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Thread: Rear Wheel Brake Cylinder removal and rebuild help

  1. #1
    Registered User 280z1975's Avatar
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    Default Rear Wheel Brake Cylinder removal and rebuild help

    Hello all,

    So this is the last main problem with my Z before it is road worthy to be driven.

    I had a problem with the brakes being REALLY bad, so I bleed the brakes and it would feel good for about 5 pumps of the brakes and then go back to bad after that. I thought it was my Master Cylinder, but after replacing it (it needed to be done anyways) I learned that both of my rear wheel hydralic cylinders were leaking. So after a couple of pumps of the brakes and most of the fulid would leak out.

    Is it a common problem for a wheel cylinder to leak and fail? The car was sitting for four years when I got it? (see the first photo for referance) Does someone have a part number for this?

    Second, I am trying to remove the brake lines to this part. My FSM says to disconect in at the bottom near the bleeding valve, point #2, but that point doesn't want to budge. In fact I rounded the bolt a little and wanted to ask if I am removing the right bolt. I have included a photo for referance. The #1 lable is for behind the metal plate where the bolt attaches to the rubber brake line.

    Thanks for the help.
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    -Gregg Germer -

    1975 280z - HLS30-210542
    My 280z's Webpage - http://www.gregggermer.com/280z.htm - a chronicle of it's transformation

  2. #2
    Semi-retired admin Arne's Avatar
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    Yup, any hydraulic part that sits for years is likely to fail, and wheel cylinder failures are common. They are at the lowest point of the system, so moisture in the fluid migrates there and corrodes it from the inside out.

    #2 is where you need to disconnect it. You should not use a normal wrench on these line fittings, as there is a very great risk of rounding off the fitting (as you have now seen). You should have used a flare nut wrench instead. But it may now be too late even for that, and you may need to use a vice-grips or something similar to get it loose. Unfortunately, to get it back tight again, you may now have to replace the metal line itself - which runs from #1 to #2.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

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    Registered User 280z1975's Avatar
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    Thanks for the help Arne ... I think the metal might have to be replaced, which sucks.
    -Gregg Germer -

    1975 280z - HLS30-210542
    My 280z's Webpage - http://www.gregggermer.com/280z.htm - a chronicle of it's transformation

  4. #4
    Furthur GreenZZZ's Avatar
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    One of my wheel cylinders just failed. I went through my records and thought this would be an interesting datapoint for folks. I installed new aftermarket wheel cylinders ($37.41 per side) in June, 1989. I've only put 20K miles on the car since then with many years putting less than 300 miles per year. Reading what Arne posted, I'm just going to order new parts and not attempt a rebuild.

  5. #5
    Semi-retired admin Arne's Avatar
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    Many modern cars now recommend changing the brake fluid every couple of years or so. This is excellent advise as well for classic car owners whose cars don't get a lot of miles put on them. Changing the fluid removes the moisture and can help prevent corrosion. I change mine at least bi-annually on all my vehicles, even those that don't have a factory service interval for that.
    Arne - Former owner, HLS30-37705, 7/71, 905 Red
    Car blogs - 240Z - Porsche 911

  6. #6
    Registered User 280z1975's Avatar
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    To further comment on Arne's points (this point was brought up by another member, but the name eludes me at the moment) it's a good ideal to DRIVE your cars ... when you drive it helps heat up the brake fluid which intern helps evaporate the moisture in the lines. The member had his brake cylinders go bad cause he was 'babying' his car. The same goes for the electrics (at least I have been told) that using them is good cause the heat generated from the electricity helps keep moisture from forming.

    Enjoy the car and enjoy the road, cause these were meant to be driven ...
    -Gregg Germer -

    1975 280z - HLS30-210542
    My 280z's Webpage - http://www.gregggermer.com/280z.htm - a chronicle of it's transformation

  7. #7
    ZCOOR #109
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    #1 Gotta bleed brakes on a regular basis, full bleeding, that is a replacement of all the fluid.
    #2 synthetic helps, but is not a cure all, as water still can get in the system, it just doesn't MIX with the synthetic, it stays separate to cause rust.

    #3 The flare nut wrench mentioned is a must for brake work. I believe it is a 10mm for the 240Z. This type wrench is a "box" end type, with a "cut out" made in one side so you can slip it over the metal brake line and onto the nut. Thus, you have a wrench touching the flare nut surface on five of six sides.

    You may be able to salvage this. First buy the correct wrench. Then buy a small fine cross cut file. Try the wrench first, if it won't go on the nut, then file each side of the nut slightly to take off the burr that has formed. Don't take off much, and do it in steps trying the wrench each time to see if the wrench will slip on.

    ALSO, use some wd40 or similar fluid on the threads and peck with a small hammer on the area to vibrate the wd40 into the tread area.

    BE SURE you are trying to turn the nut the correct direction. If it moves a little, retighten slightly, going back and forth to loosen the rust/corrosion.
    Tease it out/loose is what I'm saying.

    You will want to replace the line probably if the nut is damaged much. That is a trying thing, as there are some tight bends to duplicate, or buy a replacement factory item.

    The wheel cylinders are aluminum, and I don't believe can be honed and rebuildt with a kit. I think you will have to buy new. pitting of the surface will not allow new rubber to seal.

    Some Corvette owners have an issue with front calipers corroding terribly, and they have an after market supplier that bores out the cylinder and sleaves with stainless. $$$$, but last a long time. Maybe someday we will have such support?

    good luck
    Lowell
    original owner 72-240Z
    Original Blue w/White, 79,000Miles

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    Furthur GreenZZZ's Avatar
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    Quote Originally Posted by 280z1975 View Post
    Enjoy the car and enjoy the road, cause these were meant to be driven ...
    I'm convinced!
    Last edited by GreenZZZ; 04-18-2007 at 12:48 PM.

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