Need some advice on power break booster pump noise

[tin-man]

Should get my Cobra in time for Thanksgiving and have been reviewing the videos I took prior to the 78 mile debacle, one thing I noticed was when I turned on the ignition key the power break booster pump made a loud humming noise, like it was priming itself, I was told this is normal by the installer. Also, when I hit the break pedal, same thing, a loud humming noise, so is this what I can generally expect or should it be silent?? I have never driven a car with a power break booster pump that I was aware of so I don't have such knowledge on the correct noise level, if any.

Can anyone share their experiences with such an application?

Thanks, John, AKA, tin-man

[cobish]

Originally Posted by tin-man

Should get my Cobra in time for Thanksgiving and have been reviewing the videos I took prior to the 78 mile debacle, one thing I noticed was when I turned on the ignition key the power break booster pump made a loud humming noise, like it was priming itself, I was told this is normal by the installer. Also, when I hit the break pedal, same thing, a loud humming noise, so is this what I can generally expect or should it be silent?? I have never driven a car with a power break booster pump that I was aware of so I don't have such knowledge on the correct noise level, if any.

Can anyone share their experiences with such an application?

Thanks, John, AKA, tin-man

Maybe this will help


Now, the whine you hear when you rev your pump is one of three things. The first is the whine caused by pressure relief. It sounds kind of like a 'Shhhhhhhhh!' If you turn your wheel until it wont turn anymore, the fliud flow to the pump is cut off, and the pump is forced into pressure relief. On the F-car, this means a pressure of between 1200 and 1600 PSI. The pump has to recirculate this high pressure fluid within itself because the fluid has nowhere to go. If left in pressure relief for very long, the fluid can quickly exceed 325 degF, and break down, causing the pump to begin experiencing metal-to-metal contact.

The second noise is caused by cavitation. As you increase pump speed, more and more fluid is forced through the ports per unit time. There comes a velocity where the fluid just doesn't want to move that fast, and the vanes inside the pump will cause a vacuum, which is instantly filled with oil vapor. When the vane reaches the high pressure port, this vacuum cell is opened into a high pressure cell, and oil rushes to fill the void. A little 'sonic boom' results. These individual 'booms' are virtually microscopic, but they add up. What they translate into is a sound that sounds suspiciously like a whine. Now every pump cavitates. It's in the nature of moving fluid. By smoothing the radius of the ports, and relocating supercharge holes (I'm not going into that), engineers can reduce cavitation or push the frequency spectrum of the whine to a less noticable frequency. It is, in fact, where the bulk of pump engineering hours are spent.

Anyway, that funny high pitched whining that Mike Martin is hearing after his autocross run is the third type of noise. This type of whine is from the oil being aerated. When the pump is really screaming, the oil in the resivoir really gets churned up. This allows the occasional air bubble to pass into the pump, where it is totally pulverised into smaller bubbles. Eventually, the oil gets enough of these bubbles in it that you begin to hear it. If you want to really experience aeration, just run your pump low on oil!

None of these three types of noises will cause your pump to die. What kills a pump is heat and oil viscosity breakdown. The pressure relief example will overheat a pump in the extreme case causing galling of the bushing, or wear of the pump ring. The cavitation example, when extreme, like 7000-9000 RPM endurance runs, will cause microfractures to the pump internals and literally blow little flakes of metal off the walls. The extreme aeration example will cause increased heat to the internals, because air does not carry the heat away like oil does. But the common denominator to these is the word EXTREME. Most PS pumps never see this kind of duty, unless the person runs their pump low on oil. But none of us does this, because we all check our PS fluid as often as we check our trans fluid, right?

[tin-man]

Originally Posted by cobish

Maybe this will help


Now, the whine you hear when you rev your pump is one of three things. The first is the whine caused by pressure relief. It sounds kind of like a 'Shhhhhhhhh!' If you turn your wheel until it wont turn anymore, the fliud flow to the pump is cut off, and the pump is forced into pressure relief. On the F-car, this means a pressure of between 1200 and 1600 PSI. The pump has to recirculate this high pressure fluid within itself because the fluid has nowhere to go. If left in pressure relief for very long, the fluid can quickly exceed 325 degF, and break down, causing the pump to begin experiencing metal-to-metal contact.

