Hey guys, so I was heading to work and got a bit of a scare on the freeway this morning. It looks like an off and on issue though. When I press on my brakes, there are times when they work just fine and other times when the pedal becomes rock hard and takes all my stregnth to put the pedal down. Out of 10 stops this will happen 1/10 times though so it's not consistant. When they do work they work just fine though, what could the issue be? I have liquid in my brake reservoir so I don't believe it's a bleed issue. Any suggestions would be welcome.
Brake works off and on
- Thread starter crespoh69
- Start date
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19963.4lsr5
New member
The check valve in the brake booster can cause it.
What year?
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What year?
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Hard pedal is caused by low vacuum in the brake booster. That can be caused by several different things: clogged/leaking vacuum hose from the intake to the brake booster check valve, a bad brake booster check valve, a bad brake booster check valve grommet, or a bad brake booster. Has your warm idle rpm changed any?
It's a 99
Idle has not changed any as far as I can see. How common is it for the valve/grommet itself to go bad? Is there a part number for me to get this? Seems like the cheaper approach compared to the whole booster.
Pretty common for people to have problems with the grommet in freezing climates. I'm not sure that would apply to you since I see your location says Long Beach. I would try checking the brake booster vacuum line for cracks/tears then try spraying carb cleaner or similar on the vacuum hose and brake booster check valve grommet while the engine is at warm idle and listen for any rpm change. If you want to try replacing the brake booster check valve and grommet I think they are fairly cheap. I'd really recommend OEM but that's my personal religion lol
Thanks, I was actually thinking of your reply this morning and did notice a slight rise in RPM when pressing the brake actually, what would that mean? I'm going to reach out to Toyota to see if they can get it for me by Friday, they're charging ~$50 for it and a generic booster will run me $70 on Amazon. Really don't want to buy the $50 part and not be able to return it
I haven’t had that happen with my 4Runners, but generically speaking it’s typically a leaking diaphragm in the brake booster itself which requires brake booster replacement.
as others have said....check valve. remove ...clean with brake cleaner or what ever. ...shake it...blow it out or let it dry , shoot full of wd40 or in my case silicone lube. I would try that b4 replacing a entire booster. in my years of multiple 4runners , that has been my fix for what you describe.....but I could be wrong for your particular rig. but that would be a quick cheap diagnosis
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19963.4lsr5
New member
Yes, however, that didn’t fix mine I needed a replacement.
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19963.4lsr5
New member
I had a spare.
I don’t like AUtoZone “duracrap” brand.
I wouldn’t hesitate putting in one from napa or a Borg Warner part from advanced auto.
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yes , but remove it first from booster. clean, dry, lubricate. New are not terrible in price, although I said I have cleaned them in the past, this winter i got a new one.
