Brake pedal fade

[Peteprod]

Question All, I R & I my front brake pads and now my brake pedal goes to the floor. When I replaced the front only brake pads I just compressed the caliper pistons enough to install the new pads. Do I now have air in my system? Master cylinder is at the FULL mark. I never opened up the hydraulic system. Please let me know what you think.
Thanks!

 

[buckeyexx]

Will it build up pressure when you pump the brake pedal? It should after a couple of times. Or does it go straight to the floor with no resistance at all no matter how many times you pump the pedal?

 

[Elvira]

It does sound like the master cyl may have failed, it doesnt lose fluid, it bypasses internally and that is why it fades and or goes to the floor. The chances of a complete failure are very slim, dual type system, so you will have brake at the end of pedal travel because it becomes mechanical after that and not solely relying on hydraulics. The piston and seals in the master cyl get used to travelling a certain distance, once you do brake work and need to pump the brake pedal up, it may cause the seals to venture past a ridge they have created over time, in which case this is the failure of the seal to compress fluid and causing the internal leak.

 

[buckeyexx]

I agree. Ive actually heard of people blowing the seals if they don’t open the reservoir to allow pressure to release.

 

[Peteprod]

Will it build up pressure when you pump the brake pedal? It should after a couple of times. Or does it go straight to the floor with no resistance at all no matter how many times you pump the pedal?

Soft resistance then at the last “ of pedal travel igets a little stiffer.

 

[Peteprod]

It does sound like the master cyl may have failed, it doesnt lose fluid, it bypasses internally and that is why it fades and or goes to the floor. The chances of a complete failure are very slim, dual type system, so you will have brake at the end of pedal travel bevause it becomes mechanical after that and not solely relying on hydraulics. The piston and seals in the master cyl get used to travelling a certain distance, once you do brake work and need to pump the brake pedal up, it may cause the seals to venture past a ridge they have created over time, in which case this is the failure of the seal to compress fluid and causing the internal leak.

I do feel more resistance at the end of the pedal travel and the brake gently applies and eventually will bring the truck to a stop. It worked fine till I replaced the pads and I did open the master cylinder fill cap before I moved the caliper pistons. My truck has 50k on it.

 

[Peteprod]

Soft resistance then at the last “ of pedal travel igets a little stiffer.

The pedal return is

Will it build up pressure when you pump the brake pedal? It should after a couple of times. Or does it go straight to the floor with no resistance at all no matter how many times you pump the pedal?

psi doesn’t build up. Pedal gets a little bit more resistance in the last 2” of travel.

 

[buckeyexx]

Well you either have air pockets or your master cylinder is shot. Hopefully it’s just air pockets and you can just bleed your brakes. Have you bled your brakes?

 

[Nick@GotExhaust]

I would bleed the system and while doing so fill with new fluid entirely. Then see how the pedal feels. If problem persist I think you may of blew the seals installing the pads. I like to crack the bleeder when I compress the calipers to allow pressure to release there instead of back through the master cylinder.

 

[2003F350]

I haven't done brakes in a LONG time (probably getting close on the Wagon), but if you are not VERY careful when compressing the pistons back you can cause this issue. Hopefully it's air pockets, and you're pretty much stuck bleeding the system.

 

[Sherman Bird]

Question All, I R & I my front brake pads and now my brake pedal goes to the floor. When I replaced the front only brake pads I just compressed the caliper pistons enough to install the new pads. Do I now have air in my system? Master cylinder is at the FULL mark. I never opened up the hydraulic system. Please let me know what you think.
Thanks!

If you pushed the piston back without relieving the fluid at the bleeder by opening the bleeder, then you may have pushed contaminants back into the ABS hydraulic unit, thus getting one or more valves stuck. Get a scanner and perform automated bleed. Then rebleed the entire system. If that fails, and you have a modicum of pedal sufficient to stop the vehicle, you can perform a risky maneuver which may unstick a valve in the hydraulic control unit (ABS) by going to an empty parking lot and driving backwards at 15 or so MPH and slamming on the brakes to energize the ABS function. I've freed up many stuck valves in that manner.... but I AM a professional. I strongly CAUTION you that it has risk of accident or injury!!!!

 

[JRS950]

Wow, so much to consider doing brakes on these trucks. Hopefully I'll get many more miles out of mine before tackling them. Good information here.

 

[Sherman Bird]

Wow, so much to consider doing brakes on these trucks. Hopefully I'll get many more miles out of mine before tackling them. Good information here.

If the manufacturer had their way, you nor me could work on vehicles!

 

[JRS950]

#Sherman Bird, I completely agree with your statement.

 

[njjeff201]

If the bleeders weren’t opened theoretically there’s no need to bleed. The master cylinder cap is vented so any excess fluid would blow out onto the ground… never heard of blown caliper seals by pushing back the piston(s). If the seals did leak they were ready to go anyway. If you have no external leaks then the master is bad. Front brakes are using rear larger reservoir & vice versa. Bench bleed new master then bleed again once in vehicle. Flushing out old fluid is a good idea!! Brake fluid absorbs moisture so flush out old fluid

 

[TomB 1269]

If pistons where not compressed smooth and evenly there is a chance that the piston seals where / are damaged and that is how air got in. I've seen new calipers **** in the bore and cause soft pedal problems.
I'd suggested pulling calipers and check for fluid leak around the piston boots.

 

[buckeyexx]

Wow, so much to consider doing brakes on these trucks. Hopefully I'll get many more miles out of mine before tackling them. Good information here.

They really aren’t any different than doing any other brakes. Just bigger and more heavy duty

 

[stldodge]

Before you start replacing parts. Try bleeding the system and bleed the ABS system. Had a 04 after replacing pads, had same problem. Bleed system same problem with brake fade. Had to bleed the ABS system three times to get the air out. You have to use a scanner to bleed the system.