Brakes Looking to upgrade or get the most out of what you have stock? All brake discussions go here!

Brake Overhaul on 88 IROC... need help

Old 04-02-2019, 05:24 PM
  #1  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Brake Overhaul on 88 IROC... need help

Fellow Thirdgeners, I need your help. For reference, here are some threads from the fall.... Here and Here.

Long Story Short... brakes pulling to one side, bad hose and found a rotor measuring out of spec. Decided to do Stillen Rotors and Pads in the rear and a Powerstop Kit for the front. New bearings, seals... you know the deal. Also, added Russel braided lines. Not building a track car, but while I am in there might as well use more up to date parts.

I can't seem to get a firm pedal. Even got a re-manufactured Master Cylinder to eliminate it as a cause. Bench bled it until it was firm, and the re-bled all the brakes. Still not firm... then MI winter came and just didn't have garage time. With Spring here, it is time to get back to the garage. I am just not sure where to start trouble shooting. I am usually really good with figuring things like this out, but this one has just got me stumped.

Rear brakes are adjusted to where they almost drag, parking brake works excellent and so do the brakes when the pedal is pushed. Parking brake travel at the arm is also in spec. To get to 12-14 clicks requires you to either really yank on it hard and quick or use a lot of force to slowly pull it up. The fronts seem to also work great. I can't find any leaks around any of the hose fittings, was never losing fluid. I can build a firm pedal with the car off, but once turned on and the booster comes into play, the pedal will just sink, not completely but has to travel very far to hit a hard stop.

When I say bleed... I have sent pint after pint through this thing at each corner to try and be damn sure I have all the air out. Using a vacuum operated system to pull it through.

Now I do see air bubbles sometime when bleeding, but I have confirmed this seems to be from the seal at the bleeder screw. If I don't use the vacuum system and have my son push the pedal, solid stream of fluid comes out. Is there possibly air entering elsewhere? If so, shouldn't fluid be leaking there too?

What should my next steps be?

Last edited by KyleF; 04-02-2019 at 05:28 PM.
KyleF is offline  
Old 04-04-2019, 03:53 PM
  #2  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

I guess this stumps others and I am not alone.

Any ideas/suggestions appreciated.
KyleF is offline  
Old 04-13-2019, 09:38 AM
  #3  
Member
 
Join Date: Feb 2006
Location: Snellville, Georgia
Posts: 118
Car: 1985 Iroc, t-top
Engine: 5.0L HO L69
Transmission: Mt 5 speed
Axle/Gears: 3.73 Non Posi, Alum Drums
Re: Brake Overhaul on 88 IROC... need help

Can you adjust the rod from the brake booster into the master cylinder. Had the same issue with my dodge Shelby daytona, adjusted the rod. The rod was too short with the new master cylinder, so there was some space between the rod and the master. Lengthened the rod coming out of the brake booster a bit (was adjustable from factory)
855speed is online now  
Old 04-15-2019, 09:34 AM
  #4  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by 855speed View Post
Can you adjust the rod from the brake booster into the master cylinder. Had the same issue with my dodge Shelby daytona, adjusted the rod. The rod was too short with the new master cylinder, so there was some space between the rod and the master. Lengthened the rod coming out of the brake booster a bit (was adjustable from factory)
Seems reasonable. I wasn't happy with the brake travel before, so it's something worth checking. I figured it was due to old fluid and old rubber hoses. I think it is worse now than before I started so I didn't think that would be the culprit, but at this point anything is worth checking. I am sure there is a factory specification on length, but you said you had an issue when you changed masters. If I am reading between the lines, you would have adjusted yours out past the spec due to the replacement master. How did you determine your new length?
KyleF is offline  
Old 04-15-2019, 11:09 AM
  #5  
Member
iTrader: (7)
 
daferris's Avatar
 
Join Date: Aug 2008
Location: Lansing, Mi
Posts: 256
Car: One owner '88 IROC 50k
Engine: L98 with bolt ons.
Transmission: T56
Axle/Gears: 4:10
Re: Brake Overhaul on 88 IROC... need help

