prittyboy

Ok,,, Here we go!!! I spent 2 hours last night reading everything in could find here about the dreaded ABS/ Brake light issues, My symptoms are a little different than others( that i could find) with brake problems, Heres what i have replaced, Hydroboost, speed sensor, calipers, rotors, pads, drums, master cylinder, repaired all vacuum lines, Now for my symtoms, get in the truck in the morning no ABS/Brake light on, after driving about 8 to 10 miles the brakes on the front begin to engage without me even touching the pedal,when this happens the pedal is hard as a rock with no travel whatsoever, and if i keep driving they will eventually bring the truck to a halt, i have to get out and bleed the brakes to get them to disengage, when i get back in the truck the ABS/Brake lights are on, as long as these 2 lights are on the truck will not lock the brakes up and drive normal, when i shut the truck off and start it back up i have no dummy lights on at all and the process starts all over again, this is happening on my 98 12v in my signature, I havent replaced the brake lines because of the symptoms,and they only lock when the dummy lights are off, IM STUMPED!!! Any help with this is greatly appreciated because God is tired of me asking, Why Me!!!

cm979

Well I replaced my Hydro boost. Not to days later when I went to turn the brakes would lock up. Had to put it in 4 low just to turn if it was in 2wd it would just burn out. I know it is a different problem. Point being I spent over 2 grand on parts before I figured out it was one I had already replaced.

torquefan

I have seen several ABS controller failures on these trucks. (1998-2002) Never for the problem you are describing, but I'd say it is the most common ABS related problem on these trucks. It would be nice to plug in a scanner and see what's going on with the data stream when it starts acting up.

prittyboy

Ya know with my luck that controller probably is bad!!! isnt that one of the most expensive parts on the ABS system??? Is there any way to disengage the ABS and still have a speedo and no dummy lights coming on??

Crimedog

Has anyone tried pulling the ABS fuse? Does it still let your speedo work? I'd try that and see if your problem comes back. Pulling the fuse should take all control out of the computer's hands and allow you to narrow down the problem. From what it sounds it should be electrical...

j-fox

Are you sure the push rod for the brake pedal to booster is not too long? I think they are adjustable-- it has been a while since I had one off. If it is too long and pushing it is applying the brakes.

Dinner

Also, what type of fluid are you running? My 99 did the same, except it was only the master cylinder. The compensating ports would not allow the calipers and fluid to flow back up into the master cylinder.

Number47

correct me if i'm wrong but the abs system can only release the brakes, never applie so we are talking about somthing other than the abs in my opinion.

prittyboy

number 47 i havent thought about that,,, but i think ur right,,, and that being said i wonder if i have gotten a crappy mastercylinder like Dinner was talking about, Im gonna check that mastercylinder out and see if that dont fix it!

prittyboy

Ok,, last night i drove the truck until it started to drag the front brakes, and for once in was within eyeshot of my house, so i pulled it in the driveway and did some investigation, i pulled the abs fuse and did nothing,{ not shocked at that} i unplugged the abs wiring and did nothing, { not shocked at that either} instead of bleeding them to release the pressure i just let it sit until morning, went out this morning cranked the truck and low and behold they had released, Soo,, my question is this, how can i do a check to see if it is the brake lines or the mastercylinder? im leaning toward the mastercylinder due to the fact in can bleed one side and not the other and it will release both front brakes, am i right in my thinking, or is there another way of testing this? I called the guy i bought the truck from and he said that he hadnt drove the truck in quite some time, i didnt know if this information could help in the diagnoses of my problem. thanks for everyones help thus far.

Number47

it would be a master cylinder. when brake lines fail, which are normally the ones on the front because people let the caliper hang from the rubber hose, tend to act like a one way check valve and leave the brakes applied. with that said check bindeage and if none is found R+R mastercylinder again.

Dinner

If you think it is the lines (more so the two front rubber lines). You should be able to crack them where the rubber meets the steel. If the rubber lines are bad, the pressure should stay for a bit. Right after cracking, spin the tires, if they are freed up then you know the problem is elsewhere. Through cracking the lines, you have made it all the way to the Master Cylinder. Pump up the brakes, get the fronts locked and crack the Front Brake line on the master cylinder. If the wheels free up, I would assume the MC is faulty..IMO

prittyboy

Well instead of doing any more diagnosis i went ahead and bought a new mastercylinder{ not rebuilt} and two new brake lines for the front, im gonna put them on tomorrow weather permitting, I feel like it will be one or the other causing the problems so i will give an update tomorrow, thanks again for all the replys

prittyboy

well guys thanks for all the help, I installed the mastercylinder and have driven the truck about 20 or so miles and not a problem, brakes feel much better and no locking up, from now on i am NOT gunna buy remanufactured anything!!! its new parts or nothing!!! I bought new brake lines also but didnot install them, im sure before too long they will go bad so i will have them on hand. Thanks for everyones thoughts and advice , Michael

Dinner

Glad to hear your brakes are working now!!