Edward'TLS

Every morning, I literally have to stand with my weight on the brake pedal to depress it low enough, so as to engage the brake interlock system to start my 2014 AWD MDX.

The Honda power assist braking system is designed such that there will be power assist to the brake pedal for at least a few pedal pumps before the pedal goes completely hard.

It seems that the vacuum reserve for the brake assist system has all leaked out over the night, and so the brake pedal goes completely hard as if there is no brake assist at all.

But no such issue if the MDX has only shut off for a few hours.

Looks like a trip to the dealership is in order.

RL06tech

Agreed.
Just a couple of things the brakes dont have a pump for vaccum the "pump" is the engine itself. What is mysterious is that it is fine after sitting overnight. You would expect that once vaccum is lost it would stay lost until you ran the engine again, might be an electric gremlin with the interlocking system. Ive always had my concerns with pushbutton systems, Im also worried about the fact that you cant start the car with the key at all. On my RL at least you could start the car with the little fob key if the electronic system had a fault. Im sure that having a non electronic mode to start the car would save many rides on tow trucks. Let us know what it turns out to be. Unfortunately the totally keyless car is becoming the norm rather than the exception even cheap cars have keyless systems now.

Edward'TLS

I believe the culprit is in the brake system, and has nothing to do with the brake interlocking system.

The brake interlocking system prevents a runaway car by making sure that the driver has his/her foot on the brake pedal before the engine can be started (either by a turn-key or by a push-button).

The brake pedal has to travel downwards far enough to engage the brake (interlock) switch and also the brake lights.

If the brake pedal can be depressed normally, then everything is good. But the problem is that every morning, the brake pedal goes hard (just like the ancient type brake system with no power assist) and can't be depressed downwards for even that small distance to engage the brake switch, unless I virtually put all my body weight onto the pedal.

But if the engine has only shut down for a few short hours, the brake pedal can be depressed normally. Only that if I pumped the brake pedal repeatedly after the engine is off, then the brake pedal will go harder and harder to depress.

Every morning, the brake pedal becomes so hard to depress that as if someone had, in the middle of the night, pumped the brake pedal until all brake assist reserve vacuum had been used up.

So, it is definitely a brake system issue, highly likely a slow vacuum leak.

RL06tech

Sorry I misunderstood, I thought after sitting around a few Hours it got better. Yep it does sound like you have a leak somewhere, in fact it might be something you can spot such as a loose hose or fitting somewhere. There's really not that many, just look for the hose that connects the intake manifold to the master brake cylinder.

fjfjfjfj

Several users seem to be discussing the same issue here with reported fix being replacement of the 'Brake Booster Check Valve"? Not sure if that makes sense.

http://www.mdxers.org/forums/94-new-...t-problem.html

RL06tech

Makes 100% sense.

Edward'TLS

Yes, that's exactly what my brake problem is.

RL06tech

Should be a 15 min pitstop.

Edward'TLS

I dropped off the MDX last night, so that the mechs could try to duplicate the "hard brake pedal" problem in the following morning.

As always, the mechanic couldn't duplicate the hard pedal problem.

But the advisor told me that the mech managed to adjust the brake cable to alleviate the problem !? I said "OK, I'll give it a try".

Looks like it'll take multiple trips to fix this simple problem once again.

RL06tech

Frack! Sometimes you just have to print out the stupid TSB so that they get it. Luckily the service people and mechanics at my dealer have been topnotch.

RL06tech

Did a quick check for you, at this time there is no official tsb on the issue

Edward'TLS

Ok, I guess I'll have to wait a bit more.

weather

^^^ I have the EXACT same problem with my 2013 RDX. You have described it very well and you are not alone experiencing this. If you find the source of the problem, I'll be interested to know what the fix consist of. I have not takenit to the dealership as they are a few hours away.

syntax53

Just curious, do any of you experiencing this problem park on hills? I noticed yesterday when I was stopped on a steep hill and pulled my foot off the brake that the car did not have any backwards roll down the hill, like it was keeping the brake pressed itself. Because when I went to put my foot back on the brake there was barely any movement, like I hadn't even taken my foot off. I assumed it was some kind of automatic hill assist feature that's I've seen in other makes like Ford.

Edward'TLS

^^^^^

That is the Acura "hill start assist" function doing it's work.

db22

Hey, you have been reading the manual haven't you?

Edward'TLS

^^^^^

No, I tried but failed. Every times I tried to read through those multiple thick-ass manuals, I fell into sleep. So I gave up.

The reason why I know about the "hill start assist" thing is that I had gone through all the 2014 MDX information (especially features and specs) in the Acura website many times over, first to decide on the SUV, and then to pick the trim level with only the features/gadgets that I intended to pay for.

Edward'TLS

As for that 3G MDX owner, in the MDXers forum, who has the brake booster control valve replaced; the fix doesn't work.

The hard brake pedal problem comes back a few days after the valve replacement.

Edward'TLS

Now that the weather has chilled out, this "hard brake pedal" problem is happening in the mornings once again, after all those uneventful warm summer days have gone by.

CheeseyPoofs McNut

As a point of interest my 2 month old TLX Tech is doing the exact same thing. It started about a week ago (when the weather started dropping into the low 30's and upper 20's) and has been doing it consistently over the past 3 or 4 days. Not sure I want to mess with a trip to the dealer if there's no known resolution.

maxAmillion

iTrader: (1)

I have a 2010 TL doing the same thing. Any luck finding a fix?

Edward'TLS

Nop. Acura still has no clue !