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Mercedes Bendz Cgi, brake pedal too hard. No fault. Can that be a vacuum pump?

Posted by Winston Havana on


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Hello you might want to look at the brake booster first. also confirm that the brakes have been bled.

Posted on Nov 28, 2019


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  • 4 Answers

SOURCE: 1993 f250 7.3 diesel - hard pedal, hard to stop,

Change the master cylinder on your booster. had the same problem with early 90's ford ranger. The pistons inside the master cylinder are probably worn...... Make sure to bench bleed the new master cylinder....

Posted on May 19, 2009



  • 106 Answers

SOURCE: abs light on buzzing sound fault code 55 hard

Possible causes for this check engine light code include:
Blown oxygen sensor fuse
Open circuit in oxygen sensor harness
Open circuit internal to oxygen sensor
Open circuit in PCM
Short circuit in oxygen sensor harness
Short circuit internal to oxygen sensor
Short circuit internal to PCM

If you find this helpful, please rate me, thank you.

Posted on Jun 04, 2009



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SOURCE: a few seconds after brakes are applied the pedal

you have two problems here, your master cylinder has a leaking seal, the low pedal is resault, the power brake booster rubber diaphram is damaged and leaking from the brake fluid that is getting into it from the master cylinder, these are sold as a unit that has been rebuilt.

Posted on Sep 28, 2009

Testimonial: "Thank You for your response. However there is a new twist that I posted."


gord storey

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SOURCE: have a 93 ford f250, blead the brakes but brakes

Sounds like you still have air in the system.
Also may need to adjust rear brakes so they don't have to travel as far to contact drums. They are supposed to self adjust as the brake linings wear down but most cars do not do this as well as they are supposed to.

Posted on Nov 08, 2009

Eric Yaryan

  • 200 Answers

SOURCE: brake pedal has alot of

The air seeping is a dead giveaway. Your power brakes are now manual brakes, but stiffer. The diaphram in the brake booster has torn and the hissing noise is the engine vacuum escaping (you hear it louder when you depress the pedal right?). Replace the booster and you will be fine. The brake lights probably don't work because you can't push the pedal down far enought to release the switch. Please rate. Thanks.

Posted on Sep 03, 2011

Testimonial: "I am grateful for your help.I was told so by a mechanic that it was brake booster diaphram or abs pump.pedal has so much pressure and hissing."

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4 Answers

Why is it hard to push on the brakes

The most obvious cause for a hard pedal is simply not enough vacuum. Check the brake power booster by pumping on the brake pedal while the car isn't running. Continue pumping until you've "bled off" the vacuum from the booster. Hold the pedal down while you start the car. The pedal should go down a bit more beneath your foot. If it doesn't, then you should examine the connection between the vacuum hose of the brake power and the engine's vacuum.
Replace the brake power booster if the connection's fine, which would fix the hard brake pedal problem.

It may be your calipers need replaced. Check them for signs of wear. Look at the metal spring where the brake pads sit.
Apply tension to the pad and see whether you hear a pop. If you do, the brake pad is moving too much on the bracket. Replace the caliper. This could help the hard brake pedal.

Jul 09, 2014 | 2000 Isuzu Rodeo

1 Answer

Why is it so hard to apply brake pedal?

_______power brake booster, check vacuum to booster and the check valve for brake booster. primary symtom is high hard pedal that requires greater then normal pedal pressure to stop car. testing booster= pump brakes several times with engine off to deplete stored vacuum. turn on engine with pushing slightly on brake pedal. you should be able to feel the pedal fade away a bit, and then become firm. But not hard. if you feel nothing at the pedal when engine starts. Brake booster is not working. Good-day! make sure vacuum is going to booster with engine running. it may just be a bad vacuum line or check valve.

Apr 30, 2014 | 1984 Buick Skyhawk

1 Answer

Clogged line

When your brake pedal is hard, you may need to check your brake booster and the vacuum line to the brake booster if their is sanction, if their is sanction in vacuum pipe to the brake booster you need to have your brake booster replaced.
You also need to check your vacuum pump and the piping.

Oct 18, 2013 | Nissan Cars & Trucks

1 Answer

Ball park quote for parts to my smart for2 coupe

The value would depend on where you live and the overall condition of the car. Websites such as autotrader or edmunds can give you a general value for your area.
I would also check with a good import garage on cost of repairs.

May 09, 2013 | 2005 Smart Fortwo Coupe

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Are there vacuum hose on the brakes hydraulic system?

