Team Chevelle banner
Cancel
Create thread New Garage Forums

Problem with Front Corvette & Rear Cadillac disc brakes

Jump to Latest
41 - 60 of 70 Posts
Discussion starter · #41 ·
Joe,

The local Chevy dealer parts people are kind of jerks... They can only order the whole MC and I just need the reservoir. Can you tell me what years & models are the third gen f-body or '91+ B-body cars? This way I can get a remanufactured MC from an autoparts store, with actually helpful people...

I made some progress today... I removed the stock drum/drum valve & lines and I bought new brake lines and connectors. I expect to do the work tomorrow. I am keeping my fingers crossed.

Theo.
 
#42 ·
Theo,
A junkyard might be a better shot than the GM dealer for the reservoir.

I do believe all third gen f-bodies '82-'92 had the right one and '91+ Caprices (could be used earlier...I haven't snooped around enough to check that out) should also have the angled reservoir.

If you can't find one let me know and I'll see if I can grab one for you.

Joe
 
#43 ·
CarlC,

Questions about my '67 camaro's "pdqCBB" setup..

I finally got over here and have to ask if I will have a problem with my big single piston Van front calipers and 1980 Seville rear calipers balance-wise?

The Van calipers are 2-15/16" dia. and the Seville calipers are right at 2.00" dia.

I have installed my prop. valve on the M/C port closet the firewall which should be the rear brakes then to my stock four wheel drum brake block under the M/C. This is correct isn't it.

AND since I am hard-headed, I am going to try a 1.25" M/C and will have to can it if it doesn't work!! Per david Pozzi's thought's too..

Please advise. Awaiting your and anybody else's comments..

Thanks in advance.

pdq67

PS., the big calipers and 13" Vette rotors on the front look like they are stock!!!

Best Car Insurance | Auto Protection Today | FREE Trade-In Quote
 
Discussion starter · #44 ·
I finally run all the hard lines needed when I removed the stock drum/drum combination valve. Now I have a 1/4" line for the rear brakes and two separate 3/16" lines for the front brakes. The front MC outlet feeds the rear brakes. There are no leaks that I can see. I also got a camaro reservoir, which is perfect! Thank you guys! Joe, thank you for the offer. I appreciate it. Do you need a new remanufactured Camaro MC without the the reservoir?

I vacuum bled the system. I am not sure if this is a good way for this MC and calipers but I had no helper available. My wife will not come close to the garage... The pedal is hard and moves about 1" with the engine OFF. With the engine ON, the pedal moves almost all the way to the floor. Again, I cannot lock the front or rear wheels no matter how hard I try. The pedal feels spongy. It stops a little better than before though.

I am not sure if there is more air in the system. If there isn't, I may have to eliminate the MP Brakes disc/disc Combination valve Combination Valve Info and install just a proportioning valve Prop. Valve Info on the rear circuit. I ordered a brake pressure bleeder adaptor for my compressor so that I bleed the brakes again.

This is the MP Brakes troubleshooting for spongy pedal: Spongy Pedal Reasons. It may be that the MC is too small diameter for the rear brakes...

What do you guys think?

Theo.
 
#45 ·
Originally posted by Theo:
Do you need a new remanufactured Camaro MC without the reservoir?
Click to expand...
What size bore is it?


Originally posted by Theo:
It may be that the MC is too small diameter for the rear brakes...
Click to expand...
True, the MC might not have enough pump stroke to move enough fluid volume to fill the huge pistons that are in the rear disc calipers.

What I would do is make sure the combo valve from MP is plumbed right. That other front brake port is used on the valve also and not capped off like it was when you got the valve.

If that doesn’t work I would use the stock junction block with a knob style adjustable proportioning valve in the rear brake line.

Bleed the system again. Follow David Pozzi’s recommendations when bleeding the MC. Tell the wife she has to help ;)


Let us know how things are going. And don’t forget the beer when this is all done!

Joe
 
Discussion starter · #46 ·
Joe,

I did another test. I pinched the rear brake lines, right before the calipers, and the pedal was hard with the engine OFF. So, the rear calipers have something to do with the spongy pedal.

In addition, the car hardly stops with the pinched rear brake lines. Shouldn't the front brakes still stop the car? Is this a by-product of the combination valve or something else is wrong?

The pinched brake line test confirmed to me that my MC is OK. It seems that it might be undersized for the rear Cadillac calipers.

My connections are like this:
The forward MC port is connected to the rear brake IN of the Combination valve. The front brakes are connected to the two front OUT of the Combination valve. So, I used all the Combination valve ports.


Now, I am on a search for Corvette C4 rear calipers and rotors. Does anyone know if the 1st gen. Camaro axle housing flange is the same as the '68 Chevelle? I think they should be...

I feel that I am getting closer, slowly...

Regarding the reman. Camaro MC, I believe it is 15/16" bore. The Cardone # is 10-2057. If you can use it, it's yours.

Theo.
 
#47 ·
Originally posted by Theo:
Joe,

So, the rear calipers have something to do with the spongy pedal.

