Question about 1991 Toyota Land Cruiser

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Vacuum pump on braking system has no electrical current

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Is it meant too doesnt this vehicle have the vacumn pump on the back of the alternator or am i getting old and suffering from oldtimers

Posted on May 02, 2010


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Posted on Jan 02, 2017

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SOURCE: electric vacuum pump has six wires, where do they go

you might be looking at an air suspension pump. it is not designed to work for long periods of time.

Posted on Jun 02, 2009

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My 2008 Ford f-450 with the 6.4 tubodeisal is cutting out at 1800rpm n or out of drive also dash say check brake system and won't build boost

You might have a problem with the vacuum pump or the brake booster diaphragm is leaking vacuum. Disconnect vacuum line at pump with engine off and draw vacuum through this disconnected line. If the line will not hold vacuum, find the leak.

Aug 14, 2015 | Ford Cars & Trucks

1 Answer

Oil in brake booster

The vacuum is created via a mechanical pump driven from the cam, Or a separate, electrical pump.

The only liquid I have ever found in any servo (booster) is brake fluid from a leaking master cylinder.
If the vacuum is low/absent, due to a faulty cam driven vacuum pump, and crankcase pressure rises, along with a faulty one-way valve in the vacuum plumbing, it's possible the oil could be forced into the servo housing, and operating the brakes would help it happen as the servo could act as a pump itself and draw oil from the engine.

Found some diagrams:

What colour is the oil?

Nov 08, 2013 | 1999 Saab 9-5

2 Answers


The power brakes vacuum booster... may have a vacuum leak. you can check it with an engine vacuum meter, or remove the rubber hose from the booster and plug it.. and see if the engine changes pase, idle smooths out, revs a bit higher, etc. noticeable change in engine idle would confirm a leak.

Oct 01, 2012 | 1990 Lincoln Mark VII

1 Answer

Is it normal for the vacuum tester to bounce back and forth when testing on my 1977 Mercedes 300d

Hi Robert, I know that on the older models of the Benz a vacuum pump was fitted into the trunk for operating various units on the vehicle inclusive of the central locking system. The vacuum pump which operates on the braking system creates a much higher low pressure area than that used for other units. I believe if you fitted your gauge directly onto the brake booster pump you may have damaged your gauge. Regards John

Sep 09, 2012 | Cars & Trucks

1 Answer

Stalls when turn lights on or hit brakes

Check the plugs to make sure they aren't fouled. Then maybe the fuel pump. If it dies when you hit the brakes, that's electrical. I'd say it's the fuel pump, filter, etc.
When plugs are fouled, it probably wouldn't want to start, and brakes aren't electrical and the fuel pump isn't real likely either.
Actually when you step on the brakes, it takes power from the battery or alternator to run the pump for the master cylinder on the brakes. (not true)
Doing so will cause your car to stall if the idle is too low. Turn the idle up and see if it happens again.
Same thing with the in gear driving. Putting the car in gear will drop the rpm to half or less than what it is already.
The brakes have no pump. If they are power brakes, then it has a booster (and the booster uses engine vacuum, not electrical power) you can't adjust the idle speed in a FIed car. When you put the car in gear, the rpm should stay steady since the FI system should adjust for loads on the engine (turning the a/c on, putting car in gear, turning on lights etc) Do a tune up and go from there. By the sounds of it though, this is a lock-up torque convertor problem. The convertor lock is stuck on so the torque convertor is "solid" when you put it in gear.
If it is not an engine problem, it should be a problem with the transmission. When the gearshift is in drive, in this case, the gears get jammed with each other, causing the whole engine/drivetrain to lock up, stalling the engine. You should get a repair as soon as possible.
Either your power brake assist booster has a bad check valve in it causing a huge vacuum leak when you step on the brake (Vacuum leaks lean out the fuel/air mixture causing stalling) or you have an 'engine protect' sensor that kills the ignition/fuel pump when the oil level's too low and it's either got crud in it from running the oil too low or has otherwise malfunctioned

Dec 31, 2011 | 1988 Chevrolet C1500

1 Answer

90 f250 dsl has no brakes fluid full and no leaks. what would it be?

assuming dsl means diesel...these engines are not capable of creating vacuum to driveyour power brakes, they use an external source of vacuum, called a vacuum pump. they are either belt driven or electrical...given your age i would say belt driven...

Jun 17, 2011 | Ford F-250 Cars & Trucks

1 Answer

I have 2 larger f series ford diesels. Both have the Bendix Convac vacuum pump, both are broken/leaking oil. Neither truck needs vacuum to assist the brakes (1 air brakes, 1 hydromax assist) but both...

When you say airbrakes, do you mean that the vehicle has airbrakes, or does it have hydraulic brakes with a vacuum brake booster? As far as replacing it with a 12v vac pump, there might be some DOT regulations prohibiting this as it involves safety issues. If one has the vac booster, it is leaking brake fluid and not oil. The hydrovac booster will leak either as it uses power steering fluid from the P/S pump to do the job.

Feb 28, 2011 | 1999 Ford Super Duty F 450

2 Answers

1990 Trofeo .. brakes pedal goes hard .. loss of power brakes. Fluid is up and I can't find any leaks

There are two things to look for regarding this problem. You have the "teves" ABS system, as do I in my 1989 trofeo. They were NOT that good, and tend to be somewhat trouble--prone. I DID have the same problem you do, mine was the ABS pump relay. There are two brake system relays mounted on the firewall of our cars, near the center, above the A/C blower motor. One is for the pump--the other one is for the whole brake system. If the pump relay goes bad(due to it running too much, from a "bad acumulator" which I DID have--and you probably do too..), it will not turn on the brake pump, and if the acumulator is either bad, or will NOT get ANY power assist at ALL!! Our cars do NOT use vacuum brake assist--it is ALL done by the hydraulic pressure, stored in the accumulator. The relays are only about 10 each, and not hard to get. Another somewhat possible problem is the brake pressure switch, which triggers the pump relay, and it sometimes goes bad. If so, it causes the same problem as the relay. It is on the brake master cylinder assembly, and has about 4 wires or so on it may have a bad accumulator. This is the ball--shaped thing on top of the master cylinder.It stores brake pressure, between pump runs. If it goes bad but the pump still WILL have brakes, but SOMETIMES...the pedal will be hard at first, and then work. They go bad after some years of use, and mine was bad. A new one is available from GM, for about 150.

Once these "sore spots" are taken care of...the Teves system DOES work nice, and stop quick. Just have someone check these things that knows what they are doing. Good luck with your Trofeo--I love mine.


Sep 29, 2009 | 1990 Oldsmobile Toronado

1 Answer

Electric vacuum pump has six wires, where do they go

you might be looking at an air suspension pump. it is not designed to work for long periods of time.

Jun 02, 2009 | 1986 Chevrolet Chevy

1 Answer

Oversize CAM on rebuilt 302 & reduced vacuum to breaks

Ran into this problem the same way you did, but back in '75 with a Ford 289.
First of all,and you've probably done it already, is to make CERTAIN all vacuum hoses and connections, tees etc. are leak free. Then move on to diaphram actuated valves (egr valve, heater core valve, vacuum modulator valve, distributor vacuum advance.... and then there's the diaphram actuated dampers for a/c and heat in the dash) ALSO, a good idea is to add a larger than stock vacuum canister, such as a large coffee can - metal of course!

Jan 16, 2009 | 1965 Ford Mustang

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