Possible Brake Booster Issue

[Z Tyler Z]

So after Dave and I did quite a bit of electoral work my car is running a lot better. The engine missing is almost completely gone.

Only problem is my engine RPMs are still dropping when I brake, when they start dropping in the 500 area my engine begins to miss.

When I first start the car up and I'm letting it warm up if I push on the brakes i hear a distinct Whoosh/hissing sound. Then my engine rpms drop 100-300. This also happens when I put the car into neutral at stop lights and signs. Which sometimes puts my car into the danger zone RPM wise and stalls the car on occasion.

Does this sound like the symptoms of a failing/leaky brake booster? I never thought anything of the hissing noise until I started searching on here about brake boosters. Couldn't find anyone with the exact symptoms as me and just need a little reassurance before i drop $100 on a new one.

As always thanks for any and all feedback. Hopping to get rid of the last of this running issues so I can finally start on the interior.

[psdenno]

Bad booster.

Dennis

[motorman7]

I have a similar Brake Booster problem on my '71 only my RPM's increase; they go from 700 up to 1200. I wonder why they respond differently. I get the same whoosh/hissing sound. Also takes a lot of pressure on the brakes to get them to stop. I am planning on replacing the booster in a month or so.

[Curtis240Z]

A small leak will increase the idle. A large leak and the motor can't stay running thus the lower than normal idle.

To verify, block off the manifold at the large rubber hose to the brake booster. Start your engine and pump the brake pedal. If you now have no idle speed change you have found your leak in the brake booster. Be careful NOT to drive your Z around like this because the brakes will be severely compromised without the booster.

Edited February 2, 2010 by Curtis240Z

[Z Tyler Z]

A small leak will increase the idle. A large leak and the motor can't stay running thus the lower than normal idle.

/QUOTE]

Ok, that's the part I was confused on when searching around this forum. Seems like people were having a similar noise problem but their idle was increasing. Thanks for clarifying.

I think I should also point out that my problem goes away after driving a lot. I still hear the hissing/woosh sound when I brake but my idle doesn't drop.

.

Also takes a lot of pressure on the brakes to get them to stop.

Mines the same way, when I start the car I can feel the booster "engage" but I still have to muscle the pedal if I want to stop quickly.

Curtis240Z

To verify, block off the manifold at the large rubber hose to the brake booster. Start your engine and pump the brake pedal. If you now have no idle speed change you have found your leak in the brake booster. Be careful NOT to drive your Z around like this because the brakes will be severely compromised without the booster.

I'll give this a try tomorrow after college, if I remember right Dave and I tried this when I was first experiencing brake problems, I just can't remember what verdict we came up with after trying it.

At the time my rear brakes were completely overhauled but not adjusted, so they weren't really working but Dave adjusted them for me and it seemed to solve my braking problem.

No rear brakes plus shot suspension made me noise dive when braking, luckily Dave helped me re-do the entire suspension and adjusted the rear brakes.

Thanks for everyone's feedback I'll post again tomorrow after testing the booster.

[Zs-ondabrain]

So aparently, "I AM THE MAN"

We did'nt test your booster that way (as described by Curtis) but that's easy enough to do. I have a brake line/ hose clamp (looks like a duck-billed locking plyer) that we could easily clamp on there and test it that way.

So the next question Tyler will have is......

Who has a booster for cheap for a 76' 280Z???

Dave

[AnthonyG]

I have a 76 280z and i got a booster from rock auto. works great.

http://www.rockauto.com/

worst case is $160 from them. I couldnt send mine back for the core charge cause it was not in remotely good shape.

[Zs-ondabrain]

Who has a booster for cheap for a 76' 280Z???

Hense the word "Cheap"

Rock auto and others are great if you're not a college student.

Does any one have a USED and in decent working shape, booster for Tyler?

[Travel'n Man]

http://www.napaonline.com/Search/Results.aspx?Ntt=brake%20booster&Ntk=Keyword&N=599001+101976+50018+2018014

Not used but............available. Be sure to give a new one a coat or two of paint and a shot of clear..........

[Z Tyler Z]

Ended up ordering one through Autozone. It was 92 plus a 21 core charge, came out to be 125 with tax. So it should be around 100 when I bring back my core.

It's a re-manufactured one but has a lifetime warranty against defects. I like Autozone because they tend not to ask questions when you bring back something that's still under warranty and they keep everything in their system so you don't need to track down the receipt.

Dave and I will probably install it Saturday and I'll get back to everyone to tell how it went. I drove my Z today to get gas and surprisingly it drove very well. Hissing sound was still there and Rpms dropped a tad but not enough to stall the car like they did in the past.

Not used but............available. Be sure to give a new one a coat or two of paint and a shot of clear

What kind of paint should I use? I'll be sure to pick up some when I go and pick up the booster.

Thanks for everyone's help I hope this finally solves the last of my issues.

[Travel'n Man]

I used Rustoleum from Lowes Hardware - not to high gloss - and a clear coat. If not, in a weeks you will wish you did!

[Z Tyler Z]

Yep it was definitely the brake booster. Dave and I put in the new one yesterday and now the idle doesn't drop at all when I brake. Brakes are more sensitive too, I have a feeling the old brake booster wasn't doing much at all.

We also put air in my front tires...I never realized they were low because the tires were installed only a few months ago. I always thought manual steering was just a pain, but now the car steers much easier and my steering wheel doesn't vibrate at freeway speeds anymore.

Dave also adjusted my clutch, before it would engage right when you lifted it off the floor, now there is a little leeway and I don't pop the clutch as much (I'm pretty new to driving manuals).

Needless to say my car seems to drive much better every time I visit Dave.