DSE Brake Booster & Master Cylinder Problems

[thomaspe]

To All,


Just bought & installed the DSE Booster / Master Cylinder combo Part Number 050102. I have an LSX motor with new brake lines, rear brakes (Right Stuff Disc Brakes) and stock from brakes connected to a Summit Proportion Valve.

The system has been bleed several times & "appears" to have no air in the lines. The pedal seems soft & even though the brakes catch, the pedal still goes further down when the car is stopped. Stopping distance seems to take too long. The pedal is harder when car is off & softer upon start-up.

I have enlarged firewall opening to make sure boot is not snagging.

Are the master cylinder ports designated to the front / rear or is this indifferent?

I have 12" of vacuum at the booster.

Could my rear brakes be a problem, someone has suggested plugging rears & seeing if improvements are made. Hate to have to get new brakes if these "Seville type calipers" are not cooperating.

Any suggestions would be greatly appreciated.

Regards,

Thomas

[MrQuick]

what is the pedal travel with engine off?

[thomaspe]

I'll measure & post back in the morning. Car is at shop.

Thanks

[MrQuick]

cool, just use a tape measure and a spot on your shoe for reference. While your there get your travel with the engine running too and how much travel required to stop the car.

Pedal isn't going to the floor right?

[Apogee]

I think your pedal travel issue is associated with the relatively small bore size of the master cylinder at 1" IIRC. Most would run a 1.125" bore MC with your caliper combination, and that would reduce your pedal travel by ~25%. As for the outlet ports, I believe that the newest DSE MC is front/rear and rear/front, but I wouldn't assume anything in that regard since MC's vary. Finally, the rear parking brake calipers do need to be adjusted properly, otherwise they can contribute to a low pedal as well.

Tobin
KORE3

[thomaspe]

To All,

Here are measurements of pedal rod travel:
Engine off: 0.75 inches
Engine idling: 1.1875 inches

Plugged front MC port to block off rear brake calipers, marginal improvement.

DSE suggested setting proportion valve & 70%, manual bleed & no residual valve needed. All this has been done.

Going to buy another DSE booster (for 67 Camaro) & see if this works on T/A. DSE said may have to add a little threaded rod to match newer pedal setup. DSE will fix first booster if second works.

Any more suggestions appreciated!

Have a great Turkey Day.

Thomas

[formula jg]

Bringing this thread back to life as I have strong doubts about my new DSE MC/booster for my 2nd Gen and would like to know if you resolved your brake issues? If yes, was the DSE product the culprit?

[71RS/SS396]

Bringing this thread back to life as I have strong doubts about my new DSE MC/booster for my 2nd Gen and would like to know if you resolved your brake issues? If yes, was the DSE product the culprit?

What exactly is your problem? You'll likely get better feedback if you describe your symptoms. I'm using the DSE booster/master on my car, I had some problems with the boot dragging on the firewall but once I clearanced the hole it has worked fine since.

[formula jg]

MC was bench bleed and pressure bleed and the rest of the system was gravity, vacuum, brake pedal and reverse bleed several times each.

With engine on and running I apply the brakes and the following happens:
- 75 RPM increase
-2" pedal travel before it starts to firm up
-0.75"Hg increase in vacuum (when idling in Park and I depress brake)
-vac. In Park 15"Hg and it drops to 13"Hg when brake is pressed and shift into Drive

With engine off I pump the brake and then turn eng. on and pedal will drop approx. 1/2".

With foot on the brake I turn eng. off and pedal will rise (push back against my foot) is that normal?

[6t9 camaro]

Hey formula jg
Any luck with your brake issues? I'm in the exact same situation! I've been adjusting my clevis on the booster where it attaches to the pedal and I've been getting a slightly firmer pedal but I've got that adjustment pretty much zeroed in and it's still way to soft and not how it's supposed to be! Is this a dse booster/cyl issue?

[formula jg]

6t9, great success for me. I'll try to make a very long story somewhat short.

First-I removed the brake pedal and drilled a new hole at a lower location than the original disc/drum hole (see this link http://www.nastyz28.com/forum/showthread.php?t=81867&highlight=disc+pedal). When reinstalling I noticed the booster rod had a perfectly straight path from pedal to booster and my foot felt more comfortable on the pedal. However this did not resolve all the unusual symptoms.

2nd-I vacuum tested the booster and it would barely move the needle on the gauge and did not hold vac at all so I thought I found the culprit. But wait, after removing the MC I had a thought, what the heck I'll retest the booster and to my happy surprise it pumped up nicely and held vac for at least 15min (this was such a relief that it didn't have to be removed).

Third-Checked booster to MC pin length...OK...that's when it hit me that the pin was applying pressure to the MC because the booster to pedal rod was in the wrong location at the pedal thereby keeping the MC piston slightly off its seat and causing all kinds of head scratch issues.

4th-Bench bleed the MC again and power bleed the rest of system and the pedal is now high and hard (no road test until next week).

Hope you get yours sorted out soon I know for me I was loosing sleep over it.

[formula jg]

Update
I pulled a dumb-dumb move prior to my previous post #11. I tested the brakes but forgot to connect the vacuum line to booster obviously giving me false results, my bad. So I bled some more but the pedal still travels 2" before it firms up and then heavy pedal pressure is needed to stop the rears from turning while the car is on stands, running in drive (and that's only at an idle rpm).

More bleeding is the plan for this weekend but I will do it the old school way using a very slow pump action on the pedal (open screw, slowly apply the brakes, hold, tighten screw and repeat...correct?)

[MattG]

Any updates on this? I'm having exactly the same problem!

[formula jg]

Matt, I did resolve this issue turns out the booster had an engineering design flaw so I sent it back for a replacement at my expense because I live in Canada, it was freak'n costly. When I rec'd the new one it came with a firewall template and special note which basically explains what may occure if the opening in the firewall doesn't match their template you would experience exactly what I was. Also noticed that the replacement booster/mc had a different setup for the plunger rod in the booster which now included an O-ring around the rod.
It's been a year now and all has been flawless, very happy but the diagnosis was frustrating to say the least.

Here are some pics that help tell the story:

[MattG]

Thanks so much for the detailed response! I'll give DSE another call and point out this thread to them.

Thanks again,

Matt