Question about GMC Sonoma

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My power brake assist went out. I can still stop the truck with pressure on the pedal, but my legs are getting tired from this exercise. What are the possible causes?

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The booster diaphram has probably failed. Check to see if the vacuum line to the booster is still holding vacuum when the car is turned off. Also check the other end of the hose to make sure it is not leaking where it attaches to the engine intake manifold. With the engine running, stick your head under the dash and press the brake with your hand. Listen for an air leak in the booster, which is in front of the brake pedal, in the engine compartment. If the booster is getting vacuum, but is not boosting, replace the booster. Let us know if you need the procedure or if you have other questions.

Posted on Oct 08, 2010


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I was stopped and pushing on the brake when the brake went to the floor and now I have no brakes.

Check your brake lines. It seems that one of the lines burst or cracked. Also check the brake diverter box it's the box that the lines run to under the vehicle and disperses the pressure for the abs. Also check fluid level in the master cylinder it could just be low. One more thing to check is look at the inside of tires where the brake calipers are and check for fluid. If you can see fluid or inside of tire is wet you have a bad caliper.

Jan 24, 2015 | 2005 Buick Rendezvous

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Brakes are hard to depress causing stopping problem

1: inspect all brake linings first.
no pulling left or right braking?
the car has 100% full manual brakes. if the brake booster fails.
(its only and assist !!! for 50lb small folks)
so does it? it takes more pedal pressure but has 100% full braking.
this is no accident its by design.
make sure none of the brake shoes/pads are soaked in DoT3/4 fluid
or grease or gear oil.
and no brake fluid leaks end to end, this is really #1 on all cars.
look, then look again. even behind and in front of the master cylinder.
look at tires (inside for fluid leaks>)
2: do the booster test. did the vacuum hose to it fall off?
or got pinched, or ?

google brake booster test
if ABS system. get it all checked,
if ABS get the ABS scanned.

if you cant stop correctly,,,,???? , dont drive.
get it fixed.

May 06, 2014 | 1999 Jeep Wrangler

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Power brakes stopped working

Brake booster vacuum hose , inspect that, if the hose is good then brake booster has went bad.e1320de5-8a99-48ed-84e9-c42d2e2274cb.jpg

Dec 10, 2013 | 1997 Ford Taurus

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Polo 1.4 - Im used to driving an automatic, but the Polo is manual. When I stall th engine, the foot brakes won't work. This is scary, especially on a hill!

Most likely the car has Power-Assisted brakes, Almost all vehicles today do. They allow us to stop the car with very little pressure required on the brake pedal, as the system uses engine vacuum to do the work of our leg. When you stall the car, you lose engine vacuum. This means that the brake pedal will still work, but requires far more effort to push since there is no vacuum assist. Most vehicles have a check valve at the input to the power brake booster to hold vacuum on the booster when the vehicle shuts down. This provides you with one last free press of the pedal. If you are not getting that, either your car does not have a check valve, or the valve is faulty.

Nov 14, 2013 | Cars & Trucks

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Brakes won't release

does your model have an abs unit as this can be the fault, some areas when sold did not have this abs unit but with the abs unit it has valves to assist braking. if a piston in the abs has failed it stop it from working and only manual braking is used but this is limited.

Jun 13, 2017 | 1992 Honda Accord

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The van stars shaking after 60 and the the brakes get really hard

If the vehicle start shaking at a set speed range and disappears in all other ranges you got a tire balance problem.form 25 then 50 if there no shaking then you get to 60, You got a balance problem but still youll need to look at the wear of the tire make sure you feel it. Do you see or feel anything protruding out? If its yes you'll need to replace the tire. also check the tires do you see cracks especially near the rim. If you see crack that is called seperation and youll need to replace the tire. Now for the Brakes once the brakes get hard you have no power assist. 1999 Oldsmobile used what they called Bendix 9 or Bendix 10. This replaced the vacuum brake booster you can identify it . It will have a black ball that is filled with nitrogen after the 3 pedal stop it depletes and drains the power brake assist.And that is a issue of concern. Another reason for hard brake if called brake fade.The friction of the brake pedal gets hard you have no power assist. This you'll need to correct at a repair shop,why not ? There is an important person in there,and its you.

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1 Answer

Brake pedal gets hard when braking, no normal braking

If there is a malfunction in the brake servo assist system, and your assistance is reduced, the brake pedal will become hard and you will need much more pressure on the brake pedal to stop the car.

It is possible that there is a vacuum leak in the brake servo assist system and you are only getting 50% or less assistance when you are applying the brakes.

You need to have the vehicle checked out without delay because if you lose brake assistance entirely it will be very difficult to stop the car.

Dec 22, 2010 | 2007 Toyota Camry

1 Answer

On my 2004 Jetta 1,8T the brakes are starting to get hard. Taking s little more pressure on the brake pedal to stop the car. What could be causing this??? Thanks

The most likely cause is loss of power assistance to the braking system which means you will need to apply increased brake pressure to compensate for the loss of assistance.

The problem will be with the brake servo assist. It is possible there is a leak in the brake servo assist system, which reduces the vacuum, so you are not getting sufficient mechanical assistance when applying the brakes.

It is unwise to be driving the car with this condition. If you lose all power assistance to the brakes, which could easily occur with this fault, the pedal will become very hard, you will need to apply very high pedal pressure and the vehicle will be very difficult to stop. You need to take the car to a VW dealer for service or to a competent brake specialist in your area to inspect the system and rectify the fault.

VW did a recall on some earlier year models for a leaking brake servo and I understand the problem was a faulty vacuum hose which would fail and leak. I am not aware of any recall for this item on later models like your 2004 vehicle.

All the best.

Dec 03, 2010 | 1997 Volkswagen Jetta

1 Answer

Part 2 of my first question. TO: JWVPOOL3: I don't think I explained whats really going on with my ABS. My ABS light NEVER went on at all. The first time it happened the brake pedal kept...

The ABS "thinks" that a wheel is locking up because its getting a bad wheel speed signal. Fix it correctly, or pay someone that know what they are doing. your life and the life of others is on the line.

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1 Answer

Brake issue on 2000 plymouth neon

Well booster goes pedal would be hard as rock! two legs to stop!>> if your master cylinder is gone pedal goes to floor no pressure it would behave a s if you had air in your lines but you really would not!////////....So tell me this have you pressure tested each individual well for pressure check???light car one side at a time have someone press brake and try to turn that wheel i think you have pressure but not to all if you want me to Gide you keep your request updated I will watch!

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