try bleeding the rears with the parking brake applied. It's possible that you have a leak in the caliper.
Also have you confirmed no leaks at any of the fittings?
If you need the dimension I have my master and booster out of the car. I can measure the push rod out of the booster.
PM me if you need it I am on TGO a few times a week...
Dave
daferris is offline  
Old 04-15-2019, 11:37 AM
  #6  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by daferris View Post
try bleeding the rears with the parking brake applied. It's possible that you have a leak in the caliper.
Also have you confirmed no leaks at any of the fittings?
If you need the dimension I have my master and booster out of the car. I can measure the push rod out of the booster.
PM me if you need it I am on TGO a few times a week...
Dave
Well, no information is bad information. I will shoot you a PM, but having posted on here may help someone searching threads in the future.

I am pretty sure I bled the rear brakes with the parking brake applied, but not a 100% sure. I know for sure between bleeds I cycled the parking brake and pedal, just can't remember if I did it with the parking brake still applied.

I have the front up right now.

Any ideas on how to isolate the front/rear. I have not seen any fluid leaks, I have a feeling the issue is in the fronts, but can't confirm that. The rear parking brakes and when I had my son pressing the pedal in the car just seemed to work better than expected but that's all off visual and feel. The pads are close, withing a couple of thousandths of an inch from the rotors. The calipers that were on it when I bought it are still there. Didn't have fluid loss issues and don't see anywhere it had leaked around the bore or fittings except when I took them loose to replace the hoses and of course on the drivers side I had to disconnect the hard line.
KyleF is offline  
Old 04-15-2019, 11:53 AM
  #7  
Supreme Member
iTrader: (2)
 
Tootie Pang's Avatar
 
Join Date: Aug 2009
Location: Los Angeles
Posts: 1,209
Car: 1989 IROC Convertible
Engine: 305 TPI (F)
Transmission: 700R
Axle/Gears: 3.42
Re: Brake Overhaul on 88 IROC... need help

I'm going to bet that everything is fine. It's probably your pads. Your not racing so ditch the racing stuff. If you want a "firm" pedal (factory?) then you need regular old pads. I don't recommend ceramic as a first choice. Go with semi metallic if you can. I had the same problem after I replaced all four corners with all new stuff. It took a while for the pads to settle in but now they bite hard, no random pulling to one side, and a light pedal to stop. It just took some driving and the problem went away. Weird I know.
Tootie Pang is offline  
Old 04-15-2019, 12:00 PM
  #8  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by Tootie Pang View Post
I'm going to bet that everything is fine. It's probably your pads. Your not racing so ditch the racing stuff. If you want a "firm" pedal (factory?) then you need regular old pads. I don't recommend ceramic as a first choice. Go with semi metallic if you can. I had the same problem after I replaced all four corners with all new stuff. It took a while for the pads to settle in but now they bite hard, no random pulling to one side, and a light pedal to stop. It just took some driving and the problem went away. Weird I know.
You mean the pads are too thin? This is pedal travel non-moving. Just straight up travel until the I get a firm stop of travel, not of the car. Once the brakes are pumped up, the pads should set close to the rotor just as if they had worn and the pedal travel should remain the same no? To be honest, I do not feel it is safe to drive in the condition it is in to try to settle them in. The fronts were broken in before I tore the rear apart, but the car had more pedal travel than it should have to begin with and after the fronts were replaced. At the time, I had not touched the rears. So, I figured it would be better after doing the rears.

Also, there has been plenty of pedal pumping and bleeding, then more pumping... rinse wash repeat.

Last edited by KyleF; 04-15-2019 at 02:46 PM.
KyleF is offline  
Old 04-15-2019, 03:02 PM
  #9  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by Tootie Pang View Post
I'm going to bet that everything is fine. It's probably your pads. Your not racing so ditch the racing stuff. If you want a "firm" pedal (factory?) then you need regular old pads. I don't recommend ceramic as a first choice. Go with semi metallic if you can. I had the same problem after I replaced all four corners with all new stuff. It took a while for the pads to settle in but now they bite hard, no random pulling to one side, and a light pedal to stop. It just took some driving and the problem went away. Weird I know.

