Toyota Supra 1993 Mk 4 Rear Brakes Overhaul

The rear brakes on the Toyota Supra 1993 Mk4 non-turbo comprise an outer disc with an inner drum parking brake, other models may be similar and candidates for the following.

supra

To replace the pads, shoes and disc the following procedure should be carried out. This is designed to supplement the manual with tips and procedures to solve common problems.

On this model the brake pads are standard thickness of 11.0 mm (0.433 inch) with a minimum of 1.0mm (0.039 inch). Disc thickness 16mm (0.630 inch), minimum 15.0 mm (0.591 inch). Parking brake shoes 2.5mm (0.0985 inch), minimum 1.0mm (0.039 inch).

Before you start stages of work check the new parts against the old for dimensions etc when and where possible. Keep the parts in any plastic bags during the comparison if possible. This will ease any return to the supplier as will clean and tidy packaging.  Always aim to keep a roadworthy state close should a job need to be abandoned temporarily and the vehicle required to be put back in service.

Apply the parking brake and engage the lowest gear. Raise the car on a jack on the relevant rear side. If using a hydraulic jack use a wooden block between the jack and the jacking point. If the jacking point is the sill use a block of soft wood approximately 5 x 3 x 1.75 inch. Cut a slot 0.75 inch wide x 0.75 inch deep across the grain 1.75 inch from one end to accommodate the sill fin. These may not be the optimum dimensions for your vehicle so check.  You may need to have an assistant to heave the vehicle up a fraction to slide the block between the jack and vehicle.

Chock the other three wheels on both sides of the tire, sections of 3×3 inch lumber are suitable. Slightly loosen the road wheel lug nuts just before the tire leaves the ground. Note loosening the road wheel lug nuts at this point is not strictly necessary here as the wheel is locked by the brake and transmission, but is useful on non driven wheels.

Insert one or more safety backup axle stands under the inner part of the lower suspension member such that if the main jack fails the load on the axle stand will not bend any part of the suspension. Use wood packing to spread the load. Never place any part of your body under a vehicle sitting on a single support.

Remove the road wheel.

Remove the brake pads.

Remove the part of the brake disc caliper which holds the pads by removing the two bolts on the slide rods part of the assembly. Tie the caliper up out of the way.

Apply a small amount of penetrating oil to the two bolts holding the remaining part of the  brake caliper to the hub assembly. Let the oil soak in and remove the bolts. These are tightened to a torque of 77 ft lbs but should loosen easily.

The next part of the job is usually tricky as the disc will have rusted onto the hub. Apply penetrating oil through all the drilled holes the front of the disc, including the holes where the threads pass through. Prise out the rubber bung to expose the parking brake adjuster.

Release the parking brake and put the drive in neutral, watching for any movement on the jack and axle stands.

Rotate the hub so that the adjuster hole is at the bottom, just off center (backwards or forward depending on side). If you shine a flash light in the hole you should see a coarse toothed wheel. Use a flat screwdriver to rotate the wheel down using the teeth until at the end of its travel. This will contract the two brake shoes. The toothed wheel clicks against a spring which acts as a detent.

Pull the disc forward to see if is loose (unlikely). The disc is normally well rusted onto the hub. Try a pry bar inserted behind the disc as far as it will go down against inner lower part of the hub casting where the lower caliper bolt hole is. Do not lever further up the casting closer to the bolt hole as it could possibly crack the casting. This usually just flexes the disc which can be observed by the penetrating oil sucking and squeezing in and out around the multiple drilled holes.

Whilst under tension on the pry bar use a soft hammer to tap the back of the disc. Rotating the disc between prying and tapping sessions. It may be possible to use a puller with the brake plate removed, but this may be unnecessary, read on.

At this stage the situation may look hopeless and the application of heat, brute force or major replacement work approaches on the horizon.

Toyota has thought of this and cunningly provides two tapped holes diametrically opposite near the large central hole in the disc. These will generally be hidden by muck and rust. The holes are 8mm diameter with a metric thread. Dig out the rust and muck to get the threads as clean as possible. Find two suitable good quality well-fitting flat ended bolts. The bolts used were a fence type with a flattish domed head with a square shank underneath, measuring 7.7mm across the threads with a thread pitch of 1mm. If the tip of the bolt is irregular or rounded run a nut up the thread then file the end to give a flat surface. Finish with a light cleanup of the end of the thread. Remove the nut to further reinstate the thread.  The object is to maximise the number of threads available to engage in the disc hole

Ease one of the bolts into the disc hole with plenty of oil using a half turn forward and a quarter back sequence to clean the thread. Remove the bolt after a couple of turns and clean out the thread. Reinsert and continue like this in small steps until the bolts hits the hub. The size of the threaded holes do not look like they will take the load but surprisingly it works. (Similar holes are provided in the engine front pulley and this takes even more load! A tool must be made up to use the holes on the pulley and an additional puller is recommended for the initial stage of the pulley dismantling).

Two bolts should now be in place. It is helpful to run a sharp point around the joint where the disc meets the hub to break up the rust and generally scrape away rust on the hub protusion. Inch the bolts in alternatively until there are one or two distinct cracks heard. Be careful the disc does not fly off (unlikely). Continue winding the disc forward until the inner disc to hub rust is finally broken and cleared.

