For what it's worth, here are the instructions for adjusting the rear disc parking brake from a 1987 GM Camaro manual.
I apologize for the poor picture quality.

 

Yes that is what Chilton's manual said as well but my brakes are different from the ones described in the manual.
There is no adjustment in the console it is all underneath bolted to the bottom of the car.

 

Not sure what you mean by adjustment in the console. The adjustment they describe refers to the cable adjuster in the transmission tunnel.

 

ive got the same setup as u... 87 formula 350 tpi... stock 4 wheel disks with the iron calipers in the rear.

all 350tpis came with 4 wheel disk brakes as well as 9bolt BW rears. they are stronger than the stock 10bolt. my 86 TA 305 TPI has 4 wheel disks and a 9bolt but it was an option on the TA.

all of the adjusting for the rear calipers is on the underside of the trans tunnle... kinda annoying i kno. the rear calipers also are not suppose to be "pushed" or clamped in to compress the pistons... they have to be squeezed as well as rotated at the same time... there is a tool for this. mine was cheap looks like a steel square with steel blocks randomly on it to catch the piston on the caliper to rotate it as its pressed in. simply squeezing the piston in can ruin the caliper.

as you should kno the brakes on most cars is 80% all braking done with the front calipers/brakes the rear usually only sees 20% of the braking... which is why rear brakes are always less beefy... the stock proprorting valve is poo... and since he gutted it basically what you have it full brakes all the time to the front and rear.... NOT GOOD!


your rear brakes will lock up too fast and u will lose control. either find the correct stock replacement proporting valve or delete it completely and run a Tee for the front brakes and get an adjustable proportioning valve for the rear.... this is what i did. i got mine from SSBC for cheap like 40-60$ off jegs. you will however have to buy a bag of 1/4" assorted brake fittings and get a flaring tool. front brakes use 3/16" fittings.

the master cylinders on these cars came in 2 designs. one for rear drums and one for rear disks. they are the same on the outside but inside they are diff. swap the wrong one and u lose the rear brakes. this is common for the part numbers to be wrong. i got mine replaced as well chasing a bad brake problem... got mine from autozone. the rear disk brake master cylinders have a smaller inner bore for the master cylinder piston... this creates higher pressures and firmer pedals. disk brakes require more than 600psi to stop... most disk brakes average 1200-1400psi... 1400psi being a PANIC stop. rear drums need alot less pressure to stop. by getting rid of the stock proportioning valve and running the front brakes with a brake TEE fitting u can get full pressure all the time to the fronts... which u want. the rear brakes using an adjustable proportioning valve will be able to be adjusted for rear brake bias.... allowing you to tune the rear brakes so they lock up after the fronts. you will find that the setting will be around 80-20 or 70-30.

get a brake pressure kit from SSBC... its a gauge u screw into the bleeder screw port and will tell u the PSI at the caliper ur getting at each one... u could also use it on the proportioning valve and master cylinder to diagnose brake problems.... IT IS A MUST!! ive had mine for 4 yrs and it helps alot.

http://www.xtremediesel.com/ssbcbrak...egaugekit.aspx

the stock iron calipers have no brake shoes in the rotor... its just a manual spring loaded cable that will turn and push out the caliper pistons without brake fluid... this tightens the piston and pad to the rotor causing it to lock up... I feel this is wayyy better than new styles with shoes in the rotor... they are just annoying. also the stock rubber lines are ok if they are replaced regularly... but they are by no means good... i would have saved my money and stuck braided stainless lines in... cost about 90$ for a complete set by russel or earl... they will increase pedal firmness (no buldging like stock rubber lines) and they last longer.

 

@CUSTOMBLACKBIRD

I have never heard of a 350 with drums but when my buddy with the shop ordered a new prop. valve from GMpartsdirect he used my vin number. This new prop. valve had to be gutted as well to get it the rear brakes to work as well.

I thought it was 70/30 but yeah right now from 70mph i can slam on the brakes and lock up all four wheels no problem. Sure isn't a good thing.. specially in the rain! Right now im just trying to drive safe.
I want to go the route of an adjustable valve because I have heard good things but my father has heard horror stories of people killing themselves with these things so I'm having a hard time convinving him.