Rear Pads - call for street use.

Front Kit - Z23 Evolution Sport High Carbon Ceramic Brake Pads Engineered for the enthusiastr that wants to get the most out of their vehicle without sacrificing everyday driveability

So I hope I am not in that same spot.
KyleF is offline  
Old 04-15-2019, 04:14 PM
  #10  
Member
 
Join Date: Jan 2005
Location: N. CA
Posts: 272
Car: 1989 IROC-Z 305 LB9 AT Convertible
Engine: LB9 305
Transmission: AT
Re: Brake Overhaul on 88 IROC... need help

Are you by any chance using Silicone brake fluid? That crap is hard to bleed.
mikeceli is offline  
Old 04-15-2019, 04:42 PM
  #11  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by mikeceli View Post
Are you by any chance using Silicone brake fluid? That crap is hard to bleed.
That is DOT 5 if I am not mistaken. I am using This DOT 3


Keep the ideas coming. It has to be something.
KyleF is offline  
Old 04-15-2019, 08:12 PM
  #12  
Member
 
Join Date: Oct 1999
Location: Philly
Posts: 180
Car: 1987 GTA 350 auto
Re: Brake Overhaul on 88 IROC... need help

a quick question, why do you have to ;put the parking brake on to bleed the rears?
TOM305T/A is offline  
Old 04-15-2019, 08:33 PM
  #13  
Member
 
Join Date: Jan 2005
Location: N. CA
Posts: 272
Car: 1989 IROC-Z 305 LB9 AT Convertible
Engine: LB9 305
Transmission: AT
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by KyleF View Post
That is DOT 5 if I am not mistaken. I am using This DOT 3


Keep the ideas coming. It has to be something.
Correct. Nothing unusual about bleeding Dot3
mikeceli is offline  
Old 04-15-2019, 08:55 PM
  #14  
Member
 
Jbuchanan's Avatar
 
Join Date: Mar 2017
Location: Sweet home Alabama
Posts: 455
Car: 1987 GTA
Engine: 5.0
Transmission: Automatic
Re: Brake Overhaul on 88 IROC... need help

Re: complete brake overhaul in progressIf you still have the old rubber lines put them back on and rebleed. Then clamp off the rear rubber hose, bleed the front, if nothing changes in pedal travel leave rear clamped and clamp right front and bleed left, if nothing changes clamp left line off and bleed the right. If nothing changes you have eliminated the calipers/wheel cylinders or calipers/calipers. I have replaced a few remanufactured master cylinders that have done this very thing. They were bad from the store.
Jbuchanan is offline  
Old 04-15-2019, 09:07 PM
  #15  
Member
iTrader: (7)
 
daferris's Avatar
 
Join Date: Aug 2008
Location: Lansing, Mi
Posts: 256
Car: One owner '88 IROC 50k
Engine: L98 with bolt ons.
Transmission: T56
Axle/Gears: 4:10
Re: Brake Overhaul on 88 IROC... need help

Here is the photo of how far the rod sticks out of the booster. The photo is with the tape measure in the top side of the rod.
daferris is offline  
Old 04-15-2019, 09:10 PM
  #16  
Member
iTrader: (7)
 
