Have fitted single pot discs to the front of my 61 and still have original drums on the back via a balance valve . I have bled them by the good old pedal and one way valve method but still have spongy brakes which I presume is air ?
I have finally rigged up a power bleed system to fit the master cylinder and am about to re bleed the system , Questions ??
1 do I bleed with the hand brake in on of off position ?
2 should the balance valve be turned fully down or up ?
3 bleed furthest brake first moving towards the nearest ?
TIA
Mike .

 

My opinion?
1. Doesn't matter
2. Doesn't matter either
3. Yes

 

On the front, did you mount the calipers with the bleeders on the top?

 

Yep bleed nipples are on the top .

 

In my opinion:
1. Might be better with the hand brake off.
2. probably doesn't matter
3. Doesn't matter, but if it makes you feel better go to the furthest first. I assume you have a dual MC, and the front and rear are completely independent.
4 You didn't mention it, but the MC needs to be bench bled. Otherwise it may take a lot of fluid to bleed the system, even with the power bleeder.

 

You MUST bench bleed the master cylinder first. The rule is after that, follow the lines and go to the wheel farthest away from the master and bleed it first, then the next farthest and so on. I would not adjust the porportioning valve (balancing valve) until after they are bled. Then you will want to make sure the front discs are first to grab before the rear drum. Also adjust the rear drum before bleeding. Make sure there is some minor drag on the rear drums, not much, just a little. I also assume you have a dual master cylinder as single will not work with disk/drum combination as far as I know unless you have a power booster. I run disc/drum on my hotrod with a remote power booster and single master cylinder but it is not what I recommend. If I ever want to do all 4 discs I will have to change it. The power booster is the only way you can get away with it.

 

Ken,
Don't want to Hijack this thread but I have a question for you. I see you show your Deuce Coupe as your avatar and didn't see any Corvette's listed in your profile. Nothing wrong with that I am also into Street Rods having a 34' Ford Coupe that I built from a bare frame. Pictures are in my Corvette Photo's. Just curious what brought you to the Corvette Forum if I may ask? Also are there any good Street Rod forums that you can recommend to me. I always like to see what others are doing plus where they are sourcing their parts.

Fred

 

Fred,

I started my 32 coupe about 8 years ago and took about 4 years to complete. Did 90% in my garage. Been showing the car for a few years and now interested in possibly starting a new project with a C1 or C2. But I really would like to build one with a custom frame so I can have the ride and control of a C5. I'm thinking of a show car but also one that I can drive anywhere and have a ton of fun with it. Regarding streetrod sites, I really don't go to many as I had finished my rod so kind of lost interest. Trying to get more on Corvettes now. This is a good forum to learn about Corvettes. I'll most likely have one within the next 6 months when winter hits. Nothing to do to the 32 so kind of bored at times. Need a fun project. I like your 34. Have a neighbor down the street with a yellow 34 who just won a nice trophy at the last NSRA show here in Sacramento. 34's are hot right now.

 

Cheers for all the advice , but now I am a little confused .
I do not have a Dual MC only the original it is all in one line with the balancer fitted between front and rear . Corvette Central who supply the "big brake" kit suggest you should be able to run with the original MC , I would be interested to hear your thoughts . Also what do you mean by "bench bleed" ? not a term I am familiar with in the UK .
Cheers
Mike .

 

Mike,

Dual means two lines exiting the resevoir of the master. One line feeds the front, the other feeds the rear. It will have two pistons inside. This way if you have a failure in one brake line you have the second one still in use so you will not lose all 4 brakes. Bench bleed is when you remove the master and bleed it on a bench to remove all the air before installing it. You do this with a new master before installing. The fluid will displace the air as you bleed. Never let the fluid get low as this can cause air to enter the master. Then you have to start all over. It is critical to remove all air from the lines or you will have a very soft pedal. The air in the lines or master will compress unlike hydraulic or brake fluid. That compression results in poor brake performance. You can go to almost any brake repair or sales web site and find anything you need to know. It is really not a complicated process at all.

 

Here's a typical bench-bleed setup; you just run a line from the outlet back into the reservoir, below the fluid level, and stroke the rear piston with a phillips screwdriver until you see no bubbles exiting the tube - that removes all the trapped air in the master cylinder bore, which can't be removed any other way. This is a dual master - yours would only use one line.



I wouldn't recommend using a single master cylinder with a disc/drum setup, as the front and rear system requirements are different. Drum brakes use a residual pressure valve (RPV) in the master cylinder outlet(s) that maintains 10 psi in the lines at all times - that overcomes the initial tension of the shoe pull-back springs and holds the shoes out close to the drum surface so they don't have to travel so far before you get braking action.

Discs DO NOT use an RPV, and if a disc system has an RPV in the master cylinder, it will maintain pressure in the calipers and cause the pads to drag on the rotors, which will eventually fry the pads and the rotors. Also, the fluid displacement (volume) is different between discs and drums, which is why OEM disc/drum systems always use a dual master cylinder (with an RPV in the drum system outlet and none in the disc system outlet).

