Stiff Brake pedal at first start
 

All-
2014 TL FWD Advanced Pkg, just had the car in to the dealer for ~40k A1 service last Thursday. I had them look at the brake system because the past month or so I go to start the car, and the brake pedal is stiff, almost to the point that it won't depress far enough to trigger the starter. They diagnosed a Brake Booster Hose failure, ordered the 46402-TK4-A01 part. It didn't come in until late Friday (good thing I got a loaner), and they replaced the brake booster hose. They call me Monday morning to let me know the car is ready. I go to start the car in the lot (about 30 degrees outside), and the brake pedal is still stiff. I figure, probably didn't build enough vac after they pulled it outside. Drove home about fifteen minutes.

Go out to the garage this morning, its about 30 deg in the garage, and depress the pedal...still stiff. I am not noticing any issues while driving. Thoughts? Anyone have this issue in the past?

Mine did that for years. It would be stiff if parked anywhere from sitting overnight, to getting gas. (more rare). Timing seemed inconsistent. Dealer kept telling me it was normal.

Then one time a few days after a brake flush, the brakes felt different all of a sudden, and the stiff pedal never came back. I had done multiple brake flushes before this one, and the stiff pedal was always there.
Before anybody goes off, it's been years since that happened and the brakes are still perfectly fine.

Edit: with that being said, you should probably still get it checked out by an independent mechanic, as i did, just to be sure.

When was the last time the fluid was replaced?

As far as I know, never. The car is just short of 40k miles on the odo. Bought it from the dealer with ~5k mi on it, serviced there ever since.

Brake fluid is hygroscopic meaning it absorbs water. Water freezes. It may explain the stiff brake pedal in the morning when it's colder out. :dunno:

Right, but as soon as the car starts, it is fine. Seems more like a vacuum thing to me. Perhaps a bad master cylinder (or whatever they call them these days).

There was a thread on "hard brake pedal when starting vehicle especially on cold winter mornings" back in 2014 :

https://acurazine.com/forums/3g-mdx-...rnight-898831/

There is no permanent fix on this problem.

I feel like this has to be a brake booster issue itself...not just the hose.

Thanks for the link, but when going through that thread (and subsequent threads linked to it), it doesn't appear as if anyone had a resolution other than "when it is cold, it does that in your car".

It only seems to happen in colder climate areas, from what I am seeing in the threads referenced.

I'd try changing the fluid. Brake fluid can become contaminated with minute quantities of water over time. It doesn't take much to mess with the braking action.

Yeah brake fluid should be changed every 3 years. Your '14 is due for a change if it's never had one.

2014 TL - Brake Booster Test
https://techinfo.honda.com/rjanisis/...untry=1&lang=0