At wits end with fixing brake system (Page 1/1)
NuClearFuRy SEP 28, 06:02 PM
So my buddy and I are trying to fix the rear brakes on a 85 Fiero and we thought we only needed to replace 1 rear caliper. Well 3 calipers later (all rear) and new parking brake cables and the car hardly brakes. The one caliper ended up stripping the threads from the first banjo bolt before getting to 30 ft/lbs, we got to 30 once but it kept leaking we replaced the crush washers and around 20 the bolt suddenly got very easy to turn.

We have fully swapped out both rear calipers and bled the the fronts and the backs and even did the master bleed kit with the hoses where it just goes in a loop until the hoses stop pulling bubbles. I will also note the old system, was likely DOT 3 and my partner opted for a mix of DOT 4 Sythetic and Max Synthetic (whatever that means). We dont believe there should be much of an issue there and that we only would have seen issues if we did DOT 5. We are about 3 or 4 bottles into this whole ordeal.

We have also completely replaced the parking brake cables and equalizer nut.

So my list of questions are:

1. How much gap should we see in the rear brake pads while resting?
- I havent measured but I would say we are at maybe 3+ ish playing cards total on driver side and maybe 2 ish on the passenger.
- I will update a better measurement tonight.

2. How much stopping power should the parking brake afford us?
- We can definatly still move the wheel at half pull and at full pull the wheel will mostly fight us to spin but can still be spun with out the wheel on.

3. Is that trick in the Ogres cave really that useless to try where you prop out the piston by the dust boot and try to tighten the arm with the spring on it?
- It seemed to help on the passneger side even when I did it wrong and I will have a better oppotunity this evening.
- That driver side sucks to tighten, any tips to keep thatarms from moving while tightening?

4. What might make both bleeders still leak out the threads just a smidge?
- We clean the hell out of the area with brake cleaner, do some work, then go up and down the drive way a few times and there still appears to be some small amount of brake fluid at the pit of the bleeder threads. Do you think we still have a bad control group or you would expect that?

5. Will the bleeder threads still leak if there is air in the system?
- My father who has worked on many cars successfully claims if there is air still in the system then stuff can leak from everywhere, but we just keep bleeding and see no bubbles.

6. Is there some process we need to do to calibrate the pistons?
- My friend claims that he read somewhere that there was some process you need to do with pressing on the brake or something while working the parking brake to get the piston to auto adjust to be correct.

7. How much slack should the parking brake cables have at rest?
- We have tried heavy slack, no slack, some slack, pretty taught and the parking brake just alwasy allows us to hard turn the wheel.

8. Would tightening that arm with the spring on it on the caliper help or hurt how much the piston moves when the brake or parking brake are engaged?
- I know the arm is only supposed to move about 1/4" but one side definatly moves more than the other and they both move at least a 1/2" and we can still move the wheels.

9. Wouldn't I expect to see the front resevoir go down at a diminished rate compared to the back but still down if the master was leaking anywhere into the booster or elsewhere while we are bleeding the brakes?
- We have another friend who is insistant that the booster is bad, but I fished a ton of string into the booaster and it came back dry. The booster also seems to hold pressure fine inbetween sessions. The check vavle seems solid and you cant blow backwards into it. The brakes get noticeably softer when the car is turned on and get stiffer than they were with the car on when the car is off.

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MJM

cvxjet SEP 28, 06:15 PM
Just wanted to chime in with a couple of points;

I just did a transmission/clutch swap on my 85....When I was re-installing the rear brake calipers, I had an issue with the parking brake lever on the driver's side...I don't really use the parking brakes because they tend to develop leaks, so I just turned the screw-jack 1/6 turn looser and then installed the lever...When I test drove the car the brakes didn't work well...i figured that is there was any problem with moving that screw-jack, the hydraulic system would adjust to it....after a few weeks of testing I decided to attempt to adjust that arm back to it's original position....and then the brakes started working properly...moral of this story; pay attention to adjustments on those parking brake screw-jacks.

Also, the Torque specs for the hose-to-caliper bolts and the bleeder valves is for DRY threads...any fluid at all, and that torque value should be MUCH less...here is a list of torque specs for the brake system;


1984-87 BRAKE SYSTEM


Calipers mounting bolts = 35 lb/ft

Brake hose to caliper = 19 lb/ft (Book says 33- maybe dry but brake fluid is usually on threads)

Caliper bleeder valve = 132 lb/INCH (11 lb/ft)

Master Cylinder to booster nuts = 20 lb/ft

Parking brake lever to caliper nut = 35 lb/ft

Splash shield bolts = 84 lb/INCH (7 lb/ft)

Lines to Master Cylinder = 19 lb/ft (84-85) 15 lb/ft (86-87)

[This message has been edited by cvxjet (edited 09-28-2024).]

Patrick SEP 28, 06:29 PM

quote
Originally posted by NuClearFuRy:

The one caliper ended up stripping the threads from the first banjo bolt before getting to 30 ft/lbs, we got to 30 once but it kept leaking we replaced the crush washers and around 20 the bolt suddenly got very easy to turn.



