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Discussion Starter · #1 ·
When I'm stopped at a red light for more than a minute or so, the car will slowly start creeping forward at an almost undetectable speed, so much so that several times I barely caught it before tapping the car in front of me. The brake pads and rotors all look and measure good and the car stops normally. There's no "sponginess" to the brakes so I don't think it's air in the fluid. The car has 105,000 miles but I only put on the last 8k so I don't know if the brake fluid has been changed. I checked for brake fluid leaks and found none. Transmission level is just below full mark at operating temp. Power assist seems normal under routine driving. No pedal pumping required when starting out after the car sits for any period of time and none needed between stops either on the highway or in town in stop and go traffic.

As a temporary "fix" until I can determine what's wrong, I now put the car in neutral or park at red lights and that eliminates the creeping problem. If and when I notice the forward movement, a little more brake pedal pressue or a simple release and reapply of the brake pedal will hold things still for another minute or until the light changes green whichever happens first. My wife and daughter say they don't notice the problem at all. Now that I'm aware of this I'm careful not to unintentionally let off pressure on the brake pedal.

I'm thinking a new master cylinder and full vacuum bleed of the brake fluid on all four corners? Overkill? Or is this a known wear and tear issue at 100k or something else with a simpler fix? What tests can I run? Is changing the master cylinder or replacing the piston seal a relatively easy job or harder than it looks? I notice the bottom fastener(s) holding the assembly to the firewall aren't readily visible.
 

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If brake fluid hasn't been changed since 2012 or you don't know if it was done then it is long over due. Brake fluid should be changed and brakes bled every 3 years. Water contamination will cause the issue you are speaking of. Other things will as well such as a failing master cylinder, however changing the brake fluid would be the first place I start as it is cheap to do. If that doesn't solve it then it is likely a master cylinder issue.
 

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Is there really something wrong? Our '17 Ridgeline, '09 RAV4 both slightly creep. The '17 CRV (from new) we traded in on the Ridgeline did a slight creep as well. When the creep occurs, I do not feel the pedal drop/change any. Sitting at a red light for a bit, I notice the vehicle to my left/right may creep forward slightly also. I think it's normal......just apply the brake pedal slightly harder. Maybe the rotors cool slightly while sitting, thus contract a little.🤷‍♂️
 

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I'd flush the brake system with new fluid and see if it improves. Inspect pads at the same time, replace as needed.

Meanwhile, I've adjusted my stopping technique some to actually let off the pedal slightly, and creep the last feet before adding just enough pedal pressure to hold position. If I push hard on the pedal after stopping, it will eventually cause the pulsing-pedal syndrome that many mistake for warped rotors. I don't remember if applying constant hard pressure at a stop will eventually cause the pedal to fall; I adjusted pedal technique just months into ownership.

Try sitting with cold brakes and foot hard on the pedal. Does it sink slowly until it gets to the end of master cylinder travel? In a safe place, try and duplicate the hot-brakes stop and hold, again feeling for the master cylinder reaching end of travel and the pad pressure falling off. Try pumping the pedal up first and see if the pedal still bleeds down. Do the same tests again after fluid flush/replace and see if it improves.

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The toy fleet here has some examples with big 4-pot Brembo brake calipers as factory fit. In normal street driving they take just featherweight pressure on the pedal, and the pedal is very high and firm compared with the Pilot's brakes. The Pilot pedal pumps up easily, so I often find myself giving it a gentle pump or two while stopping to get some of the pedal feel I'm used to in the other cars. The brake fluid gets changed at least every two years, DOT 5.1 now, and usually every year if any of the other cars see HPDE days. Once set up to change fluid in one, they all get the same treatment. As expected, the Pilot brakes so far haven't shown any change in pedal feel or brake performance with fluid changes. It still has a lot of original pad left at just north of 50k gentle driving miles, but will get harder pads when they do get changed. It will never stop like a 3200lb German GT car with huge brakes, but maybe some upgraded pads will improve the pedal feel and reduce the pad material deposition problem.
 

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Discussion Starter · #6 ·
If there is enough water in the brake fluid to cause this problem do I now have to consider damage to the entire system including master cylinder, all the connecting steel lines and all the brake calipers?

I'd like to do a pressure bleed since I already have several pump bottles for doing other fluids but I can't find a spec for the cap thread.
 

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Discussion Starter · #7 ·
I'd flush the brake system with new fluid and see if it improves. Inspect pads at the same time, replace as needed.

Meanwhile, I've adjusted my stopping technique some to actually let off the pedal slightly, and creep the last feet before adding just enough pedal pressure to hold position. If I push hard on the pedal after stopping, it will eventually cause the pulsing-pedal syndrome that many mistake for warped rotors. I don't remember if applying constant hard pressure at a stop will eventually cause the pedal to fall; I adjusted pedal technique just months into ownership.