Be careful that brake shoes are not hampering the removal as they may catch in a wear depression in the disc (unlikely), be tight against the disc or twist. If they do catch they will ultimately pull the spring shoe retaining clip out of the round slotted plate and do damage.  So check the shoes are not moving with the disc by frequent checks and rotation of the hub to try to part them from the disc. If the shoes are moving with the disc you will need to push the disc right back before it can be rotated.

Assuming that you have now removed the disc without injury and mayhem the next stage can be pursued.

Use a face mask for the next stage to prevent the ingress of any harmful dust.

Remove the brakes shoes noting the relative locations of all the springs (colors), clips, rods and adjuster. To unlink the parking brake cable from the lever force the tip of a pair of thin nosed pliers between the spring and the lever and slide the spring back about half an inch then grip the cable and maneuver the retaining collar out of the lever.

Clean the area behind the hub face using a paper towel soaked in mineral spirit to catch the dust and any oil.

Clean the face of the hub with a wire brush, glass-paper and a small flat file to take down any high rust spots. Use a small round file on the angle between the face and the disc locating round part. Be careful with the filing to just remove high spots and surface rust.

Install the new brake shoes. This is much easier with two persons. Apply a dab of copper based grease to points where the shoes slide on the back plate. Clean the thread and tube of the adjuster and reassemble with a light coating  of copper based grease. The circlip holding the lever to the brake shoe is not sprung so has to be opened out with a small chisel in the top and should be replaced? The gap between the lever and the shoe should be less than 0.35mm (0.0138 in), if not replace the shim which goes on top of the lever. Apply a dab of copper based grease under the lever on just the sections that contact during the sliding.

Check the brake shoe spring restraining pins for straightness as they may bend if the disc catches the shoes on removal. One of the pins has a bent section to clear the lever so ensure all the sections are straight and the ends line up with each other. Also check the pin retaining collar slots are not distorted. To attach the shoe retaining clips align the thumb sized hole in the hub over the clip and use thin nosed pliers with their tips in the ends of the depression in the slotted collar to push the spring whilst holding the pin from the rear of the disc cover plate. When the spring is sufficiently compressed twist the collar 90 degrees and release so that flat end of the pin lays in the depression. The blue short spring goes on the left and the longer pink spring on the right. Align the bend in the right hand pin so that it clears the shoe lever. Align the springs so they are centered round the pin hole in the brake shoes.

Check the new disc locates on the hub OK with a temporary fitting.

Clean the face of the hub and in any depressions. The object is remove al loose material that could prejudice the disc alignment. Apply a thin coat of copper based grease to the face. Leave a small margin around the adjuster hole. See this post regarding lubricating the wheel lug nut threads http://www.theglobalstore.com/info/?p=338

Clean any corrosion preventing coating from the pad and disc contact surfaces of the new disc. Apply a thin coat of copper based grease to the face of the disc where the road wheel sits. Work the grease into the multiple drilled holes to cover all surfaces thinly. Leave a small margin around the adjuster hole.

Locate the disc on the hub and temporarily hold it is place with two opposite finger tight lug nuts. Rotate the disc so the adjuster hole is at the bottom. Using a flat bladed screwdriver turn the adjuster wheel upwards until the brakes contact the disc and lock the wheel. Turn the adjuster back (down) eight teeth. Clean any copper grease from around the hole. Replace the rubber grommet in the adjuster hole.

Check the disc run out with a dial gauge (0.05 mm of 0.0020 in). If a gauge is not to hand hold a piece of small thin piece of metal such that it can be held tightly against a static point and contacts the outer face of the disc as the disc is rotated. This will give some idea by eye of any run out. If you are able to clamp the piece of metal you can check run out with a feeler gauge. If run out is found check for grit or rust between the hub and disc. Check the wheel lug nuts are sufficiently tight by hand or light wrench tightening and centered with the conical end of the lug nut engaging in the slightly oversize disc hole (in the absence of the wheel).

Check the parking brake operates OK.

Reassemble the caliper using 77 ft lbs on the caliper to hub bolts and check the slide rods are free. Insert the new pads using a dab of copper based grease on the sliding contact points (sides and bottom of the two lugs on each pad) and the shim.

Apply the parking brake and engage the lowest gear. Remove the wheel chocks before releasing the jack as they may get trapped as the vehicle is lowered depending on the shape of the chocks.

Check your work with a careful test drive. Apply the parking park lightly a couple of times during the drive to set and bed them in. The manual details a procedure for this as follows:

SETTLING PARKING BRAKE SHOES AND DISC
(a) Drive the vehicle at about 50 km/h (31 mph) on a safe, level and dry road.
(b) With the parking brake release button pushed in, pull on the lever with 88 N (9 kgf, 19.8 lbf) of force.
(c) Drive the vehicle for about 400 meters (0.25 mile) in this condition.
(d) Repeat this procedure 2 or 3 times.

Check the parking brake lever travel is between 5 – 8 clicks if not adjust by removing the console and adjusting.

Avoid fierce braking until the new brake pads and disc have bedded in. Bon voyage.

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