Vacuum Check Valve for Brake Booster

I did a search and couldn't find instructions to change the valve and grommet.


My brakes are having the same issue! My mechanic is all about changing the booster too but this could be an easier fix if it works.

Here's what's happening to my 4R. Brakes start very hard and are intermittently normal and hard to depress. Theres also a hissing and squishing sound when brakes are applied. My idle appears normal which makes me think based on the other threads it might not be the booster itself. But what do I know?

It's been about a day and I've only gone a few miles from home and back just to diagnose it.

Appreciate any input from the brain trust.

:hail:
 
I replaced my power booster and valve. Booster was an O'Reilly's and the valve was Toyota. I still have a hard pedal. Should I try another check valve?
When the booster went out I had a hard pedal but no stopping. Now I have a hard pedal but at least it feels power assisted.

The check valve is on the front of the power booster. It has the vacuum line going to it. To remove wiggle it back and forth while pulling it out.
 
I replaced my power booster and valve. Booster was an O'Reilly's and the valve was Toyota. I still have a hard pedal. Should I try another check valve?
When the booster went out I had a hard pedal but no stopping. Now I have a hard pedal but at least it feels power assisted.

The check valve is on the front of the power booster. It has the vacuum line going to it. To remove wiggle it back and forth while pulling it out.

My 2002 has an issue where the brakes are extremely sensitive when I depress the pedal. Usually happens when I first start the truck. Would this be a check valve issue? I also hear the motor in the dash running a lot.. Thanks for any help.
 
Motor in the dash? Motor for what?

And a bad brake check valve would give you brick pedal. Meaning it would be very hard if not impossible to budge and would not activate the brakes at all.

It shouldn't make your brakes sensitive.

It sounds like you could be having an ABS issue.
 
this is so timely for me. I was thinking my periodic hard pedal was either the valve or the booster. gonna order me a new valve and grommet today.

I don't notice the hard pedal until after it's in reverse and moving down the snow covered driveway, and then... no brakes.... now i'm making sure i have a good pedal before moving....

good job guys.
 
So, for those that this is less obvious to, is there a write-up on replacing this valve? I've had this issue for years in the winter, and I just would take it easy on the truck and pump the brakes as I drove out of the neighborhood. Eventually the pedal would drop and I'd get normal braking, but it would be nice not to have to do this!

Ordering the parts from CamelBack after this.
 
I've had this issue for 4 yrs now but as soon as the engine gets warm it's fine. I assumed the heat from the engine thawed it and all was good. Are we saying that this could happen while driving?
 
this is so timely for me. I was thinking my periodic hard pedal was either the valve or the booster. gonna order me a new valve and grommet today.

I don't notice the hard pedal until after it's in reverse and moving down the snow covered driveway, and then... no brakes.... now i'm making sure i have a good pedal before moving....

good job guys.

Yep, this was me this morning. I've known that it needed replaced, but the issue normally only shows up when the temps drop down to the single digits and that's just not a constant occurrence here in central Oklahoma, so I tend to forget about it until I'm realizing that my pedal is hard and the neighbor's fire hydrant is quickly approaching my rear bumper.
 
There is a nut to remove that holds a J shaped piece of metal. Then just pull it out and push new one into the grommet. That's what I remember doing mine two years ago.


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Bumping this thread from the dead because it's nowhere near freezing and my brake pedal has gone stiff on me 3-4 times in the last week. Nothing appears to be "off" in a visual inspection; vacuum hose is tight and intact and no vacuum leak observed (idle quality, etc).

I can do a DrCoffee and WD-40 the check valve, or I can replace the check valve and grommet but I fear the booster may be going south.

286K as of yesterday, and I'm sure the booster is factory original. Any thoughts?
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It’s worth replacing it with that milage on it. I think they are around 40 from the dealer.


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I got an OEM booster from DeathCougar 4 years ago or so. Way better than what the dealership or aftermarket wants for one. I seem to remember that it was around the same price as a replacement check valve, plus it came with a check valve, so that was a good option.
 
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I replaced the check valve & grommet to combat the symptom of hard pedal within 30 seconds after shutting off engine. No change. Presumably there remains an issue with the vacuum booster itself.
 
I been dealing with this for three years. I found that pressing the brake for a good 10 seconds pops it open and I am good to go.
 
Symptoms continue to progress to frequent hard pedal, but it will go back to full assist; brakes continue to operate/stop the vehicle.

I am leaning towards a check valve issue because sometimes the pedal will push back during prolonged light braking, and I also often hear vacuum leaking in the cab during pedal depression/hold. Both of which seem to indicate a faulty valve - unless I'm wrong.

I will order a replacement valve and grommet, regardless if the WD-40 flush works or not, but LKQ is having a sale this weekend so I might just snag a junkyard booster.

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I had the same issues, hissing sound from inside the cab, hard pedal etc. Mine turned out to be a bad brake booster. BTW, I have a 2000 4runner. My money is on bad brake booster. Good luck.

Mike M
 
Yup, bad booster.

Replaced with a junk yard unit that had a good valve in it. All done for $45 and got a $3 core charge back. Stylin.

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