Brake booster check valve?

[miltoney]

Lately My brake pedal is rock hard (lol) when I press it right before I start the car. It is fine once the car starts. I suspected a bad brake booster check valve, but I can't seem to find the part anywhere. Does this car have one? And are there any other things that could be causing this?

[Alexmed2002]

So are you saying that you are pressing the brake while the car is off, then starting the car with your foot still on it?

[dgoodhue]

It is plausible that it could be leaking down and cause the symptoms that you are describing. The check valve is the plastic connection to the brake booster that the engine vacuum line connects to.

[tony saurus]

Odd initial suggestion: check your vacuum lines and fluid level/ condition in the reservoir.

 

Are you experiencing any other drivability issues? Maybe you could do a bleed on your brakes hydraulic fluid to check for general condition. Make sure that all of the calipers are moving freely and that any maintenance on that system is up to date. Only because it is a system full of wearable components, I recommend an awful lot of things before replacing other components.

 

Thankfully valves can be tested for proper operation quite easily and if you are to need to replace one, then you can be certain it has failed.

 

 

Sent from my iPhone using Tapatalk

[cww516]

I've had that same issue since I bought the car 7 years ago- never really paid it much mind, since I can probably count the times I've parked on an actual hill (not just a mild flat-lander hill) on one hand. From looking at the factory service manual and the parts breakdown, it doesn't look like that check valve is available separate from the booster, so odds of replacing just the check valve aren't all that great. Not really adding much, I know, but I'll be keeping an eye on this thread to see where it ends up.

[miltoney]

Yes, I push the brake pedal out of habit from driving vehicles with push button start, I know it isn't actually necessary with this car.

 

I think I MAY have found my problem. I have completely replaced my front brakes, including calipers, and they were fine at first, but after a week or two really started to feel like crap...vibrating when braking at high speed, excess dust on the wheels, clunking over small cracks/gravel roads, and the problem I made this thread for, the hard brake with engine off. I was watching youtube videos to make sure I didn't miss something obvious, and I saw a video from "mr. subaru" where he applied some synthetic brake grease to the pins and then stated that it was the incorrect grease, and that it would cause swelling of the bushings on the slide pins. I used synthetic grease, and sticking slide pins from swollen bushings would explain all of my problems.

 

I am going to tear it all apart tomorrow, I will report back with what I find.

[DrD123]

Was it the slide pins? I wouldn't think stuck slide pins would be causing a hard brake pedal... what did they want you to use for a grease?

[miltoney]

It was the cause of most of my problems, but the hard pedal still persists. A silicone based grease is supposed to be used on the pins. I don't care anymore, the car has bigger issues and I have decided to bail on it.