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Discussion Starter #1
I bought my new 2011 Cruze LT 4years ago and put 57,000 miles on it. I love my car, my dealer and the 32 miles per gallon I get. However I have a brake problem. I think I need a new power brake booster. Two years ago I had a problem with braking on a cold engine but the recall to replace the booster pump fixed that problem. Since the recall
was installed I now see several problems. I have an occasional whistle under the drivers side dash whenever I accelerate slightly. Also, whenever I accelerate hard I hear a gush of air under the drivers side dash. Finally, this is a serious problem, whenever I am on a trip and cruise for a while and try to stop there are no power assisted brakes. I have to push hard and after a quarter of a second or so the power brakes apply normally. The pedal never goes to the floor, it is hard to push for that fraction of a second. I tried the test for the brake booster check valve and it worked OK.

Any suggestions?
 

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Discussion Starter #4
I believe the microswitch was replaced when the booster pump was replaced when the recall was done two years ago.
 

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If it is the booster pump or switch again, you should be able to get GM to pay to cover the replacement again. PM our Chevy Customer Care account for assistance. If that doesn't work, open a case with the NHTSA and they may be able to assist you.
 

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I'm tempted to say the odds are the switch has a intermittent failure and it would be the first component I'd replace.
I'd base my decision to replace it because it is a intermittent problem, the part is comparatively inexpensive and easy to exchange, and knowing it will cause the concern you describe.
The vacuum pump could have a problem but if it did, odds are it would not work at all.....so you would have a situation of no vacuum assist regardless of how many pedal applications occured.

The booster itself is the least likely failed component.....if it failed, the vacuum pump would be continually running in an attempt to reach the pre-determined vacuum shut off point.

As far as warranty......I am of the belief that the replacement switch would not have any warranty beyond the original 3yr/36k coverage.

For example, say the switch was replaced under recall at 50,000 miles.....the replacement expense is covered, one time with a upgraded part, for the vehicles lifetime......so, whether 50,000 or 150,000 or more miles, regardless of age, one switch replacement, using the upgraded part, is no charge to the current owner.

Since you indicate the switch was replaced, the recall guidelines have been met, and the part/labor from that time forward are only covered for any remaining base or extended warranty purchassed by the owner.

Anyways, try a new switch.

Rob
 

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Discussion Starter #8
I will take your advice and replace the switch. But please explain to me how the switch comes into play at all. I thought that the turbo only is used under acceleration. At cruising speeds of 60 mph the turbo is not working so the throttle should be almost closed and the manifold pressure should be relatively high so there should be ample pressure to operate the power brake booster. Am I right?
 

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The brake booster switch is used when there is no or little load on the engine, so when cruising at 60 MPH with just enough load to maintain speed is when the brake booster switch is needed.
 

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I will take your advice and replace the switch. But please explain to me how the switch comes into play at all. I thought that the turbo only is used under acceleration. At cruising speeds of 60 mph the turbo is not working so the throttle should be almost closed and the manifold pressure should be relatively high so there should be ample pressure to operate the power brake booster. Am I right?
There is a target vacuum that is required for the booster to assist.
The switch engages the pump anytime the target is not being met, or there is vacuum used.

You should hear the pump cycle while idling in the driveway, everytime the brake pedal is applied and released.
It will run for less than five seconds......I akin the sound of it to a old electric train whistle.....very soft but audible.

Yes, at speed, vacuum from the manifold is at its highest but evidently it is never high enouph to provide the booster with enouph vacuum for the application......kinda like a V-8 performance car with a aggressive cam.....enouph vacuum for maybe one pedal application before it is exausted.....thats why we add vacuum pumps or change over to a hydro-boost design when a cam with a lot of overlap is installed.

Rob
 

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Vacuum booster is only required when the turbo is active, changes the intake manifold pressure from around 15-20 inches of Hg to a very positive up to a 35 psi peak. Switch is a valve, to switch the vacuum booster from the intake manifold to the vacuum booster pump.

Of course when you take your foot off the gas, in less than a second or so, intake manifold pressure drops from a very high positive to a very low negative pressure. So suspecting a vacuum booster leak, should not hear that rush of air.

Very simple test, kill the engine, and you should get a soft brake pedal for three consecutive tries. About the 4th try, should be a hard pedal. If not doing this, have a vacuum booster leak.

For whatever reason, that vacuum switch recall was only for automatics, not for manual transmission. You will only find that vacuum pump and switch on turbo equipped engines. Vacuum booster does have a check valve in it, only lets air flow out, not in. Really not this difficult to troubleshoot.
 

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Discussion Starter #12
Great discussion. I now understand the operation. Thanks.

But now I have another question, If the booster pump operates when the turbo is on, why do we need a booster pump at all? who needs brakes during WOT?????
 

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Great discussion. I now understand the operation. Thanks.