Try sitting with cold brakes and foot hard on the pedal. Does it sink slowly until it gets to the end of master cylinder travel? In a safe place, try and duplicate the hot-brakes stop and hold, again feeling for the master cylinder reaching end of travel and the pad pressure falling off. Try pumping the pedal up first and see if the pedal still bleeds down. Do the same tests again after fluid flush/replace and see if it improves.
The top of the brake pedal measures 5" to to the floor. It travels 1" before any braking actions starts. I can push it down another 1" with hard pressure until it stops. If I really lean into it I can get it to go down another 1/2" so it's only a total of 2-1/2" from the floor but I'm pushing so hard at that point I think metal parts are just starting to flex. I can't tell if the master cylinder is at the end of it's travel, the pedal is not touching the floor. At full force on the brake pedal, the car does not move no matter how long I hold it down so I don't think pad pressure drops off. Pumping it first makes little to no difference in how far down the pedal goes although it does engage the brakes slightly sooner. I'm wondering if some adjustment isn't needed. The pads have about 10lk easy miles on them. Cold vs hot doesn't seem to make much difference. There is some brake fade doing multiple fast stops from higher speeds but it recovers quickly.

When you say "flush/refill" do you actually flush the brake lines? With what? I was planning on just bleeding the existing fluid until I saw new fluid at each bleed port.

Once I find a cap to seal the reservoir to do a pressure bleed, I'll run the same tests after a flush/refill. I'm not familiar with a "HPDE day" ... racing term?
 

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If there is enough water in the brake fluid to cause this problem do I now have to consider damage to the entire system including master cylinder, all the connecting steel lines and all the brake calipers?

I'd like to do a pressure bleed since I already have several pump bottles for doing other fluids but I can't find a spec for the cap thread.
At 105K miles, a brake bleed may be called for anyway. Water in the system decreases the brake fluid boiling point and may cause rust/corrosion. When right foot is on the brake pedal, try keeping your heel off the floor board.
 

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If its not maintaining brake pressure while constant pedal pressure at a stop, that’s the classic symptom of a master cylinder going bad. You can try new fluid or whatever, but if it were me I’d be doing a new master. When replacing the master you will HAVE to bleed all the brakes.
 

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Discussion Starter · #10 ·
At 105K miles, a brake bleed may be called for anyway. Water in the system decreases the brake fluid boiling point and may cause rust/corrosion. When right foot is on the brake pedal, try keeping your heel off the floor board.
i was afraid of that. (rust) I don't think I keep my heel on the floor when braking but I'll watch out for it.
 

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Discussion Starter · #11 ·
If its not maintaining brake pressure while constant pedal pressure at a stop, that’s the classic symptom of a master cylinder going bad. You can try new fluid or whatever, but if it were me I’d be doing a new master. When replacing the master you will HAVE to bleed all the brakes.
I was considering that. But since I can't get the brake pedal to go all the way down using continuous hard pressure, I don't think the master cylinder is leaking. I'm going to pay attention to make sure I am in fact keeping constant pedal pressure at a stop. I guess it's possible I'm just "relaxing" some slight pressure after a while due to muscle fatigue? I'll watch it but it's a difficult thing to measure quantitatively. Is replacing the master a difficult job?
 

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Flushing brake fluid with new fluid is pretty easy recently did it on my 03' same procedure as in this video. Bought two bottles of Motul DOT 5.1 and ended up using one and a half bottles. I used a turkey baster to empty the reservoir first then topped of with new fluid and began the bleed/flush process.



 

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Flushing brake fluid with new fluid is pretty easy recently did it on my 03' same procedure as in this video. Bought two bottles of Motul DOT 5.1 and ended up using one and a half bottles. I used a turkey baster to empty the reservoir first then topped of with new fluid and began the bleed/flush process.



Wrong hoe to video... here is the one I followed:

 

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Flush the brake fluid and report back. Whenever I buy a used car, I always change all the fluids out to get a service baseline. There's a reason Honda specs 3 yr brake fluid changes in the manual, so if it hasn't ever been done, the pedal will feel like trash. The Pilot already tends to have a mushy pedal but I find it feels better after a flush.
 

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I was considering that. But since I can't get the brake pedal to go all the way down using continuous hard pressure, I don't think the master cylinder is leaking. I'm going to pay attention to make sure I am in fact keeping constant pedal pressure at a stop. I guess it's possible I'm just "relaxing" some slight pressure after a while due to muscle fatigue? I'll watch it but it's a difficult thing to measure quantitatively. Is replacing the master a difficult job?
Yeah, it can be tough to "confirm" but I've had the same symptoms on two different cars - RX-7 and an old Maxima. Thought it might be just me or me relaxing a bit. It wasnt. Neither time was it "in my head" and both times fully resolved by doing a master cylinder.

I'm not sure how hard it is to do on a Pilot, but was straight forward on the two old non-abs cars I needed it on. Just make sure you use a flare nut wrench to prevent stripping the fittings.
 
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