Brake pedal becomes extremely stiff overnight

F

Fire0nic3FX

Member
What's up guys. When my I start my FX first thing in the morning and I put my foot down on the brake pedal to push the start button and start the car the brake pedal I can't even push it down all the way. It'd extremely stiff. It softens up after the car starts. Never use to be like this before.

It becomes stiff like how if you pump the brake pedal a few times after the car has been shut off. The only thing is that I'm not doing that. It stiffens up after sitting overnight.

Sent from my SPH-L720
 
did you do your most recent brake job or somewhere else? I wonder if the right amount of brake fluid was used.

Also, I wonder if your brake booster is failing, booster push rod is out of adjustment, or vacuum leak in your booster system.

Make sure the booster is getting good vacuum. Whoever did your brakes last could had plugged up the vacuum line. Most likely it's with your vacuum line. Could be as simple as a gasket giving a slow leak that would just be detected when your car is parked over several hours over night.
 
Mine is usually stiff when I get up in the morning too, oops, you were talking about the car, sorry.

Seriously though, I have never noticed the pedal being stiff, when I start the car I barely touch the pedal, just enough for the push start button to work.
 
Thanks Jonas. I changed the brakes last but that was like 10k miles ago. I haven't checked the brake fluid level in months so I'll give that a try. Also how do I check for vacuum leaks? Might just head over to the dealer since I have a warranty.
 
You can just get a cheap vacuum gauge at the autoparts store to see if you have a leak. Or you can listen for hissing noises from the lines. And if your brake pedal is still, it's likely not a vacuum leak. Vacuum leaks cause a weak brake booster and mushy braking. When I had my old turbo car, I had to add a bunch of vacuum hoses to run the wastegates, BOV, etc. That nightmare of plumbing caused a vacuum leak that led to terrible braking. Had to individually unplug and check all the hoses and it turns out one of my fittings was loose. Fixed that and brakes were normal.

Your issue almost sounds like fluid expansion, but that's not supposed to happen to brake fluid.
 
If it stays stiff for longer than four hours you need to call your doctor (sounds like a vacuum issue BTW).
 
I randomly saw a post similar to this on a bmw forum. It apparently is a common problem on some models. The issue is loss of vacuum while sitting which causes the brake booster to stop working. There is a check valve that allows you to pump your brakes once or twice before they become stiff while the car is off. If there is a leak, vacuum is lost overnight and it will be stiff.
 
LMAO!!! Omg when I read the thread title I knew someone would crack a joke... good one man! I'm dying here...

GEE50FX said:
Mine is usually stiff when I get up in the morning too, oops, you were talking about the car, sorry.

Seriously though, I have never noticed the pedal being stiff, when I start the car I barely touch the pedal, just enough for the push start button to work.
Click to expand...
 
Ok my FX has been at the dealer for like 3 days getting this taken care of. After much arguing with the manager they finally admit that there is a problem and that the brake pedal shouldn't be losing pressure over night.

Shadow191 was right on point with this one. The problem is a rubber hose to the brake booster that has a check valve inside. That check valve went bad so they are replacing it. Had to order it since the part isn't in stock.

Sent from my SPH-L720

---------- Post added at 11:35 AM ---------- Previous post was at 11:34 AM ----------

I should have my car back by Wednesday

Sent from my SPH-L720
 
Yup the same dealer. This is the first time I've had an issue with them on fixing stuff. I never applied to there though.

I can't really complain as I'm going to be having this Q50 loaner for the next week. I do miss the FX though.

---------- Post added at 09:55 PM ---------- Previous post was at 09:54 PM ----------

By the way they told me if this doesn't fix it they will replace the whole brake booster.
 
Crap just got a call from the dealer telling me this hose with the check valve is on a 7 week back order from Japan. Damn it that means this issue probably won't be solved till after the new year. We'll this sucks!

Sent from my SPH-L720
 
Fire0nic3FX said:
Crap just got a call from the dealer telling me this hose with the check valve is on a 7 week back order from Japan. Damn it that means this issue probably won't be solved till after the new year. We'll this sucks!

Sent from my SPH-L720
Click to expand...
Rats. Does this mean you will have the Q50 until then
 
7 weeks sounds excessive... So why would you have to drop it off so early if they won't have the part for so long? That seems odd and where will they store the car until them?

Sent from my SGH-I747
 
Phantom said:
7 weeks sounds excessive... So why would you have to drop it off so early if they won't have the part for so long? That seems odd and where will they store the car until them?

Sent from my SGH-I747
Click to expand...
I think they gave Aaron his FX back and told him to bring it in when the part arrives at the Stealership.
 
That would make more sense, no point in keeping a car for no good reason. Sometimes I wonder how dealerships come up with these silly ideas.

Sent from my SGH-I747
 
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