Three problems related to brake master cylinder have been reported for the 2004 GMC Sierra 2500. The most recently reported issues are listed below. Please also check out the statistics and reliability analysis of the 2004 GMC Sierra 2500 based on all problems reported for the 2004 Sierra 2500.
On 2/1/2015, at approximately 11:30 am, I was stopping at my brothers mailbox to get his mail while he was on vacation. When I went to stop at his mailbox, the brake pedal on my truck went to the floor with no resistance on the pedal. I pumped the brakes several times, put the truck in neutral and it came to a gradual stop over an extended braking distance of 20 to 30 feet (which is slightly uphill). There were no lights lit on the dash and the master cylinder was between the maximum and minimum levels on the reservoir, when I examined it after the occurrence. We live on a dirt road without much traffic, so I placed the truck in low range 4wd and drove it the 1/2 mile home. Upon returning home the top brake line which runs along the frame from the anti lock brake block back towards the drivers side rear of the truck had ruptured. The brake fluid in the master never went below the minimum level, so I attempted to refill it to see if I could get any brake pedal pressure back. The pedal went to the floor still after multiple tries with a full master cylinder. The brake line had ruptured where it is attached at a green plastic factory hanger. The brake line was corroded/rusted where it had failed. If I would not have stopped at my brothers mailbox, it is 1 mile down hill on an approximate 12 degree grade to the main road. The intersection at the bottom of the road is a 90 degree, t intersection in a creek bottom, where I am supposed to stop prior to entering the main road. We had just came home on 1/31/2015 from a 8. 0 hour round trip to see my son at college through the mountains of maryland and west virginia on I-68 and had driven various major busy highways including I-79, I-68 and I-81. Due to the amount of fuel which we would have used, we decided to take my other son's wrangler on the trip or I may have been sending this email from the hospital if we were lucky.
Brake pedal went to the floor. Almost impossible to drive like that. Takes over 100x longer to stop a 3/4 ton truck. I found that the brake lines rusted out. I also found several hundred reports of the same things on gm truck online. I also heard you were investigating this issue already. I wanted to make sure I am counted as one of the effected people. I also read where gm does not consider this a safty issue. I disagree. The line from the master cylinder to the abs unit blew so I had zero brake presure and pedel. I think this should be recalled as it is a huge safty issue. I have already spent over $1000 and a week trying to fix this and replace all the rusted line. I still do not have the truck back on the road. Thanks.
Experienced a complete loss of service brakes. Fortunately this occured after completing a trip while towing a trailer. Had this happened during the trip serious injuries and multiple deaths could have been the result. Investigation of the problem indicated premture rusting through of the steel brake line to the right front disc brake. The brake line to the left front caliper is also badly rusted. The brake lines from the master cylinder are mildly rusted as well.