I have a big problem. My brakes, wont give me a consistant pedal pressure. From stop light to stoplight I go from normal, to the pedal going to the floor, to only an inch worth of travel on it. Help, I don't pull and everything looks great from a visual inspection. My fluid levels are perfect and I get good vacume. I have an 89 Iroc 350 TPI with 4 wheel discs. Please help, I need to fix this before it gets me killed!

 

Your Master Cylinder is dying. That happened on my mom's Blazer one time and it scared the living crap out of me. It would that same thing and would drive me crazy b/c on a visual everything looked fine. Just replace the MC and everything should be fine. Later bro

- Mike Harvey -


------------------
The '86 Firebird http://www.geocities.com/flash_point2002

 

Thanks Mike... Any suggestions on what brake fluid to use since it seems I am going to be swapping in a new master cyl. soon (joy.) Anything else that I should take a look at while I am in there?

 

I would just go w/ regular brake fluid, I use the Chevron brand and w/ brake fluid & power steering fluid it's just fluid, ya know. To be honest w/ you I would ask a tech at like Kragen or Pep Boys or Auto Zone or any parts shop as to what to do and what to expect w/ this replacement b/c my mechanic did my mom's master cylinder so I am clueless on this area. Sorry bro

- Mike Harvey -

------------------
The '86 Firebird http://www.geocities.com/flash_point2002

 

If this just started you more than likely have a hydraulic leak and should have the brakes professionally inspected. There could also be air trapped in the system. Try bleeding the brakes and doing a fluid flush. Only replace the master cylinder unless it is your last option. I have an 84 Camaro with the stock master cylinder and it works like new. Just flush the fluid on a regular basis.

------------------
84 Camaro ZZ4 with HOT cam. 1.88 60' (12.98 @ 105MPH E.T.)
Other Mods: You name it and I have probably changed it.

91 Firebird 5.0L TBI

ASE Certified CHEVY DEALER Auto Tech
LIVE AND DIE BY THE ALMIGHTY BOWTIE!

 

I had them inspected and they didn't see anything wrong. This has been going on for a while now, and I have just learned to live with it. But I had to drive in heavy traffic the other night and that was a huge pain because I never knew how much room I needed to give myself from the car infornt of me. I haven't done anything to my car that would get air into the lines, unless my shop did it to try and make some extra money off of me, but they are the ones that inspected it after it started and said nothing was wrong. I think the master cylinder makes sense, I wish it was something easier, but it could be worse...

 

Just remember to famiarize yourself w/ the e-brake location. I had a Crustang w/ the same problem and I had to milk the e-brake as the ONLY brake I had the whole way home. (I live out in the country>>>>>not much traffic if any)

------------------
Alex (AKA chevyboy) '91 RS 327 stroker, trans-go shift kit>> manual valve body, cat-delete, MSD (ignition, coil, 2-step, timing retard/ advance),Flowmaster, complete Edelbrock suspension including shocks, struts and lowering springs. CRAGAR drag wheels. Lowered 2.25" in front and 1.5" in rear....Best E/T 12.84 @109 mph...(got spray?)plus more!!

 

It's definitely the master cylinder, the same exact thing happened to me. I spent $25 on a rebuilt unit and the problem went away completely.

 

thanks, what about the porportioning valve? should I replace that or even worry about it? I don't think so, but I thought it is worth asking.
Thanks again for the help guys!

------------------
'89 Iroc-Z
350 TPI
No mods... yet!

 

I had the same thing happen to me in my 79 CJ-7. Went gradually from good pedal pressure to none at all during an afternoon's worth of driving in day time desert temperatures. It used to happen only in warm weather. I found out that even though master cylinder wasn't leaking, the washers and valves inside it had lost the ability to hold pressure under demanding conditions. Thanks to 4WD and a manual 5 speed, I didn't even need the brakes, even though I was blasting down a twisty desert track behind another vehicle.

------------------
'88 IROC 305 TPI
Gutted airboxes
160 degree T-stat
Advanced base TPS voltage
Relocated IAT sensor
Momo steering wheel
Ram-air setup coming soon
Flowmaster muffler
Taylor SpiroPro wires
Accel cap and rotor

 

Ok... I will try to make a long story short... Bought the new master cyl, read the directions with it (first mistake) pulled my old one w/ the proportioning valve, bench bleeded the system, started installing and I cross threaded one of the lines into the pro.vavle. So I went to the junkyard and got a new one... went thru all that $#!T again, crossthreaded and different line... did it all again... ended up stripping one of the lines. At that point I said screw it, and called my mechanic to come pick up the car. Anyway, thanks for all your help, and it truns out the master cyl. was the problem.
PS. learn from my mistake, when changing the master cylinder, it is not nessary to pull the proportioning vavle.

------------------
'89 Iroc-Z
350 TPI
No mods... yet!