Please Help!!!!!!!!!

I have a 1993 SC400 and the power brake booster started hissing and the brakes were nearly nonexistent, so I got another power brake booster from a wrecking yard and replaced it. I also replaced the air intake breather hose at the same time( I have no idea what this would have to do with anything, but I thought I would mention it just in case). When I started the car to check it out before bleeding the brakes it now runs very poorly and has a terrible dull knock. Before I replaced the booster she ran beautifully and nearly silent. Is there anything that I may have bumped under the brake pedal or around the booster\master cylinder area that could cause this? I always try to be extremely careful. There are no check lights lit up and I am afraid to run it for very long, since I have no idea what could have happened? Any suggestions would be appreciated. I am completely at a loss.

Thanks,

Cory

Are you talking about the line that runs from you're brake booster box to your intake manifold? Did you buy a new line or did you use one from the junk yard? Seems like you might have a vaccum leak somewhere. Is it idling rough?

Where is the "dull knock" sound like its from?

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Welcome to Club Lexus!

4...5...6 retitled "please help" doesn't quite define the issue at hand.

hissing would seem to signify a vac hose leak. buy some new hose and start replacing them - beginning w/the brake booster. it may also be as simple as one of the hoses that you replaced is not entirely secure.

No. The air breather hose or air in take hose - nothing to do with the brakes at all. I just replaced it at the same time.

Thanks

I'm not exactly sure? From the engine itself maybe lower? The idle seems lower and weird too? I was wondering if something vacuum or electrical couls have be knocked off? The car was perfect before I replaced the power brake booster.

Thanks

We checked the hoses and did the booster tests suggested in the Lexus mauals. It failed the tests so we replaced the booster.

Thanks