on a 2004 era camry or other toyota pad replacement what does the factory service manual say on preventing brake fluid from back flowing up to the master cylinder when the caliper piston is pushed back in to allow room for the new pads???
prevent brake fluid flow back into master cylinder
- Thread starter edwardh1
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asking how the factory says to prevent backflow. what is the factory specified procedure
open the bleeder?
clamp the hose?
other?
open the bleeder?
clamp the hose?
other?
Hopefully someone with the FSM will chime in, but in case they don't here's one way:
-Get a stick or sticklike device to hold the brake pedal down at least a quarter inch or so. This prevents backflow.
-If you're being neat, run a bit of rubber hose or plastic tubing from the bleeder valve to a suitable container.
-Apply pressure using your method and tool of choice to push the caliper piston back in. There will be great resistance.
-Crack the bleed valce slightly, just enough for fluid to ooze out slowly.
-Keep the pressure on steadily. Close the bleed valve just before the piston is fully returned. If you seat the piston fully before closing the bleed valve there is a possibility you can let a small bubble of air into the caliper. If so: after all else is done, do a manual two person bleed (one pump should be enough) to clear that small amount of air.
-Rinse away all spilled brake fluid with copious amounts of water.
-Get a stick or sticklike device to hold the brake pedal down at least a quarter inch or so. This prevents backflow.
-If you're being neat, run a bit of rubber hose or plastic tubing from the bleeder valve to a suitable container.
-Apply pressure using your method and tool of choice to push the caliper piston back in. There will be great resistance.
-Crack the bleed valce slightly, just enough for fluid to ooze out slowly.
-Keep the pressure on steadily. Close the bleed valve just before the piston is fully returned. If you seat the piston fully before closing the bleed valve there is a possibility you can let a small bubble of air into the caliper. If so: after all else is done, do a manual two person bleed (one pump should be enough) to clear that small amount of air.
-Rinse away all spilled brake fluid with copious amounts of water.
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
Sometimes bits of the caliper seal and rust get into the brake fluid, and if the fluid is pushed back, it might damage the ABS hydraulics, at least that is what I was taught in automotive brake class back in 2006.
Anyway, if you return the brake caliper pistons while the bleeder screw is open, brake fluid will not go back up to the master cylinder.
Anyway, if you return the brake caliper pistons while the bleeder screw is open, brake fluid will not go back up to the master cylinder.
Just opening the bleeders should stop most of the fluid from going back to the master, but may not stop a little of it from going back. This is especially true if one pushes the piston in quickly or if the bleeder is partially clogged. Such a small amount of fluid flowing back shouldn't cause any problem, but putting a stick or a weight on the brake pedal is easy enough and prevents any fluid from flowing back.
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
Originally Posted By: ltslimjim
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
You shouldn't pinch a brake hose, it'll likely damage them.
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
You shouldn't pinch a brake hose, it'll likely damage them.
Originally Posted By: ledslinger
Originally Posted By: ltslimjim
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
You shouldn't pinch a brake hose, it'll likely damage them.
I don't see how if rubber is pinching rubber, I've seen so many mechanics do this just enough to prevent free blow of fluid without pressure at the brake pedal.
Originally Posted By: ltslimjim
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
You shouldn't pinch a brake hose, it'll likely damage them.
I don't see how if rubber is pinching rubber, I've seen so many mechanics do this just enough to prevent free blow of fluid without pressure at the brake pedal.
As far as I know most factory service manuals do not say you have to prevent backflow when compressing the calipers to change pads. They usually just tell you first remove any excess fluid from the master cylinder then compress the caliper. Some manuals even say do not add brake fluid as the pads wear so that at pad change fluid removal won't be necessary.
It is not a bad idea to open the bleeder to prevent any debris being pushed up into the ABS unit and to make sure the bleeders do not get locked up. this was discussed on BITOG befoer. I think few mechanics do this because you risk opening a can of worms with broken off bleeders that were corroded.
If you push fluid out the bleeder and leave the master cylinder cap on, being a sealed cap, you may draw in some air back through the bleeder as you let tension off the C-clamp before closing the bleeder. So it might be a good idea to open the master cylinder cap and/or tighten the bleeder while the C-clamp is full tensioned.
It is not a bad idea to open the bleeder to prevent any debris being pushed up into the ABS unit and to make sure the bleeders do not get locked up. this was discussed on BITOG befoer. I think few mechanics do this because you risk opening a can of worms with broken off bleeders that were corroded.
If you push fluid out the bleeder and leave the master cylinder cap on, being a sealed cap, you may draw in some air back through the bleeder as you let tension off the C-clamp before closing the bleeder. So it might be a good idea to open the master cylinder cap and/or tighten the bleeder while the C-clamp is full tensioned.
Originally Posted By: ltslimjim
Originally Posted By: ledslinger
Originally Posted By: ltslimjim
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
You shouldn't pinch a brake hose, it'll likely damage them.
I don't see how if rubber is pinching rubber, I've seen so many mechanics do this just enough to prevent free blow of fluid without pressure at the brake pedal.