The pinched brake line test confirmed to me that my MC is OK. It seems that it might be undersized for the rear Cadillac calipers.
Click to expand...
I think you are right. There just doesn't seem to be enough fluid volume being pushed back to your rear calipers. But I would recommend before you start swapping out expensive parts to bleed this MC following David Pozzi's recommendations though to see what happens.

From David Pozzi’s website
This Master cyl can take a lot of time to bleed the rear brakes on, due to the small refill port from reservoir to rear bore. You must take at least thirty seconds or more before applying the brakes for each stroke when bleeding, to allow time for the rear bore to refill.
Click to expand...
Originally posted by Theo:

Now, I am on a search for Corvette C4 rear calipers and rotors. Does anyone know if the 1st gen. Camaro axle housing flange is the same as the '68 Chevelle? I think they should be...
Click to expand...
Yes, they are the same. The LT1 setup bolts up with the calipers facing the back of the car on LT1 F-bodies (if I can remember correctly). You’ll want to swap the LH side setup onto the RH side of your Chevelle and vice versa for the other side to avoid interference with shocks and their studs.


Originally posted by Theo:

Regarding the reman. Camaro MC, I believe it is 15/16" bore. The Cardone # is 10-2057. If you can use it, it's yours.

Theo.
Click to expand...
Yeah, I can always use it and if not I can chuck it up on a lathe to turn down the O.D. for someone else to use on the early style Moraine booster for this kind of swap.

e-mail me: Joseph.Whiles@harley-davidson.com

Let me know how your bleeding goes and what you decide to do.

Joe
 
#48 ·
Theo,

I'll bet there's still some air in the system. I too used both a vacuum pump and pressurized setup but still could not get all of the air out. 20 minutes using Torker's leg and the pedal firmed up nicely.

Once you know for sure (and that's not easy) that the air is out you may want to pinch the front lines to find out if there is enough MC volume to fully actuate the rear caliper. Don't pinch the front lines if they are braided steel. Teflon does not like to be squished.

I don't know about the interchangabilty of early Camaro and your car but if the backing plates are the same, or have the same bolt pattern, you may very well be able to use the 93-96 Z-28 rear setup. Torker's website has some good pictures and some measurements that may be helpful. Looks like Joe's got the lowdown as well.

pdq,

I'll have to re-find the piston sizes for 3-4 OEM setups and start comparing.
 
Discussion starter · #50 ·
I really hope that you guys are right.

The way I see it, the rear calipers do not retract as much as the front ones, as they are not the quick take take-up (?) type. So, the rears should (hopefully) require almost equivalent fluid requirements as the fronts. The MC is designed to handle this situation.

I am using the Valvoline Synthetic brake fluid. That's the best I can find locally.

I just received the pressure bleeded and I plan to bleed the system again today. I hope I see a difference. I also plan to recruit my wife... It has to be good exercise for her legs...

Theo.
 
Discussion starter · #51 ·
I pressure bled the whole system twice and used 2 quarts of new brake fluid. No change in brake pedal. It is still soft and goes all the way to the floor when the engine is ON. I still cannot lock the front brakes.

What the hell???? What else can be wrong???

Here is a summary of my system:
Front - Double Piston Corvette C4 12" calipers
Rear - Single piston Cadillac 11" calipers
Booster - MP Brakes Dual 8". It seems to work.
MC - S10 15/16" manual brake. The front outlet (front of the car) is connected to the rear brakes with 1/4" line.
Combination Valve - MP Brake disc/disc combination valve. Rear Brakes connected with single 1/4" line. Front brakes use their one outlet from the comb. valve with 3/16" lines.
Here is a picture: MC & Combination Valve.

Is it the combination valve or the rear calipers?
When I clamp the rear caliper lines, the pedal is hard but the car barely stops.

Theo
 
#52 ·
I'm a little confused about the pedal. When you clamp the rear lines you have good pedal with the engine running but the car still won't stop? You should be able to drive with front brakes only and have fairly decent stopping power.

The synthetic fluid could be the problem. The DOT5 stuff is a major major pain to bleed. I had to drill the port from the reservoir to the cylinder in the master to get it to work for me. It tends to get saturated with small air bubbles when you work with it that are hard to get out.

How are you pressurizing the plastic reservoir? IF you are, try putting the vacuum pump on it for a while, or just hook a vacuum line from there to an engine vacuum port and leave the car idling for a bit and operate the brakes at the same time. Maybe that will suck some of the air out of the fluid?

The only other thing I can think of is that the operating (push) rod in the booster is the wrong length and it's either not pushing the pistons in enough or it's not letting the piston all the way back in the bore.

Peter
 
Discussion starter · #54 ·
Peter,

I used the pressure bleeder system that pushes fluid directly in the fluid inlets with two metal tubes (it is made KD tools). It is kind of hard to describe... I used it with a Garden sprayer for pressure. It works well. I've used a similar setup for my race car for a long time. I used to flash the brake fluid every couple of races.

The fluid I am using is DOT 3 & DOT 4 compatible Valvoline synthetic. It is not DOT 5, which is silicon based. So, the fluid should be OK.

