brake problem

Ed,

I drive an 88' C1500 and am currently experiencing the EXACT same problem. The other day I noticed I had maybe 55-60% of my normal braking power. The next day I pulled the drums off and snugged up the adjusters, put it all back together, pedal now goes straight to the floor and brake light stays on. Maybe 5% of normal braking power.

I also replaced the master cylinder first, and it accomplished nothing. I have ordered a power booster and ABS hyrdaulic module (does yours have RWAL like mine does?). I was going to change the booster first as I don't feel like bleeding all four lines again, but I might swap in the new ABS module first and see what happens. I'll let ya know what I find.

Doc

probably the ABS, the booster will not let the pedal go to the floor.

. (distressed......Ed cried out with this)

Thanks Ed ........... (which brought the Doctor out of surgery for a counsultation.........) Mon, Sep 22, 2003, 4:59am (CDT+5) From: snipped-for-privacy@noway.com (Doc) Ed, I drive an 88' C1500 and am currently experiencing the EXACT same problem. The other day I noticed I had maybe 55-60% of my normal braking power. The next day I pulled the drums off and snugged up the adjusters, put it all back together, pedal now goes straight to the floor and brake light stays on. Maybe 5% of normal braking power. I also replaced the master cylinder first, and it accomplished nothing. I have ordered a power booster and ABS hyrdaulic module (does yours have RWAL like mine does?). I was going to change the booster first as I don't feel like bleeding all four lines again, but I might swap in the new ABS module first and see what happens. I'll let ya know what I find.

Doc ....................................................................... ==================================== yo, Doc

Try unhooking the RWAL sensor first and putting the system into non-ABS braking mode, (Failsafe Mode), giving it old fashioned power brakes.

See if the prob goes away.

Unless the ABS light is on......then disregard this dribble cuz it's already in failsafe.

Scrib Able

utilized for it's intended purpose, the following is a vengfull tool.............

the easiest way to get a job done..................is to get the shop braggart to "show" you how to do it..................and look astonished when he's through...............

Marsh,

That was the first thing I tried. No dice.

Doc

On RWAL systems, only my rears are affected, which account for 25% of total braking, so if it was the ABS hydraulics, I should, in theorey, have 75% braking power. I have around 5% right now. Took the day off to fix er' up, will let you know how it goes.

Doc

I will be watching this closely Doc, my '90 earned the name "White Devil" because of this same problem. I had TWO pro mechanics who are good friends with over 40 years combined experience, (one has worked at a Chevy dealer 20 years) totally stumped over this braking problem for THREE DAYS. We literally replaced EVERY PIECE of the braking system and some of them TWICE, except for the lines and it just would not get the pedal back. They bled it one last time before we were going to give up (and do what?) and we got about 75% of the pedal and left it there. I wonder if one of those commercial power bleeding systems would have worked? Since that time it has actually gotten a little firmer but on some mornings it seems like I can pump it up.

Ugh, see the new thread I've started "update on brake problem".

Doc

What brand of master cylinder are you using? I've got a few that were bad out the box. Many of these cheapo rebuilders will throw new seals in a pitted bore and sprinkle it with some holy water before tossing it in a box. Put a couple plugs in place of the lines, and see if it still goes down. Brass plugs are real cheap, and may save you a few grey hairs. At least you will know for sure that booster and MC are good at that point.

My record so far was 3 bad EGR valves in a row from the dealer. Yeah, they were bad, the 4th ran it like a clock. I'd had a known good one I tested it with before I bought the first replacement.

The MC I bought from Advance was brand-spankin' new (not rebuilt).

Doc

Re: brake problem ___ (distressed......Ed cried out with this)

Hello everyone, I own a 1990 1500 4x4 std. Cab pickup. The other day, the brake pedal started jumping down....................

Thanks Ed ..........

(which brought the Doctor out of surgery for a counsultation.........) =A0=A0

=A0=A0 Ed, I drive an 88' C1500 and am currently experiencing the EXACT same problem. The other day I noticed I had maybe 55-60% of my normal braking power. The next day I pulled the drums off and snugged up the adjusters, put it all back together, pedal now goes straight to the floor and brake light stays on. Maybe 5% of normal braking power. I also replaced the master cylinder first, and it accomplished nothing. I have ordered a power booster and ABS hyrdaulic module (does yours have RWAL like mine does?). I was going to change the booster first as I don't feel like bleeding all four lines again, but I might swap in the new ABS module first and see what happens. I'll let ya know what I find. Doc ............................................. =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

yo, Doc =A0=A0=A0=A0=A0=A0=A0=A0=A0=A0Try unhooking the RWAL sensor first and putting the system into non-ABS braking mode, (Failsafe Mode), giving it old fashioned power brakes................................... Scrib Able =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

Marsh, That was the first thing I tried. No dice.

Doc =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D= =3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D=3D

yo-yo Doc, Before you chunk the gold card at it........

Check the firewall where the booster bolts up, for cracks around the bolt area. In the cab. (firewall flexing....but not likely the prob)

Check the linkage under the dash for worn out bushings....cracked Z-Bar.

if alls well.............

Clamp off all the hoses and check the pedal feel......and never mind all the drivel headed my way about clamping hoses.

I own clamps made for the job..... you can use vise grips with heater hose on the jaws. Needle nose work great, but reg ole grips work fine too. No excessive grip preasure needed......use a piece of fuel line and you'll get a quick feel that will show you it only takes a very slight amount of preasure on the vice grips to do the job.

" I F " the pedal feels firm.....release the clamps one at a time and recheck the feel. Isolate the area....if it seems to help......then bleed the affected areas with the rest of the clamps applied. Repeat till full pedal is achieved. If you don't get air on any of the bleeders and the system HAS NOT been opened

if the pedal does not firm up on the initial clamping off.......and the Master is known good.......Z-Bar, bushings, and firewall are good.......

or you subscribe to the "No Clamps" on brake hoses idealogy..................

please disregarard this dribble.

fer whut eets werth, Scrib Abel ~hopes a bunch of ASE Certified Master Techs don't bombard ole Scribble Abel with a bunch of "destroyed for life" brake hose replies....and drive him back in the Marsh with Nubbs fer fangers~

utilized for it's intended purpose, the following is a vengfull tool.............

the easiest way to get a job done..................is to get the shop braggart to "show" you how to do it..................and look astonished when he's through...............

Hey there.

Ok, this is my update. New Master cylinder - no improvement New Booster - No improvement Reset ABS - no improvement, but the light went away. Another new Master Cylinder - no improvement

The problem HAS to be with the anti lock system or the proportioning valve.

Let me know how it goes...

Later

Ed

Ed,

I just replaced the ABS hydraulic module (had previously replaced master and booster) and still no farkin' pedal. Do you have RWAL or 4WAL? If RWAL, how do you go about resetting the ABS? IIRC, RWAL just needs bled after component replacement.

Doc

It might still be worth inspecting the bore. I've seen rebuilt stuff being passed as new. Mike

Doc, my truck is RWAL. I just read scott m's reply in the other topic, and I would have to say that it is worth a try. I'm on my way out to give it a shot, let me know how it goes for you..

Later

Ed,

You mean recentering the prop valve? If you do it before I get to it this afternoon, post back and let me know HOW you did it and if it worked.

TIA,

Doc