The second noise is caused by cavitation. As you increase pump speed, more and more fluid is forced through the ports per unit time. There comes a velocity where the fluid just doesn't want to move that fast, and the vanes inside the pump will cause a vacuum, which is instantly filled with oil vapor. When the vane reaches the high pressure port, this vacuum cell is opened into a high pressure cell, and oil rushes to fill the void. A little 'sonic boom' results. These individual 'booms' are virtually microscopic, but they add up. What they translate into is a sound that sounds suspiciously like a whine. Now every pump cavitates. It's in the nature of moving fluid. By smoothing the radius of the ports, and relocating supercharge holes (I'm not going into that), engineers can reduce cavitation or push the frequency spectrum of the whine to a less noticable frequency. It is, in fact, where the bulk of pump engineering hours are spent.

Anyway, that funny high pitched whining that Mike Martin is hearing after his autocross run is the third type of noise. This type of whine is from the oil being aerated. When the pump is really screaming, the oil in the resivoir really gets churned up. This allows the occasional air bubble to pass into the pump, where it is totally pulverised into smaller bubbles. Eventually, the oil gets enough of these bubbles in it that you begin to hear it. If you want to really experience aeration, just run your pump low on oil!

None of these three types of noises will cause your pump to die. What kills a pump is heat and oil viscosity breakdown. The pressure relief example will overheat a pump in the extreme case causing galling of the bushing, or wear of the pump ring. The cavitation example, when extreme, like 7000-9000 RPM endurance runs, will cause microfractures to the pump internals and literally blow little flakes of metal off the walls. The extreme aeration example will cause increased heat to the internals, because air does not carry the heat away like oil does. But the common denominator to these is the word EXTREME. Most PS pumps never see this kind of duty, unless the person runs their pump low on oil. But none of us does this, because we all check our PS fluid as often as we check our trans fluid, right?

Thanks Cobish, I am guessing the same applies to power break booster pumps as well, thus what I am experiencing,based on this article,appears to be normal.

Cheers, John, AKA, tin-man

[Barnsnake]

The power steering pump is hydraulic and the power brake booster pump is probably an air pump. They likely have little in common.

I have no experience with a brake booster pump, but i've never seen a quiet vacuum pump. It is possible mounting the pump with better (softer) isolation could help with resonating vibration, but if it is intake noise in the pump itself, it might not.

[tin-man]

Originally Posted by Barnsnake

The power steering pump is hydraulic and the power brake booster pump is probably an air pump. They likely have little in common.

I have no experience with a brake booster pump, but i've never seen a quiet vacuum pump. It is possible mounting the pump with better (softer) isolation could help with resonating vibration, but if it is intake noise in the pump itself, it might not.

Thanks, I was advised by the installer he could hook up the power breaks to the power steering pump, but likely would lose some efficiency, thus my comments on the sameness on the Cobish post. However in either case, hydraulic or air pump I am hearing some noise is the norm. tin-man

[RICK LAKE]

tin man John what kind of system do you have??
Vacuum booster with master attached?
Vacuum booster with aux vacuum pump and engine vacuum?
Hydro boost with power steering?
Electrical pump like old GM Teves design. Pump runs when pressure gets below 1,200 pounds.
Do you have any pictures? Some system make noise, others you should hear nothing.
If there is an electric pump for hydro pressure under the master assembly, you can rubber insolate it to quiet the noise. Rap the pump in fire proof cloth and leave loose to quiet down noise. It is normal for electric pump systems to start running when key is turned on if pressure is not within spec.
Hydro booster you should hear nothing at all except if you are turning parking lot speed and hit the steering limiters and load the system. Most hydro system pumps run about 2-300 psi.
If you are running a electric vacuum pump, you can switch to a vacuum assist one like on the older diesels that run off a little belt. They are quiet and make about 15 hg of pressure with the motor running.
Unless you are racing the car, manual brakes should work fine with a 2,700 car and 11" rotors in the front. More info would help. Rick L.

[Danr55]

Power brakes, power steering?? what about power seats and power windows? Or maybe a power convertable top? Is this a cobra or a Thunderbird?

[Karl Bebout]

Power cup holders and power seat belt retrievers? Power door locks, power trunk release? God forbid it would be a sports car.

