Brake pads are okay but I have to press the brake pedal all the way down to stop

Tiny
YOURMINKY
  • MEMBER
  • 1997 NISSAN SENTRA
  • 140,000 MILES
I drive my car every week but only for a few miles. Lately I noticed that I have to press the brake pedal all the way down to the floor to stop the car when driving fast as if the brake pads are worn out. I cleaned the rotor and pads, added sil-glyde to the caliper pins. The front brake pads have more than 60% materials left on them but they are 10+ years old. What could be the reason I have to press the brake pedal all the way down to stop the car?
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Wednesday, September 11th, 2019 AT 5:08 AM

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Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome to 2CarPros.

If the pedal reaches the floor, the brakes aren't the issue. Chances are either you have a leak in the system or the brake master cylinder is bad. Have you confirmed the brake fluid is full? Take a look through this link.

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

Now, was there any evidence at the rotors indicating they are working, such as rust? Also, you didn't mention the rear brakes. Were they checked? Are they working?

Honestly, if the brake fluid is full and the pedal goes to the floor, I suspect the master cylinder is bad. If the master cylinder is empty or extremely low, check for leaks. Steel brake hoses can rust and fail.

If after checking everything you find it is the master cylinder, here is a link that shows in general how one is replaced:

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

_______________________________

Let me know if this helps or if you have other questions.

Take care,
Joe
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Wednesday, September 11th, 2019 AT 5:20 PM
Tiny
YOURMINKY
  • MEMBER
Thank you for your response.
The brake pads are 10 years old, can the age affect performance?
Last time a mechanic checked the rear brakes was last year. He said they were in acceptable shape. I'll check them again over the weekend. I think the rear brakes are even older than the front brakes.
The rotors are old and the inner-most and outer-most edges are rusty but the main friction surface looked OK even though it had many very thin circular lines. I will try to take photos and upload.
The backing plates of the pads were slightly rusty (10 years old) on the left and right sides but the center parts that press against the piston were fine.
Brake fluid was full last week.
The brake pedal does not go all the way to the floor. I just have to press it harder than usual only when I am stopping from over 40 MPH. At lower speed it stops with about the same force applied to the brake pedal as before.
The brake is not too hard or too soft or spongy, it feels normal.
If I pressed on the brake at the same force as before and the pedal stayed at the same height as before, now the car would travel further before stopping.
The brake fluid hasn't been changed lately, is it something that I should change?
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Wednesday, September 11th, 2019 AT 10:17 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:

Okay, if the pedal isn't going to the floor, then it isn't the master cylinder. Even though the brake pads are that old doesn't make them go bad. Of course, you would need to remove them and check for cracks or anything out of the ordinary. Next, the rust you described is totally normal. That isn't an issue. If you replaced the rotors today, they would rust in the same places in very little time.

What I suspect may be happening is the hardware related to the calipers may be sticking or hanging up. There are slide pins on the calipers so pressure is applied to both the inner and outer pads at the same time. If they are getting tight, and that is very possible considering the amount of time they have been installed, it makes it more likely that one of the pads is doing more work than the other and taking longer to stop the vehicle. Usually in this case, one pad will be worn thinner than the other.

I attached a few pics. In the first pic, I circled the slid pins. They should be easy to move in and out. If they are not, remove them, clean both the pins and where they mount, and then using brake component grease, grease them, making sure they slide easily.

Next, there is hardware where the pad mounts to the caliper mount. The hardware is aluminum and it is attached to a steel caliper. What happens very often is the steel caliper mount will rust. When that happens, it swells against the aluminum causing the aluminum hardware to tighten against the pad and not allow it to move. If you look at picture 2, it shows the aluminum hardware components I am referring to. Make sure the brake pads can move in the mounts.

The next concern is a possible caliper piston is sticking. To check that, you will need to remove the caliper and try to depress the piston to see if it moves freely.

______________________________________________________________________-

Now, if you want to do it yourself, here are the directions. The remaining pictures will correlate with the directions.

