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Power brake vac question

This is a discussion on Power brake vac question within the General Help forums, part of the LSx Technical Help Section category; I have a 98 LS1 in a 56 street rod. Running a 1984 Corvette brake/sup system. The corvette brake boster ...

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    Power brake vac question

    I have a 98 LS1 in a 56 street rod. Running a 1984 Corvette brake/sup system. The corvette brake boster has a filter betwwen it and the engine hose. Is this filter needed. It seems my brakes are not really power. Does anyone know if the LS1 makes less vacume then the 84 Corvette engine and this filter needs to be removed? Thanks

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    Senior Member bigrondownhiller's Avatar
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    Do they just not stop all that well or do they require a lot of effort? What size booster is it?

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    It is a 9" GM booster. I really just started bleeding the system so I don't know what my problem is yet. It seems to still have air in it as I have no petal. But I can pump it up. The reason I think it may be a booster problem is there is no resistance when the car is not running. Most PB systems I have dealt with had good resistance when no vacum was going to it. I will check the vac from the engine next as I understand it needs to be at least 15 inches. Also I have been told the filter is just for dirt and oil and it will not reduce vacum.
    Last edited by Ken Glowacky; 01-08-2009 at 09:11 PM.

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    Are you sure it's only just a filter and not a check valve also? if it is indeed a check valve you realy need it. trust me on this i thought that was the problem with my 80 Malibu and removed it. everyting works fine unless your engine dies and then you have little to no brakes at all. i found this out at the track, I ended up in the gravels at the end.

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    I will do some research on my so called filter. I agree there needs to be a check valve. I thought it was in the booster itself. It has some writing on it I will check.

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    Senior Member casperss's Avatar
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    Anyways a new valve is only a couple of bucks. you can find them in most parts stores in the help section.

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    It is a new booster and it has a new check valve that snaps in the booster. This is a canister looking filter that has a 90 degree bend coming out of one side and a straight nipple out the other. I am going to check ther vacume and bleed the brakes again. Thanks

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    No problem and good luck..

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    Make sure when you are bleeding the brakes you are starting from the furthest wheel from the master and work towards it. Forgot to ask, is the brake booster mounted on the firewall or framerail?

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    on the firewall. Everything is from a donnor 84 corvette. I wanted to keep everything the same as factory so there isn't any questions about mixing up products and not working togetner.

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    well I have now driven the car and here is where I am at. I bled the brakes with speed bleeders and before that vac pump. I still have spongy brakes. They will stop me but not to responsive. I checked the vac to the boster by pulling off the hose while it was running. It is getting vac, will hold my finger in place. Even when I pump them they don't get any better. Any idea's??? Thanks

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    Is the master cylinder the original one from the corvette?

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    No, it is brand new corvette replacement from Napa. I bought it on E-bay still in the box. I guess it could be bad???? I would hope not.

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    Senior Member bigrondownhiller's Avatar
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    Before you put it in did you bench bleed it? What about all the other parts like calipers or wheel cylinders? Do you have 4 wheel disc or disc/drum? Do you have a proportioning valve or combination valve?

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    4 wheel disc. All new calipers, did not bench bleed the master cyl. before install. Prop. valve is built in MC. The 84 vette never had an outside prop. valve. I know this for sure as I personally removed the entire system off the car myself. Thanks

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    Senior Member bigrondownhiller's Avatar
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    You still have some air in the system. Just remembered are the bleed screws on the calipers facing up? also without bench bleeding the mc it takes a while to get all the air out. Wait a day and rebleed.

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