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 ? :help:

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......https://static1.pt-content.com/images/pt/2011/10/bananahump-1.gif

[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/benchbleedinggmquicktakeup.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

[RamAir]

Thanks Tobin for sharing your expertise.
The video shows the behavior of the MC when the outlets are not connected to brake pipes (tubing direct to the reservoir). With it connected to the brake pipes I could press the pedal almost to floor
With the engine off the pedal also moving slowly but not as slow as with the engine on. I appreciate the Bendix document that you added. I will do the bleeding procedure tomorrow.
Since you are on this thread I have a question. I will order brakes from you soon (325 mm GMSS or AFX-kit) but I observed that the KORE3-Logo C6 std caliper are no longer available (according to your website). Should I go with Corvette C6 or are the C5 Kore3-logo strong enough.

[Apogee]

Okay, that explains the stroke versus effort on the master cylinder.

PBR discontinued the C6 2-piston front calipers for the aftermarket without any notification when they shifted production of these part numbers to the US under Akebono's direction. I've been told that they didn't include the tooling for the "generic" calipers when they moved these production lines from Australia, however they machined the faces of the C5 calipers for years without any issues as they did not have dedicated tooling for the non-logo versions, so I'm not sure why they can't or won't do the same with the C6 variants now. The best way at this time to get the C6 calipers is to opt for the GM "Corvette" logo'd option if you want the added 25% to 30% rigidity over the C5 calipers. That said, the C5 calipers are still excellent calipers and are more than strong/rigid enough for all but the most severe-duty applications.

Tobin
KORE3

[andrewb70]

Tobin,

Are you aware of any quick take-up MC that has a deep hole in the back of the piston for use in a manual set-up?

Andrew

[Apogee]

Tobin,

Are you aware of any quick take-up MC that has a deep hole in the back of the piston for use in a manual set-up?

Andrew

I am not, but have had the same thought and done some research without any success. Machining the piston wouldn't be all that difficult, although it would require disassembly of the unit and there's always a risk associated with such operations. An alternative might be to make some sort of spacer/guide to be mounted between the firewall and MC and then run a longer pushrod...it seems like it could work in my head anyway.

Tobin
KORE3

[TnBlkC230WZ]

Bench bleeding is just that, bleeding on the bench. You need to have the master cylinder level to get all the air out. You can do it in the car with manual brakes, but not power.

I have one in my Nova and it works very nicely on the road and track.

[JD'sTT55]

I second Tobins post. The quick take up cylinders can be a bear to bleed sometimes. Once you've bled in the vice w the tubes. Blocking the ports w plugs further confirms all the air is out of the quick take up valve. Upon pushing the piston it should only move slightly with a little fluid flow into the reservoir and firmly stopping. Any sign of air bubbles into reservoir or spongyness indicates some air is still trapped in cylinder.

[RamAir]

So I have not been successful with my new MC/BB. I Have done the bench bleeding according to the Bendix procedure that Tobin provided me with (Thanks !). The pedal is firm, but it will still not release instant. I have now mounted the brake booster in the vise without the MC attached to the BB. If you look at the the video on youtube, http://www.youtube.com/watch?v=y1fAzOc5Fdw as you can see the push-rod will return somewhat slow to its default position. Is this normal or is something wrong with the BB. :banghead:

[JD'sTT55]

The video of the booster action appears normal to me. Compared to the many I have replaced. Also one other thing to check would be your rear shoe adjustment excessive clearance could cause a low pedal.

[JD'sTT55]

I am unsure of the method you are using to bleed your brakes but I have found that sometimes the pumping the pedal method causes the air to break up in smaller bubbles and harder to get out. What has worked for me was to have a buddy help. I would open the furthest bleeder from the master cylinder first and have my buddy slowly depress the pedal to the floor and I would close the bleeder when he hollered that it was at the floor. Then he would allow the pedal up slowly and repeat at each cylinder Until no air bubbles were seen and a firm pedal was obtained. Which with no vacuum from the engine should usually be just a small amount of pedal travel. And when the engine is started should only drop a little with the assist. Sometimes I would leave the cylinder cap off as to not create a suction on the reservoir side as I was displacing so much fluid. Just dont push the pedal fast or hard with the cap off or it will make a mess. Been there done that. Hope this helps. :cheers:

[RamAir]

Since it so difficult to bleed the system should I invest in a power bleeder just to be sure that no air are trapped.

[TnBlkC230WZ]

Since it so difficult to bleed the system should I invest in a power bleeder just to be sure that no air are trapped.

They do make the job much easier.