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Robert R
Robert R, ASE Certified Technician
Category: Jeep
Satisfied Customers: 4531
Experience:  ASE Master Certified, Jeep Certified
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I have a 2003 jeep Cherokee with 31 in tires that is

Customer Question

I have a 2003 jeep Cherokee with 31 in tires that is noticeably hard to stop. The fluid level is full and see no leaks. When driving I noticed that when I slam on the brakes it is hard to stop and doesn't screech to a halt.. All the brakes are in good operable order and newer.
Does this sound like a master cylinder.
I am pushing pretty hard on the pedal, harder than I should to stop.
Submitted: 9 months ago.
Category: Jeep
Expert:  Robert R replied 9 months ago.

Hello, welcome and thanks for asking your question. My name is*****'m a Certified Auto Technician with 29+ years experience. I will do my best to assist you. please keep in mind that I may need to ask questions of you before I can answer. When you reply please feel free to add as much detailed information as possible pertaining to your concern.

Not likely to be a master cylinder. It is more likely that the brake booster is leaking and not providing enough boost. Do you hear any hissing sounds when you push down on the brake pedal coming from that area??

Customer: replied 9 months ago.
No
Expert:  Robert R replied 9 months ago.

How long have you had the 31" tires? Was this condition happening before installing these tires?

Customer: replied 9 months ago.
it was and I just changed back to the stock rims
Expert:  Robert R replied 9 months ago.

Are the 31's on the stock rims or do you have a second set of wheels and tires?

Is the problem still present with the stock rims>??

Have you verified that the vacuum hose is properly connected to the vacuum brake booster?

Customer: replied 9 months ago.
it is still there
Expert:  Robert R replied 9 months ago.

From what I have to go on I am suspecting a bad vacuum brake booster causing the problem.

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

Expert:  Robert R replied 9 months ago.

At this time, I recommend getting a test vacuum gauge and use it to check to be sure full engine vacuum at idle is reaching the brake booster. You would hook it to the vacuum hose at the brake booster and start the engine, vacuum should be at least 14" at idle. If that passes, next check would be to test the vacuum check valve at the booster to be sure it can hold vacuum in one direction and allow flow in the other direction. If that is ok, then you would need a vacuum pump to test the brake booster for leaks, you would remove the vacuum check valve from the brake booster and hook an appropriate hose adapter to the brake booster port, hook up a vacuum pump and apply 15" of vacuum to the booster, let it set a couple minutes with vacuum applied to check for any leaks. If it loses vacuum or you are unable to reach at least 10" of vacuum then the booster is bad and needs to be replaced....

Keep me posted and let me know if you have any additional questions...

Thank you,

Robert

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Expert:  Robert R replied 9 months ago.

Hello,

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