DSE Brake booster

[RamAir]

Hi !
I have a -68 Firebird and I have order the Kore3 C5/C6 325 mm front disc kit. I planning to replace the old single diaphragm to a 9" dual diaphragm. I have looked on the DSE unit but I wonder if someone have some experience with this ?

Magnus

[ProdigyCustoms]

Excellent booster, works well with slightly low vacuum also

[MuscleRodz]

it will give you more than enough stopping power, we have run a number of them.

[MattG]

Had it in my last car and look forward to having it again...feels like something from a brand new performance car.

[RamAir]

I have now bought a brake booster/master cylinder from DSE to my -68
Firebird. It is now mounted on the car and I have bleeded the system.
Unfortunately it will not work properly, do not know if I have done
something wrong. With the engine off the pedal feels ok. With the engine
running the pedal goes straight to the bottom and when I move my feet from
the pedal it will release slowly, almost stucked at the bottom. I have
bleeded the system like 20 times, can not find any air trapped in the
system. The the brake pipe from the rear outlet on the master cylinder goes
to the front ditribution block (Firebird original). The front outlet on the
master cylinder goes to the rear via the Wilwood proportioning valve
(mounted in right direction).
Do you have any idea what is wrong? Is it still not bleeded properly. Have
I use wrong diameter on the pipe from the master cylinder (5/16" MC ->
distribution block then 3/16" to front wheels, 1/4" MC
-> rear axel then 3/16". Are there any thing else I have overlook.

[mild2wildpaintngraphics]

Did you bench bleed the master?

[CarlC]

Do you have the aluminum master cylinder with the 1/2" and 9/16" inverted flare ports?

[RamAir]

No, I did not bench bleed the master cylinder. Do you think that this is the problem even if I hade bleed the hole system ?
My master cylinder is made in cast iron, the one that DSE provide with their brake booster. It has 1/2" and 9/16" inverted flares.

[CreepinDeth]

What is the difference between DSE's dual 9" and a regular say 79 Trans Am 9" dual diaphragm you can get for $95 on rock auto ??

I put a regular 9" DD in my 2nd gen z28.

[zombiekiller]

No, I did not bench bleed the master cylinder. Do you think that this is the problem even if I hade bleed the hole system ?
My master cylinder is made in cast iron, the one that DSE provide with their brake booster. It has 1/2" and 9/16" inverted flares.

if you didnt bench bleed, thats your problem.

Unless you used or plan on using a power bleeder, you need to pull the master back out and bench bleed it. you'll never get all of the air out bleeding the brakes the old fashioned way.

[RamAir]

Ok, back to the garage and bench bleed the MC. Tanks
About the DSE 9" DD, I do not know what the difference is. I is more expensive than the rock auto unit, but it is $395 with MC and bracket.

[RamAir]

I have now bench bleeded the master cylinder. Unfurtenately the master cylinder does not work properly. The mc is now mounted on the brake booster but not connected the brake pipes. When I release the brake pedal it will go back slowly. With engine running the release of the pedal will be even slower. It feels like the force that moves the pedal to its top position is to small. Any help on this, please.

[CreepinDeth]

About the DSE 9" DD, I do not know what the difference is. I is more expensive than the rock auto unit, but it is $395 with MC and bracket.

Ow......

[zombiekiller]

I have now bench bleeded the master cylinder. Unfurtenately the master cylinder does not work properly. The mc is now mounted on the brake booster but not connected the brake pipes. When I release the brake pedal it will go back slowly. With engine running the release of the pedal will be even slower. It feels like the force that moves the pedal to its top position is to small. Any help on this, please.

1. The brake fluid level is lower than it should be.

2. are there any bubbles at all in the fluid?

3. What is the vacuum pressure at?

4. Where are you pulling your vacuum from?

5. are you running rear disc or rear drum?

6. if drum, do you have a residual valve in the line?

7. Is your proportioning valve ( if you are running one) set to all the way open ( " more brake") ( if you dont have one in there, it is a good idea)

8. You may seriously want to consider investing in a power bleeder. It is by far one of the best tools that I've purchased.

9. also make sure that you're cracked all of the bleeders if your calipers have multiple. Do the ones that face up first, followed by the ones that point down.

