2000 Silverado Low Resistance Brake Pedal


mriggs90
09-03-2011, 05:46 PM
Hey,
Just recently the brakes on my silverado go almost to the floor before I encounter any resistance. When I first saw this we could hear whooshing as I pressed on the pedal so I figured it was a vacuum leak. Forgive me for not knowing the terminology, but there's a rubber gromet and a check valve I think going into some black case near the master cylinder (I think a vacuum booster), which sounded like where the whooshing was coming from. I popped the hose off and checked the valve which was still good, and replaced the rubber gromet which had worn. This about got rid of the whooshing sound, but the pedal still feels the same. When I got back home after it had been sitting a while I noticed that the fluid reservior was low by about 1/2 - 3/4" below min line (I don't think it was before, but I may not have noticed). I filled it up and now the pedal still feels the same and now it sounds like I'm squirting fluid when I push the brakes, but I can't figure out where the fluid leaked out. I will try to bleed the brakes just in case that was the only problem, but I think there's something else going on here. The guy at Advance said if the gromet and valve didn't fix it it could be an internal leak. I read somewhere about this and tried taking out the abs fuse, which I thought bypassed the internal parts (I haven't researched enough to fully understand this), but this again changed nothing. I'm worried this is a bad master cylinder, but am hoping to get some good suggestions.
Thanks guys.

P.S. Also, previously I had been having problems intermittently where when I would step on the brakes and it would kind of groan and it felt as if I didn't have power brakes. I took it to a shop, and they disconnected that same hose and plugged it back in the vacuum booster and checked other things but couldn't find anything. After this though I don't remember it happening hardly even again if it ever did it again.

2000 Chevrolet Silverado 4.8L 4x4 (4 wheel disk brake)
~ 172,000 mi
no recent brake work done
never had abs light on

MT-2500
09-04-2011, 04:03 AM
Hey,
Just recently the brakes on my silverado go almost to the floor before I encounter any resistance. When I first saw this we could hear whooshing as I pressed on the pedal so I figured it was a vacuum leak. Forgive me for not knowing the terminology, but there's a rubber gromet and a check valve I think going into some black case near the master cylinder (I think a vacuum booster), which sounded like where the whooshing was coming from. I popped the hose off and checked the valve which was still good, and replaced the rubber gromet which had worn. This about got rid of the whooshing sound, but the pedal still feels the same. When I got back home after it had been sitting a while I noticed that the fluid reservior was low by about 1/2 - 3/4" below min line (I don't think it was before, but I may not have noticed). I filled it up and now the pedal still feels the same and now it sounds like I'm squirting fluid when I push the brakes, but I can't figure out where the fluid leaked out. I will try to bleed the brakes just in case that was the only problem, but I think there's something else going on here. The guy at Advance said if the gromet and valve didn't fix it it could be an internal leak. I read somewhere about this and tried taking out the abs fuse, which I thought bypassed the internal parts (I haven't researched enough to fully understand this), but this again changed nothing. I'm worried this is a bad master cylinder, but am hoping to get some good suggestions.
Thanks guys.

P.S. Also, previously I had been having problems intermittently where when I would step on the brakes and it would kind of groan and it felt as if I didn't have power brakes. I took it to a shop, and they disconnected that same hose and plugged it back in the vacuum booster and checked other things but couldn't find anything. After this though I don't remember it happening hardly even again if it ever did it again.

2000 Chevrolet Silverado 4.8L 4x4 (4 wheel disk brake)
~ 172,000 mi
no recent brake work done
never had abs light on

Whooshing \Swooshing noise from brake boster is usually bad vacumn booster.

With engine off pump up brake pedal 3-4 times and then release and hit the brakes and tell us how much brake pedal you have.
Also check for prdal seaping down engine off or engine running sitting at stop sign.


Watch the brake flud level for going down.
Check all brake lines and calipers/abs unit for leaks and or leaking out rear of master cylinder.
If fluid going down you have a leak some place.

Let us know what you find and about the pedal height engine off.

j cAT
09-04-2011, 09:02 AM
since you have the same vehicle that I have owned since april 2000 your problem is most likely a brake line leak.. the leak is most likely the one going to the rear calipers where it rusts out between the fuel tank and frame rail. not very easy to see .

brake pedal issues are soft pedal to floor or a hard pedal.


soft pedal/pedal to floor is a fluid leak, master cylinder, or the ABS valves are leaking..

the hard pedal is the vacuum booster has a leak/ or the hose /gromet is leaking...you may notice a slight drop in RPM when the pedal is depressed.

