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New brake pads, pedal goes to the floor


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I decided to put new pads on the front and after I was done the brake pedal goes to the floor. I pumped the pedal for probably 30-40 times and nothing has changed. Took it for a short test drive and the brakes barely stop the truck. I removed the pads after my test drive and I could tell the pads had barely hit the rotor. The reservoir is and was full of fluid. I did not let any air enter the system unless I have an unnoticed leak, no hoses were removed and I haven't touched the bleeders. Two things I noticed while doing the brake job: 1. After I used a c-clamp to push the pistons back in on the right side, one of the rubber seals on the piston was puffed out very slightly and I was able to smooth it over with my finger to get it to lay flat where it belonged. 2. I removed the cap to the brake fluid reservoir and noticed that the previous owner had placed the wrong rubber seal inside the cap. It was too large and slightly torn, brake fluid was between the cap and rubber seal. Did not appear that any moisture had entered the reservoir. Before this all happened the brakes worked beautifully. Any suggestions would be appreciated.

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You can't tell by looking if there is water in the brake fluid.  It will draw moisture from the air.

 

When you wrote "The reservoir is and was full of fluid.", that would mean you drained some fluid out of the master cylinder when you did this, as it would be over-full afterwards, if it was full prior to changing your pads.

 

It's possible when you used the c-clamps to push the pistons back that you wedged the pistons in their bores.  But that would still give you a hard pedal if everything else was working properly.

 

I would suggest flushing your brake system (as in suck out most of the fluid in the master cylinder, fill with new fluid, then bleed/refilled MC all 4 corners).

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Personally, whenever I change my brakes (front and/or rear) I always flush and bleed the brake fluid. I also use the synthetic DOT4 brake fluid because it has a higher boiling point. I live in Georgia and we have a lot of humidity here. Brake fluid is Hygroscopic, which means that every time it comes in contact with air it readily absorbs and retains moisture. That in turn leads to corrosion (rust) and crud in the brake hydraulic system. In our climate it is recommended to flush the system every two years. I also clean and properly lubricate everything with synthetic high temp brake grease. Everything that needs replacing or has a tendency to wear out gets changed. There is no worse feeling than driving along and pushing down on the brake pedal only to find out that you do not have any brakes when you need them the most.

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13 hours ago, davester said:

You can't tell by looking if there is water in the brake fluid.  It will draw moisture from the air.

 

When you wrote "The reservoir is and was full of fluid.", that would mean you drained some fluid out of the master cylinder when you did this, as it would be over-full afterwards, if it was full prior to changing your pads.

 

It's possible when you used the c-clamps to push the pistons back that you wedged the pistons in their bores.  But that would still give you a hard pedal if everything else was working properly.

 

I would suggest flushing your brake system (as in suck out most of the fluid in the master cylinder, fill with new fluid, then bleed/refilled MC all 4 corners).

Full is a relative term, full when I started was at the full line, when I finished it was still full only I guess I should have said over the full mark and up to the neck. I did not drain any fluid and fluid did not leak out over the top as the pads were not fully worn out, probably less than half. I recently bought the vehicle and I always go through the systems and replace items so I know when and what was replaced.

I had a friend who is a mechanic stop by and he didn't have a lot of time and is going to stop back tomorrow, he seems to think it is the master cylinder.

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5 hours ago, Grubbworm said:

Personally, whenever I change my brakes (front and/or rear) I always flush and bleed the brake fluid. I also use the synthetic DOT4 brake fluid because it has a higher boiling point. I live in Georgia and we have a lot of humidity here. Brake fluid is Hygroscopic, which means that every time it comes in contact with air it readily absorbs and retains moisture. That in turn leads to corrosion (rust) and crud in the brake hydraulic system. In our climate it is recommended to flush the system every two years. I also clean and properly lubricate everything with synthetic high temp brake grease. Everything that needs replacing or has a tendency to wear out gets changed. There is no worse feeling than driving along and pushing down on the brake pedal only to find out that you do not have any brakes when you need them the most.

Thanks. There seems to be something more than just air in the system as I never opened the system and it was working fine before, if I have air or moisture in the system I need to find what caused it because otherwise I will bleed them and end up with the same problem and have to bleed them again. Something has failed to let the air in to begin with. I live up north and heat is certainly not a problem with me, I have the opposite problem...it is still freezing here. No, I don't know why I stay here.  :-)

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Heres a good question for you. If the pedal goes to the floor so easy, will it even pump fluid to the bleeders, and if the master cylinder is bad will it still pump fluid to the wheels. I was just thinking it may be a good test, if it does not give me fluid through the bleeders then it must be a bad master cylinder?