10. Is your pedal linkage free from binding? Does it hit anywhere?

11. Were the brakes manual to start and you converted to power?

12. How is the booster to master engagement? I'm starting to think that the engagement is not strong enough and your pushrod is too short.

[RamAir]

1. Level is ok
2. There are no visible bubbles
3. I have not measure the vaccum, I will hook up the EFI live and check.
4. I am pulling vaccum from the port just behind the TB (DBW) on the LS2.
5. Rear drums
6. No residual valve
7. I have a Wilwood adjustable proportion valve.
8. Good idea
9.I have only one per wheel
10. I am not shure what you mean.
11. Before I changed to the DSE unit the car was equipped with standard power brakes.
12. I assumed that the push rod and pedal should be ok since DSE marketing this unit as a "bolt-on"
Even with the engine off the pedal release somewhat slowly. With the engine on I almost have to put my feet underneeth and pull it up.

[zombiekiller]

1. Level is ok
2. There are no visible bubbles
3. I have not measure the vaccum, I will hook up the EFI live and check.
4. I am pulling vaccum from the port just behind the TB (DBW) on the LS2.
5. Rear drums
6. No residual valve
7. I have a Wilwood adjustable proportion valve.
8. Good idea
9.I have only one per wheel
10. I am not shure what you mean.
11. Before I changed to the DSE unit the car was equipped with standard power brakes.
12. I assumed that the push rod and pedal should be ok since DSE marketing this unit as a "bolt-on"
Even with the engine off the pedal release somewhat slowly. With the engine on I almost have to put my feet underneeth and pull it up.

10- the pushrod for the booster is connected to your brake pedal via some linkage. Does it hit the firewall or anything else or is it completely free from obstruction?

12- there is still some adjustment in there. It certainly sounds like you are pushing your hardest to push the plunger in on the master cylinder, but the booster to master plunger does not have positive contact, so it doesnt push the pedal back out.

nothing is ever 100% bolt in without adjustment.

When you push the pedal in, are the calipers actually grabbing?

Also, if you do not have a residual valve in line to your rear drums, you need one.

[Apogee]

Bench bleeding the quick take-up type master cylinders can be a little different than a traditional tandem MC. Here's a good link on what Bendix recommends: http://www.remanbrakes.com/pdfs/benc...uicktakeup.pdf

To confirm any MC has been fully bleed, plug both outlet ports and stroke the MC piston...it should hydraulically lock in less than ~1/4" of piston travel.

Tobin
KORE3

[RamAir]

10. No it does not hit any part of the firewall.

The brakes are grabbing, but it feels like it is in the end of the travel.

I have disconnected the clevis from the pedal, then I have pushed the push-rod by hand. With the engine running it will not release instant, it is a short delay and then it moves slowly to its default position.
I have made a short video to visualize the movement.
Please look at http://youtu.be/1qYiL2J_QBY

[RamAir]

Some more information. Today I have the single piston (GM -71) brakes as front brakes. I will change these soon to the Kore3 C6 front brakes. As I understand after read about the Quick Take-up master cylinder is that that is should be used with the Low-Drag calipers. Is this the reason to my problem?
Should I use the Wilwood 10 lb Residual Pressure Valve (Red)

[Apogee]

Magnus,

Quick take-up master cylinders were utilized by GM to overcome excessive pedal travel associated with low-drag calipers, however they should work equally well with standard calipers in providing what effectively behaves like two master cylinders in one; a large bore unit to move a lot of fluid at low pressure and minimize pedal travel and a smaller bore unit to generate higher pressures with less pedal effort. Based on your symptoms, I don't think the type of MC is related to your issue unless it is related to bleeding issues.

As for a 10 psi RPV, you should use one if you're running drums in the rear to keep a small amount of pressure on the wheel cylinder cup seals so that they don't "burp" fluid past the seals and air into the system when the wheel cylinders are compressed by the shoe return springs. The symptom of not running one is usually air in the rear wheel cylinders and slightly mushy pedal because of it...not the symptoms you're describing.

Does your pedal return slowly when the engine isn't running or only when it's running?

Based on the video you posted, it really looks like you have air in the system if you can stroke the pushrod as far as you did by hand.

Tobin
KORE3