daferris's Avatar
 
Join Date: Aug 2008
Location: Lansing, Mi
Posts: 256
Car: One owner '88 IROC 50k
Engine: L98 with bolt ons.
Transmission: T56
Axle/Gears: 4:10
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by TOM305T/A View Post
a quick question, why do you have to ;put the parking brake on to bleed the rears?
With the Iron rear calipers the parking brake is a multi lead screw that pushes the piston out to clamp the pad to the rotor.
daferris is offline  
Old 04-16-2019, 12:56 PM
  #17  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by daferris View Post
With the Iron rear calipers the parking brake is a multi lead screw that pushes the piston out to clamp the pad to the rotor.
Yup, so it actually pushes the cylinder forward and should fill with more fluid. More volume to pull air from. Then when you release, it goes back to the MC.
KyleF is offline  
Old 04-16-2019, 12:59 PM
  #18  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Originally Posted by Jbuchanan View Post
Re: complete brake overhaul in progressIf you still have the old rubber lines put them back on and rebleed. Then clamp off the rear rubber hose, bleed the front, if nothing changes in pedal travel leave rear clamped and clamp right front and bleed left, if nothing changes clamp left line off and bleed the right. If nothing changes you have eliminated the calipers/wheel cylinders or calipers/calipers. I have replaced a few remanufactured master cylinders that have done this very thing. They were bad from the store.
I put a master cylinder on because of this issue. It didn't make it any better. This was the reason I suspected the old one.

Somewhere in the other threads I mentioned I had the MC capped while I installed it, and pushed the pedal without the car running(no booster). It was firm as could be.
KyleF is offline  
Old 04-17-2019, 07:16 AM
  #19  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Well, I got the C4 ready to go last night. Will be putting hands on the IROC soon.
KyleF is offline  
Old Today, 09:34 AM
  #20  
Member
Thread Starter
 
KyleF's Avatar
 
Join Date: Nov 2004
Location: Lansing, MI
Posts: 334
Car: 1988 IROC-Z
Engine: 5.7 TPI
Transmission: 700R4
Axle/Gears: 3.70
Re: Brake Overhaul on 88 IROC... need help

Car has had all fluids checked and has been started, brought up to temp and all that good stuff from sitting over the winter. I can't tell you how much a Batter Tender and Stabil are my friends.

Taking the advice above, I started at the beginning. Brake pedal mount is nice and firm with no play and same for the actuator rod attached to the pedal assembly. Seems silly I know, but starting from the beginning.
Usually a booster failing doesn't cause a soft pedal, but ran it through the checks anyway. Pull the vacuum hose off and inspected it. Looks like it is fairly new. Blew through it and the check valve is working properly. Allows suck, but not blow. Then I started the car, yup pedal goes to almost bottom of travel. Let it back up, shut car off... pressed the pedal 4 times. Each time got a little more difficult and the pedal got higher. Then while holding pressure on the brake pedal, started the car and the pedal went down easy as vacuum built (Watching the Boost/Vacuum gauge - didn't take long). Shut the car back off and the pedal slowly got harder to hold down.

So it seems all is well as far as the booster.

I guess the next step is to remove the master, re-bench bleed. My only issue there is that means having to re-bleed the entire system before I can check again. What would happen if I left the rear channel connected, took the front lines off and used the nylon bleeding plug to seal it and secure the plug with a large C-Clamp. Thus isolating the rears. I have the old Delco Morain calipers that are know the be a PITA, but have a hunch my issue is not in the rear that I would like to confirm.
KyleF is offline  
Related Topics
Thread
Thread Starter
Forum
Replies
Last Post
BOTTLEDZ28
Brakes
4
04-15-2019 08:50 PM
Convoy25
Brakes
2
11-30-2010 02:00 PM
82karr
Brakes
4
03-17-2008 06:09 AM
TunedPortZ
Suspension and Chassis
1
09-09-2002 03:01 PM
PLANT PROTECTION
Suspension and Chassis
1
10-24-2001 06:14 AM


Thread Tools
Search this Thread
Quick Reply: Brake Overhaul on 88 IROC... need help


Advertising
Featured Sponsors
Vendor Directory

Contact Us - Advertising - Cookie Policy - Privacy Statement - Terms of Service

© 2019 MH Sub I, LLC dba Internet Brands

We are a participant in the Amazon Services LLC Associates Program, an affiliate advertising program designed to provide a means for us to earn fees by linking to Amazon.com and affiliated sites.
 
  • Ask a Question
    Get answers from community experts
Question Title:
Description:
Your question will be posted in: