buell

So I have no rear brakes. Heres the story:

I live in MD and went to emissions to get the car test; I failed. The operator told me I failed because I have no rear brakes .

So take it home jack it up and start the car up, sure enough my rear brakes are not holding the rotors (we took off the tires); they did slow down how fast they were rotating but did not stop the rotor.
So we bleed the brakes, they bleed fine, we start the car back up and get the same result.
After talking to a few people we go ahead and replace both rear calipers. Ended up getting rebuilt Fenco calipers from autozone (with lifetime warranty) and we get the same result.
Next we replace the master cylinder with a rebuilt one from I believe autozone again. Bench bleed the master cylinder and put it on the car and
still get the same result.

So we take it to a local shop and they keep it for two days look at it for two hours and think that I got a bad set of calipers...
I'm going to another shop this Thursday to get a second opinion but want to see if anyone else had any ideas.

Only other things I can add is that:
* We bled the brakes after every change (think we've used 8 bottles of brake fluid now).
* When the car was jacked up and I put the brake pedal to the floor it would stop the wheels for a second and then let them spin. After that it would not hold them again (foot stayed steady).
* My father watched the pistons when this happened and could only describe what he saw this way: "The pistons are pulsating". The rotation never sped up or slowed down though after the initial let go.
* Checked on a concrete floor and this car does not leak brake fluid.

So I figured with as much experience as the people on this site have I would give it a try.
When I find out the answer I will let everyone know.

Thanks in advance for any answers,
-Nick

buell

Ohh its a 1987 iroc-z.
5.7L only changes are exhaust and b&M hammer shifter.

Rear brake pads look like they have never been used

Atilla the Fun

Try this thought: If some previous owner replaced the distribution block below the master cylinder to one for a car with rear drums. The reason this makes sense is that drums must operate at much lower fluid pressures than discs, to avoid locking up.

buell

That was the last thing I was going to replace.
Is there anyway I can tell hat block I have to see if it is the right one?

Reason I haven't replaced this yet is:
1) Heard that when these go bad it causes the rear to lock up (i'm having the opposite issue)
2) Having a hard time finding the part

CBR1000RR

iTrader: (1)

Metering valve?

buell

Is the same as the distribution block yes?

If these are all different then please inform me as to where each is located on the car.

Thanks again for trying to help here as it has me and my father banging our heads against the wall

Atilla the Fun

the metering valve, also called the proportioning valve, is built into the distribution block. Buell, I don't have your answers for those last questions, sorry.

Atilla the Fun

I take that back. I bet hawks third gen parts could help.

buell

okay I thought those were all the same I didn't realize that the proportioning valve/ metering valve went into the distribution block.

I will look at the website but does anyone know of anyways to "test" these or find out if they are the problem?

Atilla the Fun

You test them by hooking up a pressure gauge that can hold over 1000, yes, a thousand, PSI.

buell

Wow thats alot... Well I don't have one at home but I think the place I am taking the car to does so I will make sure I have them take a look at it.

I couldn't find the part listed in the brake section of hawks.

l_dis_travlr

An incorrect proportioning valve should not account for the kind
of problem your seeing.

In the recent issue of Chevy Hi-Perf, someone wrote in with a similar
brake problem. The answer had to do with the various types of brake
fluid, that are not all compatible if mixed together, i.e. can leave a
residue that can clog internal of master cylinder & prop valve.
One possible suggestion would be to disassemble the entire system,
clean & flush thoroughly, and then start with fresh fluid.

Also, the rear caliper has to "float" on the mounting pins, so squeezing
pressure is distributed evenly across the rotor. Make sure that
the caliper/pins are not rusted together.

Good luck,
kk

naf

iTrader: (7)

The cast iron saginaw rear disc brakes are subject to a recall for the exact problem you're having. The brakes would not self adjust as the pads wore down. There's a recall kit that provides different pistons that's supposed to fix this problem. Your rebuilt calipers 'should' have had the new pistons installed but...

I rebuilt my own disc brakes a few years back with the kit from GM Parts Direct. A search will turn up more info.

ghettocruiser

iTrader: (4)

I didnt read anywhere that you changed the rear brake hoses??? That'd be my next step for sure. Actually...I would have done that with the new calipers. Get the hose that goes off the axle, as well as the hoses on each caliper. If they are collapsed or blocked, your brakes wont do squat. And its possible for both sides to fail close to each other...