I went thru autozone as well and specified for a disc set-up (got that tool you mentioned there as well). Gutting the prop. valve is the only thing that made the rear work so I'm looking that way now.

Someone here said that they like 60-40 is this to much in the rear in your opinion?
What pressure should i be looking at up front and in the rear? 1200/600psi?

I have only had the car a year and wouldn't be surprised if the owner before me never replaced the lines.

 

A 350 could be had with either drums or discs so ordering the prop valve by VIN number wouldn't guarantee the correct PV. EBMiller, on these boards, may have access to the correct valve and may even be able to help with identifying which valve you actually have.

 

I skimmed through this post very quickly but I think I got the run down of what has happened so far.

Right off the bat I suspected the 'prop' valve. You say you have had the calipers looked at and they are functioning, then you have your mechanic take a new prop valve and "gut it" so you now have too much rear brakes...
..So in other words, we have now confirmed the rear calipers are functioning, AND have confirmed THE PROBLEM IS IN THE PROP VALVE.

Lets go further to the correct solution-

1st off, the factory prop valvee is actually called a "Combo Valve". It is a combo valve because it does a combination of things including being partially a prop valve. SOOOOO an aftermarket prop valve alone is not the good replacement here for a combo valve on a street car, Neither is a gutted combo valve. A combo valve has a risidual pressure valve in it, a safety sensor light for low fluid, a bias proportioning assembly which also included the yaw feature which allows a spontaenious rear first feed to track the car straight then front pressure builds-- hence the rear residual pressure part.

So why did he have to gut the prop valve? Because you bought what is actualy thought to be the correct valve from the factory BUT that factory vavle has an inherit defect in its proportions and was a problem from the get go from the factory.

What is the best and safest solution?----
Pre 1989 1/2 cars, GM manufatured 2 (two) different types of "4 wheel disc combo valves". The standard one (which you bought recently) and the 1LE combo valve which is what I HIGHLY RECOMMEND you go purchase and put on the vehicle EVEN THOUGH YOU DO NOT HAVE THE 1LE brakes- It will work great for you- Trust me. I am well respected around here for my knowledge of these cars and have in fact years ago run into the very same problem you are describing.

Get the pre 1989 1/2 1LE Combo Valve - and DO NOT gut it.

Dean

 

Rear disc, only requires proportioning and an idiot light. Rear drum requires metering for the front calipers, so that the drums get pressure slightly before the front. This way the rear pads contact the drums at the same time the front pads contact the rotors.

I fixed the problem by gutting the prop valve and installing an adjustable valve. Then I adjusted it to not lock the rears before the fronts in a panic stop. This is how I installed, so A) I could always put it back, B) keep the idiot light, and C)I think its the cleanest way to install it.

 

That's kind of funny. I've never been able to get a VIN pre-90 to go into my catalog. I was always told 89/90 was the cut off year and GM didn't save info on RPO and such before that.

In which case, having the VIN wouldn't do squat.

 

i tend to agree with vetruck. and he is correct in what the stock combo/proportioning valve does. you could replace it with the 1LE combo valve that he stated... but you will have stock type brakes.

Or u could Tee the front and put a quality adjustable proportioning valve in and then be able to fully adjust the rear brakes. IDK where your father heard about ppl killing themselves with this... but they are very safe. IF YOU HAVE IT ADJUSTED CORRECTLY... i think the stock lines are poo and the look even worse. ive run my own lines and tucked it nicely against the strut tower.

i stuck with SSBC for my proportioning valve. they are cheap and good quality. other companies sell good ones as well. they say to start the valve out as open as possible (least pressure) and test drive it... then increase 1/4 or 1/2 turns untill the rear brakes lock up, then u back off alil. should be in the instructions... im goin from memory and i did this 2-3yrs ago

rear disk brakes will want same pressure as the fronts... fronts range from 1100-1400psi(1400psi being panic stop) the rear calipers are basiaclly the same as the fronts... only real diff being the Ebrake spring etc. same size rotors as well. the rears wont take as much pressure to lock up as the fronts tho... so it might only take 900psi-1100psi since the rears on our cars are lighter and the weight slides to the front of the car as u brake and the front of the nose dips down. which is why front brakes take 80-70% of all the braking. id say 60-40 is not close. 80-20 or 70-30% is more accurate. and brakes should be adjusted appropraitly

 

A properly set up adjustable valve is completely safe (in my experience) and is great for a street car with disc/discs... I run one in both my vehicles, and daily drive them as well as take 8+ hour trips. No issues what so ever, and Ive had the valve in my bird for around 3 years.

