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R&R Rear calipers, rotors, pads and bleed.
(R&R = remove and replace)
Subject Vehicle: 1995 900 SE Turbo, 130000 miles.
Degree of difficulty: Two beers.
drs_install <-- search keyword
Problem: The the outboard piston was siezed one of the RH calipers.
Work: Replace rear calipers, rotors and pads.
Note: Some bleeder valve hex sizes can be different. The brakes were changed a bit in 1997 model year but the work should be mostly as described.
Tools: 3/4" socket, six sided prefered, 1/2" breaker bar and torque wrench. 9mm, 10mm flare wrenches, 7mm deep shell socket or others for the bleeder valve bolts... read the text.
I used four flat top axle stands and remove a four wheels. Other arrangements will work.
1) Loosen the brake line nut. It is 10mm nex. You will need a box end wrench that has a 6 sided end with a slot cut in it to allow it to go over the steel brake line. These nuts can be rust bound and lesser tools often just lead to the nut being rounded off. Penetrating oil may be needed. If the nut will move, watch the brake line it self where it goes through the nut. If the line is stuck in the nut, removing the nut will destroy the brake line. If the nut will turn independant of the steel brake line then things should go well. You could sample this before ordering your parts, incase you decide that you want a mechanic to deal with it.
2) Remove the #30 torx screw that secures the rotor to the hub. If this will not come out you will need to try penetrating oil and other methods.
3) If replacing the rotors, degrease them now. They all have a oil film to prevent rust in storage. It must be removed. Almost any solvent will do. There are spray cans of brake wash that work well. Be sure to degrease the parking brake shoe area on the inside too.
4) Remove the lower 3/4 hex bolt and mostly remove the upper one.
5) Place a tray under the caliper to catch the leakine brake fluid. Use something impermiable like glass or metal. (Don't use tupper ware and take it back to the kitchen.)
6) Remove the brake line and lift it up a bit to release it from its plastic hold down on the axle fabrication. With the brake line lifted up and out and lowered back behind the caliper, hold the caliper in one hand while removing the top 3/4 bolt. Move the caliper to one side and note that it will leak fluid.
7) Remove the rotor and put on the new one. Don't worry about the torx screw or rotor index postion yet.
8) Locate the new caliper to the rear hub and insert the upper 3/4 bolt a bit.
9) Place the brake line into the caliper and run down the flare nut snuggly so that it will not leak. I had previously loosened the bleed valve and left open, so that the fluid would continue to flow and fill the caliper while other work was being done. Keep an eye on the brake fluid level in the reservoir. You did purchase a 1 liter bottle of DOT #4 brake fluid didn't you? If you are concerned about the dripping while you are working, the top of the reservour can be covered with some poly film and the lid screwed down on it. If you get that air tight it should limit the fluid drip rate.
10) Examine the lower 3/4 bolt and remove any rust from the threads if neccessary. I suggest that you use never sieze on the threads. If that is in there, water will not be. I also put never sieze under the bolt head contact surface for the same reason. Run in the lower bolt and then remove and do the same to the upper. Snug them both up and torque to 60 ft-lbs. The rebuilt units with gold epoxy coatings are an issue. The paint is on the bolted joint contact surfaces and did not seem like it was going to be easily scraped off. So I left it on. I could feel it as I torqued it up. The 60 ft-lb spec did not feel secure enough. I took the bolts to a bit over 65 ft-lbs.
11) Rotate the rotor to line up the holes and run in the #30 torx screw with plenty of anti sieze on the threads and under the head bevel. Do not make it to tight! Put anti sieze over the screw on the outside or use another rust preventative.
12) Tighen down the flare nut. You are not going to be using a torque wrench with a flare nut, so use common sense and feel. Close the bleeder valve at some point, but you can allow the fluid to fill and flow through the caliper by gravity if you want. Watch the reservoir.
13) Secure the steel brake line in its plastic clip on the axle.
14) Place stick on brake pad shims on the back of the pads if supplied. If the back of the brake pads are a bit rough from dirt in the pain, rub them on the garage floor first to remove the high spots. Insert the pads [shims] into the calipers, insert the pins and hold down springs. Drive the pins home.
