Hard Brake Pedal ~ Chevrolet Tahoe And GMC Yukon ~ 14-18

All right so i’m working on this 2015 tahoe and on the test drive i damn near crashed to the person in front of me because the brake pedal got stiff it got hard as a rock i could hardly yeah sorry that sounded a little weird uh yeah it got really stiff um and it didn’t want to stop i had to stand on the brake photo force to stop and i did i looked through it

Real quick and i figured out what the problem was it didn’t take long at all um but obviously if you’re watching this you’re probably not a mechanic and you might not know what to look for so let me show you what the problem is on this thing and apparently it’s a pretty common problem let’s turn off the ac so you can hear me so um okay so typically the way

This works is you’ve got your brake booster it contains the vacuum it holds the vacuum the engine creates the vacuum this vacuum is what assists the brake pedal and going down just imagine it helping you suck the pedal down to the floor okay and usually gm has the vacuum just coming off of the engine because it creates an infinite amount of vacuum but for some

Reason they decided to go with a mechanical belt driven vacuum pump on this um now i have seen electric pumps electric vacuum pumps are really common on cars that have like the auto off and on feature i guess the electric electronic pump helps it uh maintain the vacuum while the car isn’t running but that’s kind of beside the point because this this does not

Have that this um i guess that’s why they went mechanical driven so i’m kind of rambling now but um so that that’s the problem with this it’s the mechanical the belt driven pump is not creating vacuum anymore and to test that it’s it’s very similar in in how i test ac compressors because you know obviously that too is also different by the belt so when a

Compressor isn’t working you know it’s not cooling as well as it should be you can feel it in the vents it’s not it’s not cold but then when you give it some revs if you i’m just talking like a thousand 1500 rpms when you rev it up a little bit you can feel it start to cool because you’re you’re over spinning the compressor and you’re kind of compensating for

The internal fault that it develops it’s uh it’s also a pump just like the the vacuum pump it’s not it’s it’s leaking internally it’s not pumping the way it was designed to do same thing with the with the vacuum pump it’s you push the pedal two times and it’s hard the second time the pedal is hard as a rock that is not normal it’s supposed to hold a vacuum and

The system’s supposed to be creating vacuum sufficient enough to give you the vacuum assist in the brake pedal but so to show you how you can figure out that it is the pump just pump it two times the pedal gets stiff give it some revs and then you can feel the pedal sink to the floor about two thousand rpms the pedal sinks to the floor that’s because i’m over

The mechanical vacuum pump and it’s helping it create the vacuum needed to bring the pedal down i get one pump two pump three hard as a rock rev it and the pedal sinks to the floor so apparently this is a really common problem in these i think it’s 14 and up uh tahoes yukons that means it’s gonna be the same in your probably silverados and sierras whatever has

A mechanical pump it’s probably going to have this problem so yeah that’s real quick how you can diagnose to see if if your mechanical vacuum pump is going out without using any fancy like scan tools or anything like that because you can look at live data and see the psi that your system has or the the the vacuum that’s creating from because there’s a sensor

On the brake booster that reads the vacuum in the system but if you do have a scanner hook it up check the vacuum look what it’s doing when you pump it two three times uh if you’re a mechanic you might have access to one of those but if you’re just you know a diy guy just do what i do what i said pump the pedal two times get it stiff rev it see if the pedal

Sinks to the floor that’s a very good indication that your vacuum pump is bad anyways i hope you like this video anyways i hope this video was helpful in the next video i’m going to be replacing this pump um yeah don’t forget to like subscribe see you next video later

Transcribed from video
Hard Brake Pedal ~ Chevrolet Tahoe And GMC Yukon ~ 14-18 By GreaseMonkeyRepairs