Confession.

[IRLGW]

Ok so I bought 2 X front calipers off eBay from a reputable seller. Changed all my lower brake components...cannot get any front brakes. Made a pressure bleeder from a garden sprayer and nicked the filler cap from my father's previa. I have fluid coming from every outlet and in any direction I choose but no pistons moving. Have I bought items which do not posses any moving parts! Or have I missed a procedure required for new calipers?

Yes I did remove the blanking bungs from the banjo bolt location! The pressure bleeder is strong enough to activate the rear calipers but fronts just won't budge.

Theory is to remove calipers and see if I can extract the pistons out a bit with mole grips and then backfill with brake fluid. Surely for £72 each at least one piston should move?

Don't you just hate aftermarket parts.

 

[Chris]

OK, first thing to consider is that there are 2 circuits. Front and rear. Each has a seal in the master cylinder. If the seal pushing fluid to the front brakes has gone then you can suck all the air out, put calipers from a Ferrari on there and still get no piston movement. I doubt that the new pistons are the problem. You could swap a front onto a rear perhaps and see if they push out. Pretty sure you can connect the hose, from memory. Leading question, at any point did you press the brake pedal completely to the floor?

OK next question is have you bled the master cylinder? Yes you have pressure bled, but there is a procedure to bleed the master cylinder too. And it might just be there there is air in the front circuit

 

[guyc]

I feel your pain. I went through the same issue and I think it turned out that, as Chris has eruditely hinted at, I'd depressed the brake pedal all the way and that had moved the piston in the master brake cylinder on to a dirty / rough bit which had destroyed the seal.

I changed the master cylinder and it all worked again.

I was also concerned that I'd got air in the ABS pump?

 

[chapel gate]

Don't you just hate aftermarket parts.

yes.

 

[Shayne]

Similar thing on the 90 series, i ended up just loosening a pipe on the master so it could weep slightly as i bled the brakes again . Idea was if theres air trapped somewhere then it has to come out or move one way or another . Once i had some brakes i tightened the pipe and bled as normal again .

 

[IRLGW]

Right so bleed bleed and bleed again. I was using a pressure bleeder to avoid having to pump the pedal. When I had steady flow at each corner it should have worked but the fronts didn't budge. In the end I had to manipulate the pistons out of the calipers and work them in and out a few times to lube the seals. In hindsight I should have pulled the pistons out of the crate and put brake fluid on the seals and reseated before going anywhere near fitting them. This would be my no 1 point

Don't both the outputs on the cylinder feed the abs unit first and then the front rear split from there? I loosened the two unions on top of the abs modulator and just let the pressure push the fluid through to that point. It seems to be thereafter that problems arise.

I think Shayne's idea is a good compromise in that if you leave the system pressurised then just crack all the unions a turn and wait for the fluid to find its own way around.

 

[frank rabbets]

Sometimes it helps to have the engine running so the servo gives a bit of a kick.

 

[frank rabbets]

If it is the master the pedal will go down to the floor a bit more than normal, just leaving you enough for the rears. I doubt whether it's the calipers. They can't get only one moving part wrong can they?

 

[IRLGW]

Defo think with new cheap parts that they should be stripped down to their components, checked for imperfections, toleranced, lubed, reassembled and then wonder why one didn't buy OEM to begin with.