Did you see this thread? Destroying my brand new caliper

I'm wondering if the torque wrench being used is part of the problem here. Let's say the torque wrench goes up to 150 ft lbs. I suspect it would be very imprecise at 30 ft lbs... which I feel is too high for aluminum calipers in the first place.


quote
Originally posted by Patrick Here:

When I'm tightening a bolt into aluminum, I'm always very careful not to overdo it. I'm not saying you necessarily overtightened the bolt, but you just want to make sure that you don't have this same issue with the next caliper.

I did some further research, and the banjo bolt torque into aluminum calipers on a Subaru is 13 ft lbs. That to me makes a whole lot more sense than 33 ft lbs!

I've never had this problem of stripping the calipers, as I've never used a torque wrench on the banjo bolts (or bleeders). I've always felt that the Fiero factory torque specs were awfully high for aluminum calipers.


[This message has been edited by Patrick (edited 09-28-2024).]

Doggo SEP 28, 06:46 PM

quote
Originally posted by Patrick:




Hi Patrick, the author of this thread is my roommate, so this is the same fiero as the thread you linked.

When we tightened the banjo to 30 initially, I had not yet consulted the forum and was following my service manual. It got down to 30 one time, but still was leaking. So later on i undid it to try your 2 washer method and upon tightening back down, the banjo gave out at ~15 lbs. That was the first caliper, the one warrantied by the fiero store. We have since learned our lesson on not using torque wrenches on aluminum cast parts.

This is turning into the longest brake job ever
Signupacct SEP 28, 07:03 PM

quote
Originally posted by Doggo:

This is turning into the longest brake job ever




I am on the one hand not ready to compare project start dates but I think I am in the running for the longest brake job ever award


when I saw the subject line of the thread I thought it was my discussion thread that I started on issues I was having lol


Joe k

[This message has been edited by Signupacct (edited 09-28-2024).]

cartercarbaficionado SEP 28, 08:17 PM

quote
Originally posted by Signupacct:
I am on the one hand not ready to compare project start dates but I think I am in the running for the longest brake job ever award


when I saw the subject line of the thread I thought it was my discussion thread that I started on issues I was having lol


Joe k



if we exclude fieros then I do.
50 years of brake issues on my international bc164 when I got it and I threw the towel in. air brake time
Dennis LaGrua SEP 29, 05:14 PM
Good news. All Fiero brake calipers including both rear units seem to be available new but availability is erratic. They are Chinese made but with all new components. They are probably better than the many times rebuilt calipers that we have been using.
You can find them on eBay

------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-29-2024).]

Patrick SEP 29, 05:27 PM

quote
Originally posted by Doggo:

Hi Patrick, the author of this thread is my roommate, so this is the same fiero as the thread you linked.



Ah... I thought the issues seemed awfully similar!
Doggo SEP 29, 08:05 PM

quote
Originally posted by Dennis LaGrua:

Good news. All Fiero brake calipers including both rear units seem to be available new but availability is erratic. They are Chinese made but with all new components. They are probably better than the many times rebuilt calipers that we have been using.
You can find them on eBay



Yeah, I just saw some today on Amazon, the ones by A-premium. If all else fails it looks like I’ll be buying a set of those. Sucks that I wasted $300 trusting the fiero store with quality rebuilds, though.
Dennis LaGrua SEP 30, 07:03 PM

quote
Originally posted by Doggo:


Yeah, I just saw some today on Amazon, the ones by A-premium. If all else fails it looks like I’ll be buying a set of those. Sucks that I wasted $300 trusting the fiero store with quality rebuilds, though.


The question that I have is how many times can our well used beat up 35 yr old calipers be rebuilt before they're no good anymore. In the future I will be buying new. This A1-Premium outfit seems to be reissuing many parts discontinued by the major companies. I just purchased a new distributor from them for the 4.9L Cadillac engine in my 85GT ragtop . It fit and worked perfectly. The cost was an affordable $69.95. GM discontinued the part a while ago. The new part is Chinese made but it worked and came with a 1 year warranty .
As I once said Chinese parts can be very good but also very bad. New Buicks are made by GM in China and they seem to be reliable. The companies in that factory supply chain are making good products, Not many choices left for Canadian American or European car parts.


------------------
" THE BLACK PARALYZER" -87GT 3800SC Series III engine, custom ZZP /Frozen Boost Intercooler setup, 3.4" Pulley, Northstar TB, LS1 MAF, 3" Spintech/Hedman Exhaust, P-log Manifold, Autolite 104's, MSD wires, Custom CAI, 4T65eHD w. custom axles, Champion Radiator, S10 Brake Booster, HP Tuners VCM Suite.
"THE COLUSSUS"
87GT - ALL OUT 3.4L Turbocharged engine, Garrett Hybrid Turbo, MSD ign., modified TH125H
" ON THE LOOSE WITHOUT THE JUICE "

[This message has been edited by Dennis LaGrua (edited 09-30-2024).]