NO. the vacuum is used to make the brake pedal easy to push, power brakes. the pedal would be hard without vacuum, that is why the pedal gets hard with the key off and engine not running. the problem you are having is more of a hydraulic problem.
Have the brakes checked asap. the brake system may have a leak causing the pedal to go low. check the fluid level and if it is low or empty then there is a problem, could be a rotted brake line leaking or a wheel cylinder leaking.

Dec 07, 2012 | 1997 Ford Probe

1 Answer

Brake booster appears not to be working properly. brakes work ok for 1 or 2 apps then pedal gets hard. cannot hear any vacume leaks. the car does have a vacume switch in the booster

the booster is the problem, or a hole or leak in vacuum line to booster check the check valve also ! from manifold. heres the symtoms of a bad brake booster. primary symtom is a hard pedal on application, to test booster. pump brakes several times with engine off. to deplete stored vacuum. turn on engine with pushing slightly on brake pedal. you should feel the pedal fade away abit and then become firm. but not hard. if you feel nothing at pedal when engine starts, brake booster is not working! check the vacuum lines first!!

Jun 11, 2011 | 1985 Pontiac 6000

1 Answer

1992 F250 460 cid automatic 2w drive 85000 mi. Just replaced my master cylinder, all 4 brakes, and both front rotors. Afterward I blead the brakes and got bubbles out of fluid. Problem is : when not...

There is never a test or reason to pump your brakes

Accomplishes absolutely nothing.

There is no pressure in a braking system at all,
until you SLOWLY apply the brake pedal.

Then less than 1" off movement in the master cyl,
will develop 600 to 1800 lbs at the wheels

Release the brake pedal, the system goes to zero,

To answer your question

You not suppost to press the pedal hard
The saying goes--you apply the brakes,
not force the pedal arm and pin into the
vacuum booster, as though you want to damage it

When your driving what happens ?
You have higher manifold vacuum and
thus your pedal is normal,why the VACUUM
brake booster

Mar 31, 2011 | 1992 Ford F250

1 Answer

My 2004 prius abs and brake light came on and the the brakes became very hard and constant beeeep noise, so i would shut the car off and pump the breaks and it would work fine so i decided to bleed the...

well, a hard firm pedal, usually indicates a bad brake booster or a vacuum leak to booster or the vacuum check valve, on booster. TO TEST BRAKE BOOSTER; pump brakes several times with engine off to deplete stored vacuum. turn on engine with pushing slightly on pedal. you should feel the pedal fade away a bit and then become firm, but not hard. if you feel nothing at the pedal when engine starts the booster is at fault. good-luck !!

Feb 03, 2011 | 2003 Toyota Prius

1 Answer

Brake system for 1980 300sd. Replaced front brake assem and pads. The brake pedel still to the floor. Replaced the master cylinder and hve some pedal off the floor. I rebuilt the vacuum pump but I still do...

I have the solution to your problem I have been thinking about it sir what is going on with you is you have air in your system and you did not properly bleed out your braking system that is why your pedal is touching the ground

Feb 06, 2018 | Mercedes-Benz 300-Class Cars & Trucks

1 Answer


hi from uk you do not say if engine is petrol/diesel ? reason for asking is that on petrol engine the vacuum for b/servo is from inlet manifold whereas on diesel it is created by a seperate vacuum pump usually on uk models by being bolted/driven on the alternator by belt ? however from what symptoms you describe i would suspect that on 1st application on brake pedal ? the vacuum is gone hence pedal goes hard due to loss of vac assistance ? whereas vac should last for 2 or 3 applications ?b4 all vac is gone when vehicle/engine is off so the problem may be the vacuum hose to servo unit is leaking or split ? or the servo inner piston diagphram is leaking as you press pedal resulting in no assistance unfortunately servo is not serviceable and req's replacement this is not beyond diy if you wish to? on diesel vacuum is from pump but same principle as to vacuum for servo this may be pump thet is worn out ? or hose split ? or on some occasions thedrive belt slack? also on some diesels the vac pump can be driven off therear of camshaft ? in which case pump considering age of car +milage ? may be pump fault SO hope you understand all above? try this run engine then stop press b/pedal and if pedal goes hard or slowly pushes back ? this is vacuum being used and leaking you can test pump with vacuum guage then check if operating and holding good vacuum if not pump is worn if yes then may well be servo diagphram you can buy servo units without the b/master cyl which you will not require

Dec 07, 2009 | 2000 GMC Sierra

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