Pinching off brake lines can damage the hose: http://www.brakequip.com/rubber.html look at the construction picture of a typical DOT rubber hose and I would think that pinching off a rubber line could damage it (not so much the EPDM but I could see the PVA reinforcements not being as flexible as the EPDM). I was also taught in my brakes and suspension class that you shouldn't pinch off a rubber brake line/hose.
Originally Posted By: ledslinger
Originally Posted By: ltslimjim
Originally Posted By: mechtech2
Could be an ABS thing.
But it is good practice with any system to open the bleeder when retracting caliper pistons.
If the brake line leading to your wheels @ the caliper is rubber, one could also pinch the line with needle nose vice grips that have rubber stuck on them for safely using, and not allow fluid from the caliper depress to push fluid towards the reservoir.
That + always crack open the bleeder, do w/e job and bleed that wheel for air again after is the way I'd do it.
You shouldn't pinch a brake hose, it'll likely damage them.
I don't see how if rubber is pinching rubber, I've seen so many mechanics do this just enough to prevent free blow of fluid without pressure at the brake pedal.
Pinching off brake lines can damage the hose: http://www.brakequip.com/rubber.html look at the construction picture of a typical DOT rubber hose and I would think that pinching off a rubber line could damage it (not so much the EPDM but I could see the PVA reinforcements not being as flexible as the EPDM). I was also taught in my brakes and suspension class that you shouldn't pinch off a rubber brake line/hose.
You're not really supposed to pinch off brake line hoses due to possible damage. That doesn't stop tech's from doing it though.
but the basic question is what does the toyota factory service manual say?
If the bleeder is open, there is absolutely no need to pinch the brake line.
None.
None.
Originally Posted By: mechtech2
If the bleeder is open, there is absolutely no need to pinch the brake line.
None.
Agreed. There is no way that air would go back into the system through the bleeder if there is any fluid above it at a higher point than that open point. Your master cylinder is usually always higher than any bleeder screw, so that is fluid higher than the open point. I believe this is the general idea behind gravity bleeding. Correct me if I'm wrong in this thinking.
Aside, if I know there is no air in the system, and provided I am going to do a fluid change after pad replacement, I don't crack the bleeder to prevent back-flow into the system. This is also assuming that no fluid was added to the system to cause the reservoir to overflow when doing so, and that the fluid has been regularly serviced so there is little to no 'cruddy' fluid at the piston. My additional assumption is that regularly serviced fluid would prevent any corrosion/pitting on the piston surface, so the chance of piston corrosion causing the seal to leak when being puched back into the caliper would be minimal (and at this point if there was, then the calipers need rebuilding or replacement in my opinion). Also assuming all seals have been or are in good shape.
If the bleeder is open, there is absolutely no need to pinch the brake line.
None.
Agreed. There is no way that air would go back into the system through the bleeder if there is any fluid above it at a higher point than that open point. Your master cylinder is usually always higher than any bleeder screw, so that is fluid higher than the open point. I believe this is the general idea behind gravity bleeding. Correct me if I'm wrong in this thinking.
Aside, if I know there is no air in the system, and provided I am going to do a fluid change after pad replacement, I don't crack the bleeder to prevent back-flow into the system. This is also assuming that no fluid was added to the system to cause the reservoir to overflow when doing so, and that the fluid has been regularly serviced so there is little to no 'cruddy' fluid at the piston. My additional assumption is that regularly serviced fluid would prevent any corrosion/pitting on the piston surface, so the chance of piston corrosion causing the seal to leak when being puched back into the caliper would be minimal (and at this point if there was, then the calipers need rebuilding or replacement in my opinion). Also assuming all seals have been or are in good shape.
Originally Posted By: edwardh1
but the basic question is what does the toyota factory service manual say?
L/T Service Manuals I've read tell you to make sure master cylinder does not overflow while you compress the caliper piston. However, I haven't seen one since the early 2000's so things may have changed.
but the basic question is what does the toyota factory service manual say?
L/T Service Manuals I've read tell you to make sure master cylinder does not overflow while you compress the caliper piston. However, I haven't seen one since the early 2000's so things may have changed.
the danger is getting junk back up into the abs part
Originally Posted By: edwardh1
the danger is getting junk back up into the abs part
Those valves (in the modulator) are closed if the car is off/ABS is not active? Or at least I've always thought that the brakes function normally [as in a non-abs straight off a master cylinder] until ABS is needed that's when the modulator kicks in and all. Someone correct me if I'm wrong. I think it may be different if car has electric brake-force distribution as this may use the modulator in non-abs situations as well?
the danger is getting junk back up into the abs part
Those valves (in the modulator) are closed if the car is off/ABS is not active? Or at least I've always thought that the brakes function normally [as in a non-abs straight off a master cylinder] until ABS is needed that's when the modulator kicks in and all. Someone correct me if I'm wrong. I think it may be different if car has electric brake-force distribution as this may use the modulator in non-abs situations as well?
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