How a Brake Booster works and diagnosing with a pedal check (Season 7/E8)

[@stevenpellegrino997]

Very cool I never knew Rock Auto had video 👍👍🔥🔥🔥🔥🤩🤩

[@Scrapla1]

I have a 07 Tacoma and randomly my brakes will lock up while driving and the only fix I found is to unplug the vacuum off the booster for a few seconds and this usually lasts a while. My factory booster did this and now my rebuilt used Toyota OEM one started doing it after about three years after being installed.

[@jrconn0609]

Thanks for the excellent explanation! This was a lot of fun :)

[@RogueArcher24]

feel like im back in school! this is dope. subd. and that pedal test just came in handy!

[@creatingher]

Thank you so much. This helped a low as my vehicle is currently doing this

[@harrytuttle4069]

I thought the pedal was supposed to stay firm, almost replaced the booster for no reason... Thanks!!

[@manginips92]

What did you fix in the end? Booster was replaced?

[@Borrgar-ki1pu]

Mine chatters when I do this almost like abs. Should it do that? I feel like my brakes work good expept I feel like the loss of boost at idle is more then it should be.

[@isidrosevier1125]

What if the pedal drops more than what you showed and becomes soft?

[@shawgeasland2096]

Yes . Answer this one. I also have this question. My pedal is hard with the motor off, then goes to the floor when I turn on the engine. Super long pedal travel before brake engagement. Vehicle has all new lines, pads, roters, calipers, and master cylinder. And has been bled multiple times. Ideas?

[@BENFrankaka-sandstorm]

I do the petal check. After I do that it works for 5 or 10min. But then it gets hard again. And stoppes working. The only way to get it working again it to do the petal check again. Any idea why this would be??

[@dilojansenanayake7795]

The bolt on the (1997 Accord) Brake Power Booster broke while I was tightning the nut during a brake master cylinder replacement. Do I need to replace the entire Brake Power Booster or can I just replace the bolt on the Brake Power Booster ?

[@hawaiian7760]

what if i installed. new hydro boost on my 01 dodge cummins 2500 and all for wheels start locking up after driving it for 10 minutes, people say it’s the way the built the new boosters but what do you say?

[@jasonhazelton8875]

Can you mount a vacuum booster upside-down?

[@appliancedude63]

I absolutely love Rock Auto. How do I contact them though?

[@HazyTown01]

"That's the neat thing: You don't."

[@azimmey]

I wonder if my motorhome has hydroboost because the pedal does not travel more than an inch or two but it will throw you through the front windshield. It’s not like regular car breaks or you have to push on the pedal when you have some travel

[@auntigingy8666]

Master cylinder could be bad or the booster might be going but typically the system isn’t getting air.

[@juliansorokin5632]

I did this and my brake did drop down 2 inch about but when I plug in my obd reader it still says brake booster lost communication general failure.. does anyone know what to do ?

[@WaabiiSaabii]

Does anyone know how to test if a booster isn't releasing pressure?

[@sumdude4]

What if it goes all the way down to the floor and the pedal doesn't come back up? When the engine is also running.

[@JaytheIceMan]

I know this is probably a year too late but that’s usually an indication that there’s a bad leak or the brake master cylinder went out.

[@shawgeasland2096]

​​@@JaytheIceManI changed my lines, pads, rotors, calipers, and master. Same result. Super long brake pedal travel, to the floor. And only engages in the last half inch. Engages heavy, there is no gradual slowing down. No discernable leaks, bled and rebled and then my husband gave it a go. What the heck am I missing?

[@gordonl8319]

once in while, after pressing on the brake, the car goes forward 15 feet before it stops. the RPM goes up and down to normal. it is unpredictable. All articles say it is caused by a leak in diaphragm, air is being suck into the engine, fuel and air mixture is lean, so the engine compensate that with more fuel injected, RPM goes up. follow all the instruction to test the booster with applying the brake different ways, no sign of leak in the vacuum hose. What is the reason that it happens once in while, unpredictable ? it is really the leak of diaphragm ?

[@davidandrade2201]

If you have access to a scan tool and can watch fuel trim data, you can see your fuel trims go lean when depressing the brake pedal if your diaphragm is leaking. I have encountered this on a 2013 Malibu before and was causing engine performance issues and braking performance issues.