The proportioning valve rarely goes bad. Atleast in my experience. Replace the hoses, and see where you stand. Those Fenco calipers are fairly decent...I doubt you got two faulty calipers.

J.

50bmgshooter

iTrader: (4)

thats what i would do

buell

I have asked the shop that I had dropped off the car with check all these things.
Umm I had originally thought a partial blockage of the lines would be the cause but the lines bleed very well. Do you still think it is the lines even if they bleed well.

Normally I work on my own cars and am very good about figuring out what is wrong with them and solving that issue.
The rear brakes on this car have me, my father who has worked on his own cars his whole life, and one mechanic so far/ make that two hopefully not going on the third, confused.
So yeah at this point my head hurts from banging it against the wall and I'm ready to just spend some money and get it fixed lol so far this method hasn't worked either

ghettocruiser

iTrader: (4)

Hmmm...Well if the rear brakes are bleeding fine, you might be ok. However...Ide probably toss new hoses on anyway. They might seem to be bleeding fine, but pressure could still be inadequate for pushing the pistons.

I cant recall if the master cylinders are split up into front/rear circuits...been so long since Ive had thirdgen parts in my thirdgen. haha. But it could be a messed up umbrella seal in the master cylinder. Could be pushing fluid fine when the bleeder is open, but once it meets resistence, the fluid could be blowing through the rip or tear or whatever. Stock master cylinders are pretty cheap and easy to swap.

If you want to really boost your braking performance, and rule out the proportioning valve as the issue...ditch that stock valve for an adjustable valve. Run your front brakes straight off the master cylinder, and run your rear brakes through the new adjustable valve. Tune the brake bias accordingly. Its how I run all my cars...I like having control over the way my brakes feel. That will wake those rear calipers up...assuming they arent the issue.

J.

buell

Ohh I really do like the idea of this adjustable valve and all. Could you send me links to parts and an idea of how much?
I am still in high school and so money is kinda tight. Don't you just hate the economy?

naf

iTrader: (7)

IF these are the saginaw rears (PBR came out in 89) the master cylinder AND prop valve are specific to the disc brakes. The saginaw rears require more fluid (different master) and pressure (prop valve). The factory prop valve for these brakes can be found for around $100, an adjustable Wilwood for around $60. There is also a prop valve mod that will increase line pressure to the rears but I believe its intended to be done to a drum prop valve for a disc swap. A search can turn up more.

Before spending any money though, I'd ensure the pads have been installed correctly and the pistons adjusted tight. These discs are very finicky and require CONSTANT use of the e-brake to maintain that adjustment. If you've taken them apart you've seen how the e-brake ratchets the piston out towards the pad.

If you've got PBRs (you haven't said) they were likely swapped over. The PBRs are supposed to work fine with the drum master/prop although I have no personal experience with them, least on a third gen.

ghettocruiser

iTrader: (4)

You can get the valve for pretty cheap. Here it is on JEGS for $41...that was just a quick search i did. You can probably find it cheaper if you look around.

http://www.jegs.com/i/Wilwood/950/260-8419/10002/-1

ANNNNNND....here is a write up on this site on how to do it

https://www.thirdgen.org/propvalve

I didnt read it, but it gives you the gist of it all.

I dont know much about the older rear calipers. Sounds like there are others on here that could steer you in the right direction as far as adjustment and what not. All I can say is, Im running 4th gen discs front and rear. Also running the 4th gen master cylinder and booster. I have the adjustable valve like the link...and Ive never had such wonderful braking in ANY car Ive driven. The seat belts hurt if you really step into the brakes. And its a very simple set up once you ditch the valve and see how things work.

My set up came from SJM Manufacturing. They sell ABS delete kits and line lock kits and what not. They have an 82-92 section that is "coming soon"...but I was able to use the 4th gen stuff since I was running the newer master and all. Might give them a call to see if they can hook you up with pre-bent lines and all the parts you need to make it a plug and play deal.

Good luck!

J.

buell

Yes its an 87 but the guy before me swapped out the rear back in 2001 but I have no idea with what though. And far as the calipers go they are now the rebuilt ones from fenco.