Im not 100% sure... but my 4th gen master cylinder has the switch for the idiot light built into the body or the master. Im pretty sure this isnt just for fluid level, because its down in the body. The 4th gen doesnt have a switch anywhere else between it and the ABS module. The ABS module acts as the proportioning valve.

Anyway...some good advice in here. If you can find a stock style combo valve that will do what you need it too....sweet. Go with it.

J.

 

The LS1 style has this switch, while I think the LT1 doesn't. I've been running the LS master and adjustable prop for ~4 years now with no problems.

 

Sorry to hijack the thread but I have an 88 IROC 5.7 with same issue and have been researching for months. and I think you guys may have answered my question.

I understand the different options:
1- plug the CV mod
2- adjustable PV mod
3- change to 1LE CV
4- add washers to the original plug on the CV to tune the rear brake pressure you want so they do not lock up before the fronts like plug mod or gut mod.

Vetruck, are you confirming that changing to a 1 LE CV will give added rear brake performance to the non 1LE rear discs? If so how much as compared to the plug or shim method? This could fix Buell's issue as well as it seems the brake shop gave him brake pressure but created anew issue of driver safety, as a Dad I know I wouldn't want my sons car setup that way.

I prefer the 1LE method if it will work. But I hate to drop a Benjamin on my own guess.

Thanks in advance!!!!!

 

I finally did this on my car with original disc drum. I converted it to disc /disc (Iron caliper 10.5" rotors- Non 1LE brakes). I kept the stock master cylinder and gutted the combo valve. Ran into the said issues with the gutted prop valve, so I changed it to the Non-1LE combo valve and just did not have the rear brake pressure it needed. I research more and found the 1LE combo valve to have a slightly higher rear bias (Going off of memory the figures are something like Non 1LE 62/38, 1LE 58/42).

I put 1LE onto my setup and it worked great. Only reason I then changed my factory setup Iron caliper 10.5 brakes intot he custom Wilwood setups I have is becasue I could not keep brake under this car that could control the heat I was putting into them (pad to rotor material buildup) AND I could not stand that notorious brake pad clicking/rattling at low speeds through parking lots. It was embarassing to hear that rolling past people like the car was ill maintinenced. Heat would reduce the pad tab bend and they would rattle within weeks use. I was very hard on this car.

In conclusion, I drove the car for about 1 full year with the single piston Delco Moraine calipers and 10.5" rotors on all four wheels WITH the 1LE combo valve AND HAD GREAT BIAS and stopping power, just not reliably becuase theye could not control the heat weeks on end and would warp (pulsing in the brake pedal from pad buildup)

Dean

The first page of this cardomain site I did mainly for the Camaro shows a picture of the car with the factory style front brakes on it. I think page 6 later shows the Wilwoods I custom built for it. The 1LE combo valve stayed on it before and after and is still on the car today working great.
http://www.cardomain.com/ride/518752

 

Thanks man, that helps me alot, my personal opinion is that this would probably be the best option. I will give it a shot and see what happens.

And I know what you mean about that clankity clank sound. Hard to look cool in a muscle car that sounds like a loose chain link fence in the wind.

 

I went back to your original post. Check out this article.
It describes your disc brake problem perfectly.
Maybe the repair parts are still available.

