# Power brake assist pump question



## iKermit (Dec 13, 2010)

Hey i don't know the answer to this question but i wanted to welcome you to Cruzetalk!


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## Robby (Mar 1, 2013)

I believe we have a Chevy tech on the forum.....be patient.

Great idea though!
One of my fleet includes a supercharged T-Bird......with a Ford variation of a self powered power brake system.
Kind of along the lines of a G.M. hydroboost but with a self contained pump motor.

Known to fail a frighteningly expensive I too have though I may be able to go to vacuum system with the Cruze pump as assist.......just like the turbo motor, the bird has vacuum most of the time.....till you're on it and the manifold goes positive.

Do post with results, wherever you end up and thanks in advance.

Rob


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## rel3rd (Dec 21, 2013)

iKermit said:


> Hey i don't know the answer to this question but i wanted to welcome you to Cruzetalk!


Thank you. 
And I will post back here regardless of whether the answer is found here or elsewhere. 
I "think" it will work well, but I'd like to know what the extra prong and hose are for. 

As quick as this pump provides vacuum my plan is to figure out how to have the car engine and the pump both provide vacuum so there should never be a "no brake" situation.

I plan to use the brake light switch activate the assist pump. I'm guessing I'll need some sort of one way valve to block off the electric pump vacuum from trying to draw from the engine...if that makes sense?


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## Robby (Mar 1, 2013)

Currently there is a pressure (vacuum switch) located inline with the manifold vacuum/pump vacuum 'T'.......It is the switch just now being replaced under recall and it triggers the pump anytime line vacuum drops below a prescribed level.

Rob


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## rel3rd (Dec 21, 2013)

So I guess I could see a tech at the local Chevy dealer and get a used one really cheap? 

Do you know if that switch is only on the turbo cars that are being recalled?


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## Robby (Mar 1, 2013)

Only the turbo automatics are recalled......the switch may be on the turbo manuals but may not be failing, not sure.

The new switch is like ten bucks......but as you said, the parts dept. may have a hundred of them waiting for the GM scrap order.

Rob

BTW....the switch plugs into a adapter the vacuum lines are attached to....may be the trigger mechanism for the switch.
Just open the hood on a turbo auto cruze....it is next to the one way valve at the booster unit.


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## rel3rd (Dec 21, 2013)

Thanks for the info Rob. I appreciate it!


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## Aussie (Sep 16, 2012)

Looks to me like your car would take a lot more to safely stop than a small vacuum pump so I did a bit of searching and found this.

Diesels regulate engine power by how much fuel is injected, they don't have a throttle body. It's the drawing of air past the restriction of a throttle body that creates a partial vacuum in the intake of a petrol car.
So, no throttle body, no intake vacuum, so you have to come up with some other way of boosting brake effort.
Nothing to do with a turbo.
I'd like to add that some diesels use a vacuum pump which would be more durable as they are the only source of vacuum?


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## rel3rd (Dec 21, 2013)

Aussie said:


> Looks to me like your car would take a lot more to safely stop than a small vacuum pump so I did a bit of searching and found this.
> 
> Diesels regulate engine power by how much fuel is injected, they don't have a throttle body. It's the drawing of air past the restriction of a throttle body that creates a partial vacuum in the intake of a petrol car.
> So, no throttle body, no intake vacuum, so you have to come up with some other way of boosting brake effort.
> ...


That was actually my first hope...to find a vacuum pump from a mid 80's Chevy diesel truck. They used a pump that simply plugged into the same hole on the brake booster that the check valves plug into. It was ugly, but would have been a simple solution. I didn't have any luck with that search, unfortunately.

I'd like to use this Cruze pump if possible, but the more I think about it, rather than use a stock (or stock type) vacuum switch to turn it on and off, I think I'll find a 3/8" vacuum "T" and a one way check valve. You can see in the video I made how quickly that pump provides 25" of vacuum. I'll use the engine vacuum as my "fail safe" (always there) power assist, and have the vacuum pump only kick on when I apply the brake pedal. That way even if the electric Cruze assist pump should fail, I'd at least have "OK" braking power to stop with like I do now.

I do plan to go to the local dealership since (as a fleet mechanic/manager) I buy parts from them regularly, and even use their service department sometimes. Maybe they'll be able to give me some solid info on what the extra small hose on this pump is. Who knows, I may even be better off using the pump as a standalone option like pictured above in my original post?

Thanks for the replies so far everyone.


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## Robby (Mar 1, 2013)

I'm thinkin the vacuum port you are asking about is actually a exit port for the vacuum you draw out of the reservour........airs gotta go somewhere and answers your 'makes vacuum much slower question.'

Rob


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## Nosman (Apr 28, 2013)

I think you'll find the second hose barb is the exhaust for that pump since it has to create a differential to have vacuum on the other fitting that goes to the brakes. By plugging the second one you effectively stop the pump from moving air and thus your vacuum drops off. 

Sent from AutoGuide.com Free App


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