Top Etc.
Dean

Did you sort this out? I have exactly the symtoms you describe but haven't done anything to the brakes to induce the problem. I had some calipers fitted around 18 months ago and they were fine, just in the past few months the feel has got progressively worse. I've tried bleeding to solve the problem so now have new fluid throughout but no change.