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Thread: TR7 brake booster

  1. #1

    TR7 brake booster

    Anybody know where to get a reasonably priced brake booster? Wedge shop is too pricey for me and noticed there are others that have rebuild kits for them. Anyone try to rebuild one and are they difficult to do?

  2. #2
    Jedi Knight
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    Re: TR7 brake booster

    They are not that hard to rebuild. Taking them apart is the tricky part. Its basically a big rubber bladder sandwiched between the two outer shells with some other seals in the middle. Sending one out to be rebuilt gets expensive because they come back all shiny and new looking. I have a shelf full of used ones if you want to take a chance with one of those. I haven't really seen them go bad unless the master cylinder starts to leak and they fill up with brake fluid. The brake fluid damages the seals and bladder. New masters are around $250.

  3. #3

    Re: TR7 brake booster

    Took some time to look at it a little closer. You can see the stains on the booster. Evidence that it may have been leaking plus the master cy. looks relatively new and I think the PO said it was recently replaced. That hissing sound is very noticeable when you push hard on the brakes and may have been part of my complaint of poor braking.
    To open it looks like you pinch the tabs out then I would imagine separating them and getting them squeezed back together to seal would be the hardest part. Still going to look around for a new one.
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  4. #4
    Jedi Knight Darrell_Walker's Avatar
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    Re: TR7 brake booster


    The two halves of the booster screw apart.

    What symptoms are you seeing?
    Darrell Walker
    66 TR4A IRS-SC CTC67956L
    81 TR8 SATPZ458XBA406206 (daily driver)
    Vancouver, WA, USA

  5. #5

    Re: TR7 brake booster

    I can mostly hear a hissing sound when pushing the peddle and poor breaking. When I first bought the car I complained about the hard breaking and discounted the fact that it could have been the booster, because at start up with your foot on the break the peddle moves down. It still does that but the hissing is very noticable now.

  6. #6
    Jedi Knight Darrell_Walker's Avatar
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    Re: TR7 brake booster


    It could be the booster, but if the master cylinder was replaced, it could also be the seal between the cylinder and the booster wasn't transferred over (BTDT).
    Darrell Walker
    66 TR4A IRS-SC CTC67956L
    81 TR8 SATPZ458XBA406206 (daily driver)
    Vancouver, WA, USA

  7. #7
    Jedi Knight
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    Re: TR7 brake booster

    The TR7 has an inline check valve on the vacuum hose. Make sure you have it or you will get the symptoms you describe. TR7 and TR8 boosters are different in that the TR8 booster is a little bigger. In the real world you can't really notice the difference between them.

  8. #8

    Re: TR7 brake booster

    I don't see one. The vacuum line goes from the plenum (PI model) into the black inlet on the booster. Now my question would be why would I be hearing a hissing noise if the check valve is missing? I see in the Victoria British catalog that there is one available. They also have a rebuilt unit.

  9. #9
    Jedi Knight
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    Re: TR7 brake booster

    The hissing is most likely coming from where the white plastic elbow fitting pushes into the booster. If either the seal dries out or the fitting cracks, it will leak. The hose in the picture looks more like heater hose than the rigid vacuum hose. If that's the case, the constant flexing of the hose will lead to harder brakes as well. The check valve just helps keep vacuum pressure in the booster at all times, even under low vacuum situations and or repeated braking. Many of the TR8s with big cams develop low manifold vacuum pressure, which result in a very hard pedal the second time you step down on the brakes if enough time doesn't go by between pushes. Makes repeated braking in stop and go traffic difficult. A buddy of mine just installed a vacuum pump on his car that just creates vacuum for the braking system. Things may be a little different on the FI cars from what I'm used to.

  10. #10

    Re: TR7 brake booster

    Defiantly not the heater hose unless you mean that is the type of hose they used?
    That is possible and I think what your saying there is it can't handle the vacuum and may slightly collapse effecting the braking ability? I'll have to see if I can locate a check valve too. Stopped at a local parts store today with no luck. It is also possible the elbow is leaking. It seems a little loose in the rubber grommet.
    Is there a way to check for leaks? What if I put some pressure into the hose. I would think I could hear the leaks or use a little soapy water to find them.

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