Other things that you should know or consider:
Often the bleed valve bolts will be rusted in and cannot be removed. If you are replacing the caliper it is not a big deal. But is you need to bleed the brakes for preventative maintenance it is a big deal. Some brakes come with snti sieze pre applied to the bleeder threads. Some come without. If there is none, apply to the threads only. If you are bleeding the brakes properly, there is no danger of that stuff getting into the system. When you get a new vehicle, spray some penetrating rust preventative in the bleeder valve and on its exterior. The valve needs to always be covered with it rubber sealing cap.
Clean the threads of the brake line flare nut and clean out the grud between the nut and the brake line. Rotate the nut to loosen the dirt and slide the nut and wipe the pipe unit you get all of the dirt and rust out. Move the nut up and wipe the pipe dry, noting that there will be fluid dripping from end of the pipe. Apply never sieze to the pipe blow the nut, but don't get it on the flaired end of the pipe. Apply to the flare nut threads. Move the nut dowm, rotating to distribute the never sieze. Apply to the brake line above the nut and move the nut up, rotating. Now locate the pipe flared end into the caliper and run in the flare nut. After tightening the flare nut, apply never sieze to the pile above the nut, on the top of the nut and around the nut where it is inserted into caliper. This should prevent rust damage. When you get a new vehicle, put some penetrating rust preventative on these bits. With some care, there will be no danger of getting any of the never sieze inside the caliper.
The rebuild bleeder valves are usually small. So your 9 or 10 mm bleader valve will be replaced with a 7mm, 1/4" or 5/16" inch unit. So before you do your capliper replacement or system bleed, survey the sizes of the fittings currently on your vehicle before getting too far along. For the small bleeder valve sizes you will not find 6 sided flare wrenches. So a deep socket that will get past the bleed bold nipple to engage the hex flats is needed. If the bolts have been protected from rust then they will be on size and be less likely to get rounded off.
The front calipers have 10mm bleed valve bolts.
Before you bleed the system or replace calipers, you want to remove as much of the old fluid from the reservior as possible and replace with new DOT #4 brake fluid. The only location in the system where the fluid can get water contamination is the reservior. So you do not want to flush that material through the systen. If your pads are worn, the push their pistons back in to force more fluid back to the reservoir to remove it first. Do this fluid renewal at the reservoir every year, whether bleeding the brakes or not.
While bleeding the system, make sure that you do not pump the reservoir dry!!!
Put a piece of 2x4 behind the brake petal to limit its travel. The brake petal in normal service never goes to the floor, so there are parts of the master cylinder that are never stroked and these parts can have deposits that can tear up the master cylinder seals. It is common obervation that master cylinders need serice after brake work where the brakes have been bled with the petal going to the floor.
Brake fluid is water soluable and easy to clean up. It will damage most rubber and paint, do be careful with it. Do not spill it as you fill or empty the reservoir.
Put anti sieze on the rear brake pad backing plate edges, pins and hold down springs. These things all can rust severely. DO do a trial fit of the pads and pins before you get things greased up. The calipers can be mis machined, it has happend to me, and often brake pads are supplied for the Saabs which need the pin holes elongaged :( You will need to elengate the holes with a rat tail file or dremel grinder. You don't want to do this after the backing plate top and bottom edges are greased. For new calipers, put the pads and pins in for a trial fit before you get started. I had a caliper where the outboard lower pin hole was mis-located low by 3.5mm!
If your replacement calipers are painted or epoxy coated, the coating may extrude at the bolted joint, where it should never be anyways! So some time later on it would be a good idea to get out the torque wrench and give the 3/4" bolts another go. If your brakes get to be clunking when braking in reverse, you will have an idea about what has happened. Time and heat will be factors in this coating material extrusion. The coating material also cannot take the shear forces across the bolted surfaces either. Good high strenght bolted joint design NEVER depends on the bolts taking any shear load, the bolts should be purely in tension. The coating should be removed from the joint contact surfaces. The contact surfaces resist shear across the joint by friction induced by the bolt tensile forces. I will post any issues with torque retention which I detect.
posted by 208.24.17...
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