Finally got a chance to test the car yesterday and the brakes showed that they are still a bit ugly. As background I corrected the pedal ratio, I bleed the piss out of them and sitting around here over the winter, moving the car a bit they seemed to be okay. But - go to do the first burnout and I realize that the pedal still feels spongy for the first part of it, then pressing it further down it feels solid. Pumping them helps a bit and after doing that, then setting the linelock it allowed me to do the burnouts without any issues. Bumping into the beams was not happening or least I couldn't get it right because of the softness in the first part of the pedal. (On another note, the looser convertor really helped the car and I finally got my first string of decent RTs with the car.) Down track at 120 I could get the car slowed down easily to make the first turnout (just beyond the 1/4). The car has Aerospace up front, GM Metrics at the back, hoses and connections are all good and this is a Strange Eng. master cylinder (Chrysler style). Short of back to bleeding again and not seeing any leaks does anyone think it would be worthwhile to rebuild the master? Or should I consider a different size cylinder, I am pretty sure this is a 1.032" unit?

this is what I've learned thru the years. When it comes to bleeding brakes for a spongy feeling,try to locate the highest point in the car that you can open. If you have a brake pressure gauge mounted in the dash or rear brake line Tee mounted higher than the rear axle, that's where you want to start. You'll never get the air out of a high area bleeding them at the wheel.

Buy 2 plugs that fit the MC outlet ports. Crew the plugs in and step on the pedal. Hard pedal it's not the MC. Soft pedal or the pedal drops it's in the MC. Is there any difference in the Strange MC compared to a factory Mopar MC? If not I'd just go buy a Mopar MC at the parts store, probably $30 new.

This sounds just like my cobalt. I just got my camaro roadster out last year with a 1.032" mc and Lamb residual pressure valves(Strange mc mounted on floor) The pedal is always very firm with no sponginess. I believe I put the 1.125" mc on my cobalt with no valves. Cobalt is always spongy on first hit. I'm putting a 1.032" mc and Lamb valves on the cobalt this year.

If the MC is floor mounted, you must have residual pressure valves for a solid pedal.

No valve in mine. Have to be careful. Can lock them up in a split second and get to a bouncing real quick.

Just $.02 from a pretty much non-mechanic.

Some brake pads can 'give' more than others.
I think the 'organic' pads would be typical of those, being more compressible than the traditional metallic brake pads.

Are stainless steel-braided brake hoses in place or planned? Some racers claim a pretty big difference in brake feel. I'm not entirely sold on them myself, but it seems they have improved my RT slightly by allowing the brakes to apparently release quicker.

The usual advice applies too about tapping on the calipers to dislodge air bubbles while bleeding; insure that the bleeder screw is properly positioned while bleeding, even to the point of removing the caliper, etc. etc.
Proper bleeding of the MC is a must as well, but I think it likely you've already done all that.

One thing nice about Mopar master cylinders is the screw-on reservoir caps. To me they look like they'd make attaching a pressure bleeder a breeze.

Do you still have the stock, 1/4" brake line in place to the rear brakes? 3/16" line may help a little bit.

About those GM 'metric' calipers on the rear; would they be stock, factory-original front calipers by chance? Some of them were 'low-drag' calipers that were designed to retract slightly. As such, they would take more fluid to push them against the pad.

I a$$/u/me then they're not actually the GM locking 'Caddy' calipers?

And I assume your pedal ratio is about 5:1?

Insure too that the firewall is not flexing too much or is cracked or anything, unless the MC is mounted to the tube frame or something

I imagine that you have eliminated excess play between the brake pin and the MC piston?

I have a Speedway Motors brake pressure gauge permanently installed in the front brake circuit of my S10. It's a little superfluous now, but it was really helpful in troubleshooting brake issues I was having and as a learning tool.

This message has been edited. Last edited by: Bad Nusz,

Have you bled the master again ??? If not, give that a try . Do it just like you do the calipers. Spongy and having to pump the pedal to get a pedal are really two different issues. Sounds like there's still air in the system, not the wrong bore diameter.

Best thing I have found if starting from empty is to open bleeders on calipers . Take line off MC push fluid thru with large cattle syringe filled with brake fluid. Then bleed normally. Yes I had to use residual valves on my ride with low mounted MC.I have used this trick on many street rod builds.

Here is what I have been doing for years.Works for me. I Attach two lines to bleeds,open them with lines going into a bottle I pump fluid thru them. I keep close check on master fluid level. I run three or 4 master cylinders of fluid. I close the valves and ready to go. The lines will fill with fluid and keep brakes from pulling air back into them as you go. Don't pump them fast,but you don't have to be real slow either.

I started this after we spent most of weekend trying to get brakes on our first funny car. I still have a picture that shows the asphalt with huge stain from the fluid.The 3 hot gals in picture with chassis makes it little harder to see.LOL

Regarding residual valves, I removed mine in my dragster a couple years ago to install a line lock in its place.

