Car Pedal Goes to Floor at First, Then is Fine?

2014 Acura TSX 120k miles

Don’t know if it is related but first started noticing this issue only recently and am in the rust belt area were it is below freezing this time of year at night and early morning.

When first starting the car and backing up at low speed out of the driveway brakes work fine. Then when going forward and stopping for first time while in Drive, brake pedal goes to floor. Then next attempt at stopping everything works fine.

Any ideas on what could be causing this issue? I guess air could be in the loop, or the brake booster is going out, or there could be an air leak small one?

… or, your master cylinder is going bad and is about to get much worse.


Check all 4 wheels for loose wheel bearings… I have seen many loose wheel/hub bearings act like a bypassing master cylinder… But it could still be something brake related…
A Booster normally makes the brake pedal harder, not go to the floor…


Is the brake fluid level ok for both circuits? If so, my first guess is the same as VDC’s above, a faulty brake master cylinder.

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Thanks guys.

I’ll check wheel bearings. No whine sounds while driving. Will bang on tires and check for play. Will spin tires and listen closely.

Brake fluid was ok last checked.

Will do oil change soon and will report back.

Only checking for a loose wheel bearing for your brake pedal issue… If all good then you start doing checks to confirm the master cylinder is bypassing…
With the wheel being checked on a jack stand, grab the wheel at the top and bottom and push with one hand and pull with the other hand, if any movement then confirm it is in the bearing and not a ball joint, HINT: if you can see the rotor moving in and out but the caliper bracket is not, it is the bearing… If you have movement and can not tell if bearing or ball joint then it is time for a real mechanic to check it out…

Or you can just be a parts changer and throw a master cylinder at it and hope it sticks, most of the time it will, but not always… Anytime I had a mechanic tell me a vehicle had a master cylinder bypassing, I always asked them to prove it…

Replace the brake master cylinder.


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I have had this problem on two of my previous cars, a 1965 Rambler Classic and a 1978 Oldsmobile Cutlass. In both cases, the problem was the master cylinder. There was no external fluid leak, but internally, the master cylinder was leaking fluid past the piston. Replace the master cylinder.


How would that be proved? When I run up against this problem and wheel bearings etc are solid, and there’s no visible brake fluid leak, I just presume the problem is the MC. In theory I could remove the wheels & whatever else is required to inspect the brake’s workings, but I’ve never gone to that bother. And so far it always has been the MC . But if I knew an easy way to prove it, I’d do that first.

One word, experience… lol

Very simple, just as simple as checking for a loose bearing… But like I said most mechanics just throw a mc at it and most of the time it works, but again, not always… I have explained on here before how to properly check for it…
You clamp off all the brake hoses and push on the brake pedal, if the pedal is hard then the mc is good, if it drops then it is most likely the mc… if the pedal doesn’t drop then you release one brake hose at a time while still pushing the pedal and it should only drop about a 1/2 to 1 inch, if good then let up and re-clamp the hose, repeat until the pedal drops much lower or to the floor, that wheel is were the issue is… This obviously takes two people to do the test…
I have also had calipers making the pedal drop, by clamping off all the hoses you eliminate everything below the hose…

I have seen master cylinders get replaced over a loose bearing multiple times, and yes most of the time it is a bad master but not 100% of the time… again, you can be a parts changer or take a few minutes to confirm problem…

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I’ve always been reluctant to clamp brake hoses willy-nilly for fear of damaging them in the process. But I now understand how you do it, thanks.

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Well you don’t clamp it as hard as you can or you will damage the hose… I use something like these…

Or small needle nose vice grips with high pressure fuel line over both needle nose ends… That way you are basically clamping a hose with two other hoses, hard to damage it that way…

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So I did a visual inspection on my car.

Little to no play in the tires, so I presume little to no play in the hubs as well. Also no whine sound while driving. However I did notice that it is wet around the axle shaft around the support bearing that is mounted to the engine. I don’t know if I should be worried about this? Based on the wetness, I guess some grease leaked out of the bearing or something there is no other oil stains above it or around it, looks like it’s coming from there only.

The brake fluid was below what I remember it was the last time I checked, but still above the minimum line. There is no maximum line. I checked with the brake fluid pen tester, there was 0 % water in it and was not black.

Looking at the brake calipers, two of them are wet.

So I guess that’s were my brake fluid is going. If I have a leak, air can also be getting into the lines, resulting in my symptom of the brake pedal going to the floor at times.

Looking at the wet stains, it doesn’t appear to be leaking from around the hose area or the bleader nipple. So I presume it is likely leaking from the seal?

I find it very odd that two calipers would be leaking at the same time? Both are the originals.

Yes, leak is coming from the piston to caliper seal… If that seal is already leaking, it is just a matter of time before it lets go and your pedal goes to the floor with a great reduction in braking power and the more you pump them, the more fluid you will loose… and always remember, if your brakes don’t stop you, something else will!!!

Replace BOTH calipers, best to get semi loaded or fully loaded calipers so you get all new brackets, pins, slides and boots etc etc etc… Semi means no pads…

Not uncommon at all, you don’t drive around only using one caliper anymore than the other one do you?? How often do the shoes on your feet only need to be replaced one at a time under normal circumstances??? And with your mileage and rust, I would replace both front or rear brake hoses at the same time as the calipers (thinking fronts but you never said)…

EDIT: Looks like you are showing both a front and a rear caliper after looking at the pictures closer… relace all 4 of each…

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If the caliper seals are leaking, you can pretty well bet the master cylinder seals are leaking too.

That should also be replaced.



Thanks for the reply. Sorry for not specifying. Yes one is in the rear and one is in back. I see what you mean that it is nothing abnormal.

As mentioned already, YES all 4 calipers (and brake hoses)…The last thing you want is unequal braking/pulling to either right or left side… Need to probably spray penetrating oil on the metal brake lines around the fittings (so they can be soaking) so you don’t twist the lines and break them…

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Looks like an oily film. Did you coat the brake pads/shims with chassis grease?

Hi thanks for the reply. No I use the permatex orange stuff meant for brakes, Permatex 80653. You think it could be this stuff?

I also have never undercoated the car before.

You suggested that last summer when my brakes we’re driving me crazy but I didn’t have a second person and also didn’t have proper brake hose clamps ……bled, power bled again and again , replaced master.
Turned out to be a ( 16 year old )caliper boot had a slight tear and the piston was sticking but not frozen solid.