Instructables

Step 9: Pump the brakes!

Picture of Pump the brakes!
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This step is extremely important! Before you start the vehicle, pump the breaks until they are firm. If you skip this, nothing will happen the first time you step on the brakes.

Included in this step are photos from doing the rear wheels. Because of the lack of room, I had to use a torch to remove the caliper bracket bolts. Use caution. You don’t want to burn up your anti-lock brake sensors.
 
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wdexter1 year ago
It's been over a decade since I worked on cars professionally, but the trainers always were very clear that we should NOT push fluid out of the calipers back up into the master cylinder. Instead, it should be pushed out of the bleeders.

The idea was that the ABS system is pretty sensitive, and it might not like fluid being pushed that direction or the bits of gunk and grit that tend to accumulate in the caliper being pushed back into it and gumming up the little valves.

We usually just let the fluid go on the floor then thew down some oil dry (aka cat litter) but you can also use a tube and collect it up.
In this case, I have to respectfully ask where does the fluid go when in normal driving the brakes are applied and then released? Unless I am wrong that fluid goes through all the ABS valves into the caliper to push the pistons out thus squeezing the brake pads against the brake disk. Then, upon release, that very same fluid has to travel backwards. I have always been taught that it is perfectly normal practise to push those pistons back when replacing brake pads. Unless I and millions of others have being doing wrong all these years? :) Oh, if your brake hydraulic fluid does have all those contaminants in it then I would suggest it be completely drained before even thinking about driving the car again.

Somebody else said about hydraulic fluid being hydrophillic or hydrofillic? The word I know is hygroscopic in that it is a fluid which absorbs water (moisture) from the atmosphere. If you use silicon hydraulic fluid this does not absorb water. You do need to replace all the seals in the system though if normal hydraulic fluid has been used.
under normal driving conditions, the piston/pads move on the order of thousands of an inch. You're moving a lot more fluid when replacing the pads and pushing pistons back in.

I agree that the risk is minimal, however, as your fluid should be relatively clean in the first place.
Most manufactures now require a brake fluid flush at some interval. This helps remove the particles in question. I have always backed up the fluid when changing pads and always will. Follow the manufacturers interval for brake fluid flushing, or if it makes you feel better, be a little more conservative and shorten the intervals.
Agreed. Most manufacturers specify 2 years with 3 years the absolute maximum for standard brake fluid. This is because at the end of 3 years there is a significant amount of water absorbed into the fluid. The exception is where silicon brake fluid has been used. That can be left for the life of the vehicle. Decades if that is the life of the car. Silicon brake fluid does not absorb atmospheric water/moisture. So, it doesn't create brake fluid boil and it also does not promote any corrosion in the brake mechanism. The only thing you must do if converting to silicon fluid from ordinary brake fluid is to remove and replace all the seals. They will be contaminated with the old brake fluid and it's a good time to change them anyway :)
When it gets towards the end of the life of those brake pads they have actually moved a heck of a lot more than just a few thousands of an inch. Unless you are using very thin pad material? So, during the lifetime of the pads the fluid is steadily moving more and more into the pistons. It is quite normal and standard practice, at least here in the UK, to use a spreader tool to push the pistons back fully into their respective housings. If you don't you seriously risk having an airlock in the system.
sschoemann1 year ago
Ummm there is no need to pump up the breaks before starting the vehicle if you have simply replaced the rotor and pads. Your break lines are still sealed, so the application of vacuum to the booster will not matter. one way or another. Not starting the vehicle before pumping the breaks up is only necessary id you have opened the lines or bleeders so that you can tell if there is air in the lines as felt by a "spongy brake pedal". Also instead of a torch a dead blow hammer on a breaker bar with an impact socket will work to free the bracket bolts. If you are not familiar with dead blows, they look like a large mallet (depending on weight) made of a polymer (usually orange) with the head filled with a specified weight of loose shot, to prevent the head from bouncing, when used, this has the effect of multiplying the force of the blow exponentially. making a 4 lb hammer act like a 16 and so on.
tiger125061 year ago
I would like to say that this is a great 'ible. It is great to see you mention lubricating the guide pins. It's probably more of a local thing, but it seems like the majority of brake shops, garages, and whatnot completely ignore that brake parts need lubrication. They'll change the pads and then *force* them into place. If you want smooth brakes, you *must* clean and lightly grease every surface that the edges of the pad plate backing contact. And definitely the guide pens. All this lubrication sometimes can get you in trouble, so I also advise using a cleaner on the surface of the brake disc to remove any overshot, or greasy fingerprints.
Also, depending on where your brakes have been done before, you might find everything torqued to an remarkably unnatural number of ft-lbs. I've done some brake jobs where the lug nuts, guide pins, and even the bleeder nut have been torqued so hard that they *must* be loosened with a torch (>300ft-lbs). Experience tells me that I can apply great amounts of torque much more easily with a longer lever arm, than I can with an impact gun. Because of that, before resorting to heating, you should try to extend your lever arm (safely) and use 6-sided sockets (rather than 12) to avoid stripping.
Unless I missed it in your presentation and one of the most important tasks to prevent brake chatter or vibration would be to torque all the bolts including the wheel bolts. If the bolts holding the wheels to the hubs are not properly torqued they will cause vibration when you apply your brakes. You should contact your dealer who can advise you of the proper number of pounds required to tighten your wheels. This is extremely important if you have alloy wheels on your car.
jrm80691 year ago
Take the time to use a torque wrench on your lug nuts. Uneven torque on lug nuts is a major reason that rotors warp in the first place. It takes about 1500-2500 miles, but the thermal cycling with uneven clamping force, eventually contributes to the rotors getting out of shape. All major manufacturers have come to the same conclusion.
dkeach1 year ago
http://www.summitracing.com/parts/lil-25750?seid=srese1&gclid=CIqQlc-AsrgCFepZ7Aod_xUA6w
Something like this
dkeach1 year ago
Great ible again mr.b, I noticed something that might make life a little easier. Have you ever used a caliper compressor? It works almost like a caulk gun, and im sure u could probably fashion one up with your skills. You also may want to mention the importance of not keeping car on a jack incase a seal gives out. My grandfather told me once never put any part of yourself under a car on jacks that you dont wanna lose. Personally. Ive never used a torch or impact driver, ifs always been a wrench or homemade breaker bar for me