Ran it most of the season with no issue. Typically I put the chute out first time trial every day. One day there’s a head wind I put the chute out and the car stops real quick. I didn’t even put my foot on the brake it stopped so good. I get to the turnoff and go to give it a little brake and the pedal goes right to the floor. Second pump same thing. Third pump had a pedal. Took it to the pits took everything apart couldn’t find any issues.

Theory is without the residual valve and without me stepping on the brake pedal slowing down with the chute made the fluid drain back to the MC.

quote:

Originally posted by fast5982:
If the MC is floor mounted, you must have residual pressure valves for a solid pedal.

Disagree....none in mine and pedal is rock solid.....last dragster I had same deal....

To answer a few questions.

MC is mounted in normal fashion from the frame tubing tied to the chassis plus I built a support box back to the dash bar which also serves as the pivot point for the brake pedal. Very similar to a production car.

Pedal ratio is 6.3. I have gone from something around 4+ where it took forever to get the car stopped to 8+ which just killed the MC and I could not get any pedal. Between 5 & 7 is what I have read and this is the best pedal I have had in it.

All lines are 3/16". Rears use rubber lines, fronts are stainless steel/Teflon that came from Aerospace. Rear pads are semi-metallic, the fronts appear to be similar material.

No residual valves but there is an adjustable proportioning valve which is 100% open right now.

Rear calipers are GM metrics which are the same ones we use on the rear of the '89 Camaro with zero issues. There is no locking features. In fact this system is basically a duplicate of the one on the Camaro except the fronts are Wilwood on that car.

On the last go with bleeding, after all of the calipers were bleed using a homemade bleeder bottle which worked really well, I still didn't have a really tight pedal. I did a "loop bleed" between the left front caliper and the master cylinder. Took about 12-13 pumps and the pedal became solid. I thought I was home free at that point - maybe I should do that again as trapped air pockets might have worked their way back up to the master?

I've been doing brakes since I was 12 and this is first car that has ever given me this much trouble on getting a tight pedal.

I had a similar problem with my Camaro. Car was all new and I bench bled the Strange master, installed it and proceeded to bleed all 4 corners of brakes with no problems. Raced the car a few times and pedal seemed to be getting mushier over time, needed to pump it to make things happen. Bled the brakes again and no air in the system …..
Finally tried bleeding the master right at the fittings and the brakes were mint.

get rid of the rubber lines,use teflon and keep to min length.

Buy or borrow a pressure bleeder and use the correct adapter for your brand master cylinder..
Motive Products sells an economical pressure bleeder like a pump style garden sprayer thru Summit or Jegs..This tool works really well to bleed or push out any trapped air. The key when using a pressure bleeder is to leave the bleeder screw open for at least 10-12 seconds, before moving on to the next caliper or wheel cylinder.
Many times it takes that long of flowing brake fluid for the trapped air to bubble out,The stroke volume is small on most of the small bore master cylinders and its hard to push out air,,,
Think of an air bubble in a carpenters level sight glass and how far you might have to push that bubble out of your brake line unless the bubble was right next to the bleeder screw...Guys hike the front end and try to rely on gravity but its easy to run the master cyl dry doing this,,,buy a bleeder,,No doubt about getting air out..If you bleed all the air out and still have a pedal that "gives" or feels spongy then some component is flexing or moving.
When bleeding rear disc brakes with the wheel off the car, make sure to put several lug nuts on the axle studs to hold the rotor from moving..Calipers can flex with weak bridging securing the 2 halves of aftermarket calipers , warped or cracked rotors can give enough to result in a spongy feel and even master cylinder mounts can cause problems in obtaining a solid feeling pedal..

Does the MC point up? Air will go to the high spot. If it's pointing up jack the back of the car up to level it. I still say put the plugs in it and see if it's in the MC.

quote:

Originally posted by Eman:
Does the MC point up? Air will go to the high spot. If it's pointing up jack the back of the car up to level it. I still say put the plugs in it and see if it's in the MC.

I'll check that. I think it's level but with the slight rake of the car front to back, it might not be.

had very similar issue with my car called strange and was told they had a run of bad masters sent me a new one and never had another issue pedal was great after first few pumps. car would sit for a day or so then it would be soft again for a pump or 2. I agree get rid of the rear rubber line also.

Have a full chassis car with MC on the floor. No residual valves as WIlwood said I really didn't need them. No matter how I bled my brakes, always felt spongy on the 1st hit and if I pumped it again, it was a solid pedal. I did it manually, gravity bled or pressure bled. Finally spoke to a guy at WIlwood and he said I have air in the system. He said to find the highest point in the system and that would be where the air is and none of the ways I tried would clear it. My highest point was the connection on the rear frame to the hose going to the rear end. He said to pump up the system and loosen the fitting there. Sure enough I did that and plenty of air came out. Then I performed a final bleed at all 4 calipers and problem was gone. One note, I do bleed my brakes every start of the season and it has worked well each time.