2009 Chevy 2500 Brake fade

[rsgs]

I have a 2009 Chevy 2500HD 4X4 that is an occasional driver, now used mostly for towing either my 5th wheels or boat. I had noticed last year while towing that it was taking me longer to stop than in the past. I also noticed that without a trailer it was taking me longer to stop. I did a complete brake job with new rotors and pads, flushed the brake fluid and re-bled - no difference. Checked the system and no leaks viable an no puddles anywhere.

I decided to purchase a high performance brake kit from Summit thinking that would help the problem. $500 dollars later no difference in braking.

Looking for any ideas anyone has as to where to look next.

[DmaxMaverick]

What you describe doesn't sound like "brake fade". Brake fade happens when the service brakes are heated excessively due to continued heavy use, such as descending a grade, causing them to be gradually less effective. This is a normal condition, often predictable, and is avoided by experienced drivers.

When you say "takes longer to stop", do you mean braking distance is increased, relative to brake pedal pressure? What happens with full brake application when slowing (standing on the pedal, fully to the floor)? Does the ABS activate? How many full brake applications remain after the engine is shut off? The hydroboost and/or power steering system(s) may be weakening. Causes, in no specific order, may include low pump output pressure, failed/contaminated power steering fluid, a failed hydroboost unit. A failed proportioning valve may also be preventing sufficient fluid pressure to the rear brakes, but appears much less common on late model trucks.

[rsgs]

This happens when either towing or not towing. The pedal seems 'softer' (more travel) than it use to be, even though I have replaced disk and pads and flushed and re-bled the brakes. Braking distance is increased and it takes more pressure on the pedal to achieve the same results. I have not stood on the pedal or engaged the ABS so I cannot comment on that. I have not checked how many brake applications can be applied after the engine is shut off. I assume you mean pressing the pedal until it gets too hard to push.

Question: what does the power steering pump have to do with it (dummy question)?

[Kennedy]

The 2010 and prior model brakes just do not inspire confidence. 2011+ got larger rotors etc. They have also taken the slack/slop/sponginess out of the pedal. Possibly related to the stabiltrak system?

One suggestion that I can make that will not break the bank is Hawk Super Duty Ferrocarbon pads. I put a set of these on a F250 and it really stops nice yet predictable. Have not yet tried the GM application. Stay away from the fancy ceramic stuff. Make sure the caliper pistons and slides work freely. When the brakes are working well with nice aggressive pads you should be able to get the ABS to activate/chatter a bit under exceptionally hard stops at highway speeds.

I should also note that I did a Duraburb with EBC Orange stuff and they worked exceptionally well, but are VERY expensive.

[arveetek]

Question: what does the power steering pump have to do with it (dummy question)?

GM diesels use the power steering pump to supply hydraulic pressure to the brake assist mechanism - "Hydroboost" - instead of vacuum like on most passenger vehicles. Look between the master cylinder and the firewall: instead of a large vacuum canister to assist with braking, you will see a smaller mechanism with hydraulic hoses running to it. This gives you your "power" brakes. If there is an issue with the power steering pump or hydroboost unit, it could result in you having to apply more pressure to the brake pedal to overcome the lack of brake assist.

Casey

[DmaxMaverick]

This happens when either towing or not towing. The pedal seems 'softer' (more travel) than it use to be, even though I have replaced disk and pads and flushed and re-bled the brakes. Braking distance is increased and it takes more pressure on the pedal to achieve the same results. I have not stood on the pedal or engaged the ABS so I cannot comment on that. I have not checked how many brake applications can be applied after the engine is shut off. I assume you mean pressing the pedal until it gets too hard to push.

(see the answer to question #2) Yes. It should have 3-5 applications before the pedal becomes more difficult to press. This should be done immediately after a shutdown, then repeated (start engine, apply brakes a few times, shut down) after 10 minutes of shutdown. If it has zero applications immediately, the hydroboost unit has failed and needs to be replaced. If it has 3-5 applications immediately after shutdown, then zero after 10 minutes, it should be replaced soon. If it has 1 or more application after 10 minutes, the accumulator (horizontal canister sticking out forward, on the inboard side) is functioning at least minimally. A bad accumulator is often the cause of a failed or waning hydroboost unit. Service brake boost pressure can bypass through the accumulator maintenance valve, lessening the effectiveness of service brake power assist. Usually by the time this happens, the hydroboost units are fairly used up, and should be replaced anyway. There will usually be a lot of pressure bypassing internally by this point. All the internal seals are subjected to similar pressure and temperature, and will typically wear/fail similarly. A failure of one function is usually followed by others, often very quickly. A visible external fluid leak at the accumulator base is usually an early indicator, while a visible leak between the master cylinder and hydroboost unit, or a leak at the firewall (or inside the firewall) is much more immediate. Leaking fluid lines (at the crimp connections) is typical, and should be repair/replaced at your soonest convenience.

ABS engagement should vibrate/pulse the pedal, but should not push it back toward you at steady foot pressure. If it does, the hydroboost unit has failed.



Question: what does the power steering pump have to do with it (dummy question)?
The hydroboost unit (power brake assist) is powered by the power steering pump. It is a hydraulic brake assist booster, as well as a mechanical pass-through from the pedal to the master cylinder, and has 3 hydraulic lines attached (one from PS pump pressure, one pressure to PS gearbox, one return to PS pump reservoir - the gearbox has its own return - be sure to label them if ever removed). It also regulates PS fluid pressure to the PS gearbox. The unit is located where a vacuum booster would be, if it had one (between the brake master cylinder and firewall).

[rapidoxidationman]

Were the brakes bled using a computer to activate the ABS module during bleeding? If not, my money is on an air bubble or equivalent in the lines that normal bleeding didn't touch.

[rsgs]

Thank you for all the replies. I did check it over again last night and I did notice some wetness around the place where the brake arm passes through the file wall. No puddling, but there is a fair size ring of wetness around it. The PS pump fluid was down slightly. I was not able to drive it to see if the ABS engaged during a 'heavy footed' stop.

rapidoxidationman: No the brakes were not bled using a computer to activate ABS. Wasn't aware that was needed. The behavior of the brakes was the same after bleeding as it was before though.