[STL Mark]

I have a vacuum booster to assist the brakes. The engine just didn't make enough vacuum to run the SPF brakes. Yes, it makes noise and vibration when it kicks on. It starts with the fuel pump when I turn the key on. It kicks on when it needs to add vacuum - when I use the brakes. Yours may kick on a bit more often because of the automatic transmission. We added the supplied rubber bushings to minimize the noise and vibration. It helped a little. I don't mind it. It let's me know it's working. There are belt driven units that others have installed. You may want to ask about that.

[Jeff Frigo]

Simple solution, get rid of the power brakes. Are you kidding me?

[tin-man]

Originally Posted by Danr55

Power brakes, power steering?? what about power seats and power windows? Or maybe a power convertable top? Is this a cobra or a Thunderbird?

well for the amount of time I had it, it was a Cobra, a Bleck Cobra.

The only concessions I made were power steering, on account of a torn rotor cuff and if anyone has had a torn rotor cuff you will know why I made that choice, and power breaks. I am figuring with all that power I have under the hood, I'll need stopping power.

Well err, and one more, err, an automatic transmission.

I make no appologies to anyone, its my car, configured the way I want it and its all bought and paid for, nuff said. Next?

tin-man

[RICK LAKE]

Tin -man First name would be nice. Switch to a hydro boost setup. You can find them in some of the Rod mag's. You already have the PS system, it's easy to swap over the rest. If you want better brakes this is the way to go. The only thing is to add a P/S cooler under the front of the car on the radiator support to help control fluid temps. I run a P/S system with a Sweet rack. Works great, like you bad shoulder from baseball. No 90 mph any more. Lucky if I can thrown it 20'. Don't raise arm over head either. Anyway If you want more info, goggle it or I will get the people to talk to you. It's a bolt in system. The brakes will put you through the windshield in the beginning. You don't need a heavy foot. 1,400 -2,000 psi of pressure the system uses and this make the brakes stop quick. You might need a pedal stop under the dash. The pedal travel is only about 2". Just a thought. You built a car the way you need it to address you needs. It's just as fast as and 5 or 6 speed. I do have a ashtray in my car, and the other half quit smoking. Rick L.

[tin-man]

Originally Posted by RICK LAKE

tin man John what kind of system do you have??
Vacuum booster with master attached?
Vacuum booster with aux vacuum pump and engine vacuum?
Hydro boost with power steering?
Electrical pump like old GM Teves design. Pump runs when pressure gets below 1,200 pounds.
Do you have any pictures? Some system make noise, others you should hear nothing.
If there is an electric pump for hydro pressure under the master assembly, you can rubber insolate it to quiet the noise. Rap the pump in fire proof cloth and leave loose to quiet down noise. It is normal for electric pump systems to start running when key is turned on if pressure is not within spec.
Hydro booster you should hear nothing at all except if you are turning parking lot speed and hit the steering limiters and load the system. Most hydro system pumps run about 2-300 psi.
If you are running a electric vacuum pump, you can switch to a vacuum assist one like on the older diesels that run off a little belt. They are quiet and make about 15 hg of pressure with the motor running.
Unless you are racing the car, manual brakes should work fine with a 2,700 car and 11" rotors in the front. More info would help. Rick L.

Hi Rick, The only thing I have in this respect is the picture, attached and a bill stating 12 volt vacuum pump, I have asked the installer what type of system I have and I'm still waiting for a reply. Just so you know I am in China and the Cobra is in Fullerton California getting some corrections made to it after I drove 78 miles and it stopped working. I have a post on that topic. When I hear back I will respond. Cheers, John, AKA, tin-man

[tin-man]

Originally Posted by RICK LAKE

Tin -man First name would be nice. Switch to a hydro boost setup. You can find them in some of the Rod mag's. You already have the PS system, it's easy to swap over the rest. If you want better brakes this is the way to go. The only thing is to add a P/S cooler under the front of the car on the radiator support to help control fluid temps. I run a P/S system with a Sweet rack. Works great, like you bad shoulder from baseball. No 90 mph any more. Lucky if I can thrown it 20'. Don't raise arm over head either. Anyway If you want more info, goggle it or I will get the people to talk to you. It's a bolt in system. The brakes will put you through the windshield in the beginning. You don't need a heavy foot. 1,400 -2,000 psi of pressure the system uses and this make the brakes stop quick. You might need a pedal stop under the dash. The pedal travel is only about 2". Just a thought. You built a car the way you need it to address you needs. It's just as fast as and 5 or 6 speed. I do have a ashtray in my car, and the other half quit smoking. Rick L.