[@geberealx3449]

thank you,. so good explanthion

[@AhmadEl-Assuli]

Thank you

[@cruzdeleon1888]

What would cause engine to surge up and down as i am slowing down, for example as i slow down from 50mph, it shutters at around 30mph, then at 20mph, and one last time just before completely stopping at about 10mph...does it sound like a transmission issue?...or more like an engine idle issue like throttle body or similar engine issue?...OR brake booster problem..thank you

[@alexanderquilty5705]

That sounds like a really bad engine idle problem. Perhaps the problem is less prevalent when you are driving at higher speeds/RPMs but when you slow down then you start to experience the shuttering you were talking about because you are letting less fuel in. Could be a bad air/fuel mixture ratio too I guess but I don’t think it’d cause shuttering. The best way to check all that is with a good scan tool. Be sure to check the PIDs related with your fuel trim. That will tell you what your fuel to air ratio looks like. Disclaimer: I am no mechanic, this only a suggestion and as always, I recommend you to see a professional.

[@link4eva10]

My pedal gets hard the second i turn off the car. Gets soft when i turn it on again. Can hear a non stop hissing when i push the brakes.

[@link4eva10]

Can hear the engine idle fluctuate with each press, hold, and release

[@sloshedmrbones]

I have an issue where I have a new booster, new master cylinder, new wheel cylinders and when the truck is running the pedal goes to the floor and sticks at the floor until the truck is turned off. The brakes have been bled and there is new fluid going to all 4 corners. It only sticks when the truck is on, otherwise the pedal returns normal. Any thoughts?

[@borndifferentnf1]

Did u figure your issue out?

[@sloshedmrbones]

@@borndifferentnf1 no I have not. I had it towed to a shop that had it for a week and they couldn't figure it out either. The guy at the shop said in his 35 + years as a mechanic he has never seen anything like this. I have tried a different booster, different master but they still act the exact same way and everything is functional as far as wheel cylinders, lines are clear, brake fluid is still clean, boost is not leaking, calipers are getting fluid to them as well. It has baffled a lot of people with everyone scratching their head still.

[@borndifferentnf1]

@@sloshedmrbones yup me to two new master cylinder two new brake booster new brake calipers news lines bleed abs all wheels same thing people think I'm nuts

[@link4eva10]

Did you bleed that Master Cylinder before you installed it?

[@sloshedmrbones]

@link4eva10 Yes, I have bled the master cylinder

[@Dnasty1]

My car passes the pedal test but does a number of other things to make me think the booster is bad. When it’s in park and I pump the brakes a hear a lot of air noise. It does build up to make them stiff after a lot of pumping. But as soon as I release its soft again. Also the car actually revs or surges forward when I’m braking to a stop. And overall has a choppy idle. The brakes do get very stiff at random times as well usually when I need them the most (this I’m not sure if it is a brake assist function thought )

[@jasonmoonshiner]

Did you ever figure out what was wrong? I have a 2000 v6 toyota camry and have similar symptoms as you. Though my car doesn't pass the pedal test

[@Dnasty1]

@@jasonmoonshinerwell mine ended up not being the brake booster but the mag… but if you have these symptoms it’s probably the booster or the seal.

[@reggieking7839]

Ok

[@juanfo7307]

What if the pedal doesn't get hard?

[@MrMrsregor]

sounds like a failed brake booster. could be no vacuum or probably leak inside the brake booster

[@juanfo7307]

@@MrMrsregor thank you bro

[@MrMrsregor]

@@juanfo7307 so sorry, that is incorrect. I must have responded to the wrong person (I’m no mechanic, just work on vehicles on the side) If your pedal is always soft and never gets hard (gigity) it’s probably a bad master cylinder or a brake fluid leak

[@juanfo7307]

@@MrMrsregor I replaced the master with a good unit giggity and the pedal is still soft but it's an old ass truck so there is also that

[@MrMrsregor]

@@juanfo7307 might just still have some air in the system and you need to bleed it more. Sometimes it takes a lot of bleeding, especially if you replaced the master cylinder. But make sure to check for any fluid leaks. Even a small fluid leak will make the pedal softer than it should be