Brake problem on '05 Tahoe

[05TahoePPV]

Okay, how's this for a strange one. A friend and I are trying to start a business, a police driving school,and purchased an '05 Tahoe PPV out of Chicago. He flew up, drove around Chicago for a day or so and then drove it back to TX, no problems. After driving it around the area (Ft Worth) he noticed that it would slow down while driving on the freeway without reason. In fact, enough that he had to give it more throttle to keep up with traffic. Then it would go back to normal. Upon taking it to our driving area for some testing it first did well, making several runs doing some very aggressive driving. But after a few more runs the brakes started binding up. It would move but in drive with your foot off the brake it wouldn't move and you had to give it fuel to get it to move. Having worked on cars most of my adult life and being very familiar with the basics I thought it was just the rear brakes.

We let it cool down and the brakes completely freed up. But after just a little more aggressive driving, not nearly as much as earlier, it started binding up again. This time we raised the rear off the ground and could barely turn the rear wheels by hand. Then just to make sure, did the same to the front and they were also binding up. This told us that it must be something to do with the ABS since it's all four brakes. We let it cool again and removed the circuit breaker/fuse for the ABS, not knowing if it was an electronic or mechanical issue. It still had the same problem, basically eliminating electronic ABS involvement.

Now it gets really strange. It sat for about two months, undriven, and when we tried to drive it again the problem got really bad with just some very slow easy driving. So bad that the front brakes locked completely up! It had to be forced against the front tires skidding to be moved!!

Unfortunately the Tahoe is not close to either one of us so we can't run out and check things very easily but if anyone has ANY idea what might cause this please chime in. I know this is long but you can't help if you don't know details. Thanks for reading!!!

 

[erickshoe]

Sounds to me exactly like a contaminated brake fluid scenario, (contaminated meaning any fluid other than DOT 3 or 4 brake fluid). The most common culprit of contaminated brake fluid is power steering fluid being added to the brake master cylinder reservoir. Unfortunatley just a little bit of p/s fluid is enough to contaminate a whole system. Remove the master cylinder reservoir cap and inspect the cap seal, if it is swollen then you have a contamination issue. First recommended step is to replace the brake master cylinder and thoroughly flush the whole system and bleed out all the air. If that doesn't fix it then it will likely need ALL the rubber components of the hydraulic braking system replaced, ie. master cylinder, all brake hoses or flexible brake lines, brake pressure modulator valve (BPMV), and brake calipers or rebuild the calipers with new rubber pieces after thoroughly cleaning them with DOT 3 fluid. If the vehicle has been forced to drive when the brakes are applied it may have toasted the brake pads and possibly ruined the brake rotors due to the heat created. What happens with contaminated fluid is when the rubber in the sysem encounters any fluid other than DOT 3 or 4 fluid it swells up a (like the reservoir cap/diaphragm). This causes fluid to be able to be pushed past the swollen rubber when you press the brake pedal but it can't naturally return when the pedal is released because the rubber is swollen and keeps the pathway blocked. To compound this issue, as you keep driving with the brakes essentially applied, the fluid is heated and rubber components that hold the fluid swell even more due to the heat caused by the friction created by the brake pads thus exponentially compounding the problem. Basically what has been created is a one-way valve only letting fluid go TO the calipers and not letting it return until you park the vehicle and let everything cool thoroughly. Hopefully your contamination issue isn't the worst case scenario requiring replacement of EVERYTHING listed. Hope this helps.

 

[erickshoe]

Just re-read your post and since it sat for a long time (having plenty of time for the contaminated fluid to spread throughout he system), it sounds like your vehicle will need pretty much all of the rubber compnents replaced like I mentioned.