Rick, this sounds great and I will surely consider what you are recommending when I finally get my Cobra back. I'm guessing you have been down the path of the torn rotor cuff, not pleasant and never quite really heals. When I was test driving the SPF Cobra at Hillbank and turned into the parking space the shoulder rotor cuff popped, thus the power stearing option was first thing I asked for. Then the power breaks. Cheers, John, AKA, tin-man

[Danr55]

John, just in case you've forgotten my offer, I'm still willing to go to Fullerton and put some miles on your car power this or that, not withstanding. Let me know and I'll arrange to do it when I return from Europe.

[Car Nut]

Originally Posted by tin-man

Hi Rick, The only thing I have in this respect is the picture, attached and a bill stating 12 volt vacuum pump, I have asked the installer what type of system I have and I'm still waiting for a reply. Just so you know I am in China and the Cobra is in Fullerton California getting some corrections made to it after I drove 78 miles and it stopped working. I have a post on that topic. When I hear back I will respond. Cheers, John, AKA, tin-man

Apparently you have a vacuum pump which supplies sufficent vacuum to a vacuum operated power brake booster.

They make noise, that's normal.

[tin-man]

Originally Posted by Car Nut

Apparently you have a vacuum pump which supplies sufficent vacuum to a vacuum operated power brake booster.

They make noise, that's normal.

Seems you called it correctly, I have been informed what I have is a vacuum pump to give the brake booster vacuum. Being the case then the noise I should get used to, right?

Cheers, John AKA, tin-man

[RICK LAKE]

Tin-man John 2 choices, if the noise is bothering you, Move the pump to a different location if it is on the foot box. The vacuum assist doesn't care where it is mounted, just have to run the wiring and longer vacuum hose to pump. GM and Ford used them years ago on some car to assist the motor with a vacuum booster. See if there is space to mount this on the frame in front of the motor down low. These motors like a good air supply to help keep cool with the little diapham and motor running. If there are in dead air they make louder noise. If you can get a air flow to the area, you can mount sound deadener also to direct the sound away from you.
Does your motor have a big camshaft? What I mean is loping and rough idle with only 10-14 Hg of vacuum? If your motor has a higher vacuum and you are running a double vacuum booster, you should need the vacuum pump to run the system. Only a vacuum gauge inline will tell. I know it's not pretty but the diesel assist pumps work great last for 10-15 years and you never hear a noise. Hydro is the other way. How's China??? Rick Lake

[Car Nut]

Originally Posted by tin-man

Seems you called it correctly, I have been informed what I have is a vacuum pump to give the brake booster vacuum. Being the case then the noise I should get used to, right?

Cheers, John AKA, tin-man

You can't hear over the sound of the engine anyway, so why be concerned?

Oh, we don't know that yet do we? Well when it is, you shouldn't hear it over the sound of the engine.

[tin-man]

Originally Posted by RICK LAKE

Tin-man John 2 choices, if the noise is bothering you, Move the pump to a different location if it is on the foot box. The vacuum assist doesn't care where it is mounted, just have to run the wiring and longer vacuum hose to pump. GM and Ford used them years ago on some car to assist the motor with a vacuum booster. See if there is space to mount this on the frame in front of the motor down low. These motors like a good air supply to help keep cool with the little diapham and motor running. If there are in dead air they make louder noise. If you can get a air flow to the area, you can mount sound deadener also to direct the sound away from you.
Does your motor have a big camshaft? What I mean is loping and rough idle with only 10-14 Hg of vacuum? If your motor has a higher vacuum and you are running a double vacuum booster, you should need the vacuum pump to run the system. Only a vacuum gauge inline will tell. I know it's not pretty but the diesel assist pumps work great last for 10-15 years and you never hear a noise. Hydro is the other way. How's China??? Rick Lake

Rick, good points, I'll discuss these options with the installer to see if this can be done on my car. The issue is when I turn the ignition key, the booster pump kicks in, makes a racket and then stops. In traffic when I apply the brakes the sound is audible and troublesome for me. Thus my question "is this normal", apparently so.

China is awesome and is the place to be if you want to establish a footprint for your business. Free land, tax incentives up the gazoo, inexpensive labor with a great work ethic and in most parts good infrastructure development for product distribution. The tourists spots are also good too, come on over and we'll share a brew. John, AKA, tin-man