 

I bought that kit from GM parts direct. The pistons are slightly different. Buell's are fresh rebuilds.
Buell whenever you get a chance look at the caliper piston (actuator) the face. It should not have the little rubber two way check valve, if it does you still have the old actuators. My originals had it and that TSB kit does not have it in the center of the actuator.
I have seen this elsewhere on the board through my research, the only thing is his kit is designed to make sure the pads stay in contact with the rotor, they will not increase the brake presuure at the rear like the 1LE combo valve will. Basically thereare a couple things that need to be fixed to get the brakes right.

 

Irocmenace sounds like my father lol. And atm I'm having trans issues so im saving this issue for later and moving on to the trans.
I'm happy i have rear brakes right now and by winter time maybe i will have a safer set-up.. Not sure if I will spend the 60 and get adjustable or twice that and get 1LE...
Once again thank you everyone!!

 

Man thought i had it fixed and I return at least 4 pairs of rear calipers to autozone and 3 calipers to pepboys all of them had the two way check valve....

So your saying I need the ones without the two way check valve? Any idea where I can get these?

 

I never understood my parents worries until I became a parent. Now I am more protective than they were and he is only 9 months old!! I have a 5 year old daughter too and I already plan to build a roll cage in her car and program a chip to not exceed 55mph and place a GPS tracking system in the car when she starts driving 10 years from now


Trans now huh, it is always something with hot rods.
GMpartsdirect.com has the kits for like 35-40 bucks. it is a rebuild kit basically but pistons/actuators are the updated ones. I will get the part number off the box for you tomorrow.

That little check valve can be a headache too. I was messing with mine about a year ago and tore it, quick leak! Had to get the gasket kit just to get the little turd. And still didn't have rear brakes!!! Not sure what it does but they went without it on the updated ones. Remanned parts basically only replace the soft parts like the seals and gaskets. They are using the same $10 kit you get from the parts store. So unless you get lucky and buy a caliper that had an update before it was turned in as a core GMpartsdirect.com would be your best bet to get the rebuild kit. And since your calipers are newer they will be nice and clean! Good luck, be safe!!!

 

Lol I have a girlfriend who has just started driving and I'm always correcting something. I understand what it is to be protective of someone now... You'll have to let us know when you put that roll cage in the H1 for your daughter... lol no chip needed might I add!

Yeah it sure seems that way. And I still haven't done anything to make some real horsepower lol (twin turbo in the future with goals of 1200hp DD possible; i dream big)

Alright thanks alot IROCmenance I'll look at the part and see what needs to be done. Yeah I've heard those rebuilds can be a headache... Always; I plan on driving my baby alot longer

 

Part Number: 18019028 from GM Parts Direct, listed as "Actuator" and included parts for both rear calipers, pistons, springs, seals, etc.

 

I cant believe that i found someone with the same problem! I recently bought an 86 iroc 305 tpi that failed emissions for HC. The first time that i brought it they didnt say anything about the brakes being bad but i knew that they were so i replaced my catlyitic converter because the air tube was missing and it was gutted.
I went back and they told me my brakes were bad. After replacing the master cylinder and just tonight replaced my calipers i am excited to see if this prop valve will fix my problem. Do you know what they did to it exactly to gut it? Everything that you have in this post sounds like you have the same brake system setup... After replacing my calipers tonight and playing with E-brake i got a little something out of my back brakes.

 

Only the E-brake will really do anything though... My HC were over twice the limits in AZ. lol. i am going to try and get it tuned and see if the timing is off to see if that helps. I have done almost everything myself except for the welding on my cat.

 

Wow... i only read the first page before i posted my first messages. sorry so confusing. I am suprised that problem is more common. I was afraid that i was going to be the only one. Thanks

 

Okay timmy:
Umm by gutted he said he removed the internals... such as the springs and valves? if u need more info let me know and i'll see what he'll tell me...

Update:
the trans had to be flushed and it was fixed.
The brakes are still working but panic stops are a little tricky since i live on back roads and all... lol on break, off break, straighten up and if need be get on breaks again.. so far ive managed to keep from hitting anything...
Well newest issue.... flywheel is cracked... looks good too if I can remember I will post a pic of it lol. Hopefully that will be fixed within 24hrs... let me tell u dropping a trans with nothing but jack stands and jacks sucks lol

 

Just an FYI, I gutted my prop valve and added a brake bias adjustment valve between the master cyinder and prop valve alot like trumps2000. I also rebuilt the rear calipers with the update kit, bought new front calipers and Hawk HPS pads. I also bought a motive products power bleeder and bled the brakes extensively. Now may car has the best stopping power of any thirdgen I have had. The bias valve was only like 38 bucks, well worth it, it is a Summit boxed part but is identical to the wilwood piece.

