# Vacuum pump noisy



## baylisstic (Jun 18, 2017)

Hi everyone, I have a cruze 2009 European version .... a few weeks ago I changed the brake pads, and since then I realized that just switched on the frame or I brake the vacuum pump is noisy, now i do not know If it is normal that I do or is hurting ...


I hope some of you know how to answer me ... thank you.

Ps. Sorry for my English


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## jblackburn (Apr 14, 2012)

I couldn't hear mine most of the time over the engine at idle, but it is definitely noticeable with engine off. This is what a normal one sounds like.


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## baylisstic (Jun 18, 2017)

I thought that noise was the gasoline pump...


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## jblackburn (Apr 14, 2012)

baylisstic said:


> I thought that noise was the gasoline pump...


Nope. You can slightly hear that run for about 2 seconds to prime as you switch the ignition on from the rear of the car.

The noise in the video is coming from the front of the car when the brake pedal is pressed & provides vacuum assist for the brake booster when the engine is providing low vacuum (high idle, high valve overlap, cold engine, or turbo is boosting)


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## baylisstic (Jun 18, 2017)

To me this noise (vacuum pump) also makes it when i swith the ignition ...


That of gasoline I do not even feel ....

the first one is gasoline and when I pressed the brake pedal is that of the vacuum pump...


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## ChevyGuy (Dec 13, 2014)

Notice the pump starts again after pressing the brake pedal. That's the proof that it's the vacuum pump. I don't think the fuel pump will start again unless the engine is cranking or you cycle the key off.


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## NickD (Dec 10, 2011)

Never verified if the Cruze fuel pump motor is of the brushless type, for years used a permanent magnet field, and an armature with windings, commutators, and carbon brushes that would wear out soon.

Brushes use a bar rotor, no electrical contacts to it, dual stator, and electronics to produce a rotating field, far more reliable, and also much quieter. Cruze also moved the fuel regulator off the engine and mounted it on the fuel pump assembly, saves a line running from the tank to the engine.

De facto standard for practically all vehicles is to pulse the pump for two seconds when the ignition is turned on. Suppose to be enough to bring the fuel pressure up to 45 psi in the Cruze, but could vary anywhere from 35 to 65 psi in the vehicle. SUV's were close to that 65 psi mark and if you didn't hit it in that two second interval, could crank all day and the engine would not start. Trick was turn the ignition switch on, 3 or 4 times in succession to get several 2 second pulses until it will build up.

You really need a fuel pressure tester to verify these kinds of problems, could be caused by a leaking injector or a slight leak in the lines. And since air is less dense than gas, could go nuts trying to find the source of the leak, my excuse. Also a part of the fuel evaporative system, another problem. Use to mount the carbon canister and purge valve high up on the firewall, now behind the fuel tank getting hit with water puddles or worse, slusy road salt. Could draw water into the tank, more problems, plus freeze up in the cold winter months.

Practically all mount the fuel pump in the tank, why? Can use the gasoline as a coolant to make them cheaper. Using the same pump in compacts and much larger vehicles. With lower fuel pressures typical was a 4 amp load, but up to 8 amps. And since they are depending on fuel for cooling, would always treat a quarter full tank as an empty one, so the pump would last much longer. Operating these things in open air, they would burn up.

Would be nice if all vehicles had an fuel pump access plated, Impala did, Cruze did not, have to drop the tank.

With brush type motors, with electrical connectivity problems, voltage drops in the line, fuel pump current would skyrocket, brushless do not have these kinds of problems. Much quieter now with plastic rather than tin fuel tanks. Could barely hear the pump in the Cruze.

OP said he did his rear brakes, really can't figure out the connection to the fuel pump. Have more experience with our old 04 Cavalier, never had fuel pump problems, but sure had fuel evaporative problems with the canister mounted behind the tank exposed to road salt. 

I think the Cruze is using a brushless motor, but the only way to find out is to remove it and take it apart. Shop manual is worthless, only tells you how to replace parts. Dealers love to replace parts, especially after warranty.


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## baylisstic (Jun 18, 2017)

I understand ... thanks for the info you gave me !!!


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## SamyAdelOthman (Sep 2, 2019)

jblackburn said:


> Nope. You can slightly hear that run for about 2 seconds to prime as you switch the ignition on from the rear of the car.
> 
> The noise in the video is coming from the front of the car when the brake pedal is pressed & provides vacuum assist for the brake booster when the engine is providing low vacuum (high idle, high valve overlap, cold engine, or turbo is boosting)



In my car, i doesn't stop..that's not normal, right?


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## jblackburn (Apr 14, 2012)

SamyAdelOthman said:


> In my car, i doesn't stop..that's not normal, right?


Not normal; look for a broken hose or something.


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## SamyAdelOthman (Sep 2, 2019)

jblackburn said:


> Not normal; look for a broken hose or something.


Thanks, could it be the switch malfunctioning? I have no broken hoses

I think it should sense if Vacuum reservoir is empty of air to stop the pump..


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## jblackburn (Apr 14, 2012)

SamyAdelOthman said:


> Thanks, could it be the switch malfunctioning? I have no broken hoses
> 
> I think it should sense if Vacuum reservoir is empty of air to stop the pump..


Definitely could be; plenty of them act up the other way where the pump doesn't run at all.


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