But now I have another question, If the booster pump operates when the turbo is on, why do we need a booster pump at all? who needs brakes during WOT?????
For someone that hits the brakes with a wide open throttle?

88 Supra turbo has the same vacuum switch, but very high quality metal, not a cheap piece of plastic. Also has fog lamps that I can switch on independently of the headlamps with about a 30 foot beam. But like the Cruze are switched off with the brights. Don't miss this in the Supra, has plenty of side vision that the Cruze does not have. But like this vacuum switch and booster pump, don't understand this either.

Really don't understand the difference between this vacuum switch between the Cruze AT or MT, only an issue with the AT. If you hit that clutch, throttle vane sticks due to recirculating PCV through it and hit the brakes, won't have any boost at all.

Getting stuck with unplated rear calipers that wouldn't adjust anymore with a brake pedal going to the floor, they called GM tech service. They recommended the first thing they did was to replace that vacuum switch. Didn't understand this either, must be getting stupid in my old age. Never complained about lost of vacuum boost, then it was the vacuum pump, then the brake booster. What the heck replacing good parts with hopefully other good parts.
 

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Also has fog lamps that I can switch on independently of the headlamps with about a 30 foot beam. But like the Cruze are switched off with the brights. Don't miss this in the Supra, has plenty of side vision that the Cruze does not have. But like this vacuum switch and booster pump, don't understand this either.
That is interesting about the fog lights, on the Holden Cruze when I turn the fogs on they work with either bright or low beams.

A question for you if you know the answer, how does the diesel get power assist for the brakes as no butterfly in the intake?
 

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That is interesting about the fog lights, on the Holden Cruze when I turn the fogs on they work with either bright or low beams.

A question for you if you know the answer, how does the diesel get power assist for the brakes as no butterfly in the intake?
Ha, with the fog lamps, different countries, different idiots making laws, maybe your country isn't quite as bad.

Never fooled around much with diesel powered cars, diesel powered large truck and locomotives used compressed air for braking. Not quite so large trucks use a Hydroboost powered by the power steering pump.



Totally independent of the vacuum system. Historically, in the US, diesel powered passenger vehicles have a bad reputation for nearly being as robust as an engine even found in a farm tractor. Semi's are good for at least 3 million miles before an overhaul is required. Cold weather starting always has been a major problem, so stayed away from these things.

But recently noticed, diesel fuel around here finally is the same price as 87 octane gas, but recalling even back in the 60's diesel fuel was cheaper than even regular gas so was the most economical fuel for farmers to use. The way it has been, the cost per mile with a diesel was about the same as gasoline, with a lot more initial cost and maintenance problems for the consumer.

Hmm, not only technology, but politics.

With the OP with vacuum boost problems, sure isn't rocket science, have a leak someplace. Claims he hears the noise.
 

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Filled the Cruze for $1.28 per litre, at the same service station Premium was $1.60 and E10 was $1.49.
 

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Filled the Cruze for $1.28 per litre, at the same service station Premium was $1.60 and E10 was $1.49.
I would have to get a car that got better mileage if gasoline was that expensive here. $1.60 a liter, 3.78L makes a US gallon, so that would be $6.04 a gallon!!! This year its been bad when I pay $3.25, think the country would shut down at those prices.
 

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I would have to get a car that got better mileage if gasoline was that expensive here. $1.60 a liter, 3.78L makes a US gallon, so that would be $6.04 a gallon!!! This year its been bad when I pay $3.25, think the country would shut down at those prices.
When you consider that wages are higher in Australia and currently the $A is worth $0.75 US it is not much different.
 

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Diesel was $9.75 equivalent for a US gallon in Italy, but talking to home owners, property taxes were practically next to nothing. And since Italy has an extraordinary tourist trade, getting foreigners to pay for their government.

So transportation fuels are cheaper in the US, but really getting nailed, with federal, state, sales, and property taxes.

Ha, the get us one way or the other or all of these together. What we pay in taxes, could use the money to by a new car about every 16 months.
 

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Before doing this task you should ensure your safety. Like wear safety gloves and high toed shoes. In the first step engine should be in off position, thereafter you have to pedal over the brake shoes till brakes booster gets detached from the vaccum. Thereafter you have to press the brake peddle down and start engine. You should get satisfied that brakes peddle sinkd slightly and afterwards the engine to be turned off.Thereafter remove the vaccum hose from the brake booster. You have to remove the brake lines from the booster cylinder. Remove the master cylinder from the brake booster to the firewall.These nuts are located in the interior of the firewall. Remove the brake booster. Thereafter you have to get fit new brake booster to the firewall and have to tighten the nuts. After doing this you have to connect the push rod to the brake pedal then connect the vaccum hose to the brake booster. Attach master cylinder to the new brake booster and thereafter connect the brake lines. In the end blead the brakes to the master cylinder.
 
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