From what I could tell the S10 MC is the same type (short piston depth?) as the 1 1/8" Corvette MC I originally bought from MP Brakes. The Booster is made for this kind of MC. Also, I adjusted the brake pedal to not push the MC at rest. It has a little play.

Regarding what happened when I clamped the rear brakes, I am also confused. I attibute the result to the Combination valve. I am not that familiar with is function. The only thing I know is that it is connected correctly and that it is not locked in one position (Brake warning sensor is OK). Any ideas/opinions on that?

So... now, I am down to the fact that the piston size of the rear calipers might be too large for the 15/16" MC. I really thought that the "quick take-up" MC would compensate for that, but who knows. I am pretty sure I adjusted the Cadillac calipers correctly. I will try again though.

I ordered a set of C4 rear calipers and brackets. I should receive them by the end of this week. I hope that next week I'll be on the road again...

Theo.
 
#55 ·
Theo,
I think in the end of this we are going to find out the piston areas when compared to front to back is just not going to work with the size MC that the C4 calipers need to generate any amount of line pressure necessary to brake with them.

There is just a trade off with MC bores.

When the MC bore is big the stroke required to generate volume isn't as much as if the bore was small, but you generate more line pressure to operate those tiny caliper pistons.

Pressure = Force/Area

To get a little you have to give a little away. Its a catch-22 with this kind of work.

I'm thinking with a step bore MC we could make the swap work in your case, but I've yet to come across such a monster that would work with our cars :( Anyone out there know of an application that offers step bores?

Joe
 
Discussion starter · #56 ·
Joe,

So what are you saying? Will the 15/16" MC work with the front and rear C4 brakes? Is the quick take-up kind MC a step bore?

I just received the rear Camaro/Firebird (C4 BPR) calipers with parking brake assemblies. I am waiting on the mounting bracket and rotors. I should have them by middle next week.

Since I was planning on installing a posi diff and I will need to remove the rear axles to install the rear caliper mounting brackets, I will have the diff people install the brackets at the diff swap. If everything will fit, I should be set... I hope.

Theo.
 
#57 ·
Originally posted by Theo:
Joe,

So what are you saying? Will the 15/16" MC work with the front and rear C4 brakes? Is the quick take-up kind MC a step bore?

Theo.
Click to expand...
Yes, the MC you have right now will work wonderfully with the C4 front and rear setup.

Have you decided to sell the Caddy setup to guys running stock discs up front?

Joe
 
#58 ·
Once again Ih ave been following closely. I have a theory.

It seems that your problem is a lack of volume that is being sent to the rear calipers. The "quick takeup" (read more volume) function on the S10 MC was originally developed for this exact same problem that you are experiencing. The S10 pickups used large bore cylinders in the rear drums, so they needed the extra volume. However the "quick takeup" function is only on the REAR port of the MC. This is the reason I have my front brakes plumbed to the rear port. My front calipers have 6 pistons and require the extra volume. In your setup, you need the extra volume for the rear.
Have you tried plumbing the rear brakes to the rear port? Did you ever check if you have a factory prop valve on the rear crossmember?

Andrew
 
Save
Reply Quote Like Like
#59 ·
Andrew,
Good theory, but I just think the Caddy calipers require way too much volume for this MC to cope with. With the small bore the stroke required to push the necessary amount of volume to the caddy calipers makes you bottom out on the MC before the volume is reached.

That and the fact that the front calipers should be 40-50% larger than the rears or something that I talked about on the first page of this thread could happen.

What do you think?

I've also read some articles, that I could get my hands on, about the quick take up MC is that they were used in conjunction with front calipers that came with specially cut piston seals that allowed less drag when fluid volume was retracted back.

I could be wrong though as all those BB_Mike years of drinking beer in college do catch up with you later in life :D

I'm willing to bet that once Theo bolts up the C4/LT1 rear calipers & discs that he'll have a grin on his face from ear to ear
Image


Anyone else out there have any ideas?

Joe
 
#60 ·
Well, the proportioning block has a valve/switch that measure differences in pressure so if the front was making pressure and the rear wasn't the switch should be closing and putting the brake light on. Since that master should work fine with the front calipers but everyone thinks there isn't enough fluid volume for the rears then this is what should be happening. But, the light isn't going on. Because of this, I'm not totally convinced that the fluid volume is the problem.

I thought the PBR calipers required a quick take-up master because they were low drag. Doesn't this mean that both ports of the master need to be quick take up to match the calipers?

I agree with Andrew, if the quick take up port of the master is the rear one then the rear brakes should be connected to it.

Peter
 
41 - 60 of 70 Posts
About this Discussion
69 Replies
11 Participants
Last post:
Silver69Camaro
Team Chevelle
posts
5.3M
members
131K
Since
1998
A forum community dedicated to Chevrolet Chevelle owners and enthusiasts. Come join the discussion about restorations, builds, performance, modifications, classifieds, troubleshooting, maintenance, and more!
Full Forum Listing
Explore Our Forums
Bench Racing Performance Engine Chevelle Tech Body Shop