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I still have the same problem with my 94 jimmy. The brake

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pedal is still hard with...
I still have the same problem with my 94 jimmy. The brake pedal is still hard with little brakes. I bled them as you suggested, replaced brake booster, changed out ABS unit, changed master cylinder and changed the perportioner value, bled brakes several
times with penalty of fluid to each wheel, brake pedal gets hard before stopping.
Submitted: 2 years ago.Category: GMC
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Answered in 1 hour by:
12/7/2015
GMC Mechanic: Pete, GMC Mechanic replied 2 years ago
Pete
Pete, GMC Mechanic
Category: GMC
Satisfied Customers: 29,911
Experience: GM training and dealer tech for 14+ years. Diagnostics
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Hi my name is ***** ***** I will be happy to assist with this today.In some cases I may need more info to assist better.I apologize for any delay.

Check and make sure you have plenty of vacuum to the brake booster and that the brake booster check valve is working o.k. (this is the valve that usually plugs into the brake booster that the vacuum hose is connected to.If any of these have an issue at all the fault for the loss of vacuum will need corrected or the check valve replaced.In some cases intakes leaking engine vaccum cause this as well as intakes clogged with carbon.If this was all already checked and found o.k. let me know.

If more help is needed, use the reply tab to continue our conversation. If no further assistance is needed, kindly rate my service.You can rate at any time and we can continue to work on your question as this will not close out your question.Keep in mind in some cases it can be difficult to fully diagnose or help repair your vehicle without seeing it and I work on delivering the best possible answer from what I see to work with.

Thanks Pete

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Customer reply replied 2 years ago
All of the above checked ok
GMC Mechanic: Pete, GMC Mechanic replied 2 years ago

Did you test the vacuum to see how much vacuum is being pulled at the brake booster and if so how much was being pulled?

Was the brake pedal rod checked for damage at all?

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Customer reply replied 2 years ago
Pete,I checked the vacum, ,It has 18 lbs,rod checked ok what now?
GMC Mechanic: Pete, GMC Mechanic replied 2 years ago

Do you hear any grinding or groaning noises at all from the brakes when applying the brakes?

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Customer reply replied 2 years ago
No noise,the brakes worked great until i replaced a broken brake line and got air in the system,the mec. who bleed the brakes said the booster was bad and relaced it, then we replaced ABS,another brake booser,master cyl. and perportion valve.
GMC Mechanic: Pete, GMC Mechanic replied 2 years ago

Do you know if brake fluid is making through the new brake line that was installed?

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Customer reply replied 2 years ago
All 4 wheels are getting great fluid pressure when being bled
GMC Mechanic: Pete, GMC Mechanic replied 2 years ago

O.k.,this is a difficult one for me myself to be able to answer from here.

I will open your question up for others here to see if someone else can assist further on this as there may be others here that may have more info on what to check or do with this issue.I hope you can get this resolved with ease.No need to reply to my last post here unless it is a last resort as it will keep your question locked to me and others will not be able to view it.If you feel you want to continue to work with me on this feel free to reply at any time but keep in mind in some cases it can be difficult to fully diagnose or help repair this without seeing your vehicle.

Thanks Pete

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GMC Mechanic: Toolhut, ASE Certified Technician replied 1 year ago
Toolhut
Toolhut, ASE Certified Technician
Category: GMC
Satisfied Customers: 551
Experience: Owner of a mobile diagnostics company assisting auto technicians with difficult vehicles
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Hi, My Name is ***** ***** for posting your question to just answer. I am a ASE Certified Master Auto Technician with 20 years experience. I am confident we can resolve your problem together.Please remember I don't know your skill level. I can't see, smell, hear, or touch the vehicle. It may take a few back and forth replies to get to a satisfactory resolution.I also try to give all of the information you may need expecting a positive rating.

With the vacuum gauge installed how quickly does the vacuum return after a snap throttle? How steady is the needle.

Have you replaced the check valve at the booster?

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Customer reply replied 1 year ago
That checked out ok
GMC Mechanic: Toolhut, ASE Certified Technician replied 1 year ago

So just some clarification. If you hold the brake pedal when you start it does the pedal fall at all?

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Customer reply replied 1 year ago
the pedal goes down,next
GMC Mechanic: Toolhut, ASE Certified Technician replied 1 year ago

If the pedal goes down then it is getting vacuum and must be a booster problem.

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Customer reply replied 1 year ago
We puut a second booster on and is still the same.
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Toolhut
Toolhut
Toolhut, ASE Certified Technician
Category: GMC
Satisfied Customers: 551
551 Satisfied Customers
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