 

Well figure I should update everyone as to whats going on:

So the flexplate cracked from when I lost overdrive, it was really slamming into the gears for awhile, I went thru about 3-4 starters and found out the flexplate was bad on the way to senior week... Deleware Pepboys rocks lol.

So I got the starter fixed and continued 4hrs of driving to senior week. Had to leave the car in the hotel parking lot of O.c. for the whole week

Started it once and let it run all 200 miles back home.. including when I went for gas lol. So it made it home and I dropped the trans and replaced the flexplate..

About three weeks later (if that) I was heading to a friends house for a party and the auto wouldn't leave first. I really had to try a lot of playing to get it into second but no matter what it would not go into third..

So I had to drive home at about 35mph for a good 6 miles.

Turns out I lost my 3-4 clutch pack? So started researching the cost of a trans. Found one I liked that was better then stock for $2k.

I decided to put the car in storage for a bit and get a 5spd to learn on. For the past 3 months I've been driving a Dodge caravan around and have finally got a 91 chevy s10 that i can learn stick on..

In the mean time I''m gonna fix up the camaro since its no longer on the road and I don't have to worry bout a project taking to long and me missing work..

The plans never end with this car lol

 

I'll warn you guys one last time, watch out with gutting part of the combo valve. You are leaving the rear portion of the valve somewhat in tact for the dummy light and those internals out of balance will now start to fade AND YOU WILL LOOSE FRONT BRAKE PRESSURE.

Trust me, it happened to me over time. I have an extensive post on this years ago I think under the name "Afrikingoodtime" about the CV mod and then the year later reprocussion of that.

Long story short, my front brakes went to **** when that partially gutted valve finally failed.

How do I know it was only the valve that caused the failure? because I only replaced the gutted on with the appropriate 1LE CV for my year car (only the thread pitch of the lines changed from pre 89 1/2 to post) Then miraculously my front brakes started working again.

When it happens, just know I warned you all. I drove my car hard and it happened abruptly one day= I was lucky where it happened.

 

I dont know if this was posted, but Im posting it again. Its a good description of how the prop valve works.

http://auto.howstuffworks.com/auto-p...ter-brake2.htm

Ive never experienced anything like what vetruck said with removing the prop valve spring and plunger. I ran my Jeep's prop valve like that for a couple years before switching to the adjustable valve. However...I can see how gutting the valve could mess with the metering portion of the valve. Even though Ive never heard of that happening, I certainly wouldnt discount it. I dont get the feeling vetruck would make something up just for the fun of it

Im still a fan of ditching the stock valve all together and running an adjustable set up for the rear and the front brakes right off the master.

J.

 

Thanks for that link gettocruiser.

looking at that it shows the 'metering valve section' of the CV

I wonder if the disc/disc CV has a metering section? The valve I gutted and had fail on me was in fact a disc/drum CV WITH a metering valve section.

Maybe trump2000's CV did not have one and his older stayle CV was a disc/disc unit. He 'MAY" be safe (note for lack of info I say "may")

I do know factually I would never again gut the disc/drum CV. You WILL eventually loose front brake pressure. Thats a fact- Trust me, It happened to me.

Dean

 

Bump !!!!!!! for a really good Thread here !!

I have the EXACT same problem, and this thread helped me out very much.

 

Glad it helped Rob.

My setup is a disc/disc, so there is no metering system. Its no more dangerous than whats illustrated in the tech article section. I just thought it looks a little cleaner, and can be easily reverted. My brakes work great, probably the only reliable thing on the car.

 

Wonderful read. Adjustable for the rear and Tee for the front! I’ve completely destroyed the thread on my J65 prop valve after an LS swap. Thank you!