Brake pedal get mushy and goes to the floor if not pumped

Tiny
NAT JOE
  • MEMBER
  • 2003 BUICK CENTURY
  • 3.8L
  • V6
  • 2WD
  • 84,000 MILES
Okay, when you stop if you don't pump the brakes they get mushy and go to the floor, but if you pump the brake pedal one time the brakes is fine. My wife's dad says it's the master cylinder, but there is not no leaks it was just a little low on bake fluid and to me it feels like the older cars use to feel like if there was a vacuum leak or something. But there is no leak and I was wondering if it could be the power booster maybe?
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Saturday, June 29th, 2019 AT 2:43 PM

18 Replies

Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome to 2CarPros.

If the pedal goes to the floor, either there is a leak at one of the wheels, one of the brake lines / hoses, or the master cylinder is bad. What happens is when they get older, the plungers in the system get hard and fluid can bypass them. The result is what you described. Now, try this. Pump the brake so you get a good pedal. Hold steady pressure on the brake pedal. Wait a few to see if it starts slowly going to the floor. If it does, my first suspect is the master cylinder. Most times, you won't see a leak with this condition because either the fluid doesn't leak at all or it will sometimes go into the brake booster. This really doesn't sound like a vacuum issue.

Take a look through this link:

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

I really feel that is the problem. If you determine it is, here is a link that explains in general how to replace a master cylinder.

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

Here are the directions specific to your vehicle. The attached picture correlates with the directions.

_______________________

MASTER CYLINDER REPLACEMENT
Master Cylinder Replacement

Removal Procedure

see pic 1

1. Disconnect the electrical connector from the brake fluid level sensor.
2. Disconnect the brake pipes from the master cylinder.

Important: Install a rubber cap or plug to the exposed brake pipe fitting ends in order to prevent brake fluid loss and contamination.

3. Plug the open brake pipe ends.
4. Remove master cylinder mounting nuts.
5. Remove the master cylinder from the vehicle.
6. Drain the master cylinder reservoir of all brake fluid.

Installation Procedure

see pic 1

1. Bench bleed the master cylinder.
2. Install the master cylinder to the vacuum brake booster.

Notice: Refer to Fastener Notice in Service Precautions.

3. Install the master cylinder mounting nuts.
Tighten the master cylinder mounting nuts to 25 Nm (18 ft. lbs.).
4. Remove the plugs from the brake pipes
5. Connect the brake pipes to the master cylinder.
Tighten the brake pipe fittings at the master cylinder to 15 Nm (11 ft. lbs.).
6. Connect the electrical connector to the brake fluid level sensor.
7. Bleed the brake system.

++++++++++++++++++++++++++++++++++++

The link I attached regarding replacement includes directions for bench bleeding the new master cylinder and the brake system. If you need help or have other questions, let me know.

Let me know if this helps.

Take care,
Joe
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Saturday, June 29th, 2019 AT 7:42 PM
Tiny
TERRI W
  • MEMBER
  • 1995 BUICK CENTURY
  • V6
  • 2WD
  • AUTOMATIC
  • 89,000 MILES
After I had rear brakes replaced the pedal now goes to the floor it did not do this till after the rear brakes were replaced. Also replaced the wheel cylinders on back brakes. Did the bleeding on rear brakes still pedal goes to the floor. Then I went ahead and replaced the front brakes and now the pedal really goes to the floor. Now they want to replace the master cylinder or brake booster. And it was a friend not a mechanic that did the repairs. Any advice would be helpful.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Good afternoon,

This does sound like a master cylinder.

https://www.2carpros.com/articles/how-to-replace-a-brake-master-cylinder

https://www.2carpros.com/articles/brake-pedal-goes-to-the-floor

https://www.2carpros.com/articles/how-to-bleed-or-flush-a-car-brake-system

When this is done and you get a pedal, take it to a professional to have the work verified. You should only let a professional do brake work. Safety is number 1 concern. I know a lot has to do with economics but only let professional perform this important task.

Roy
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
TERRI W
  • MEMBER
Okay, thank you for your quick response and I will take your advice and replace the master cylinder by a professional.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
TERRI W
  • MEMBER
I will let you know the outcome.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
You are welcome.

Always glad to help.

Keep us updated.

Roy
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
TERRI W
  • MEMBER
Will do.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Thank you.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
TERRI W
  • MEMBER
Hi there,

Just giving an update on my brakes after I had a non professional replace both front and back. I took it to a professional and it was not the master cylinder, it was not properly put back together on rear brakes and when he replaced the wheel cylinder (not sure why in the first place) they need to be pressurized? Got that put back right and the front brakes need to be programmed with a brake scan tool. Brakes are done right now. Lesson learned when it comes to brakes and safety leave it to the professionals it will save you money in the long run. Thanks for your advice.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Front brakes reprogrammed? No such thing.

What did he do?

Glad to hear it is fixed.

Roy
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
BRANDY JONES
  • MEMBER
  • 1993 BUICK CENTURY
  • 3.3L
  • 6 CYL
  • 2WD
  • AUTOMATIC
  • 233,000 MILES
I have replaced the brake booster and master cylinder and brake lines, I have bled the brakes; back passenger, back driver, front passenger, front driver. About six times and when the car is not started I have partial pedal but when I start the car I have no pedal at all.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
SCGRANTURISMO
  • EXPERT
Hello,

This could be a problem with your vehicle's brake booster check valve or a leak on the vacuum line going to the brake booster. Have an assistant press on the brake pedal and listen to the brake booster vacuum line and check valve for any audible leaks and then get back to us with what you are able to find out.

Thanks,
Alex
2CarPros
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
TERRI W
  • MEMBER
Yes, there is such a thing as a scan tool to reprogram the ABS brakes.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
These were your words. The front brakes need to be programmed with a brake scan tool.

The scan tool opens the ABS valves for bleeding the system. It is not the programming of any sort.

Roy
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
TERRI W
  • MEMBER
Sorry am I bad but it does clear error code related to Abe.
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ASEMASTER6371
  • EXPERT
Did you have ABS codes stored?

Roy
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Thursday, February 18th, 2021 AT 5:59 PM (Merged)
Tiny
ACER516
  • MEMBER
  • 1992 BUICK CENTURY
  • 6 CYL
  • FWD
  • AUTOMATIC
  • 82,466 MILES
A month ago I had a new front to rear brake line installed along with a left front caliper and right rear wheel cylinder after driving I found my brakes weren't as high as before I had this job done. Today I was was driving and applied the brakes and the brakes started pulsating badly and the car seemed to be dragging badly as if a brake was locking up.I shhut off the car as I had business to attend to where I was. When I came back the car started ok and I headed home and it ran fine until I had to hit the brakes again then the engine became sluggish and it stopped finally and I made it home. It seemed to me that the brakes would heat up then if left alone for a while it would run ok.I checked all fluids and found my master cylinder overflowing a little from the cap.I suspect either the caliper malfunctioned or the other front side malfunctioned. Taking car back tomorrow to have them check it. Tomorrow is also my 30 day warranty deadline. Do you suspect a bad calliper too?
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Thursday, February 18th, 2021 AT 6:00 PM (Merged)
Tiny
JACOBANDNICKOLAS
  • EXPERT
It could be a bad caliper or rubber brake hose. The hoses sometimes break down inside and won't let fluid run back to the master cylender. As a result, the caliper sticks.
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Thursday, February 18th, 2021 AT 6:00 PM (Merged)

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