 

Thanks for posting that picture John Z.
I know this might be a stupid question but how do you get the master back on the car without brake fluid running out while attaching the hard lines?
I've never bench bled but would like to try it.

 

First of all look at the picture John Z provided you.

What I do is just move the 2 rubber hoses attached to the master cylinder to the side after bleeding and put the lid back on the master and attach the two holddown wires. I then tuck the 2 rubber hoses under the wires snug and mount the master cylinder. After it is mounted I unscrew one plastic bleeder fittings at a time and reconnect the metal brake line then do the other. While you are doing all of this make sure no one presses down on the brake pedal. After all this is done and all lines are tight I have someone sit in the car and press on the brake pedal while I loosen one of the fitting on the side of the master cylinder bleeding fluid right from the fitting until the person in the cars foot goes to the floor. Then tighten the fitting and have your helper release his foot from the pedal. Do the other the same way. If just replacing a master cylinder you sometimes can get away with just doing this procedure and checking to see if you have a good pedal. If a good pedal is not to be had you need to bleed all four wheels. On all 4 wheel disc brakes GM recommends that you start at the caliper on the Drivers rear in board bleeder then to the Drivers rear out board bleeder to the Passenger rear inboard bleeder to the Passenger rear outboard bleeder to the Passenger side front Caliper single bleeder to the Driver side front single bleeder. Repeat if neccessary.

Fred

 

Thanks Fred.
Those were excellent directions.

 

Bleeding Process
1. Begin at the corner furthest from the driver and proceed in order toward the driver. (Right rear, left rear, right front, left front.) While the actual sequence is not critical to the bleed performance it is easy to remember the sequence as the farthest to the closest. This will also allow the system to be bled in such a way as to minimize the amount of potential cross-contamination between the new and old fluid.

2. Locate the bleeder screw at the rear of the caliper body (or drum brake wheel cylinder.) Remove the rubber cap from the bleeder screw – and don’t lose it!

3. Place the box-end wrench over the bleeder screw. An offset wrench works best – since it allows the most room for movement.

4. Place one end of the clear plastic hose over the nipple of the bleeder screw.

5. Place the other end of the hose into the disposable bottle.

6. Place the bottle for waste fluid on top of the caliper body or drum assembly. Hold the bottle with one hand and grasp the wrench with the other hand.

7. Instruct the assistant to "apply." The assistant should pump the brake pedal three times, hold the pedal down firmly, and respond with "applied." Instruct the assistant not to release the brakes until told to do so.

8. Loosen the bleeder screw with a brief ¼ turn to release fluid into the waste line. The screw only needs to be open for one second or less. (The brake pedal will "fall" to the floor as the bleeder screw is opened. Instruct the assistant in advance not to release the brakes until instructed to do so.)

9. Close the bleeder screw by tightening it gently. Note that one does not need to pull on the wrench with ridiculous force. Usually just a quick tug will do.

10. Instruct the assistant to "release" the brakes. Note: do NOT release the brake pedal while the bleeder screw is open, as this will suck air back into the system!

11. The assistant should respond with "released."

12. Inspect the fluid within the waste line for air bubbles.

13. Continue the bleeding process (steps 11 through 16) until air bubbles are no longer present. Be sure to check the brake fluid level in the reservoir after bleeding each wheel! Add fluid as necessary to keep the level at the MAX marking. (Typically, one repeats this process 5-10 times per wheel when doing a ‘standard’ bleed.)

14. Move systematically toward the driver – right rear, left rear, right front, left front - repeating the bleeding process at each corner. Be sure to keep a watchful eye on the brake fluid reservior! Keep it full!

15. When all four corners have been bled, spray the bleeder screw (and any other parts that were moistened with spilled or dripped brake fluid) with brake cleaner and wipe dry with a clean rag. (Leaving the area clean and dry will make it easier to spot leaks through visual inspection later!) Try to avoid spraying the brake cleaner DIRECTLY on any parts made of rubber or plastic, as the cleaner can make these parts brittle after repeated exposure.

16. Test the brake pedal for a firm feel. (Bleeding the brakes will not necessarily cure a "soft" or "mushy" pedal – since pad taper and compliance elsewhere within the system can contribute to a soft pedal. But the pedal should not be any worse than it was prior to the bleeding procedure!)

17. Be sure to inspect the bleeder screws and other fittings for signs of leakage. Correct as necessary.

18. Properly dispose of the used waste fluid as you would dispose of used motor oil. Important: used brake fluid should NEVER be poured back into the master cylinder reservoir!

Vehicle Wrap-Up and Road Test
1. Re-install all four road wheels.

2. Raise the entire vehicle and remove jackstands. Torque the lug nuts to the manufacturer’s recommended limit. Re-install any hubcaps or wheel covers.

3. With the vehicle on level ground and with the car NOT running, apply and release the brake pedal several times until all clearances are taken up in the system. During this time, the brake pedal feel may improve slightly, but the brake pedal should be at least as firm as it was prior to the bleeding process.