I honestly don't know if I have the pbrs or not. Anyway to tell?

Im really liking the idea of the adjustable valve though do you keep it 70front 30 rear or different?

naf

iTrader: (7)

PBRs are aluminum Saginaws are cast iron. Fenco can provide rebuild calipers for either.

ghettocruiser

iTrader: (4)

Not sure of the actual percentages, but if I had to guess, Ide say Im at around 60/40 right now. Maybe more towards 55/45. Basically, if Im going down the road, and do a panic stop, my fronts will lock up first, followed closely by the rears. The thing is so balanced tho, that I can stop hard as crap without having to lock the tires up. The feedback is great, and the pedal is perfect for my style of driving.

J.

trumps2000

iTrader: (2)

Hey Buell, When I redid mine I found this was a common problem. To find out for sure do a search for the prop valve mod. That'll bypass the proportioning action giving full pressure to the rears. Just don't drive it around like that because the rears could lock before the fronts and you'll lose control.

buell

Did you end up finding out what caused the problem? and this car is my DD so I need to find something that will fix it for good. Thats why i was looking for something that i can do that would be easy cheap and yet effective.

My theory is:
I don't mind spending the money if its gonna fix the problem.

Ohh and the car is still in the shop and i wont get it back till tomor. So i'll let all know what is found and what i'm gonna do

buell

I like the way this sounds, Have you done or followed a tutorial on here?

ghettocruiser

iTrader: (4)

No. I winged my entire set up. haha. I went with the SJM kit basically because I wanted a line lock, and adjustable rear brakes...and the kit came with the correct fittings as well as pre-bent stainless lines. So my brake install was really easy. All I had to do was run a new 1/4" line from the rear of the car to the new prop valve, and run two lines for the front brakes. Other than that, I just hooked it up.

Did it that way in my offroad jeep as well. On that, I have the valve marked because I like my bias different offroad than I do for on road. So I just twist the **** to where it has to be and go. That valve has been working flawlessly for like 6 years now.

It helps to know how to use a brake line flaring tool...which as long as you arent flaring stainless steel is very easy. There is no "set" way to install the valve. Just know the basic idea, and be creative with your lines. Practice flaring on some spare line if you havent done it. Piece of cake!

J.

iansane

iTrader: (1)

Sounds like you've covered most of the the bases but I would've suspected the prop valve as well. If you've got some extra cash laying around put on new rubber hoses and ditch the stock prop valve for the adjustable unit. I did that 4-5 years ago.

buell

Umm what is flaring? lol
and so what did the set up cost u when u were all said and done? from factory to what u have now? (brakes system only lol)

1985hotrod

Hello, this is not as difficult of a problem as might think. Being in the Brake bus for 15 yrs maybe i can help. The first step is to open your master cylinder cap and make sure the rubber is not distorted in any way. If it iss all components with rubber must be replaced. Open rear bleeders. Do you get a steady flow of fluid? If not keep going further toward the front of the car at each connection until you get a steady fluid drip. If you get fluid before the hose and not after then you know the hose is bad. If you go up torward the proportioning valve and there is no fluid coming out of the valve but you have good fluid drip before then replace the valve. If you go all the way to the master with no fuild flow then replace the master. Let me know if I can help you further.

ghettocruiser

iTrader: (4)

Those are good general trouble shooting tips for sure. It sounds like he's getting fluid out of the rear bleeders. The only thing is...you can have fluid, but not enough pressure. If there is a partial blockage in the soft hose at the axle, or inside of the prop valve, it can act like a collapsed hose. I still think he should replace the rubber hoses at the calipers and on the axle. Its just good preventative maintenance at this point.

Haha...Flaring. Its what makes the seal at all of your brake line connections. A double flare to be exact. And dont worry...at one time I didnt know what it was either. You'll learn. Its not hard. Thats why I said practice on a spare piece of tubing first

I cant give you much of an indication on cost. I got all my parts from the donor 4th gen that I bought. It had a strange 12-bolt with the stock brakes, so I used all that. It was a 4 wheel abs car, so I had to come up with a rear flex hose. Then I bought my LS1 brake brackets and spindles from bigbreakupgrade.com. Everything else was from the 4th gen.

