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Thread: GQ Brake caliper seal replacement.

  1. #1
    Patrol Guru Family4x4's Avatar
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    GQ Brake caliper seal replacement/rebuild.

    Disclaimer: I take no responsibility for others completing this job incorrectly and injuring themselves or others. If you are not confident and competent in undertaking this task, employ a trained professional.



    The tools and seal kit I used are below. I replaced seals on both rear calipers.

    IMAG1823.jpg IMAG1751.jpg

    A few items not in the picture are a small piece of dowl, q tips, vice, brake cleaner and brake grease.



    Firstly i put a liberal amount of WD 40 into the cylinders via the brake line bolt hole, these calipers had been sitting for a while.

    Next was to undo and remove the 12mm slide pin bolt (it may be very tight), followed by pulling the caliper apart and off the 2nd slide pin.

    With the caliper in two pieces I then began the process to remove the piston.


    There is a metal retaining clip holding the dust boot on this can be removed with a pick.

    IMAG1765.jpg IMAG1767.jpg

    You may not be able to see the retaining clip, but it is on the outside rim of the boot on the cylinder wall. Once you have located the leading edge of the clip it should come out easily.

    Once the clip is off it helps to push the piston out a little then remove the dust boot.

    On these calipers the pistons were quite stuck, I used a piece of dowel(wood) in the brake line bolt hole and hammered the piston out. There are other methods of removing pistons, they can be googled if required.

    IMAG1764.jpg IMAG1769.jpg

    Once you have the piston out check the general condition of the piston and cylinder with a visual inspection. If there is severe pitting or any deep gouges in either they will need to be replaced.

    The square cut seal can now be removed from the cylinder. I use a hooked pick. Be careful not to damage or gouge the cylinder wall. The old black seal can be seen in the picture below.

    IMAG1771.jpg

    I use brake cleaner and a soft toothbrush to clean the piston and cylinder. The toothbrush should do a good job of removing any remnants of the old seal from the piston. When cleaning the cylinder pay particular attention to the notch where the new seal will seat.

    Also remove the bleed nipple and check, clean or replace if necessary.

    Once the cylinder is clean and the piston clean/polished you are ready to fit the new square cut seal. I lay out a new clean rag to avoid getting any dirt or contaminants on the new seal. It may also pay to wash your hands.

    IMAG1778.jpg

    Use a small amount of Dot 3 brake fluid to coat the outside of the seal (you may want to wear gloves). Then fit the seal into the groove in the cylinder. Ensure the seal has seated properly and not rolled.

    IMAG1781.jpg

    You can now fit the piston. Again coat the inside of the cylinder and the out side of the piston lightly with brake fluid.

    When fitting the piston pay attention to it going in straight/square. I use a clamp and impact socket to gently guide the piston in. Only seat the piston about half way, so the groove for the dust boot is still showing.

    IMAG1782.jpg

    Now you can fit the dust boot to the groove on the piston, the flatter side of the boot faces the cylinder. The picture below show the face of the boot that will be showing when fitted.

    IMAG1787.jpg IMAG1791.jpg

    When you have the boot on use your clamp and socket to further seat the piston, stop when the boot is starting to touch the cylinder housing.

    IMAG1793.jpg

    Now the boot needs to be fitted inside the cylinder housing, using your fingers or small flat blade screw driver carefully feed the boot into the cylinder housing. In the photo above you can see part of the boot has started to go into the housing.

    Once the boot is inside the housing it needs to be seated. I carefully used the curved back of a pick to seat the boot. In the second photo below on the right hand side outer part of the boot, you can see the boot is still not seated.

    IMAG1800.jpg IMAG1804.jpg

    When you have seated the boot the retaining clip needs to be fitted. Gently squeeze the retainer clip until it it the correct size to match the outer boot. Feed it on top of the very outer of the boot. Once it is in it can also be pushed carefully into place with the back of a pick.

    IMAG1809.jpg

    The piston assembly is now complete. The bleeder nipple can be refitted and its new rubber cap put on.

    Now the slide pins will need to be cleaned. Remove old grease from the pins, also remove the old rubber boots and clean the housings.

    IMAG1811.jpg

    When refitting the small boot attach it to its larger end first.

    IMAG1815.jpg IMAG1817.jpg

    With a small amount of grease and some gentle persuasion the double ended boot can be refitted.

    IMAG1818.jpg

    With a small amount of grease the bush from the double boot pin can be pushed in to the boot.

    IMAG1819.jpg

    Before putting the two halves of the caliper together check that the bolt on the fixed slide pin is tight.

    Then grease the fixed slide pin and push it through the boot into its housing ensure the boot seats in the groove.

    When swiveling the caliper the boot should not move, the pin should turn freely inside it.

    Lastly lightly grease the last slide pin bolt and fit it.

    Done.

    Thanks to the bloke who made this rebuild possible!
    Last edited by Family4x4; 10th May 2014 at 08:55 PM.
    In any moment of decision, the best thing you can do is the right thing, the next best thing is the wrong thing, and the worst thing you can do is nothing.

    Theodore Roosevelt

  2. The Following 5 Users Say Thank You to Family4x4 For This Useful Post:

    hawaiian01 (24th May 2014), mudnut (9th May 2014), my third 256 (10th May 2014), Parksy (9th May 2014), terhakas (3rd May 2016)

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  4. #2
    Patrol God mudnut's Avatar
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    I have just cleaned and greased the rear caliper slides and applied some anti-squeal to the rear brakes. After braking, one was dragging and emitting a small squeal.

    I found the left rear side dust cover on the piston is basically holes held together by a bit of rubber.

    Hoping for the best, I tried to get a major kit, but was told I need a minor kit ($17) and a piston ($50) at Auto pro. They haven't got a caliper listed.

    Repco wanted $27 for a "kit" but couldn't tell me what was in it. They also want $800 for a caliper. Must be gold plated platinum.

    Since there doesn't seem to be fluid leaking, I am hoping the caliper bore isn't too far gone, but I don't know how long the rubber has been wrecked.
    My advice is: not to follow my advice.

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