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Clamping/pinching/crushing the line shut is not a great idea. I consider it an incredibly bad idea. Like you said, open the bleed valve when retracting the piston, or separate the caliper from the line altogether.
If you think about it, clamping the line shut is going to prevent you from retracting the piston anyway. The fluid has no place to go.
[quote=”Evil-i” post=145748]Clamping/pinching/crushing the line shut is not a great idea. I consider it an incredibly bad idea. Like you said, open the bleed valve when retracting the piston, or separate the caliper from the line altogether.
If you think about it, clamping the line shut is going to prevent you from retracting the piston anyway. The fluid has no place to go.[/quote]
I am referring to how Eric does it – clamping the line and opening the bleed. Question is – if you just open the bleed without clamping the line, where will the fluid go…I suppose it’ll travel through the easiest route – out through the bleed valve or up the hose to the cylinder 🙁
For myself, I always have the caliper disconnected from the brake line when I need to retract the piston. I suppose pinching the line shut encourages the brake fluid to escape through the opened bleeder screw, (path of least resistance), but I still think crushing a hydraulic hose is not a great procedure.
If there are corrosion issues with the line’s connection at the caliper and the line is difficult to remove, or is damaged during removal, well, that was a ticking time bomb anyway which needed fixing.
I’ve done at least a thousand brake jobs at this point and, other than special circumstances, I’ve always pushed the caliper pistons back in without doing anything else as part of the process. Once in a while some fluid overflows out of the reservoir, but that only happens if someone tops it up when the brake pads were already very low (which I don’t recommend doing). It’s never even occurred to me to pinch off a hose as I’m compressing a piston, and I’ve never seen that done by anyone in anyplace I’ve ever worked.
[quote=”Fopeano” post=145763]I’ve done at least a thousand brake jobs at this point and, other than special circumstances, I’ve always pushed the caliper pistons back in without doing anything else as part of the process. Once in a while some fluid overflows out of the reservoir, but that only happens if someone tops it up when the brake pads were already very low (which I don’t recommend doing). It’s never even occurred to me to pinch off a hose as I’m compressing a piston, and I’ve never seen that done by anyone in anyplace I’ve ever worked.[/quote]
Pretty much this. As usual. I usually pull the cap off the brake fluid reservoir, then if there is any, it just comes out and doesn’t have to force it’s way. Depending on the age and condition of the vehicle, attempting to loosen the bleeder valve can be a one way trip to caliper replacement.
[quote=”DaFirnz” post=145771]attempting to loosen the bleeder valve can be a one way trip to caliper replacement.[/quote]
So how do you flush or bleed the system if you don’t open the valve?
I have been doing brake service for many years and have never opened the bleeder when pushing the piston back and have never had a problem. If you don’t open the bleeder there is no reason to bleed the system.
[quote=”wysetech” post=145796]I have been doing brake service for many years and have never opened the bleeder when pushing the piston back and have never had a problem. If you don’t open the bleeder there is no reason to bleed the system.[/quote]
I do want to, I want to change the brake fluid, but these are two separate issues I suppose. My only concern is whether or not it can cause damage to the master cylinder/brake system if you let fluid go back to the cylinder while pushing the piston.
There is a slight possibility you could force debris back into the ABS and master cylinder but I have never had a problem with that. I usually flush the system after I have assembled everything else.
I’m glad to see a couple of mechanics I really respect on this post addressing the concern of pushing the piston back without line clamping and opening the bleeder valve. I personally do not open the bleeder valve or clamp the lines either. No disrespect to those of you who do. I would add that the piston should be pushed back slowly. This enables the back pressure to stabilize rather than receive a load of pressure all at the same time. Hope your brake job turns out well…
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