I also never planned to go as far as I did with the brakes....but I had all the parts from the donor. And I never kept track of money during the project. If I did, I probably wouldnt have finished. hahaha.

J.

buell

I am grateful for every single posting on here as they just help me to knock out little things here and there. But my father is very good with cars and so we have already done and checked everything you said.
rubber on cylinder was good. fluid flow is def good. and the hoses and everything else does not leak (least that i could tell while kit was parked on the concrete floor.
I have replaced the master as well as both rear calipers. I have been debating whether or not to replace the proportioning valve but have read that the brakes would lock up when this part goes bad.
Only my passenger side has the rubber flex-line and I have not replaced it yet but have been thinking about it. The driver's side has a steel line that has a bend in it and goes straight into the caliper. So I have no flex hose to replace on the driver's side?

Once again thank you for trying to help but I really doubt it is the flex hose since only one side has one and yet both sides dont work.

buell

@ ghettocruiser:
Yes I am getting lots of fluid out the rears and all the shops I have taken it to admitted to me afterwords that they had thought when I took the car to them that they thought it was a pinched line but after looking at the car they said that they doubt there is even a partial blockage lol.
Well Like i said there is only one rubber flex hose but I think i might just replace it and be done with that. it was only $15.

Yeah I learn a little bit every time i work on the car and most times i can look at something and just "guess" how to fix it and it works. That's why this simple hydraulic system has me so frustrated... But there is a good chance that I will go to somewhere like UTI for my college so I will have all the tools and knowledge I will need to learn alot more.

Well I know a junkyard round here that probably has a 4th gen. Like I said money is tight though so I might just have to fix this and then work on the rest in the future.
Questions:
I don't want abs so if I go to 4th gen I dont have to bring over the abs system right?
Can I put on an adjustable valve with the 3rd gen system and still get a much more improved system then when I finally get the 4th gen brakes just take off the adj valve and put it on the new system?

Once again thank you everyone. One thing I love about this site is how much knowledge is on here.

1985hotrod

Well if you are getting fluid flow then there is no restriction. In all my years I have seen maybe 1 or 2 bad valves and I repaired on average 5-7 cars a day for 10 years. That is all I did was brakes. Remeber the fluid flow should drip without pumping the pedal. If you are getting good fluid flow the the problem is at the wheels. Can you tell me the shape the rotors were in. If you rear brakes were not woorking then they should have been very rusty. If memory serves me right the parking brake mechanism is internal on this calpier. If this is the case I have seen many calipers that do not like to self adjust. What we used to do was have someone pump the pedal and get the caliper piston out as far as possible and at the same time pry the piston out with a small screw driver. If this does not have an internal parking brake mechanism let me know.

skinny z

This is very important. I've experienced the same scenario as what you're describing. I even went so far as get a master cylinder and prop valve from a 3rd gen with cast iron rear discs and I still had the problem.
If the e-brake is not adjusted to 100% of it's capacity, the rear brakes don't work very well.
While it's possible to install an adjustable prop valve to up the line pressure to the discs, it's only compensating for a poorly designed system in the first place.
With the e-brake adjusted, I can manage to stop the rotors while the vehicle is on jack stands. Not great, but possibly enough to get your test pass.
The upgrade to PBR calipers around 88 was undoubtedly directed at eliminating this condition.
The cast iron single piston caliper is on the left. The picture on the right is PBR aluminum caliper.

1985hotrod

yup you are correct. GM actually paid lots of $ out on a similar problem with the w-body. There was a class action suit GM settled on regarding this style of system. The upgrade you show looks just like the system GM put on Corvettes and was a very reliable system

buell

They had a light layer of rust but since the pads get close enough to slow the rotor done it got rid of the rust and the rotors look new again. welll the ratchet is outside and then the worm gear is internal. So I don't know if you would call this internal or not...
Me and my father adjusted the e-brake to the point that it holds better then the pedal will.

UPDATE:
I literally just got off the phone with shop and found out he had ordered a part for the car. I had pointed him towards the prop valve and he ended by passing it as a test and said the rear wheels locked up right away. So he ordered a part from gm parts direct ($132) and had it overnighted ($20-30). He said that he would have it installed within another hr and hopefully that would fix it.
So if i'm lucky i will have my car back tonight for under $400 *ouch* with working brakes. the money seems worth it to me after the frustration and what i may have went thru if i was still doing the work on my own.