 

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49 minutes ago, Lee Nettnin said:

Heres a good question for you. If the pedal goes to the floor so easy, will it even pump fluid to the bleeders, and if the master cylinder is bad will it still pump fluid to the wheels. I was just thinking it may be a good test, if it does not give me fluid through the bleeders then it must be a bad master cylinder?

 

I cannot say whether the master cylinder is bad or not. If you did not loosen or remove the Master Cylinder cap when you where C-clamping the pistons back in then you might have caused an issue also. There needs to be somewhere for the pressure to go. And Yes, even if the pedal goes to the floor easily it will pump fluid to the bleeders. That is what happens when you bleed the air out of the brakes.

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Your method to retract the caliper cups is a poor one. Your method forces crap back into the master cylinder. Best open the bleeders as you are compressing the cups. Then bleed the system, putting fresh fluid in

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1 hour ago, txab said:

Your method to retract the caliper cups is a poor one. Your method forces crap back into the master cylinder. Best open the bleeders as you are compressing the cups. Then bleed the system, putting fresh fluid in

What you folks from the south (unless you are on the coast) don't understand is that salt plays havoc on our vehicles. Bleeding the brake system if it is not needed is an exercise that WILL end up with at least 50% problems. simply put out of 4 bleeders, 2 are guaranteed to snap off. I tried just one this morning and big surprise it snapped off. Simple job just turned into a major one. And yes I sprayed the fitting 1 hour before I tried to loosen it. Now I have to hope and pray that I can remove the bolt holding the rubber hose off as it also is very rusty, if that does not come out I will then have to start replacing brake lines. I tried the second front one and it also is offering way too much resistance...more spay and try again tomorrow. So as I indicated if you dont need to bleed the system we have learned to leave it alone.

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5 minutes ago, redwngr said:

Is this the 2007 Tahoe? 

 

Curious what you recommend as the proper brake fluid change interval?

 

I don't recommend that to anyone. Everybody has to do as they think is best. I have replaced plenty of brake lines and always always always the lines rust from the outside and create a hole. If you bleed the brakes you Will run the risk of creating a very large project and live without a vehicle so you have time to chase down part after part after part, fist a caliper, then a rubber brake hose then some brake line, etc. etc. I have never replaced the brake fluid until an event happens that will cause a needed fluid change and have never lost my brakes due to old fluid or rusted internal parts. BTW I am 64 and have driven an average of 15,000 miles a year since I was 16 and rarely buy new vehicles, usually vehicles with 100,000 or more. I have lived in NY all my life and you learn not to mess with rusty bolts unless absolutely necessary. Now you are probably going to tell me that I am running a risk of losing my brakes or rusting out this or that part if I dont follow some schedule of replacing the fluid, Believe me I have learned my lesson on this.

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1 hour ago, Lee Nettnin said:

What you folks from the south (unless you are on the coast) don't understand is that salt plays havoc on our vehicles. Bleeding the brake system if it is not needed is an exercise that WILL end up with at least 50% problems. simply put out of 4 bleeders, 2 are guaranteed to snap off. I tried just one this morning and big surprise it snapped off. Simple job just turned into a major one. And yes I sprayed the fitting 1 hour before I tried to loosen it. Now I have to hope and pray that I can remove the bolt holding the rubber hose off as it also is very rusty, if that does not come out I will then have to start replacing brake lines. I tried the second front one and it also is offering way too much resistance...more spay and try again tomorrow. So as I indicated if you dont need to bleed the system we have learned to leave it alone.

Having lived in "the north" for 15 years, I learned twice a year to crack the bleeders and put a touch of anti-seize on the threads. Never a problem for me. Even in "the south", I crack them once a year.

 

 

:)

Edited by txab
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14 minutes ago, txab said:

Having lived in "the north" for 15 years, I learned twice a year to crack the bleeders and put a touch of anti-seize on the threads. Never a problem for me. Even in "the south", I crack them once a year.

Which will work great if you always buy new vehicles. The latest bleed that snapped on me today...I bought that vehicle 2 weeks ago with 162,000. Must be nice to be able to afford new vehicles but by the time I buy them it is already too late to be messing with the bleed screws unless absolutely necessary.

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