In the rust belt regions many have had these brake lines fail 2X in the 10 years of life. very poor quality on this metal part to resist corrosion..

mriggs90
09-04-2011, 10:00 AM
Hey again,
No matter how many times I pump the pedal no more pressure builds up, engine on or off. After I filled up the reservoir I haven't noticed the fluid going down yet, but I haven't really driven it much of anywhere, just pumped the pedal engine on and off and moved the truck in the yard. I checked the calipers yesterday and I couldn't see a leak there, I did however find that the bleeder screw and the caliper have galvonic corrosion, so in order for me to try to bleed the brakes I'm gonna need another caliper (nothin's ever easy is it?). I looked online, and a company called Cardone makes remanufactured calipers...are these any count, or does anyone have any experience with them?
http://www.summitracing.com/parts/AAZ-18B4729/

I'll try to check for a leak near the fuel rail by next weekend and report back. Oh, and also I had noticed a small rpm drop when the brakes were pushed in.
Thanks for the continued help!

j cAT
09-04-2011, 02:20 PM
Hey again,
No matter how many times I pump the pedal no more pressure builds up, engine on or off. After I filled up the reservoir I haven't noticed the fluid going down yet, but I haven't really driven it much of anywhere, just pumped the pedal engine on and off and moved the truck in the yard. I checked the calipers yesterday and I couldn't see a leak there, I did however find that the bleeder screw and the caliper have galvonic corrosion, so in order for me to try to bleed the brakes I'm gonna need another caliper (nothin's ever easy is it?). I looked online, and a company called Cardone makes remanufactured calipers...are these any count, or does anyone have any experience with them?
http://www.summitracing.com/parts/AAZ-18B4729/

I'll try to check for a leak near the fuel rail by next weekend and report back. Oh, and also I had noticed a small rpm drop when the brakes were pushed in.
Thanks for the continued help!

If the pedal now goes to the floor and you can not get a high hard pedal with no leaks the master cylinder should be replaced...

this would be the next step if you are very sure you have no leaks..

the last step which hopefully will not be necessary would be to replace the ABS pump assy...this is a very expensive part...look to get this at the scrap yard..make sure it is the exact same part as you have...

sometimes this is the very expensive cause of the pedal to floor..


on bleed screws use a small propane torch to heat up the fitting then use a 6 point box wrench to loosen..then with the bleeder open push back the piston to see how bad the fluid looks..

always open the bleed screw before pushing back the cal pistons...this is how the abs pump valves get damaged.............

mriggs90
09-09-2011, 07:03 PM
I finally found at least part of the problem. j cAT you are good...it was a leak right where you said. I had to let it sit between then and now but when I came back this weekend I guess it had gotten worse because I could finally see the fluid shooting up and hitting the bottom of the bed. My next question is...I dropped the tank so I could get to the rear side easily to disconnect, but the front runs into that junction box and I can't get a wrench in that spot to loosen the line. Is there a special tool that I need, or am I going to have to take off all those lines to get to the one I need? Also, considering the shape that one was in, would you recommend replacing some of the other lines under there while I'm into it, or just wait until there's a problem. The other ones have some surface rust, but not nearly as bad as that one.
Thanks.

MT-2500
09-09-2011, 08:13 PM
I finally found at least part of the problem. j cAT you are good...it was a leak right where you said. I had to let it sit between then and now but when I came back this weekend I guess it had gotten worse because I could finally see the fluid shooting up and hitting the bottom of the bed. My next question is...I dropped the tank so I could get to the rear side easily to disconnect, but the front runs into that junction box and I can't get a wrench in that spot to loosen the line. Is there a special tool that I need, or am I going to have to take off all those lines to get to the one I need? Also, considering the shape that one was in, would you recommend replacing some of the other lines under there while I'm into it, or just wait until there's a problem. The other ones have some surface rust, but not nearly as bad as that one.
Thanks.

A crows foot will help get to some.
And sometimes you have to take one off to get to other.
But there is usually more than one line bad.
Check all other lines and check on lines from ABS unit to master cyliner and front wheels.
Do not mix or cross up lines on abs or master cylinder.

Unless you order brake lines from GM .
You may have to make up lines as some have different fittings on each end.
Also You will be getting into metric bubble ends
Good Luck

j cAT
09-10-2011, 09:21 AM
I would cut the brake line between the ABS pump unit and the fuel filter area . then double flare the brake line and using a inline fitting to join the old to the new which will go to the rear. to remove the lines at the abs UNIT can cause other issues..


the other area you should inspect is the frame rail behind the driverside front tire..

this area has a inner fender that is too short. as a result the brake lines get damaged.. check these lines ..I have used a product called rustfre which is applied by brush to coat the lines and stop future rust ..so far no more rust after using this product..

the inner fenders on my vehicle have been modified. I used roofing rubber to extend down the innner fender to protect the lines/underbody... I did this also in the rear ..

I posted this here on this silverado forum ...posted pictures as well ..

the problem you have with this brake line leak is well known. the fluid evaporates when the leak is small but causes a dropping soft pedal.. this is a GM defect and this being a dangerous widespread 100% failure rate issue in the rust belt, just shows how GM just don't care about safety.

THESE BRAKE LINES ARE CHEAP DEFECTIVE CRAP !

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