Question about Vacum pump
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Freshman User
Joined: Oct 2004
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From: Stoneham, MA
Question about Vacum pump
it is my understanding, that diesel engines generate very little vacuum in their intake, so unlike a gas engine, there must be some sort of pump to generate the vacuum for the brakes, etc.
Does the 6.0 PSD have an engine driven (belt driven) pump or does it use an electric pump?
Reason for me asking is, that someone claims his diesel engine died while downshifting his older auto tranny on a downhill and he consequently lost brake boost.
Loss of brake boost should only happen if pump was engine driven, not independently by an electric motor.
MY ca. 1983 Ford Escord with the 2.0 l Mazda Diesel had an electric vacuum pump.
Thank you
Rudolf
Does the 6.0 PSD have an engine driven (belt driven) pump or does it use an electric pump?
Reason for me asking is, that someone claims his diesel engine died while downshifting his older auto tranny on a downhill and he consequently lost brake boost.
Loss of brake boost should only happen if pump was engine driven, not independently by an electric motor.
MY ca. 1983 Ford Escord with the 2.0 l Mazda Diesel had an electric vacuum pump.
Thank you
Rudolf
Former Vendor
Joined: Mar 2004
Posts: 4,362
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From: Hendersonville, NC
Originally Posted by bayernrudi
it is my understanding, that diesel engines generate very little vacuum in their intake, so unlike a gas engine, there must be some sort of pump to generate the vacuum for the brakes, etc.
Does the 6.0 PSD have an engine driven (belt driven) pump or does it use an electric pump?
Reason for me asking is, that someone claims his diesel engine died while downshifting his older auto tranny on a downhill and he consequently lost brake boost.
Loss of brake boost should only happen if pump was engine driven, not independently by an electric motor.
MY ca. 1983 Ford Escord with the 2.0 l Mazda Diesel had an electric vacuum pump.
Thank you
Rudolf
Does the 6.0 PSD have an engine driven (belt driven) pump or does it use an electric pump?
Reason for me asking is, that someone claims his diesel engine died while downshifting his older auto tranny on a downhill and he consequently lost brake boost.
Loss of brake boost should only happen if pump was engine driven, not independently by an electric motor.
MY ca. 1983 Ford Escord with the 2.0 l Mazda Diesel had an electric vacuum pump.
Thank you
Rudolf
The brakes are hydro-boosted, meaning that they operate off the power steering pump, and have no vacuum assist on them. The vacuum pump could fail, and you would still have brakes, as long as the engine is running.
Senior User
Joined: Oct 2003
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PSD is correctect the vaccume pump on the 2000 and up diesels is located under the hood on the passenger side just in front of the heater box. its a miniture compressor looking thing colors are orange and black. Brakes are hydo boosted.
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Freshman User
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From: Stoneham, MA
thanks,
so what is the vacuum pump for?
cruise control actuator?
and with the brakes, if engine stops, is boost lost immediately or is there a reservoir which will give brake boost at least for one or two brake applications, like it normally is on a gas engine?
so what is the vacuum pump for?
cruise control actuator?
and with the brakes, if engine stops, is boost lost immediately or is there a reservoir which will give brake boost at least for one or two brake applications, like it normally is on a gas engine?
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The older 7.3L trucks had an engine driven vacuum pump; the newer ones just have a teeny little electric pump on the right fenderwell. The older 7.3L trucks had vacuum-bosted brakes and needed all that vacuum. When they switched to hydroboost brakes on the new 7.3s and 6.0 trucks, they didn't need so much vacuum any more so they could get away with the little pump.
The trucks are built the same regardless of engine type, so anything that's vacuum operated (like the flaps on the climate control, or the ESOF hubs) needs a vacuum source that comes free with a gas engine, but requires a pump on a diesel engine. A diesel doesn't just develop low vacuum, it develops *no* vacuum. The vacuum is caused by the pressure difference across the throttle plate on a gas engine. A diesel engine has no throttle plate, because it changes engine speed by varying the amount of fuel injected (and then when the engine spins faster it simply drags in more air).
Duncan
The trucks are built the same regardless of engine type, so anything that's vacuum operated (like the flaps on the climate control, or the ESOF hubs) needs a vacuum source that comes free with a gas engine, but requires a pump on a diesel engine. A diesel doesn't just develop low vacuum, it develops *no* vacuum. The vacuum is caused by the pressure difference across the throttle plate on a gas engine. A diesel engine has no throttle plate, because it changes engine speed by varying the amount of fuel injected (and then when the engine spins faster it simply drags in more air).
Duncan
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Joined: Apr 2004
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From: Wickenburg, AZ
There is a little accumulator on the brake booster, but it doesn't last very long. Maybe a few shots at the brakes.
Sometimes steering effort might ramp up if you leave your foot on the brakes, too. Folks occasionally complain about that.
The cruise control is handled directly by the computer. There is no moving parts other than the fuel injectors.
Vacuum is used to operate parts of the climate control system. I'm not aware of anything else. Even the EGR is electric. Most stuff is electric or oil-pressure operation.
Sometimes steering effort might ramp up if you leave your foot on the brakes, too. Folks occasionally complain about that.
The cruise control is handled directly by the computer. There is no moving parts other than the fuel injectors.
Vacuum is used to operate parts of the climate control system. I'm not aware of anything else. Even the EGR is electric. Most stuff is electric or oil-pressure operation.