4. Road test the vehicle to confirm proper function of the brakes. USE CAUTION THE FIRST TIME YOU DRIVE YOUR CAR AFTER MODIFICATION TO ENSURE THE PROPER FUNCTION OF ALL VEHICLE SYSTEMS!

Have fun.........it's a snap.

 

[QUOTE=Kensmith]Bleeding Process
1. Begin at the corner furthest from the driver and proceed in order toward the driver. (Right rear, left rear, right front, left front.) While the actual sequence is not critical to the bleed performance it is easy to remember the sequence as the farthest to the closest.

Just wanted to mention that this method is incorrect for Corvettes with 4 wheel disc brakes. GM in their manual tells you to start at the DRIVER SIDE rear caliper inboard bleeder screw first then the DRIVER SIDE outboard bleeder screw then you go to the PASS SIDE caliper inboard bleed screw to the PASS SIDE outboard bleed screw up to the PASS SIDE front caliper single bleeder screw and then to the DRIVER SIDE caliper front single bleeder screw. For years I thought the same as Ken until this was pointed out to me by a repair shop that I sell to. I saw it in writing in the GM manual myself so I know this to be true.

 

[QUOTE=ffas23]Fred,

I obtained this from the following site. It does not matter if the brakes are disc or drum or combination. I also replaced my brakes with Wilwood and they also recommend this proceedure. I don't know why Chevrolet would be any different than any other brake system. The only thing that may be different is the brake line may be longer to the driver side rear than passanger. The idea is to follow the brake line to the wheel cylinder and start at the farthest away or longest line from the master.



How to Bleed Brakes – The Right Way

by John Comeskey of SPS (http://www.spswebpage.com)
and James Walker, Jr. of scR motorsports (http://www.teamscR.com)

COPYRIGHT © 2004 STOPTECH LLC

 

WOW , my initial couple of questions have certainly opened a good debate , I never knew there could be so many ways of doing what I have always considered to be a simple task .
Since posting the initial thread I have now power bled the brake system , furthest (drivers rear ) first , working in to the nearest ( drivers front ) . Brake pedal is now good and firm and stops pretty good .
I would like to know more about the RPV valve and what dual MC I should look for with a RPV in only one of the cylinders does any one know of such a MC ?
Also when running a dual system is it best to split back to front or alternate sides ie; drivers front / passenger rear -- passenger front / drivers rear ?
Keep the ideas coming guys
Cheers
Mike .

 

[QUOTE=Kensmith]Fred,

I obtained this from the following site. It does not matter if the brakes are disc or drum or combination. I also replaced my brakes with Wilwood and they also recommend this proceedure. I don't know why Chevrolet would be any different than any other brake system. The only thing that may be different is the brake line may be longer to the driver side rear than passanger. The idea is to follow the brake line to the wheel cylinder and start at the farthest away or longest line from the master.



How to Bleed Brakes – The Right Way

by John Comeskey of SPS (http://www.spswebpage.com)
and James Walker, Jr. of scR motorsports (http://www.teamscR.com)

COPYRIGHT © 2004 STOPTECH LLC[/QUOTE

Ken,
I would always bleed brakes in the same way starting at the passenger rear brake and still do with other cars. I use to do the same with Corvette's with disc brakes before I was told differently by a repair garage about Corvette brake bleeding. I had my doubts also but he showed me right in the GM manuel what it said and it said to start on the Drivers rear on Corvettes with 4 wheel disc. The repair garage was having problems at times manually bleeding Corvette brakes on and off as one would come in the shop and I guess they were told by someone about what GM recommended. I Zeroxed a copy of that page for my own use and will fax a copy to you if you want to take a look. I don't have a scanner otherwise I would email it. Believe me I am not making this up. Even using this procedure recently in the last year I still had problems with my 73' Coupe manually bleeding it. I finally ended up purchasing a Motive Pressure bleeder for under $60 and this is the only way I will ever bleed Corvette brakes again on either my C-2 or C-3 but I still start bleeding at the Driver rear caliper. With the Motive Pressure bleeder I was done in 20 minutes. I strongly recommend purchasing a Motive Pressure bleeder to anyone who does or plans to do brakes on their Corvette. The tool is worth its weight in gold for how easy it makes this job a one man operation. No need to find a helper. My 73' Coupe never had such a good hard pedal like it does now after using the Motive pressure bleeder compared to when I bled it manually in the past.

 

[QUOTE=ffas23]I don't doubt what you say at all. I just did a ton of research when I had trouble replacing my Wilwood brakes. I must have spent 10 hours researching and talking to mechanics, some from Chevrolet, and all said start with the farthest wheel cylinder away from the master. I have no idea why, but everywhere I went said the same thing. Maybe if you follow the line on your Corvette, the farthest one is driver side rear? It depends on how the lines are run, wear they cross over, etc. That is what I was told, farthest first and then next farthest etc.