___________________________

Front

1997 Nissan-Datsun Sentra L4-1597cc 1.6L DOHC MFI (GA16DE)
Front
Vehicle Brakes and Traction Control Disc Brake System Brake Pad Service and Repair Procedures Front
FRONT
Exploded View Of Front Brake Assembly
imageOpen In New TabZoom/Print

CAUTION:
When cylinder body is open, do not depress brake pedal or piston will pop out.
Be careful not to damage piston boot or get oil on rotor.
Always replace shims when replacing pads.
If shims are rusted or show peeling of the rubber coating, replace them with new shims.

REMOVAL

WARNING: Clean brake pads with a vacuum dust collector to minimize the hazard of airborne particles or other materials.

1. Remove master cylinder reservoir cap.

Caliper Lower Pin Bolt

Pic 3

Torque Member And Fixing Bolt Removal

Pic 4

2. Remove lower pin bolt. It is not necessary to remove connecting bolt except for disassembly or replacement of caliper assembly.

3. Rotate caliper body upward and suspend caliper assembly with wire so as not to stretch brake hose.

Pad Assembly

Pic 5

4. Then remove pad retainers, return spring and inner shim and cover (if equipped) and outer shim.
5. Standard pad thickness is 11.0 mm (0.44 inches)
6. Pad wear limit is 2.0 mm (0.079 inches)
Carefully monitor brake fluid level because brake fluid will return to reservoir when pushing back piston.

INSTALLATION
1. Reverse procedure to install caliper assembly.
2. Install and secure all bolts.

_____________________________

Rear brakes.

1997 Nissan-Datsun Sentra L4-1597cc 1.6L DOHC MFI (GA16DE)
Rear
Vehicle Brakes and Traction Control Disc Brake System Brake Pad Service and Repair Procedures Rear
REAR

WARNING: Clean brake pads with a vacuum dust collector to minimize the hazard of airborne particles or other materials.

CAUTION:
When cylinder body is open, do not depress brake pedal, or piston will pop out.
Be careful not to damage piston boot or get oil on rotor.
Always replace shims when replacing pads.
If shims are rusted or show peeling of rubber coating, replace them with new shims.

Exploded View Of Rear Disc Brake Assembly

pic 7

1. Remove master cylinder reservoir cap.

Rear Disc Fasteners

pic 8

2. Remove brake cable lock spring.
3. Disconnect cable guide from caliper assembly and remove cable.
4. Remove lock spring from brake hose, then brake hose from bracket
5. Remove lower pin bolt.
It is not necessary to remove connecting bolt except for disassembly or replacement of caliper assembly. In this case, suspend cylinder body with wire so as not to stretch brake hose.
6. Rotate caliper body upward.

Rear Disc Pad Assembly

pic 9

7. Remove pad retainers, and inner and outer shims. Measure thickness of brake lining material:
Standard pad thickness is 10 mm (0.39 inches)
Pad wear limit is 1.5 mm (0.059 inches)

pic 10

pic 11

8. When installing new pads, push piston into cylinder body by turning piston "clockwise."
Carefully monitor brake fluid level because brake fluid will return to reservoir when pushing back piston.
9. Reverse procedure to install.

______________________________________________

Here are links that explain how to replace both brake pads and rotors. These links show it in general, but most people find it helpful when combining the links and the directions which are specific to the vehicle.

https://www.2carpros.com/articles/how-to-replace-front-brake-pads-and-rotors-fwd

https://www.2carpros.com/articles/how-to-replace-rear-brake-pads-and-rotors

I hope this helps. Let me know if you have other questions or need help.

Take care,
Joe

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Thursday, September 12th, 2019 AT 5:23 PM
Tiny
YOURMINKY
  • MEMBER
I took out the front driver side rotor yesterday. The back of the rotor had rust. A photo is attached. I was surprised to see the rusty ring in the middle. I wonder how that happened. I just ordered 2 new rotors from Amazon. I will keep you updated.
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Sunday, September 15th, 2019 AT 8:14 PM
Tiny
JACOBANDNICKOLAS
  • EXPERT
Welcome back:

They need replaced. Check the brake pad and I bet you will find that section of the pad either isn't making contact (and that's odd) or is cracked. What does the other side look like? Also, if you are getting new rotors, the pads should be replaced too.

Let me know if I can help.

Joe
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Monday, September 16th, 2019 AT 5:08 PM

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