I will post on here to let everyone know for sure if this fixs the problem later this week. After all this I sure hope it passes emissions as it failed the first time by .001 on something starting with a 'n' lol. Though i hadn't warmed it up completely that time...

edit:
I have the saginaw for sure

naf

iTrader: (7)

The saginaws were probably swapped in without changing the prop valve. They are finicky brakes but will work well when treated with respect. Swapping in the right prop valve for them is a MUST however.

Once you've got them working right use your parking brake EVERY time (twice on Sundays as Sofa used to say). The parking brake is the only thing that keeps them adjusted.

buell

So to adjust it should I just pull the e-brake whenever I park the car

naf

iTrader: (7)

YES

chads89ta

iTrader: (6)

let us know if your brakes are good

buell

UPDATE:
Got the car back from the shop today and I have rear brakes. Just one issue; The prop. valve that was replaced had to be gutted just like my original one was to get the rear brakes to work. He ordered the part right from gm parts direct and used my vin number to get the part.

So is it possible for my 87 iroc with a 350 (came from the factory this way) to have come with a drum brake set up?

Like I said pulling all the guts out of the new prop valve gave me rear brakes but if i push to hard (haven't driven on anything but dry black top yet) they will lock up. Easy fix: dont push so hard lol.

Still with rebuilt rear calipers, rebuilt master cylinder and new prop. valve right from gm I shouldn't be having these issues.

Ohh and went to emissions testing right after getting the car back (drove on highway for 30 mins prior) and failed again. My father had had me put 2-3 bottles of heet (dry gas) in a half full tank and pull the pcv valve out so it gets fresh air. this works for him every time. I think I may of had to sit in the line to long (20 mins) as my hydrocarbons were 5.16-- which is why i failed.

naf

iTrader: (7)

It's highly likely the brakes were swapped in. If the mechanic replaced the prop valve with the one by the vin he may have replaced it with another disc/drum prop. Have your RPO codes in the console lid or rear compartment?

buell

The program I had never worked so can anyone recommend another one for me?

1G1FP2184HN135012 1FD87 (what ever this is)
AC3 A69 AR9 AU3 A01 A31 A90 B18 B2L B34 B39 B42 B48
B84 B94 B97 CC1 CD4 C49 C60 DD8 DG7 DK6 D08 D34 DGM
D80 D88 E52 E7Z E92 FE2 GW6 G80 J65 KC4 K34 K68 L98
MD8 MX0 NA5 NOD NP5 N33 N64 N96 PB4 P20 QDZ TR9 TT4
T93 T96 UQ1 UX1 U21 U25 U26 U29 U79 VK3 V73 YR1 YS1
YTI YT9 Z28 1AZ 1HV 1SC 6ZX 7ZX 72C 72I 729 74Q 74U
BNL 88A 9NL 92P

C/CC WA - L8748 U8748 72C


This was the whole sticker.

(DGM might be D6M)
Cannot find codes for the following even though the sequence is correct:
A69, NOD, YTI, 1AZ, 1HV, BNL, 92P
The rest of them I decoded and put in notepad but not one of them was anything about the brakes far as i could tell

buell

The link I put in lists the car as a 5.7L TBI but I def. have a TPI think this was a mistake or something else?
RPO codes will tell me the story right?

jak2908

the 8th digit is an 8...which means 5.7 TPI....F is 5.0 TPI....and i believe E is 5.0 TBI and H is 5.7 TBI

buell

Yeah the decals and the engine all tell me this was/ is a tpi car (i've looked up the vin before )
Good to know all the sites on the internet are so accurate
good ole net.

buell

So where can I find out if it was drums or not?

Also my e-brake adjustment is all underneath the car. My father says that this is normal for drums but not for disc.

GFR88IROCZ

J65 - BRAKE SYSTEM, POWER, FRONT & REAR DISK

ghettocruiser

iTrader: (4)

Im pretty sure they all had the adjustment in the tunnel...just behind the brake handle. Thats for manually adjusting and setting things up for new e-brake parts. But with that style rear caliper, there might be more to it than I know. I only have experience with the newer set ups that have the little brake shoes inside the rotor.

J.